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Today, among vitamin supplements used around the world, vitamin C ranks number one (1).
This is due in large part to the potential of vitamin C—also known as ascorbic acid—to help prevent and/or treat many of the major diseases and disorders including cancer, heart disease, age-related macular degeneration, cataracts, and even the common cold (2).
Most of vitamin C's major health benefits can be linked to its important role in immune function and its role as a major water-soluble antioxidant, whereby it minimizes free radical damage (oxidative stress) to cells and tissues. Its antioxidant functions also include the regeneration (or recycling) of vitamin E—a major fat-soluble antioxidant—after it is used up in the body (2).
Vitamin C plays a role in protein metabolism and is essential in the synthesis of collagen—the “glue that holds us together.” Collagen is crucial for wound healing and for supporting the health of your skin and other connective tissues such as bone, cartilage, tendons, and ligaments (2).
Vitamin C is also required for the body’s production of various neurotransmitters (such as serotonin and dopamine, both of which impact your mood). This versatile vitamin can even improve iron status by enhancing the absorption of nonheme iron, i.e., the poorly-absorbed type of iron found mostly in plant-based foods (2).
Food sources high in vitamin C include:
Five to nine servings of fresh vitamin C-rich fruits and vegetables can provide around 200 mg of vitamin C (3). Far above the RDA of 75 mg/day (females) and 90 mg/day (males), this is the amount recommended to maximize vitamin C’s potential health benefits in adults (rather than just prevent vitamin C deficiency—scurvy) (4).
However, according to the landmark Nurse’s Health Study, women who took more than 400 mg/day for 10 years or more had a ~ 30% reduction in the risk of cardiovascular disease. Moreover, blood levels of vitamin C become saturated at intakes up to 400 mg/day, and there are no safety issues at doses up to 3,000 mg/day (5).
When you also consider that some people have a lower capacity to absorb vitamin C (6), supplementation with ~ 400 to 500 mg/day of vitamin C is a sensible and safe strategy to ensure optimal tissue concentrations of this critical vitamin.
So, does the current scientific evidence support the use of vitamin C supplementation in improving health and helping protect against diseases? Let’s take a look at some prime examples …
Vitamin C can improve cardiovascular health in different ways. For example, vitamin C increases the production of nitric oxide—a compound that causes muscles lining the inner walls of blood vessels to relax, resulting in the widening of the vessels and better blood flow. This can lead to lower blood pressure (7). In fact, higher blood levels of vitamin C have been correlated with a lower risk of high blood pressure (8).
Vitamin C also exerts beneficial effects on blood fats. Oxidative stress resulting from excessive free radical generation and/or weakened antioxidant defenses can damage (oxidize) LDL cholesterol. This oxidation of LDL within the blood vessel walls is an initial event in the formation of plaques that characterize the development of atherosclerosis (hardening of the arteries) (9). Vitamin C helps to inhibit the oxidation of LDL cholesterol (10).
As noted above in the Nurses Health Study, intakes of vitamin C greater than 400 mg/day achieved through supplementation reduced the risk of cardiovascular disease. A lower risk of heart failure (11) and stroke (12) have also been linked to higher concentrations of vitamin C in blood plasma.
In an intervention trial in China, supplementation with only 120 mg of vitamin C (along with the trace mineral molybdenum) for 5-6 years lowered the risk of stroke during a 10-year follow-up period (13).
Nevertheless, many clinical trials failed to show a protective effect of vitamin C supplementation against cardiovascular disease. Importantly, however, many of these trials did not take into account vitamin C status prior to the trial. Consequently, a participant with marginal vitamin C status would be expected to have a different outcome than someone with adequate vitamin C levels (2).
The cancer-preventive effects of vitamin C are attributed in large part to its ability to neutralize destructive free radicals that can cause DNA damage. The accumulation of DNA damage can lead to mutations and an increased risk of cancer (14). Vitamin C can also minimize the formation of potent cancer-causing carcinogens such as N-nitrosamine (15) and H. pylori bacteria (16)—both implicated in the development of stomach cancer (17).
Vitamin C also fights cancer by priming the immune system. Most immune cells accumulate high concentrations of vitamin C, which can affect immune cell function (18). Decreased immune surveillance of malignant cells in older adults (> 60 years) contributes to the increased cancer risk with age. Cancer patients often have compromised immune systems and decreased vitamin C status (19).
Supplementation with vitamin C can restore and maintain the activity of specialized immune cells known as natural killer (NK) cells. These NK cells can target and kill cancerous cells, but their numbers decrease in cancer patients (14).
According to a review of the highest-quality evidence, high vitamin C consumption was associated with a lower incidence of several types of cancer, including breast, prostate, lung, stomach, and pancreatic cancers (20).
Native Note: The majority of clinical trials don’t show a benefit of vitamin C supplementation in cancer prevention. Once again, a major limitation in most of these studies (as noted above in the section on cardiovascular disease) is the omission of vitamin C measurements before or following supplementation, which can significantly skew the study results (2).
Data from multiple studies suggest that vitamin C plays a prominent role in the development and progression of Alzheimer’s disease (AD) (21, 22, 23). Increased intake of vitamin C may lower the risk of AD, primarily by snuffing out highly reactive free radicals that cause irreversible damage to nerve cells, leading to cognitive decline. The brain is particularly susceptible to oxidative (free radical) damage due in part to its high content of unstable polyunsaturated fats (21).
Blood levels of vitamin C are decreased in Alzheimer’s disease patients (compared to healthy controls). Interestingly, levels of vitamin C in cerebrospinal fluid that surrounds the brain and spinal cord are normally about 3-4 times higher than blood levels. It has been suggested that lower vitamin C blood levels in AD may result from the brain drawing upon additional vitamin C from the periphery to bolster the antioxidant defenses in the central nervous system against oxidative stress (24).
Animal studies have demonstrated that vitamin C can reduce the buildup of amyloid plaque—a distinguishing feature of AD (22). Vitamin C also boosts the production of BDNF (brain-derived neurotrophic factor)—an important protein in the brain that strengthens connections between nerve cells that are fundamental to learning and memory (21).
Population surveys have shown consistent associations between deficient or suboptimal vitamin C intakes and a greater risk of AD (21, 23). However, findings from clinical trials have been inconsistent. As noted in the sections on cancer and cardiovascular disease, some study participants who did not experience any benefit from vitamin C supplementation may have already been saturated with the vitamin prior to the onset of the study (21, 22).
You’ve probably heard about this benefit before. Vitamin C has antihistamine effects and plays an essential role in the body’s immune response to viruses (19). In this regard, vitamin C has long been celebrated for its potential to fend off and treat the common cold.
Among the numerous studies conducted over several decades, the most recent meta-analysis of randomized trials provides strong evidence that vitamin C benefits the common cold. In this review, vitamin C considerably decreased the severity of colds by 15-26%. Greater effects were observed in people with more severe forms of the cold compared with milder colds (25).
In an earlier review, regular vitamin C intake was shown to reduce the average duration of the cold by up to 12% in adults and up to 21% in children. Additionally, the occurrence of common cold was cut in half in participants exposed to short periods of vigorous exercise (e.g., marathon runners, skiers, swimmers) (26).
Some of the numerous other health conditions that may be improved with vitamin C include the following (2, 27).
In light of its impressive health benefits and low toxicity, vitamin C supplements can be used by anyone to provide extra protection against diseases and infection. While a frank deficiency of vitamin C is rare in developed countries, suboptimal intakes are common (28).
Stress—both acute and chronic—uses up vitamin C in the process of making stress hormones (29). Dietary intake may often be inadequate to keep up with the body’s demands under stressful conditions. Also, certain groups of people have a greater vulnerability to vitamin C depletion. For these reasons, a vitamin C supplement should especially be considered for people who … (2)
Vitamin C and other water-soluble vitamins are not stored in the body to the extent that fat-soluble vitamins are. Thus, in order to maintain sufficient levels in the body, you should ingest vitamin C in divided doses to “keep your guard up” throughout the day. It’s best to take no more than 500 mg at one time since larger amounts are mostly excreted in the urine (30).
Vitamin C in capsule, powder, or liquid form is more reliably absorbed than tablets. Since regular vitamin C is acidic, some vitamin C products are buffered with minerals such as calcium, magnesium, and potassium. These non-acidic forms are better tolerated by people with sensitive digestive systems (31).
Naturally-sourced forms of vitamin C come with a bonus. Amla fruit, for example, contains various bioactive compounds in addition to vitamin C. These compounds include antioxidant polyphenols such as flavonoids and tannins that protect against cancer (32).
Liposomal vitamin C is a newer supplement form that is well-tolerated and results in substantially higher blood levels which … importantly … are sustained over a longer time (33, 34). Thus, only one dose per day is needed.
So what is liposomal vitamin C?
A liposome is a spherical-shaped sac made from the same type of fat found in the membranes of our cells. Vitamin C is encapsulated within the liposome and, after ingested, delivered to the body’s tissues. Since the liposome closely resembles the structure of the cell membrane, it can more easily penetrate targeted cells than regular vitamin C can (35).
Vitamin C can be taken anytime with or without meals. However, except for times of greater need, taking vitamin C on a regular basis with meals has the advantage of neutralizing carcinogens in food and enhancing the absorption of nonheme iron.
Yes. Vitamin C can help suppress the skin inflammation associated with acne. Its wound healing, antioxidant, and anti-hyperpigmentation properties are also beneficial for acne (36).
Pregnancy increases vitamin C requirements from 75 mg/day to 85 mg/day. Greater intake of vitamin C-rich fruits and vegetables can meet this need. In addition, most prenatal vitamin supplements include an amount of vitamin C to ensure coverage of this higher requirement as well. While there is evidence that vitamin C supplements can lower the risk of placental abruption, most studies, in general, do not show benefits for abnormal pregnancy outcomes (37).
The U.S. Institute of Medicine set an upper tolerable limit of vitamin C intake in pregnancy at 2,000 mg/day (38). Thus a 500 mg/day supplement (which is an amount that can be achieved from diet only) is certainly safe.
However, it should be noted that pregnant women should always consult with their doctor before taking any supplements.
Yes, but you may need to get up and urinate more. Unless you’re fighting a cold or other health condition, it’s better to take vitamin C during the day.
Vitamin C is a major antioxidant vitamin that may help prevent and fight the leading killer diseases (e.g., cancer, heart disease, Alzheimer’s disease) by inhibiting oxidative damage to cells caused by excess free radicals. It also has been proven to reduce the severity and duration of the common cold.
Although frank vitamin C deficiency (scurvy) is uncommon in developed countries, many people do not consume optimal amounts to help lower disease risk. While consumption of vitamin C-rich fruits and vegetables is highly recommended, vitamin C supplementation can fill in the gaps and help compensate for the vitamin-depleting effects of stress.
A practical and effective dosage of 400 to 500 mg/day of vitamin C is recommended, preferably in divided doses. Buffered forms of vitamin C are easier on the gut. Liposomal vitamin C is the most readily absorbed and results in sustained blood levels of vitamin C throughout the day, thus obviating the need for multiple doses.
Robert Iafelice, MS, RD, LDN is a functional nutritionist and freelance medical writer. He is the author of Hold On to Your Muscle, Be Free of Disease, a unique perspective on wellness and disease in the context of muscle health.
This content is for informational and educational purposes only. It is not intended to provide medical advice or to take the place of such advice or treatment from a personal physician. All readers/viewers of this content are advised to consult their doctors or qualified health professionals regarding specific health questions. Neither Dr. Chad Walding nor the publisher of this content takes responsibility for possible health consequences of any person or persons reading or following the information in this educational content. All viewers of this content, especially those taking prescription or over-the-counter medications, should consult their physicians before beginning any nutrition, supplement, or lifestyle program.
