Are Vitamins Bad for You?
We all know vitamins are an essential part of a healthy diet, without them we can develop any number of unpleasant ailments. It is therefore little wonder that there is a multi-billion dollar industry catering to our insecurities about whether we are meeting our dietary requirements. Whilst government rules on the sales of vitamins are far more relaxed than other pharmaceuticals several recent studies have highlighted the potential dangers of too much of a good thing. In extreme cases the evidence suggests that some supplements may not just waste your money, they could cost you your health. In this article I will look at some of the potential harmful effects and likelihood of side effects on some of the most commonly taken vitamin supplements.
As a fat-soluble vitamin A may be stored in the liver where it can reach toxic levels. Naturally occurring dietary sources include liver and carrots, both of which in excess can prove fatal. Overdosing on vitamin A is known as Hypervitaminosis A with symptoms such as dry skin, nausea, fatigue, weakness and headaches. Whilst the most common source of excessive dietary intake is vitamin supplements there have been cases of carrot addiction recorded. In one such case the victim had turned bright yellow and developed cirrhosis of the liver after drinking up to eight pints of carrot juice a day. Clearly this is an extreme case but it does highlight the potential toxic effects of certain vitamins.
Ascorbic acid is water soluble and therefore must be constantly replenished. Its role in healing is well known and it is also a powerful antioxidant helping defend the body. Whilst the chances of causing oneself significant harm through taking vitamin C are fairly small there are certain side effects linked to large dosages. The most common of these is diarrhoea which results from doses in excess of 2 grams, that is around 50 times the normal recommended daily intake (RDI).
Of course too little vitamin C can result in scurvy, a condition popular with 18th century sailors!
Vitamin D is largely acquired from daylight. In this context there has never been a report of overdosing on it. Given the high additional dietary intake required to cause side effects it is unlikely that most healthy adults would unwittingly consume this. There are however certain conditions that make one far more sensitive to vitamin D such as primary hyperparathyroidism. The most significant condition resulting from excessive Vitamin D intake is hypercalcemia – raised blood calcium levels. Whilst this may result in renal failure amongst other symptoms, there is also a serious risk to the development of unborn babies. For this reason both pregnant or breastfeeding women are advised to consult a doctor before taking vitamin D supplements.
Like vitamin A, vitamin E is fat-soluble so can be stored in the body. Whilst there is no particular clinical syndrome linked with deficiency of intake it is linked to brain and nervous system health. In combination with vitamin C it is reported that vitamin E can reduce the risk of certain heart conditions. Vitamin E is also an antioxidant which implies certain anti-cancer properties amongst other preventative roles, e.g. Alzheimer’s.
However, even moderately excessive intake (2 times RDI) has been reported to cause adverse effects. Far from being beneficial, these higher doses have been linked to increased risk of death in two separate studies. The most recent of these (2011) suggests that a daily dose of vitamin E could actually increase a man's risk of prostate cancer. Named the SELECT trial this was a ten year double-blind, placebo-controlled trial of 35,0000 subjects originally intended to demonstrate that vitamin E and selenium reduced risk of prostate cancer. What the researchers actually found was an increased incidence of prostate cancer by 17 percent among men who took a daily dose of 400 IU. Despite this evidence one brand of Vitamin E is still sold with a label claiming "Supports prostate health."
Even multivitamins may not be the elixir they are claimed to be. A 20 year longitudinal study by the University of Minnesota of nearly 40,000 older women (mean age 62) taking vitamin B6, folic acid, magnesium, zinc, copper and iron found evidence to suggesting these supplements might actually raise the death rate of older women. Whilst the data was observational / self reported the increased risk was 2.4%. The suggested explanation is that these substances are toxic in high amounts. So in addition to an adequate dietary intake levels of any one of these substances may be excessive and accumulate.
Conclusion: are any supplements safe?
There is no doubt we need vitamins to survive but it seems clear that excess has no benefit and may even be detrimental to our health. With today’s high dietary intakes the idea of individuals being deficient in a particular vitamin or mineral seems less likely. If one’s diet is reasonable then taking vitamin supplements has the potential to result in an accumulation of what can be toxic substances.
It is safe to say that the best way to receive all your necessary nutrients is a good, balanced diet. Simple steps such as increasing intake of fruit and vegetables can provide a more natural, high quality source of nutritional essentials. On top of this they contain nutrients that are not available in a jar such as phytochemicals which may have cancer-fighting antioxidant effects.
However, there are certain groups who can benefit from popping pills and these include women planning to get pregnant (folic acid), those who are housebound and see little sunlight (vitamin D), vegans who do not eat meat or dairy (vitamin B12) and athletes in training. For the rest of us the general advice is eat sensibly and save your money.