The vitamin supplement industry is huge and continues to grow. The U.S. market was estimated at $23 billion in 2007 whereas in 2006 UK's market share was 220 million pounds. Who do you know that doesn't take their vitamins? More than half of American and Canadian adults and almost a half of Britons use supplements on a regular basis. But is this really necessary? 1-3
To stay healthy, our bodies do need vitamins and minerals in small amounts. However, we cannot synthesize all of them, so that they have to come from our diet. But, even in our modern society, most people don't even consume the recommended daily amount (RDA) of fruit or vegetable servings. What's so sad is even if you rely on your diet, you still may not get the supplementation that you need:4-7
So, taking vitamin and mineral supplements is assumed to be one of the main and hopefully safe ways to meet our requirements and at the same time remain 'healthy'. As it is not easy to decide which vitamin and minerals to take, most people turn to taking multivitamins, aside from these being cost-effective, as well as anti-oxidants, vitamin D, folic acid, calcium and the more than ever popular omega 3's.
So, do vitamin supplements keep us healthy?
Some do and some don't. Research overwhelmingly suggests that the following supplements including multivitamins make no major difference in maintaining a healthy state and in fact, are not without risk.
Dr. Huang and colleagues from the Johns Hopkins University carefully reviewed 63 papers (after strict exclusion/inclusion criteria of originally more than 11,000 cited literature) in 2007 and concluded that there is not enough evidence supporting that multivamins prevent chronic diseases. Huang and co-authors also mentioned that there have been no adverse effects reports on multivitamins probably because there is no requirement to report, unlike prescription drugs.8
And what is even more dismaying is that there are also risks associated with multivitamins. The panelists of the 2007 National Institutes of Health State-of-the-Science Conference expressed the "potential for adverse effects in individuals consuming dietary supplements that are above the upper level" since "... by law, the listing of ingredient amounts on nutrient supplement labels is the minimum content; thus, higher intakes are probable." Ironically, people who take multivitamin supplements are usually health-conscious people, that is, those who get a balanced, fortified diet.
They also cited studies such as calcium supplementation resulting in kidney stones, ß-carotene supplementation increasing lung cancer incidence among smokers or persons exposed to asbestos in order to emphasize the current knowledge gap in how some nutrients work.9
What's also disconcerting is the contamination that may occur during the synthesis and production of supplements. A report of 21 brands of multivitamins on the market in the United States and Canada, selected by ConsumerLab.com and tested by independent laboratories, showed that "just 10 met the stated claims on their labels or satisfied other quality standards." One product was even contaminated with lead.10
The Cochrane Summaries, which investigate topics using very strict guidelines to establish whether evidence for a therapeutic strategy are conclusive, addressed the use of antioxidants Vitamins A, C, E, ß-carotene and selenium on the prevention of heart disease or cancer.
The findings were earth shattering! The meta-analysis shows that these antioxidant supplements can actually be hazardous to health: Vitamins A and E and ß-carotene, used singly or in combination, may result in increased mortality but not Vitamin C and selenium.
The review authors suggest that since supplements are synthetics they might be interfering with the body's own defense mechanisms. Or toxicities in supplements or perhaps too high a dose may be contributors. Unlike pharmaceutical products, manufacturers are not required to check for or list potential toxicities.11,12
Since the fortification of foods with folic acid, "the rate of neural-tube defects has dropped from 0.86 per 1,000 live births to 0.4, a drop of more than 50 per cent, according to a Canadian study published in the New England Journal of Medicine." Indeed, a public health success. As a result many food products, especially flour, are fortified with folic acid. However, the risks of ingesting too much may actually increase cancer risk.
A study published in the journal Cancer Research gave evidence of increased cancer incidence in rats given high amounts of folic acid. And a separate study showed that folic acid taken during late pregnancy seems to increase the risk of asthma in children.13-15
A recent meta-analysis study published in the British Medical Journal involving more than 11,900 participants showed that the benefits derived from calcium supplements are unclear, reducing fracture risks only marginally.
However calcium supplement intake leads to a 30% increase in the incidence of myocardial infarction and some insignificant increases in the risk of stroke and mortality, emphasizing the need for more research on calcium supplementation. However, the authors suggest a probable misdiagnosis in this meta-analysis, "Calcium supplements could simply be causing gastrointestinal symptoms that could be misdiagnosed as cardiac chest pain".16,17
OK, so which ones should we be taking?
Current research indicates that Vitamin D and Omega-3's are probably beneficial, but aren't perfect by any means.
Essential for calcium absoption and good bones, Vitamin D stands out as the supplement that can be produced by our own bodies. But, since vitamin D biosynthesis is dependant on sunshine, vitamin D deficiency is more common in high latitudes.18
As a result supplementation is very common, but it remains controversial, to say the least! In North America milk is fortified with Vitamin D and breastfed babies are prescribed vitamin D. But in Europe, fortification of dairy products with vitamin D is not widespread and there is a strong resistance against supplementation of breastfed infants as this practice seems to contradict the message that breast milk is still the best.
And in view of more foods being fortified with Vitamin D experts are also divided as to whether there is even a need for Vitamin D supplementation.
The pro Vitamin D group links Vitamin D to the prevention of diseases such as multiple sclerosis, type-1 diabetes, heart disease, infectious diseases and some types of cancer and says that for "an adult who spends 20 min in summer sunshine can produce an oral intake equivalent of about 10000 IU/day, the suggested dose of 1000—4000 IU/day is unlikely to be toxic".19
The anti Vitamin D supplementation group believes that there is no sufficient evidence to support whether there is a vitamin D deficiency in many populations or in the many other "wonders" of Vitamin D and calcium.For instance, a study showed that Vitamin D and calcium supplements do not decrease breast cancer risk in premenopausal women as previously thought."Evidence also suggests that high levels of vitamin D can increase the risks for fractures and can raise the risk for other diseases" like hypercalcemia.20,21
Omega-3 fatty acids
Known as "healthy fats" omega 3's have attracted a lot of attention as a huge amount of evidence shows that they prevent a wide range of health problems, including cardiovascular disease, depression, asthma, and rheumatoid arthritis. Being macronutrients, the body needs them in large amounts, contrary to vitamins. Good sources of omega-3 fats include salmon, flax seeds and walnuts.22
Although some studies report no significant effects of omega-3 fat supplementation on cardiovascular diseases, most scientists are convinced of the benefits they bring. The good news is that a recent meta-analysis involving over 30,000 patients shows that fish oil supplements can reduce deaths due to cardiac diseases although had no effect on arrhythmias or all causes of mortality.23-25
Furthermore, the Institute of Medicine at the National Academy of Sciences cited research showing increased risk of bleeding and hemorrhagic stroke in a few studies following supplementation with omega-3s. Individuals who have disorders involving bleeding, who bruise very easily, or who are taking blood thinners should consult with a medical practitioner before taking supplemental omega-3 fatty acids.26
But contamination with persistent organic pollutants (POP) including mercury, PCB's and dioxin especially the fish oil supplements, as opposed to the plant based omegas, continues to plague the industry. A Canadian study in 2007 surveyed 30 fish oil supplements and found POP in all of the products although most of the pollutants did not exceed the minimum toxic level.  To counter this, the omega-3 industry is responding with new products such as the use of microalgae instead of fish and more rigid certification exemplified by Nordic Naturals.27
As an aside, some groups of people may still need supplements:
The Bottom Line
Supplements are pills and cannot be a substitute for healthy food. Plus they do have risks. Science simply cannot copy what nature produces and cannot work like genuine vitamins.
So, what's the perfect vitamin supplement? It appears to be…duh… a healthy, balanced diet, even for lactating women. Plus you'll probably save some of your hard earned money. But, if you still want to take supplements omega 3's and vitamin D make sense.
Published July 15, 2011, updated July 29, 2012