Best Ways to Prevent Cancer: Evidence Based Review (2024 Edition)

By Dr Frank Yap, MD April 04, 2024

If your question is how to treat cancer, you are asking the wrong question. A more critical inquiry should center around cancer prevention.

We can recall notable figures like Steve Jobs, Chadwick Boseman (Black Panther), Robin Gibb (Bee Gees), Donna Summer, Farrah Fawcett, Eartha Kitt, Peter Jennings, Paul Newman, Patrick Swayze, Sydney Pollack, Michael Crichton, Bob Denver, Ted Kennedy, Jerry Orbach, Anne Bancroft, William Rehnquist, and Tony Snow, among others. What unites them? They all succumbed to 'cancer.'

Many of these individuals had access to the finest medical care available worldwide. So, what is the missing link here? Does cancer still elude our understanding? Is it preventable?

Can our dietary choices impact our susceptibility to cancer? Which foods can reduce the risk, and which might heighten it? How do vitamin and mineral supplements come into play? Do they mitigate or potentially increase the risk of cancer? Admittedly, numerous guides exist on this subject, but most tend to be product-centric, biased, and lack the most current and evidence-based information.

What is Cancer?

Cancer is the second leading cause of death in the United States, behind only heart disease. For most Americans who do not use tobacco, the most important cancer risk factors that can be changed are body weight, diet, and physical activity. At least 18% of all cancers diagnosed in the US are related to excess body weight, physical inactivity, excess alcohol consumption, and/or poor nutrition, and thus could be prevented.

Genetic changes that cause cancer can be inherited from our parents. That said, environmental factors could contribute up to 95% of cancers. They can also arise during a person’s lifetime as a result of errors that occur as cells divide or because of damage to DNA caused by certain environmental exposures. Cancer-causing environmental exposures include substances, such as the chemicals in tobacco smoke, and radiation, such as ultraviolet rays from the sun.

There are many types of cancer treatment. The types of treatment that you receive will depend on the type of cancer you have and how advanced it is. Surgery, radiation, and chemotherapy are the standard types of treatment for cancer.

There are also many phoney “cancer treatment” with amazing claims but devoid of any scientific data to back them up, typical of health scams. Cancer is a life threatening disease and therefore many consumers fell prey to these phoney cancer treatments.

Note: When interpreting scientific studies, let’s remember that cell culture results are trumped by mouse results (animal results). Mouse results are trumped by human results. Case studies & small human trial results are trumped by double-blind placebo controlled and randomised controlled (RCT) ones.

Don't use tobacco
Maintain a healthy weight and be physically active
Avoid risky behaviors
Protect yourself from the sun
Get regular medical care and Health Screening
Avoid unnecessary exposure to radiation.
Sleep Quality and Reduce Stress
Avoid exposure to environmental toxins and infections that contribute to cancer

New studies are being added almost every day. We have organised and summarised relevant and salient research information in one place. Below, we look at the most published and studied categories.

1. Diet and Cancer Prevention

Diet and nutrition are important determinants of cancer risk, both through their contributions to energy balance and via biological mechanisms that alter risk independent of body weight (R).

One major change in cancer prevention guidelines over time, which reflects the current and evolving scientific evidence, has been a shift from a reductionist or nutrient-centric approach to a more holistic concept of diet that is characterized as dietary patterns. A focus on dietary patterns, in contrast to individual nutrients and bioactive compounds, is more consistent with what and how people actually eat. People eat whole foods (not nutrients) that, in aggregate, represent an overall dietary pattern wherein dietary components often contribute additively or synergistically to modify cancer risk.

Emerging evidence, largely epidemiological but also including a few controlled intervention trials, suggests that healthy (vs unhealthy) dietary patterns are associated with reduced risk for cancer, especially colon and breast cancer (R).

Randomized controlled trials (RCTs) of dietary interventions aimed at preventing cancer, conversely, are expensive and largely impractical. Therefore, most current evidence concerning diet and cancer prevention is derived from observational epidemiologic studies, in particular prospective cohort studies, mechanistic studies of food components in laboratory animals and cell culture, and RCTs when available.

Although eating healthy foods can't ensure cancer prevention, it might reduce the risk. Consider the following in general:

Eat plenty of fruits and vegetables. Base your diet on fruits, vegetables and other foods from plant sources — such as whole grains and beans. Eat lighter and leaner by choosing fewer high-calorie foods. Limit refined sugars and fat from animal sources.
Drink alcohol only in moderation, if at all. Alcohol increases the risk of various types of cancer, including cancer of the breast, colon, lung, kidney and liver. Drinking more increases the risk.
Limit processed meats. Eating processed meat often can slightly increase the risk of certain types of cancer. This news comes from a report from the International Agency for Research on Cancer, the cancer agency of the World Health Organization.

People who eat a Mediterranean diet that includes extra-virgin olive oil and mixed nuts might have a reduced risk of breast cancer. The Mediterranean diet focuses mostly on plant-based foods, such as fruits and vegetables, whole grains, legumes and nuts. People who follow the Mediterranean diet choose healthy fats, such as olive oil, over butter. They eat fish instead of red meat.

Eating a plant-based diet rich in vegetables, whole grains, nuts and legumes can reduce the risk of bowel cancer in men by more than a fifth, according to research.

A large study that involved 79,952 US-based men found that those who ate the largest amounts of healthy plant-based foods had a 22% lower risk of bowel cancer compared with those who ate the least.

The researchers found no such link for women, of whom 93,475 were included in the research. The team suggested that the link is clearer for men, who have an overall higher risk of bowel cancer. Their findings were published in the journal BMC Medicine (Nov 2022).

The evidence for the association between dietary sugar consumption and the risk of cancer has remained limited and controversial (R). In 2018 the World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) reported that evidence was limited for the associations between consumption of sugars and food containing sugars and the risk of colorectal cancer. However, at the same time, this report recommended reducing or avoiding sugar sweetened beverage consumption for the prevention of breast cancer. Evidence from this umbrella review (BMJ 2023) supports the recommendations from the WCRF/AICR to some extent.

The ketogenic diet is a low-carbohydrate, high-fat, and protein diet that forces the body to rely on ketones instead of glucose as a predominant energy source. It has shown potential in preclinical and early clinical studies for brain cancer treatment. By altering the metabolism of cancer cells, the ketogenic diet may inhibit tumor growth and enhance the effectiveness of other therapies.

Intermittent fasting refers to periods of restricted calorie intake or complete food avoidance. Like the Ketogenic diet, fasting triggers the use of ketones as the predominant energy source and may sensitize cancer cells to treatments and potentially slow down tumor growth. Fasting-induced metabolic changes may also favor the protection of normal tissues from therapy side effects and improve tolerance and quality of life impacts to care.

Additionally, fasting reduces insulin levels. Eating continuously can contribute to hyperinsulinemia. Elevated insulin levels are linked to an increased risk of breast, prostate, and colorectal cancers.

That said, not every type of fasting is effective and safe. Intermittent fasting is the preferred option. Extended or extreme fasting can be counter-productive.

2. Cancer Fighting Foods

The development of cancer, in particular, has been shown to be heavily influenced by your diet. The term “superfood” is a fairly new term referring to foods that offer maximum nutritional benefits for minimal calories.

Do take note that we are talking about foods to prevent your risk of cancer and not about treating cancer with foods. Cancer treatments will be something that you will need to discuss with your cancer specialist.

Many foods contain beneficial compounds that could help decrease the growth of cancer. There are also several studies showing that a higher intake of certain foods could be associated with a lower risk of the disease.

Some doctors and media channels argue that there is very little evidence to support the use of foods to prevent cancer.

We will delve into the research and look at a list of foods that may lower your risk of cancer.

2.1. Fruits and Berries

Berries are high in anthocyanins, plant pigments that have antioxidant properties and may be associated with a reduced risk of cancer.

There are more than 17,000 search results on berries and cancer on PubMed and also 17,000 research studies on fruits and cancer. Do take note that most of the research studies are pre-clinical, lab, animal and non-human studies.

In one human study, 25 people with colorectal cancer were treated with bilberry extract for seven days, which was found to reduce the growth of cancer cells by 7% (Source).

Another small study gave freeze-dried black raspberries to patients with oral cancer and showed that it decreased levels of certain markers associated with cancer progression (Source).

One animal study found that giving rats freeze-dried black raspberries reduced esophageal tumor incidence by up to 54% and decreased the number of tumors by up to 62% (Source).

Similarly, another animal study showed that giving rats a berry extract was found to inhibit several biomarkers of cancer (Source).

Based on these findings, including a serving or two of berries in your diet each day may help inhibit the development of cancer. Keep in mind that these are animal and observational studies looking at the effects of a concentrated dose of berry extract, and more human research is needed.

Eating citrus fruits such as lemons, limes, grapefruits and oranges has also been associated with a lower risk of cancer in some studies.

One large study found that participants who ate a higher amount of citrus fruits had a lower risk of developing cancers of the digestive and upper respiratory tracts (Source).

A review looking at nine studies also found that a greater intake of citrus fruits was linked to a reduced risk of pancreatic cancer (Source).

Finally, a review of 14 studies showed that a high intake, or at least three servings per week, of citrus fruit reduced the risk of stomach cancer by 28% (Source).

These studies suggest that including a few servings of citrus fruits in your diet each week may lower your risk of developing certain types of cancer.

Keep in mind that these studies don’t account for other factors that may be involved. More studies are needed on how citrus fruits specifically affect cancer development.

2.2. Turmeric (Curcumin)

Turmeric is a spice well-known for its health-promoting properties. Curcumin, its active ingredient, is a chemical with anti-inflammatory, antioxidant and even anticancer effects.

The spice turmeric can be extremely helpful when it comes to fighting cancer. There are more than 7,000 search results on curcumin and cancer on PubMed and more than 50 clinical trials with curcumin and cancer, most of which are still ongoing.

However, most of the studies published on PubMed are non-human (pre-clinical) studies.

A review paper published in 2022, analysed 21 human studies. Sixteen out of 21 clinical trials were associated with the effectiveness of curcumin or turmeric on various types of cancer, and the other five clinical trials were related to the evaluation of the efficacy of curcumin or turmeric in relieving the side effects of cancer chemotherapy and radiotherapy. The emerging data from the clinical trials confirm that curcumin has the potential for cancer prevention and intervention.

For the best results, aim for at least 1/2–3 teaspoons (1–3 grams) of ground turmeric per day. Use it as a ground spice to add flavor to foods, and pair it with black pepper to help boost its absorption.

Turmeric and black pepper each have health benefits, due to the compounds curcumin and piperine. As piperine enhances curcumin absorption in the body by up to 2,000%, combining the spices magnifies their effects. (Healthline)

2.3. Tomato (Lycopene)

It has long been known that tomato consumption reduces the risk of developing cancer and cardiovascular disease, due to its high lycopene content (Ratto 2022).

There are more than 1,500 search results on lycopene and cancer on PubMed.

A 2020 study published in the journal Cancer Causes & Control (Fraser 2020) found that men who ate tomatoes almost every day had a 28 percent lower risk of prostate cancer than men who didn’t. Lycopene may also protect the skin from the sun damage that can cause skin cancer, and some research suggests that it helps women maintain bone mass as they age.

2.4. Broccoli

Broccoli contains sulforaphane, a plant compound found in cruciferous vegetables that may have potent anticancer properties.

There are more than 1,000 search results on broccoli and cancer on PubMed.

One analysis of 35 studies showed that eating more cruciferous vegetables was associated with a lower risk of colorectal and colon cancer (Ann Oncol. 2013).

Including broccoli with a few meals per week may come with some cancer-fighting benefits.

However, keep in mind that the available research hasn’t looked directly at how broccoli may affect cancer in humans.

Instead, it has been limited to test-tube, animal and observational studies that either investigated the effects of cruciferous vegetables, or the effects of a specific compound in broccoli. Thus, more human studies are needed.

2.5. Nuts

Research has found that eating nuts may be linked to a lower risk of certain types of cancer. There are more than 1,000 search results on nuts and cancer on PubMed.

For instance, a study looked at the diets of 19,386 people and found that eating a greater amount of nuts was associated with a decreased risk of dying from cancer (Br J Nutr. 2015).

Another study followed 30,708 participants for up to 30 years and found that eating nuts regularly was associated with a decreased risk of colorectal, pancreatic and endometrial cancers (Source).

Another meta-analysis of 14 cohort studies (2015), found that dietary legume consumption reduces risk of colorectal cancer. Legumes are a diverse group of foods, including soybeans, peas, beans, lentils, peanuts, and other podded plants, which are widely cultivated and consumed.

Other studies have found that specific types of nuts may be linked to a lower cancer risk. For example, Brazil nuts are high in selenium, which may help protect against lung cancer in those with a low selenium status (Trusted Source).

These results suggest that adding a serving of nuts to your diet each day may reduce your risk of developing cancer in the future.

Still, more studies in humans are needed to determine whether nuts are responsible for this association, or whether other factors are involved.

2.6. Olive Oil

Olive oil is loaded with health benefits, so it’s no wonder it’s one of the staples of the Mediterranean diet.

Research has found that eating nuts may be linked to a lower risk of certain types of cancer. There are more than 1,200 search results on olive oil and cancer on PubMed.

Several studies have even found that a higher intake of olive oil may help protect against cancer.

One massive review made up of 19 studies showed that people who consumed the greatest amount of olive oil had a lower risk of developing breast cancer and cancer of the digestive system than those with the lowest intake (Source).

Another study looked at the cancer rates in 28 countries around the world and found that areas with a higher intake of olive oil had decreased rates of colorectal cancer (Source).

Swapping out other oils in your diet for olive oil is a simple way to take advantage of its health benefits. You can drizzle it over salads and cooked vegetables, or try using it in your marinades for meat, fish or poultry.

Though these studies show that there may be an association between olive oil intake and cancer, there are likely other factors involved as well. More human studies are needed to look at the direct effects of olive oil on cancer in people.

2.7. Carrots

There are more than 300 search results on carrot and cancer on PubMed.

Several studies have found that eating more carrots is linked to a decreased risk of certain types of cancer.

For example, an analysis looked at the results of five studies and concluded that eating carrots may reduce the risk of stomach cancer by up to 26% (Source).

Another study found that a higher intake of carrots was associated with 18% lower odds of developing prostate cancer (Source).

One study analyzed the diets of 1,266 participants with and without lung cancer. It found that current smokers who did not eat carrots were three times as likely to develop lung cancer, compared to those who ate carrots more than once per week (Source).

Try incorporating carrots into your diet as a healthy snack or delicious side dish just a few times per week to increase your intake and potentially reduce your risk of cancer.

Still, remember that these studies show an association between carrot consumption and cancer, but don’t account for other factors that may play a role.

2.8. Beans

Beans are high in fiber, which some studies have found may help protect against colorectal cancer (Source, Source, Source).

One study followed 1,905 people with a history of colorectal tumors, and found that those who consumed more cooked, dried beans tended to have a decreased risk of tumor recurrence (Source).

According to these results, eating a few servings of beans each week may increase your fiber intake and help lower the risk of developing cancer.

2.9. Soy

A review of 14 studies (Plos One. 2020) found that tofu intake was associated with a
lower risk of breast cancer. Tofu (bean curd), is a popular food derived from soy in Asia.

In another study, The Shanghai Breast Cancer Survival Study (JAMA. 2009), a large, population-based cohort study of 5,042 female breast cancer survivors. Over an average follow-up of 3.9 years, soy food consumption was significantly associated with lower risk of death and breast cancer recurrence.

A review of 35 studies (Plos One. 2014) found that soy intake could lower the risk of breast cancer for both pre- and post-menopausal women in Asian countries. However, for women in Western countries, pre- or post-menopausal, there is no evidence to suggest an association between intake of soy isoflavone and breast cancer.

3. Cancer and supplements

Dietary supplements are a heterogeneous group of products defined under current US laws and regulations as containing vitamins and minerals as well as amino acids, herbs/botanicals, and other kinds of ingredients. Vitamin and/or mineral supplements are truly “dietary” because they contain micronutrients that are also present in foods. They are also “supplemental” because they have important health benefits for people whose intake of these micronutrients from foods is not sufficient or for those with malabsorption disorders. In contrast, many other products that are marketed as dietary supplements are not truly “dietary” because many come from sources other than foods and contain substances not found in foods, and they are not “supplemental” because they do not increase intake of micronutrients that have been scientifically shown to be important for human health. Furthermore, current laws and regulations do not guarantee that products sold as dietary supplements actually contain substances in the quantities claimed on their labels or that they are free from undeclared substances that can be harmful to human health.

For reasons other than cancer prevention, some vitamin and/or mineral supplements may be beneficial for some people to prevent nutrient deficiency, such as in pregnant women, women of childbearing age, and people with restricted dietary intakes. Dietary supplementation may also be indicated to correct a documented clinical deficiency or insufficiency, such as supplementation with vitamin D in those with low circulating concentrations or vitamin B12 supplementation in those with vitamin B12-associated anemias.

Although a diet rich in vegetables, fruits, and other plant-based foods may reduce the risk of cancer, there is limited and inconsistent evidence that dietary supplements can reduce cancer risk (R). Whereas 2 RCTs showed reductions in cancer risk among men taking low-dose antioxidants or low-dose multiple micronutrients, evidence for women is lacking. Furthermore, evidence exists that some high-dose supplements containing nutrients such as β-carotene and vitamins A and E can increase the risk of some cancers (R). For individual nutrients, an exception may be calcium, in which supplemental calcium may reduce the risk of colorectal cancer. However, people who have excessive calcium intake (mostly from supplements) may have a higher risk of death from all cancer types combined compared with those who have a recommended level of dietary calcium. The same study also reported no overall benefit to longevity from all dietary supplements considered together. Nonetheless, more than one-half of US adults use one or more dietary supplement(s).

Many healthful compounds are found in vegetables and fruits, and it is likely that these compounds work synergistically to exert their beneficial effect. There are likely to be important, but as yet unidentified, components of whole food that are not included in dietary supplements. Some supplements are described as containing the nutritional equivalent of vegetables and fruits. However, the small amount of dried powder in such pills frequently contains only a small fraction of the levels contained in the whole foods, and there is a lack of evidence supporting a role of these products in cancer prevention. Food is the best source of vitamins, minerals, and other bioactive food components.

When it comes to cancer of any kind, it’s important to realize that no dietary supplement can fully prevent or cure cancer, according to BreastCancer.org. No amount of supplements can replace an unhealthy lifestyle i.e. sedentary, a very stressful lifestyle, overweight and obesity.

However, there are some supplements that can potentially help prevent cancer or assist in your cancer recovery.

While many vitamins and minerals can benefit your general health, there’s a huge market of unregulated supplements that may provide no added benefit to your health. Certain supplements even have the potential to negatively impact cancer treatments. This is because some supplements can counteract medications or medical therapies. If you’re thinking about supplementing your diet with anti-cancer vitamins, always talk to your doctor first.

3.1. Vitamin D3, K2 and Magnesium

Vitamin D can absorb calcium and help the immune, muscle, and nervous systems function properly. There are more than 11,000 search results on vitamin D and cancer on PubMed.

A number of epidemiologic studies have investigated whether people with higher vitamin D intakes or higher blood levels of vitamin D have lower risks of specific cancers. The results of these studies have been inconsistent, possibly because of the challenges in carrying out such studies. For example, dietary studies do not account for vitamin D made in the skin from sunlight exposure, and the level of vitamin D measured in the blood at a single point in time (as in most studies) may not reflect a person’s true vitamin D status. Also, it is possible that people with higher vitamin D intakes or blood levels are more likely to have other healthy behaviors. It may be one of these other behaviors, rather than vitamin D intake, that influences cancer risk.

Several randomized trials of vitamin D intake have been carried out, but these were designed to assess bone health or other non-cancer outcomes. Although some of these trials have yielded information on cancer incidence and mortality, the results need to be confirmed by additional research because the trials were not designed to study cancer specifically.

The cancers for which the most human data are available are colorectal, breast, prostate, and pancreatic cancer. Numerous epidemiologic studies have shown that higher intake or blood levels of vitamin D are associated with a reduced risk of colorectal cancer (R). In contrast, the Women’s Health Initiative randomized trial found that healthy women who took vitamin D and calcium supplements for an average of 7 years did not have a reduced incidence of colorectal cancer (NEJM 2006). Some scientists have pointed out that the relatively low level of vitamin D supplementation (10 μg, or 400 IU, once a day), the ability of participants to take additional vitamin D on their own, and the short duration of participant follow-up in this trial might explain why no reduction in colorectal cancer risk was found.

According to BreastCancer.org,

research suggestsTrusted Source

that certain cancers such as breast cancer, can have a higher risk of occurring when the body has low levels of vitamin D.

Studies also show a link between vitamin D deficiency and cardiovascular disease, diabetes, and cancer (Sizar, 2020).

In 2016, a landmark study published in PLOS ONE found that women over 55 with blood concentrations of vitamin D higher than 40 ng/ml, had a 67% lower risk of cancer compared women with levels lower than 20 ng/ml.

Many experts now recommend 800 to 1,000 IU a day, a goal that's nearly impossible to attain without taking a supplement. Although protection is far from proven, evidence suggests that vitamin D may help reduce the risk of prostate cancer, colon cancer, and other malignancies.

Although the role of vitamin D in cancer prevention remains an area of research interest and debate, avoiding deficient levels is recommended. (American Cancer Society 2020)

Vitamin D can also be absorbed through sunlight, or with the following diet:

fatty fish
egg yolks
fortified milk

Make sure to take 500 mg to 1000 mg of magnesium and 150 mcg of vitamin K2, (not K1) which are important cofactors for optimizing vitamin D function. And, remember the only way you know what your vitamin D level is, is to test it. Vitamin D level should be in a therapeutic range of 50 to 70 ng/ml for treatment of rheumatoid arthritis. Most people are shocked how low their level is when they finally get around to testing it.

Related: Vitamin D Level and Cancer: Vitamin D Reduces Cancer Deaths

3.2. Turmeric (Curcumin)

The spice turmeric can be extremely helpful when it comes to fighting cancer.

There are more than 7,000 search results on curcumin and cancer on PubMed and more than 50 clinical trials with curcumin, most of which are still ongoing.

Studies show that the curcumin in turmeric may kill cancer cells and slow tumor growth. This preclinical research has taken curcumin from the lab to the clinic.

The benefits of curcumin may include:

blocking cancer cells from multiplying
killing colon, breast, prostate, and melanoma cancer cells
slowing tumor growth

Most of the studies published on PubMed are non-human (pre-clinical) studies.

Curcumin is not easily absorbed through your gastrointestinal tract, it's more effective to use a high-quality bioavailable curcumin extract, according to a 2013 study. A typical anticancer dose is just under 1 teaspoon of curcumin extract three or four times daily.

Both curcuminoids and related turmeric products have been sanctioned by the U.S. Food and Drug Administration (FDA) as safe.

3.3. Omega-3 Fatty Acids

PubMed has indexed more than 2,900 research studies on Omega-3 and cancer. Most people use fish oil supplements to enhance the amount of omega-3’s in their diet.

Findings from a study performed in mice, research from Harvard Medical School’s Beth Israel Deaconess Medical Center in Boston demonstrated omega-3 fat could reduce tumor growth by 67% (R).

The research was presented April 4, 2022 at the annual Experimental Biology meeting in Philadelphia. The animal model showed that omega-3 fatty acids helped promote the cancer-fighting activities of immunotherapy and anti-inflammatory therapy.

Many governments recommend eating omega-3 containing fatty fish, two times per week. But that is often not enough. Ideally, people would need to eat fatty fish four times per week, while also supplementing with omega-3 fatty acids, at least 1,000 mg of pure omega-3 (DHA and EPA) per day.

However, fish oil was shown in one study on mice (2015)Trusted Source to possibly reduce the effectiveness of chemotherapy, and for that reason ground flax seed is a worthy alternative.

Flax seed is rich in omega-3 fatty acids, which may reduce the risk of certain cancers. When supplementing, try to avoid flaxseed oil because it lacks the nutrients of ground flax seed. Ground flax seed can be purchased online or found in many larger grocery store chains. Simply sprinkle some ground flax seed on your food and enjoy.

Make sure you buy high-quality omega-3 fatty acid supplements, meaning that the omega-3 fatty acids are pure and have not oxidized much (having low “TOTOX” value).

TOTOX value stands for total oxidation value. The omega 3 fatty acids EPA and DHA from fish oil are highly sensitive to oxidation. This means that they are rapidly affected by contact with oxygen. Oxidised fatty acids are not beneficial to our health. For this reason, a good fish oil supplement has a low TOTOX value. The maximum TOTOX value is set at 26 by the Global Organization for EPA and DHA omega-3.

3.4. Melatonin

PubMed has indexed more than 3,300 research studies on melatonin and cancer.

Melatonin is one of the most important antioxidant molecules. In the human body — aside from having direct antioxidant effects — it also stimulates the synthesis of glutathione and other important antioxidants like superoxide dismutase and catalase.

Many people are not aware that only 5% of your body’s melatonin — which is also a potent anticancer agent — is produced in your pineal gland. The other 95% is produced inside your mitochondria — provided you get sufficient near infrared exposure which is typically from sun on your bare skin. This is why vitamin D is more than likely a biomarker for sun exposure, which is intricately involved in melatonin production. (R)

Melatonin is known to play a fundamental role in regulating the sleep-wake rhythm; however, in the last 10 years it has been discovered that it is actually involved in many other biological mechanisms, also playing an important role in the inflammatory, metabolic and neoplastic processes. In fact, the mechanisms by which melatonin performs an anti-tumor effect are many: it has an anti-oxidant effect that protects against DNA damage, acts as a scavenger of reactive oxygen species (which undermine genomic stability), stimulates DNA repair mechanisms, improves the functioning of the mitochondrial respiratory chain, and inhibits mitochondrial mitophagy and telomerase activity (Molecules 2018).

In addition, melatonin increases the expression of the p53 protein, induces its phosphorylation, inhibiting cell proliferation, promotes apoptosis, reduces the levels of the vascular endothelial growth factor and endothelin-1, fundamental for tumor growth and metastasis formation, reduces inflammatory processes and cell migration (Molecules 2018).

Reduction of melatonin production has also been seen in some types of cancer (breast and prostate) (Mogavero 2021).

A case series of 14 advanced cancer patients (Trends in Oncology 2020), treated with high dose (1,000 mg/day) of melatonin; achieved a disease control of 54% of the patients.

The authors also concluded that:

"Moreover, this preliminary study may also suggest that high dose melatonin has no toxicity in cancer patients with poor clinical status, as well as in healthy subjects."

3.5. EGCG (Green Tea)

PubMed has indexed more than 2,000 research studies on EGCG and cancer.

Several epidemiological studies have reported that the consumption of green tea may decrease cancer risk. Studies have also confirmed numerous health benefits of green tea including prevention of cancer (R, R) and cardiovascular disease, as well as anti-inflammatory, antioxidant, antiarthritic, antibacterial, and antiviral effects. (R, R, R, R).

Green tea also contains chemicals called polyphenols that have antioxidant, anti-inflammatory properties and anti-angiogenic properties, and the catechins in green tea polyphenols show very strong anti-angiogenic properties.

The Minnesota Green Tea Trial (MGTT. 2015) is the largest and longest double-blind, placebo-controlled, randomized intervention study that specifically evaluated the effects of oral GTE (green tea extract) containing defined quantities of EGCG on established biomarkers of breast cancer risk.

They randomized and stratified 1075 healthy postmenopausal women at high risk of breast cancer according to their breast tissue density and catechol-O-methyltransferase genotypes and divided them into two groups: 537 placebo and 538 green tea groups. Green tea group participants took 4 capsules that contained 843 mg EGCG, whereas the placebo group took capsules without green tea extracts.

Researchers measured changes in percent mammographic density, circulating endogenous sex hormones, and proteins of the insulin-like growth factor axis. Their results showed that supplementation with green tea extract could modify and reduce mammographic density (MD) and protect against breast cancer, even though it was only significant in younger women (50–55 years) and had no effect in older women (Samavat 2017), an age-dependent effect similar to those of tamoxifen.

If you have cancer, consider drinking up to 3 cups of green tea per day to experience the benefits. Green tea pills are also available, but may be too concentrated.

Some studies show health benefits in people who drink as little as one cup per day, while other studies deem five or more cups per day to be optimal (Source, Source).

3.6. Allicin (Garlic)

Garlic is a great choice when it comes to giving your body a little extra protection. To reap the benefits of garlic, you should eat one clove per day, or 300 to 1,000 milligrams (mg)Trusted Source of garlic extract.

The National Cancer Institute in the United States ranks garlic at the top of the cancer-fighting vegetable pyramid.

Protective effects may include:

antibacterial properties
blocking and halting the activation of cancer-causing substances
enhanced DNA repair
a reduction in cancer cells spreading

The active component in garlic is allicin, a compound that has been shown to kill off cancer cells in multiple test-tube studies (Source, Source, Source).

There is evidence demonstrating garlic can kill cancer cells in vitro. Several studies have analyzed the effects that dietary garlic may have on the development of colorectal cancer.

Several clinical studies have found an association between garlic intake and a lower risk of certain types of cancer.

A meta-analysis of 11 studies, published in January 2020, did find evidence that garlic could reduce the risk of ColoRectal Cancer.

Another study published in the Asia Pacific Journal of Clinical Oncology (2019) revealed the odds of getting ColoRectal Cancer were 79% lower in those who a diet high in allium vegetables, which include garlic, leeks and onions.

One study of 543,220 participants found that those who ate lots of Allium vegetables, such as garlic, onions, leeks and shallots, had a lower risk of stomach cancer than those who rarely consumed them (Source).

A study of 471 men showed that a higher intake of garlic was associated with a reduced risk of prostate cancer (Source).

Based on these findings, including 2–5 grams (approximately one clove) of fresh garlic into your diet per day can help you take advantage of its health-promoting properties.

Despite the promising results showing an association between garlic and a reduced risk of cancer, more human studies are needed to examine whether other factors play a role.

Related: Garlic, the ‘King of Cancer Prevention’

3.7. Molecular Hydrogen

3.8. Quercetin

Quercetin is an antioxidant flavonol that's found in foods such as red grapes, green tea, elderflower and onions, to name a few. As the health benefits of the supplement become more widely known, the market has grown rapidly (R). According to market research, quercetin market was worth $261.12 million in 2020 and is expected to reach $406.58 million in 2027.

PubMed has indexed more than 4,000 research studies on quercetin and cancer.

2022 - A paper published in August 2022 in Nutrition Research analyzed the pro-apoptotic effect that quercetin has on aging cells. The paper reviewed preclinical and early phase data using quercetin as a senolytic agent and found the data showed it was effective in “preventing or alleviating cancer formation.”

The authors reviewed the importance of cellular aging in the development of cancer cells and the effect that quercetin may have on the suppression of cancer cell proliferation.

Cellular senescence is a dynamic and multi-step process that is associated with alterations in metabolic activity and gene expression. This can compromise tissue regeneration and contribute to aging. On the other hand, by removing senescent cells, age-related dysfunction can be attenuated and potentially extend the lifespan.

2020 - Another paper (2020) identified some of the anti-inflammatory, antioxidant and antiproliferative properties quercetin has that enhances breast cancer treatment, while another (2020) evaluated its effect on the treatment of ovarian cancer, which is a serious cancer growth and threat to women's health.

2019 - Research also has demonstrated that quercetin can promote the loss of cell viability and autophagy through several pathways, including those involving mitochondrial function and glucose metabolism.

This study published in 2017 in Oncology Reports took things a step further, finding that quercetin induced cancer cell death in nine types of cancer, including prostate cancer, colon cancer, and breast caner.

Quercetin affects endothelial (thin membrane lining heart and blood vessels) cell proliferation, migration, and angiogenesis. As an anti-angiogenic compound, it has been shown to have a targeted effect on tumor angiogenesis in both in vitro and in vivo experiments. It has also been demonstrated in animal experiments that quercetin can reduce angiogenesis.

In another 2017 study, researchers gave quercetin to mice with tumors. Researchers found that mice in the quercetin-treated group showed delayed tumor growth, no significant changes in daily behavior, significantly better survival ratings, and increased rates of cell death.

Quercetin may also target bladder cancer. In 2016, researchers published a landmark study in the American Journal of Cancer Research. Researchers analyzed quercetin’s effect on cancer cells in a test tube. They concluded, “We are the first to show that quercetin displays potent inhibition on bladder cancer cells via activation of AMPK pathway.”

In 2015, researchers reviewed available test tube and animal studies on quercetin and prostate cancer. After reviewing available evidence, researchers found that quercetin suppressed cell growth and induced cell death in prostate cancer cells.

Data (2015) indicate that quercetin could play a role in cancer treatment as it reportedly has synergistic effects in combination with chemotherapy agents or radiation therapy. Quercetin has also shown promising results with chemoprotective and radioprotective properties, by protecting normal cells against the effects of chemotherapy and radiation therapy.

According to Mount Sinai, quercetin should be used with caution as it may interact with certain antibiotics by reducing the effectiveness of the drug. It may also enhance the effect of some blood thinners, which can increase your risk of bleeding. In addition to these, it may interact with corticosteroids, digoxin, cyclosporine and fluoroquinolones.

Early research on the cancer-fighting benefits of quercetin is promising, although more research needs to be performed to verify these effects in humans.

3.9. Vitamin C and B6

Obese women who took vitamin C and B6 at amounts that exceeded the recommended daily intake levels were associated with a lower risk of breast cancer, according to a five-year long South Korean cohort study. 40,432 women without a history of cancer at baseline were included in this study (published in 2022).

Vitamin C is known as an antioxidant, but at high concentrations, vitamin C can kill cancer cells through a pro-oxidant property (Transl Oncol. 2020). This study has also demonstrated that vitamin C treatment with magnesium supplementation provided more effective anticancer therapy than vitamin C treatment alone.

High-dose vitamin C cancer therapy was introduced by Linus Pauling and Ewan Cameron [R]. Clinical demonstration results by Pauling and Cameron showed that intravenous injection of 10 g/day of vitamin C extended the survival time of terminal cancer patients by about 4.2 times. However, results from the Mayo Clinic in 1979 showed that the survival time of vitamin C–treated patients was even shorter than that of the placebo group patients [R]. A significant difference between those two research groups was the route of AA administration: intravenous injection and oral administration, respectively.

To understand the mechanism of AA's anticancer activity, many research groups have treated colon, prostate, leukemia, lymphoma, brain, and stomach cancer cells and chemically or genetically transformed cancer cells with AA and showed cancer growth inhibition and even cancer cell death through hydrogen peroxide–mediated reactive oxygen species (ROS) generation [R]. In most cases, the pharmacological concentration of vitamin C required for anticancer effects (EC50 value of 1–10 mM) could only be achieved by intravenous administration. Thus, to apply vitamin C as an anticancer therapy, a high intracellular concentration in cancer cells is critically important (R).

Related: Benefits of Vitamin C in Cancer Treatment

The Hazards of Excessive Vitamin C

Vitamin C and ascorbic acid can lead to problems if your body is already loaded with oxalates as it is metabolically reduced to oxalic acid during breakdown.

Sally Norton, author of “Toxic Superfoods: How Oxalate Overload Is Making You Sick — and How to Get Better,” explains:

“The major source of internal oxalate is ascorbic acid or vitamin C ... There are lots of case studies of train wrecks from supplements, and lots of case studies about problems with intravenous vitamin C. Let me tell you my personal story. I had vitamin C chelation ... I didn't know I had an oxalate problem ...

By the third time, I became harder and harder to stab for the IV needle because now my veins were ropier and rollier and would run away from the needle. That's fibrosis ... I only had IV vitamin C maybe 10 times. But the doctor and the nurse took no notice of this side effect of the treatment — that I was becoming more fibrotic and harder to puncture ...

It's hubris to say, ‘Oh, well, it's fine. All my patients are doing great on my vitamin C IVs when you're not open to seeing the side effects. One of the studies demonstrated that just with oral supplementation, for not all that long, once they stopped the vitamin C, the level of oxalate in the urine went way up.

So, while the body's being assaulted by too much vitamin C, it's busy sequestering the oxalate that's forming and holding onto it and protecting the kidneys from devastation, from excessive oxalate load. Once you stop producing or eating too much oxalate, this holding pattern can let go, and now you see much higher oxalate levels in the blood and the urine.”

For these reasons, if you take vitamin C on a regular basis, Norton recommends limiting it to 250 mg a day. This is enough to meet your nutritional requirements and is unlikely to cause oxalic acid-related trouble. The exception would be if you are septic, in which case large doses of IV ascorbic acid can save your life.

3.10. Resveratrol

The efficacy, safety, and pharmacokinetics of resveratrol have been documented in over 244 clinical trials, with an additional 27 clinical trials currently ongoing (Pratap Singh 2019). Resveratrol is reported to potentially improve the therapeutic outcome in patients suffering from diabetes mellitus, obesity, colorectal cancer, breast cancer, multiple myeloma, metabolic syndrome, hypertension, Alzheimer's disease, stroke, cardiovascular diseases, kidney diseases, inflammatory diseases, and rhinopharyngitis.

The polyphenol is reported to be safe at doses up to 5 g/d, when used either alone or as a combination therapy. Although the clinical utility of resveratrol is well documented, the rapid metabolism and poor bioavailability have limited its therapeutic use. In this regard, the recently produced micronized resveratrol formulation called SRT501, shows promise (Pratap Singh 2019).

Early research on the cancer-fighting benefits of resveratrol is promising, although more research needs to be performed to verify these effects in humans.

3.11. Gut Microbes and Probiotics

Not only have gut bacteria been shown to influence gene expression,(R, R) turning some genes on and others off, research (R) published in 2018 found gut microbes actually control antitumor immune responses in your liver, and that antibiotics can alter the composition of immune cells in your liver, triggering tumor growth.

Harvard Medical School researchers have identified the specific population of gut microbes that modulates both localized and systemic immune response to ward off viral invaders.

Certain gut bacteria also promote inflammation, which is an underlying factor in virtually all cancers, whereas other bacteria quell it. The presence of certain gut bacteria has even been shown to boost the patient's response to anticancer drugs. (Nature 2018)

One way in which gut bacteria improve the effectiveness of cancer treatment is by activating your immune system and allowing it to function more efficiently. Researchers have actually found that when these specific microbes are absent, certain anticancer drugs may not work at all.

4. Don't use tobacco

Smoking has been linked to many types of cancer, including cancer of the lung, mouth, throat, voice box, pancreas, bladder, cervix and kidney. Even being around secondhand smoke might increase the risk of lung cancer.

But it's not only smoking that's harmful. Chewing tobacco has been linked to cancer of the mouth, throat and pancreas.

Staying away from tobacco — or deciding to stop using it — is an important way to help prevent cancer. For help quitting tobacco, ask a health care provider about stop-smoking products and other ways of quitting.

5. Maintain a healthy weight and be physically active

Being at a healthy weight might lower the risk of some types of cancer. These include cancer of the breast, prostate, lung, colon and kidney.

Physical activity counts too. Besides helping control weight, physical activity on its own might lower the risk of breast cancer and colon cancer.

Doing any amount of physical activity benefits health. But for the most benefit, strive for at least 150 minutes a week of moderate aerobic activity or 75 minutes a week of hard aerobic activity.

You can combine moderate and hard activity. As a general goal, include at least 30 minutes of physical activity in your daily routine. More is better.

6. Avoid risky behaviors

Another effective cancer prevention tactic is to avoid risky behaviors that can lead to infections that, in turn, might increase the risk of cancer. For example:

Practice safe sex. Limit the number of sexual partners and use a condom. The greater the number of sexual partners in a lifetime, the greater the chances of getting a sexually transmitted infection, such as HIV or HPV.

People who have HIV or AIDS have a higher risk of cancer of the anus, liver and lung. HPV is most often associated with cervical cancer, but it might also increase the risk of cancer of the anus, penis, throat, vulva and vagina.
Don't share needles. Injecting drugs with shared needles can lead to HIV, as well as hepatitis B and hepatitis C — which can increase the risk of liver cancer. If you're concerned about drug misuse or addiction, seek professional help.

7. Protect yourself from the sun

Skin cancer is one of the most common kinds of cancer and one of the most preventable. Try these tips:

Avoid midday sun. Stay out of the sun between 10 a.m. and 4 p.m. when the sun's rays are strongest.
Stay in the shade. When outdoors, stay in the shade as much as possible. Sunglasses and a broad-brimmed hat help too.
Cover your skin. Wear clothing that covers as much skin as possible. Wear a head cover and sunglasses. Wear bright or dark colors. They reflect more of the sun's harmful rays than do pastels or bleached cotton.
Don't skimp on sunscreen. Use a broad-spectrum sunscreen with an SPF of at least 30, even on cloudy days. Apply a lot of sunscreen. Apply again every two hours, or more often after swimming or sweating.
Don't use tanning beds or sunlamps. These can do as much harm as sunlight.

8. Sleep, Stress and Desk Job

Sleep

Many studies, especially in the last 10 years, have evaluated the association between different types of cancer and different types of sleep disorders (Mogavero 2021). The majority of sleep disorders in patients with cancer are associated with activation of the inflammatory response (Mogavero 2021).

Circadian rhythm disorders seem to represent a risk factor for gastrointestinal and breast cancer, squamous cell carcinoma, thyroid and prostate cancer (albeit with dubious evidence), lymphomas and chronic myeloid leukemia, not for ovarian cancer. Insomnia represents a risk factor for a wide range of tumors, especially breast, nose, trachea, liver and oral cavity. (Mogavero 2021)

In a 2022 study, the detrimental associations of poor sleep with all-cause and cause-specific mortality risks are exacerbated by low PA (physical activity), suggesting likely synergistic effects. The study supports the need to target both behaviours in research and clinical practice.

A 2023 study indicated that insomnia and nap during the day may be risk factors of PLC (primary liver cancer) and adequate night sleep might keep us away from PLC (primary liver cancer).

A 2021 study, concluded that both unfavorable sleep duration and evening chronotype were associated with increased lung cancer incidence, especially for those with low to moderate genetic risk. These results indicate that sleep behaviors as modifiable risk factors may have potential implications for lung cancer risk.

Another similar study, the authors concluded that they have found robust evidence for effect of sleeplessness on lung cancer risk.

Stress

High stress might be one of the most overlooked factors, especially concerning the long-term impact of being exposed to a stressful job environment.

However, it’s important to understand the role of stress on cancer progression. Scientists know that psychological stress can affect the immune system, the body’s defense against infection and disease (including cancer).

The body responds to stress by releasing stress hormones, such as epinephrine (also called adrenaline) and cortisol (also called hydrocortisone). The body produces these stress hormones to help a person react to a situation with more speed and strength. Stress hormones increase blood pressure, heart rate, and blood sugar levels. Small amounts of stress are believed to be beneficial, but chronic (persisting or progressing over a long period of time) high levels of stress are thought to be harmful.

Stress that is chronic can increase the risk of obesity, heart disease, depression, and various other illnesses. Stress also can lead to unhealthy behaviors, such as overeating, smoking, or abusing drugs or alcohol, that may affect cancer risk.

Some studies have indicated an indirect relationship between stress and certain types of virus-related growths. Evidence from both animal and human studies suggests that chronic stress weakens a person’s immune system, which in turn may affect the incidence of virus-associated cancers, such as Kaposi sarcoma and some lymphomas.

It is difficult to separate stress from other physical or emotional factors when examining cancer risk. For example, certain behaviors, such as smoking and using alcohol, and biological factors, such as growing older, becoming overweight, and having a family history of cancer, are common risk factors for cancer.

Studies have shown that stress might promote cancer indirectly by weakening the immune system's anti-tumor defense or by encouraging new tumor-feeding blood vessels to form. But a study published in The Journal of Clinical Investigation shows that stress hormones, such as adrenaline, can directly support tumor growth and spread.

Desk Job

One of the most important aspects of lifestyle is your job. If you're among the 86% of American workers who work at a desk all day, your job may have an adverse effect on your health.

Studies have found that those who sat for more than 8 hours a day with no physical activity had a risk of dying similar to the risk posed by obesity and smoking.

A 2009 study found that people who had increased sitting times had higher rates of cancer and overall mortality, even when they got some daily exercise.

The American Cancer Society has also found a link between long periods of inactivity and cancer. The group says that people who spend "prolonged leisure time sitting" — defined as more than 6 hours per day — have a 19% higher rate of death compared to people who sit an average of 3 hours per day. That number includes all causes of death, but it doesn't necessarily mean that sitting directly causes cancer or other diseases, since sick people are also likely to move around less.

9. Get regular medical care and Health Screening

Doing regular self-exams and having screenings for cancers — such as cancer of the skin, colon, cervix and breast — can raise the chances of finding cancer early. That's when treatment is most likely to succeed. Ask a health care provider about the best cancer screening schedule for you.

10. Avoid unnecessary exposure to radiation.

Get medical imaging studies only when you need them. (Harvard Health)

Check your home for residential radon, which increases the risk of lung cancer. Protect yourself from ultraviolet radiation in sunlight, which increases the risk of melanomas and other skin cancers. But don't worry about electromagnetic radiation from high-voltage power lines or radiofrequency radiation from microwaves and cell phones. They do not cause cancer.

11. Avoid exposure to environmental toxins and infections that contribute to cancer

Avoid exposure to industrial and environmental toxins such as asbestos fibers, benzene, aromatic amines, and polychlorinated biphenyls (PCBs). (Harvard Health)

Avoid infections that contribute to cancer, including hepatitis viruses, HIV, and the human papillomavirus. Many are transmitted sexually or through contaminated needles. (Harvard Health)

Related:

Hyperthermia and Immunotherapy for Cancer

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