Effect of Vitamin C on common cold, and athletic performance

Vitamin C(ascorbic acid) is a common cold remedy, and besides this, some athletes may take large doses believing it may speed recovery.

But does it actually help treat or prevent the common cold, assuming the person isn’t deficient? A great Cochrane Review, conducted at the National Centre for Epidemiology and Population Health, Australian National University, in “Vitamin C for preventing and treating the common cold“:

REVIEWERS’ CONCLUSIONS:

The failure of vitamin C supplementation to reduce the incidence of colds in the normal population indicates that routine mega-dose prophylaxis is not rationally justified for community use. But evidence shows that it could be justified in persons exposed to brief periods of severe physical exercise and/or cold environments. Also, the consistent and statistically significant small benefits on duration and severity for those using regular vitamin C prophylaxis indicates that vitamin C plays some role in respiratory defence mechanisms. The trials in which vitamin C was introduced at the onset of colds as therapy did not show any benefit in doses up to 4 grams daily, but one large trial reported equivocal benefit from an 8 gram therapeutic dose at onset of symptoms.

I won’t be taking vitamin C next time I catch a cold. But how about vitamin C and athletic performance? According to US Olympic Committee, Sport Performance, Olympic Training Center, Chula Vista, CA, in “Effect of vitamin C supplements on physical performance.“:

Vitamin C is an essential component of the diet and may reduce the adverse effects of exercise-induced reactive oxygen species, including muscle damage, immune dysfunction, and fatigue. However, reactive oxygen species may mediate beneficial training adaptations that vitamin C attenuates; indeed, from a total of 12 studies, vitamin C in doses >1 g·d(-1) impaired sport performance substantially in four of four studies, possibly by reducing mitochondrial biogenesis, while a further four studies demonstrated impairments that were not statistically significant. Doses of ∼0.2 g·d(-1) of vitamin C consumed through five or more servings of fruit and vegetables may be sufficient to reduce oxidative stress and provide other health benefits without impairing training adaptations.

It doesn’t look like supplemental vitamin C is a good idea. We only need about 60mg of vitamin C daily to prevent scurvy. Maybe a little more for smokers. This is easily obtainable by eating a diet that includes a lot of fresh fruits and vegetables, citrus fruits in particular. Vitamin C doesn’t seem to be beneficial for either athletes or for preventing/treating the cold, except maybe in some subpopulations living in extreme environments, and maybe it has some modest benefits on respiratory function.

Scurvy is still with us

Lemons are a good source of vitamin C. Wikipedia, Karwath

Beriberi. Pellagra. Scurvy. These nutritional deficiency diseases have such short, pithy names, it should be difficult to forget them. But forget them we have, since in the developed world they are relatively uncommon nowadays. On the other hand, they are still common in the developing world.

Scurvy, which is caused by lack of vitamin C, used to be much more common in the west. Sailors at sea seemed to be particularly prone to getting scurvy, some even dying from it, for reasons not well understood centuries ago. Scurvy is characterized by bleeding gums, spots on the skin, fever, weakness, and depression. These symptoms result from the body’s inability to produce collagen, which requires vitamin C(ascorbic acid) to be synthesized. Collagen is an important protein that is the main building block of the body’s connective tissues.

It was sometimes mistakenly thought that scurvy was a contagious disease, until it became clear that there was something missing from the sailor’s standard diet of dried meat, dried fish, and grain. Simply adding fresh fruits and vegetables to their diet, in particular citrus fruits, seemed to cure scurvy, though they didn’t know why.

The Royal Navy’s solution in the early 19th century was to add lemon or lime juice to their sailor’s daily ration of watered down rum(grog). This is how the word “limey“, the derogatory word for people from Britain originated. Many other countries soon followed the British example(though some used sauerkraut instead of citrus juice), thereby reducing scurvy cases among seamen.

It wasn’t until the 1930s that scientists isolated and identified the mysterious “anti-scorbotic” factor(the factor that prevents scurvy), vitamin C. Studying the history of nutrition and nutritional deficiency diseases in particular is a great way to see how science works.

Nowadays scurvy is pretty rare in the U.S, but it is more common among certain subgroups like the elderly and homeless drug addicts. According to the Mayo Clinic, Scottsdale, Arizona, in Scurvy: a disease almost forgotten(2006):

RESULTS:

In addition to our patient, seven of 11 patients whose records in the institutional database mentioned vitamin C deficiency were women. The age ranged from a neonate to 77 years (mean, 48 years). The most common associated causes were concomitant gastrointestinal disease, poor dentition, food faddism, and alcoholism. Vitamin or mineral deficiencies other than vitamin C deficiency were also found in our patients who had scurvy. The most common symptoms were bruising, arthralgias, or joint swelling. The most common signs were pedal edema, bruising, or mucosal changes. Four patients had vague symptoms of myalgias and fatigue without classic findings, and five had concomitant nutritional deficiencies. Follow-up available for six of 12 patients treated by vitamin C supplementation showed complete resolution of symptoms in five.

CONCLUSIONS:

Patients with scurvy may present with classic symptoms and signs or with nonspecific clinical symptoms and an absence of diagnostically suggestive physical findings. Concomitant deficiency states occur not uncommonly. Taking a thorough dietary history and measuring serum ascorbic acid levels should be considered for patients with classic signs and symptoms, nonspecific musculoskeletal complaints, or other vitamin or mineral deficiencies.

In other words, scurvy hasn’t been completely eradicated, and we should be on the lookout for symptoms of it in the elderly who are eating poorly. This doesn’t mean that the elderly or you should be taking vitamin C supplements, though taking the occasional multivitamin for insurance probably won’t hurt.

Drinking orange juice or eating enough fruits and vegetables will give you well beyond the 60 mg of vitamin C we need to prevent scurvy. However, there’s no good reason to mega-dose with vitamin C, or any other nutrient for that matter.

The Way of the Antioxidant

It always seemed so irresistibly simple. Oxidation = bad, therefore antioxidants = good. Free radicals(any atom or molecule that has a single unpaired electron in an outer shell, making it highly reactive and unstable) have long been seen as the “bad guys” going around our body and causing oxidative damage, by “stealing” electrons from other atoms, leading to aging and disease. This in turn can lead to a chain reaction with the atoms and molecules that had their electrons “stolen” from them becoming free radicals themselves, trying to steal electrons from other atoms.

In comes the police, uh, I mean the antioxidants to put a stop to this mayhem. Antioxidants protect the body’s tissues by donating their own electrons to the free radicals, neutralizing the threat. We actually produce our own antioxidants: glutathione peroxidase, and superoxide dismutase, among others. We also get antioxidants through our diet, such as vitamin C(ascorbic acid), vitamin E(actually a family of chemically similar fat-soluble vitamins), and beta-carotine(and other carotenoids), among so many others. Even the non-vitamin phytochemicals in many plant foods often have antioxidant effects(by definition, vitamins are absolutely essential for the body to function properly, while phytochemicals are not, though at least some of them are beneficial for health).

So taking large amounts of antioxidant supplements would obviously protect the body even more than getting smaller amounts from food, right? Wrong! Indeed, let’s look at the results of a study done on athletes who took antioxidant supplements, people whose muscles are under a great deal of oxidative stress during exercise.

Does antioxidant vitamin supplementation protect against muscle damage?
McGinley C, Shafat A, Donnelly AE.
Source

Department of Physical Education and Sport Sciences, University of Limerick, Limerick, Ireland.

Abstract

The high forces undergone during repetitive eccentric, or lengthening, contractions place skeletal muscle under considerable stress, in particular if unaccustomed. Although muscle is highly adaptive, the responses to stress may not be optimally regulated by the body. Reactive oxygen species (ROS) are one component of the stress response that may contribute to muscle damage after eccentric exercise. Antioxidants may in turn scavenge ROS, thereby preventing or attenuating muscle damage. The antioxidant vitamins C (ascorbic acid) and E (tocopherol) are among the most commonly used sport supplements, and are often taken in large doses by athletes and other sportspersons because of their potential protective effect against muscle damage. This review assesses studies that have investigated the effects of these two antioxidants, alone or in combination, on muscle damage and oxidative stress. Studies have used a variety of supplementation strategies, with variations in dosage, timing and duration of supplementation. Although there is some evidence to show that both antioxidants can reduce indices of oxidative stress, there is little evidence to support a role for vitamin C and/or vitamin E in protecting against muscle damage. Indeed, antioxidant supplementation may actually interfere with the cellular signalling functions of ROS, thereby adversely affecting muscle performance. Furthermore, recent studies have cast doubt on the benign effects of long-term, high-dosage antioxidant supplementation. High doses of vitamin E, in particular, may increase all-cause mortality. Although some equivocation remains in the extant literature regarding the beneficial effects of antioxidant vitamin supplementation on muscle damage, there is little evidence to support such a role. Since the potential for long-term harm does exist, the casual use of high doses of antioxidants by athletes and others should perhaps be curtailed.

Okay, so they don’t prevent oxidative damage to muscles, but can vitamin C at least improve athletic performance?

Effect of vitamin C supplements on physical performance.

Braakhuis AJ.
Source

US Olympic Committee, Sport Performance, Olympic Training Center, Chula Vista, CA 91915, USA. andrea.braakhuis@usoc.org

Abstract

Vitamin C is an essential component of the diet and may reduce the adverse effects of exercise-induced reactive oxygen species, including muscle damage, immune dysfunction, and fatigue. However, reactive oxygen species may mediate beneficial training adaptations that vitamin C attenuates; indeed, from a total of 12 studies, vitamin C in doses >1 g·d(-1) impaired sport performance substantially in four of four studies, possibly by reducing mitochondrial biogenesis, while a further four studies demonstrated impairments that were not statistically significant. Doses of ∼0.2 g·d(-1) of vitamin C consumed through five or more servings of fruit and vegetables may be sufficient to reduce oxidative stress and provide other health benefits without impairing training adaptations.

It appears that supplemental vitamin C impaired performance. The general idea here for why mega-doses of vitamin C and other antioxidant supplements are not protecting tissues or enhancing performance is that not all oxidation reactions are harmful; they are used in many metabolic reactions, for cell communications and are important for the immune system. So if you effectively shut down oxidation with a flood of antioxidants, you may be interfering with some important chemical reactions in your body, and doing more harm than good. Vitamin C isn’t just an antioxidant – it is needed for collagen production and immunity and not getting enough results in a serious deficiency disease called scurvy. Scurvy is very rare in the developed world, and only a small daily dose(60mg) of vitamin C is necessary to prevent it.

The best way to get antioxidants. Source: Wikipedia

Okay, then maybe, just maybe a powerful antioxidant like beta-carotine can protect smokers, who are exposing themselves to a lot of oxidative damage through the act of smoking:

Beta-carotene in multivitamins and the possible risk of lung cancer among smokers versus former smokers: a meta-analysis and evaluation of national brands.

CONCLUSIONS:

High-dose beta-carotene supplementation appears to increase the risk of lung cancer among current smokers. Although beta-carotene was prevalent in multivitamins, high-dose beta-carotene was observed among multivitamin formulas sold to promote visual health.

So far, it doesn’t look like antioxidant supplements are beneficial for anyone’s health. Beta-carotine, in particular, may even increase lung cancer risk in smokers.

This doesn’t mean that antioxidants are themselves bad for you. It just means you are better off getting them from food, where they may interact with other chemicals in the fruits and vegetables they naturally coincide with in a manner that makes them relatively harmless and likely beneficial.

Antioxidants do provide some protection, but that’s not the whole story. It’s long been thought that fruits and vegetables are beneficial largely due to their antioxidant content. This may still be true in part, but the phytochemicals in them may have other ways of protecting our health in ways science is still trying to figure out. Antioxidant content may be a proxy measure of protective phytochemical content, since many if not most phytochemicals tend to have antioxidant effects. Blueberries, with a very high antioxidant content and some possible brain-protecting effects, are a good example of this.

Good health means having a good balance between antioxidants and oxidation reactions, which taking large doses of antioxidant supplements interferes with.