Every second week, there is an article in our city paper by a local naturopath. In several previous posts, here and at Skeptic North, I’ve criticized her recommendation for supplements as a universal treatment for everyone, ill or not. It’s becoming more and more obvious that people need to be educated about the potential risks inherent in the indiscriminate use of supplements.
Dr. Chris van Tulleken is a physician who participates in a show on BBC 2 called Trust me, I’m a Doctor as well as writing for the BBC website. In a recent article, The problem with taking too many vitamins, he addresses this exact issue.
He begins with an extreme example of Antarctic survival and death from 1912. The victims suffered from starvation and an overdose.
At first sight Mawson’s story seems to be another such tale – starvation combined with a lack of some vital nutrient. In fact, Mawson’s description of his symptoms is an almost textbook description of vitamin A overdose – probably from eating dog liver. As little as 100g of husky liver could give a hungry explorer a fatal dose.
Not many of us will be eating husky liver for lunch, but it is a valuable warning of the possibility of a topic not often covered—vitamin overdose.
Vitamins are vital to our health, and the development of fortified foods has been an important of health improvements in the western world.
while you shouldn’t eat dog liver in Antarctica, vitamin A deficiency hugely increases the risk of blindness and death in children with measles and diarrhoea in developing countries. So the World Health Organization recommends a very strict amount and cautions that higher doses can cause birth defects in early pregnancy among other problems.
“We found no evidence to support antioxidant supplements for primary or secondary prevention [of diseases of any kind]. Beta-carotene and vitamin E seem to increase mortality, and so may higher doses of vitamin A…. Antioxidant supplements need to be considered as medicinal products and should undergo sufficient evaluation before marketing”.
Antioxidant supplements are not associated with lower all-cause mortality. Beta carotene, vitamin E, and higher doses of vitamin A may be associated with higher all-cause mortality.
Antioxidants do not prevent gastrointestinal cancers. In fact, in pooled results of high-quality studies, antioxidants increased overall mortality.
Then he gives a very simplified answer in why they may be harmful. Simplified because vitamins are a very diverse group of chemicals.
I’m going to include what people normally refer to as minerals under the heading of vitamins. They’re required in the diet not for energy, but as chemical partners for the enzymes involved in the body’s metabolism – cell production, tissue repair, and other vital processes.
Their functions are understood largely by their deficiency diseases so we’re not exactly sure of precisely what they all do or how they interact. Antioxidants provide a nice example. They soak up the very toxic, chemically-reactive by-products of metabolism called free radicals. These free radicals, left unchecked, can cause damage to DNA and may be linked to cancer.
Your cells are full of antioxidants but surely taking more would be better? Right? Keep those cancer causing radicals under control? Well, unfortunately, your body’s immune system fights infections by using free radicals to kill bugs. Exactly what effect huge quantities of extra antioxidants could have on this is not clear but it’s easy to imagine that it might not be good and you could get more infections.
Vitamin A is linked to increasing lung cancer in smokers. Excess zinc is linked to reduced immune function. Long-term excessive intake of manganese is linked to muscle and nerve disorders in older people. Niacin in excess has been linked to cell damage. And so on.
And it gets more complicated still when you start mixing everything up in one tablet. For example, different minerals compete for absorption. If you take large quantities of calcium you won’t be able to absorb your iron. If you take large quantities of iron you won’t be able to absorb zinc. If you take vitamin C you’ll reduce your copper level.
As most medical writers note, there are a few people who are at a real risk for deficiencies and should take supplements.
- Folic acid for all women thinking of having a baby and pregnant women up to week 12 of the pregnancy.
- Vitamin D for all pregnant and breastfeeding women, children aged six months to five years, people aged 65 and over and for people who are not exposed to much sun, for example people who cover up their skin for cultural reasons, or people who are housebound for long periods of time.
- Finally a supplement containing vitamins A, C and D is recommended for all children aged six months to four years. This is a precaution because growing children may not get enough, especially those not eating a varied diet, such as fussy eaters.
There are also specific individuals that may require supplements, such as those on restrictive diets or those with digestive disorders. If you have any questions:
- Do ask your physician or registered dietician.
- Don’t ask someone who sell the products.
- Do avoid husky liver.