When it comes to using vitamins to supplement the diet, there is a huge gap between what the science says and what many consumers think.
A recent studyfor example, found that around 52% of the Australian population takes some form of complementary medicine, with over a third of them taking vitamin pills.
Overall, almost one in five people in Australia take vitamins. Many of these people take over-the-counter supplements without professional advice, although a few practitioners prescribe megavitamin therapy (high doses).
But most are vitamins that aren’t really helpful when taken in addition to a normal diet. In fact, these supplements are potentially harmful.
Yet vitamins in all shapes, forms, combinations and doses are sold in supermarkets, health food stores and pharmacies. Consumers should therefore be aware of the uses, efficacies and potential toxicities of any vitamin products they purchase.
What are vitamins?
Vitamins are organic substances – or groups of related substances – found in many foods. They have specific biochemical functions and are generally not made by the body (or not in sufficient quantity for good health).
These are essential nutrients needed in very small amounts to maintain good health. The effects of vitamins are best known for their deficiency syndromes, many of which are life-threatening.
All other things being equal, the amount of these nutrients necessary for good health can be easily obtained through a reasonable diet and sufficient exposure to the sun.
But people still suffer from vitamin deficiencies, even in rich countries, such as Australia, especially in folate, thiamin and vitamin D.
science and vitamins
There is a popular perception that if a small amount of something is good, then more is better and a lot is better.
There is also a reasoning that goes like this: they are natural substances, so they should be safe in any amount. Fake. Science tells us that in the case of vitamins, this is rarely true.
Take the example of vitamin A. A number of recent comments found no evidence for the benefits of vitamin A in the prevention or treatment of a large number of diseases, including the incidence of age-related maculopathy, in which the retina degenerates.
Vitamin A could, indeed, be harmful. But the antioxidant vitamins – A, E and C – are sometimes used in large doses by people hoping to prevent cancer, heart disease and dementia.
Indeed, until recently, it was thought that these diseases had an oxidative component and that the use of “natural” antioxidant agents would have a beneficial effect.
Or the same old chestnut tree: at the very least they couldn’t hurt. Now it is established that this is far from the truth.
Numerous clinical tests (double-blind and placebo-controlled), involving hundreds of thousands of individuals, over a period of several years showed no statistically significant difference in morbidity and mortality between the antioxidant group and the control group.
In fact, there seems to be a small increase in mortality in the group taking vitamins.
A large study published in October showed a 1.6 increase in prostate cancers in men who used high doses of (“non-toxic”) vitamin E compared to the placebo group.
More bad news
As for mega-doses of vitamin C to prevent and treat the common cold, the news is not good.
A 2005 meta-analysis of a large number of trials found that vitamin C supplementation did not reduce the incidence and severity of colds.
Trials in which vitamin C was introduced at the onset of the common cold as therapy showed no benefit at doses up to 4 grams per day.
Multivitamin takers may also be disappointed.
At present, there is no evidence indicating any benefits from taking multivitamins. Some evidence even points to an increase in the incidence of breast cancer: in a swedish studymultivitamin use was associated with a statistically significant increase in breast cancer risk.
This is not to say that all vitamins taken in supplement form are ineffective or dangerous. Some vitamins are used in doses above nutritional value for therapeutic purposes.
Of all the vitamins, vitamin D has been the most studied and shown to have many beneficial effects at supranutrient doses, including prevent and treat osteoporosis in susceptible individuals.
The natural substance, cholecalciferol (D3), is the main active component of the various forms of vitamin D, the most common source of which is sunlight.
Some other vitamins with proven therapeutic use include:
folate (B9) in pregnant women for prevent ultimate spina bifida in the newborn;
vitamin K for all newborns prevent bleeding diseases;
thiamin (B1) in people being treated for alcoholism and malnutrition and;
vitamin B12 in older people with pernicious anemia; and
niacin (vitamin B3) in high doses for the treatment of high cholesterol where other therapies have failed (although niacin is poorly tolerated by many people and can cause serious side effects).
But these are exceptions that confirm the rule that the use of additional vitamins confers no health benefits.
People want to be healthy, and because of the hyperbole surrounding the benefits of vitamins, it’s believed that supernutritional doses will improve their quality of life. But in most cases, the perceived improvement doesn’t match what the science tells us.
Louis Roller does not work for, consult, own stock or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond his academic appointment.