Vitamin C: Benefits, Side Effects and Best Supplements 2024

Vitamin C has been a subject of controversy for many years. It may appear to be as simple as ABC, but is not. What's so confusing about Vitamin C? Let's dive into some facts and evidence.

Vitamin C - The Basics

Vitamin C, also known as L-ascorbic acid, is a water-soluble vitamin that is naturally present in some foods, added to others, and available as a dietary supplement. Humans, unlike most animals, are unable to synthesise vitamin C endogenously, so it is an essential dietary component.

The recommended daily intake for vitamin C is 75 mg for women and 90 mg for men.

While it’s commonly advised to get your vitamin C intake from foods, many people turn to supplements to meet their needs.

Benefits of vitamin C

Vitamin C plays an essential role in the body. Thanks to its antioxidant properties, it has been found to have several benefits, particularly for skin and immune health.

Found concentrated in the skin, vitamin C boosts collagen production and helps protect from UV damage (Source).

The most commonly known benefit of vitamin C, though, is for immune health, particularly as it relates to the common cold.

Some research has found that supplementing with vitamin C can shorten the duration of a cold and may help prevent and treat other infections, such as tetanus and pneumonia. But more human studies are needed (Source).

Additionally, a systematic review found that vitamin C supplementation was effective in lowering blood pressure in people with hypertension (Trusted Source).

Preliminary research also suggests that vitamin C has anticancer properties and that a high dose supplement could potentially be used as an alternative treatment in people with cancer (Trusted SourceTrusted SourceTrusted Source).

Other research has been investigating the use of vitamin C supplementation in people with stress-related disorders, such as depression and anxiety, because it has been shown to help improve mood. However, more research is still needed overall (Trusted Source).

Sources of Vitamin C - Food

Fruits and vegetables are the best sources of vitamin C. Citrus fruits, tomatoes and tomato juice, and potatoes are major contributors of vitamin C to the American diet. Other good food sources include red and green peppers, kiwifruit, broccoli, strawberries, Brussels sprouts, and cantaloupe. Although vitamin C is not naturally present in grains, it is added to some fortified breakfast cereals. The vitamin C content of food may be reduced by prolonged storage and by cooking because ascorbic acid is water soluble and is destroyed by heat. Steaming or microwaving may lessen cooking losses. Fortunately, many of the best food sources of vitamin C, such as fruits and vegetables, are usually consumed raw. Consuming five varied servings of fruits and vegetables a day can provide more than 200 mg of vitamin C.

Sources of Vitamin C - Dietary supplements and Different Forms of Vitamin C

Supplements typically contain vitamin C in the form of ascorbic acid, which has equivalent bioavailability to that of naturally occurring ascorbic acid in foods, such as orange juice and broccoli. Other forms of vitamin C supplements include sodium ascorbate; calcium ascorbate; other mineral ascorbates; ascorbic acid with bioflavonoids; and combination products, such as Ester-C®, which contains calcium ascorbate, dehydroascorbate, calcium threonate, xylonate and lyxonate.

A few studies in humans have examined whether bioavailability differs among the various forms of vitamin C. In one study, Ester-C® and ascorbic acid produced the same vitamin C plasma concentrations, but Ester-C® produced significantly higher vitamin C concentrations in leukocytes 24 hours after ingestion. Another study found no differences in plasma vitamin C levels or urinary excretion of vitamin C among three different vitamin C sources: ascorbic acid, Ester-C®, and ascorbic acid with bioflavonoids.

Liposomal Vitamin C

Liposomal vitamins don’t use capsules or tablets or powders to deliver nutrients. Instead, the vitamins are encapsulated in pockets of fat cells called liposomes (hence the name). Apparently this is the most effective way of ensuring the vitamins in the supplement actually get absorbed into your body.

Vitamin C To Boost Your Immune System

One of the main reasons people take vitamin C supplements is to boost their immunity, as vitamin C is involved in many parts of the immune system. 

First, vitamin C helps encourage the production of white blood cells known as lymphocytes and phagocytes, which help protect the body against infection (PubMed).

Second, vitamin C helps these white blood cells function more effectively while protecting them from damage by potentially harmful molecules, such as free radicals.

Third, vitamin C is an essential part of the skin’s defense system. It’s actively transported to the skin, where it can act as an antioxidant and help strengthen the skin’s barriers (ScienceDirect).

Studies have also shown that taking vitamin C may shorten wound healing time (PubMedPubMed).

What’s more, low vitamin C levels have been linked to poor health outcomes.

Vitamin C other Benefits

A review of 28 studies (Diabetes Care. 2021 Feb) in 1,574 people with type 2 diabetes mellitus, demonstrated that vitamin C supplementation may improve blood sugar control and blood pressure in people with type 2 diabetes.

People who have pneumonia tend to have lower vitamin C levels, and vitamin C supplements have been shown to shorten the recovery time (PubMedPubMed).

A large review of 29 studies in 11,306 people demonstrated that regularly supplementing with vitamin C at an average dose of 1–2 grams per day reduced the duration of colds by 8% in adults and 14% in children (PubMed).

Interestingly, the review also demonstrated that regularly taking vitamin C supplements reduced common cold occurrence in individuals under high physical stress, including marathon runners and soldiers, by up to 50% (PubMedPubMed).

Additionally, high dose intravenous vitamin C treatment has been shown to significantly improve symptoms in people with severe infections, including sepsis and acute respiratory distress syndrome (ARDS) resulting from viral infections (PubMedPubMed).

Side Effects of too much Vitamin C

Since vitamin C is water-soluble and your body excretes excess amounts of it within a few hours after you consume it, it’s quite difficult to consume too much.

The U.S. Recommended Dietary Allowance (RDA) for vitamin C is 75 to 120 milligrams per day. Taking large doses of vitamin C (ascorbic acid) on a regular basis lowers your level of copper, so if you are already deficient in copper and take high doses of vitamin C, you can compromise your immune system. It is suggested that dietary ascorbic acid reduces tissue copper concentrations primarily by interfering with intestinal copper absorption. 

In fact, it is nearly impossible for you to get too much vitamin C from your diet alone. In healthy people, any extra vitamin C consumed above the recommended daily amount simply gets flushed out of the body (PubMed). To put it in perspective, you would need to consume 29 oranges or 13 bell peppers before your intake reached the tolerable upper limit (USDA), which is 2 grams/day.

However, the risks of vitamin C overdose are higher when people take supplements, and it is possible to consume too much of the vitamin in some circumstances. For example, those with conditions that increase the risk of iron overload or are prone to kidney stones should be cautious with their vitamin C intake (PubMedPubMed).

For those with beta-thalassemia major and sickle cell anemia who suffer from iron overload due to regular blood transfusions or excessive destruction of red blood cells need specialized medical treatment with iron chelators and should also control their intake of iron (PubMed).

All the adverse effects of vitamin C, including digestive distress and kidney stones, appear to occur when people take it in mega doses greater than 2,000 mg (PubMed).

In summary, individuals with existing renal disease, Glucose-6-Phosphate Dehydrogenase Deficiency (G6PD), kidney stones, or Hemochromatosis should avoid high dose Vitamin C.

Temporarily taking megadoses of vitamin C supplements to combat a case of the cold or flu is likely not going to cause a problem. 

Many vitamin C supplements that are above the US RDA are sold in the market. It’s important to seek a physician’s advice if you intend to take high dose vitamin C on a long term basis. High doses of vitamin C (over 500 mg per day) over the long-term may increase the risk of cataracts. High-dose vitamin C can also reduce the effectiveness of certain medications and interfere with certain blood tests.

To be on the safe side, talk to your doctor and you may also request for your kidney functions to be monitored as well.

For long-term, daily use, your best bet is to eat a diet that is full of high quality organic vegetables and fruits that are minimally processed. Not only will you get vitamin C, but you will get all the other accessory nutrients and micronutrients that are needed to optimize it.

Key Takeaways

If you do choose to take a vitamin C supplement, it’s important to choose one that’s high quality and to take the correct dose.

Selecting the right vitamin C supplement depends on a variety of factors, including the form, quality, dose, and price. There are many forms of vitamin C available (ascorbic acid, sodium ascorbate, calcium ascorbate, liposomal vitamin C etc.) but there is not much evidence that one form is much better than another. 

The ascorbate forms may be easier on your stomach, but you will still run a risk of developing loose stools at too high a dose. 

You can also start by considering how you’ll be using the supplement. For instance, if you prefer to take a pill, you’ll want to check out encapsulated vitamin C supplements.

If you don’t like swallowing pills or want to mix it into beverages, your best bet is to consider liquid or powdered supplements.

Next, you want to check the supplement’s quality. Evaluate whether a brand is reputable by exploring their ingredient sourcing and manufacturing standards. A good product will also be tested by third-party organizations, such as USP, Consumer Labs, or NSF International.

Take a look at added ingredients, too. If you’re trying to limit your intake of added sugars, you want to opt for a supplement that doesn’t contain sugar.

Another factor to consider is the dosage. The recommended daily amount of vitamin C for adults is 90 mg for men, 75 mg for women, and up to 120 mg for women who are pregnant or breastfeeding. However, certain medical conditions may require that you take much higher doses (NIH).

Children have lower vitamin C requirements, which range from 25–75mg per day, depending on their age. However, it’s not generally advised to give children a vitamin C supplement unless their pediatrician has recommended it.

Note that the Tolerable Upper Intake Level (UL) for vitamin C for men, as well as women ages 19 and above, is 2,000 mg. Meanwhile, the UL for children ranges from 400–1,800 mg, depending on age. Daily intakes at or below these amounts are unlikely to result in any adverse health effects (NIH).

Vitamin C supplements come in a wide range of dosage options. If you’re looking for a high dose, it may be more economical and convenient to find a concentrated supplement. This way you won’t be stuck consuming multiple servings of a lower dose option.

Generally, high doses of vitamin C are unnecessary and could contribute to harmful side effects. Only consume high doses if your healthcare provider recommends doing so.

Finally, you want to consider your budget. Some professional-grade brands can be expensive, but keep in mind that a higher price doesn’t necessarily mean a better product. There are plenty of high quality options available at various price points.



Editor's Note: The subject on Vitamin C supplement has been controversial. Although we have tried to summarise and tried to provide important essential information on this topic, it's also likely that we have missed out some important information as well; or it's still confusing.

Let's begin with the non-controversial part. Yes, we need Vitamin C and we should ideally get it from whole fruits and vegetables.

The controversial part is on Vitamin C 'supplement'. Should we supplement our diet with Vitamin C supplement? Our answer is Yes, as most people do not take 5 servings of fruits and vegetables. Further, Vitamin C is easily destroyed by heat during cooking and our human bodies are not capable of producing and storing Vitamin C. That being said, we would not recommend taking high dose of Vitamin C as maintenance or on long term basis. Up to 500 mg/day should be reasonable.

As for high dose Vitamin C supplement, we would suggest that you discuss with your doctor. This is a more complicated subject as high dose Vitamin C is considered therapeutic dosage and is meant for 'treatment' and not 'maintenance'.

So should you just focus on Vitamin C alone or should you consider other supplements? Vitamin C alone might not be enough as an optimal strategy. A combination and a synergistic mix of supplements would be better. 

What if you have seen multiple doctors and they are giving you mixed recommendations? Our recommendation is to stick to a data driven principle, do your own research and discuss the evidence out there with doctors who are open to be updated with data-driven science and evidence based medicine.

Best Vitamin C supplements (Buying Guide)

We have sifted through various vitamin C supplement reviews and have shortlisted this best vitamin C supplements list. The supplements on this list were chosen based on quality, manufacturing standards, usability, and price.

The supplements on this list were chosen based on quality, manufacturing standards, usability, and price.

Here are our top picks for best vitamin C supplements.

1. Paleovalley Essential C Complex (Best Whole Food Vitamin C Supplement)

2. Smarter Raw Whole Food Vitamin C (Best Whole Food Vitamin C Capsule)

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3. Viva Naturals Vitamin C

Buy on Amazon

4. Nutra Champs Vitamin C

5. NOW Foods’ Chewable C 500 (Best Chewable Vitamin C Supplement)

6. Puritan's Pride - Chewable Vitamin C with Rose Hips Chewables

7. Purify Life Vitamin C Gummies for Adults & Kids

8. Pure Encapsulations’ Liposomal Vitamin C Liquid (Best Vitamin C Liquid)

9. Garden of Life’s Organic Vitamin C Spray (Best Organic Vitamin C)

10. Emergen-C Immune+ (Best Vitamin C Supplement for Immune System)


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