Science: Put A Lid On It

You can have too much of a good thing, even vitamins. Rachael Philipps reports

FOR THOSE of us who find the ideals of living more sensibly and eating a more balanced diet impossible to achieve, vitamin pills and dietary supplements appear to offer health in a bottle. But it is unclear whether rattling to work on a stomach full of pills is truly beneficial, particularly as scientists do not know how these cocktails of nutrients work in our bodies. This lack of hard knowledge, however, has done little to deter sales: in 1997, we spent pounds 335m on dietary supplements in Britain, and this figure is predicted to rise to pounds 500m by the end of next year.

One crucial reason for the lack of scientific facts in this area is that vitamin pills are currently classed as foods rather than medicines, which means they do not have to undergo the rigorous clinical tests that products sold as medicines are subjected to. Given this, we should treat the claims made for vitamins with some caution - and particularly the assertions of health gurus that huge doses of certain vitamins can help to cure cancer, prevent infections, delay ageing, heal damaged nerves and increase intelligence.

Professor Andre McLean is one of a number of scientists recently recruited to the Expert Group on Vitamins and Minerals, set up after concerns were voiced about the health risks associated with B6 (pyridoxine) supplements, which can cause nerve damage in the hands and feet if taken in large doses. Department of Health statistics showed that since 1964, there have been almost 2,000 reports of adverse reactions associated with the supplement, of which 16 were fatal. The current government drew up proposals recommending that sales of B6 should be restricted to 10mg doses, and that the larger doses of up to 50mg should only be available from pharmacies - much to the fury of thousands of women who find 100 to 200mg a day relieves pre-menstrual tension.

More damning research was carried out in 1994 and 1996 in Finland and the US into the anti-oxidant supplement beta carotene, widely claimed to fight the free radicals that roam the body and can cause cancerous cells to develop. Animal and plant studies suggested that beta carotene was highly effective in protecting against this risk. The studies looked at whether large doses of the substance would mimic this effect in humans, and scientists administered high doses to one group of heavy smokers and a placebo to another. Alarmingly, their results showed that beta carotene actually accelerated, rather than hindered, the growth of tumours in the smokers.

As Sarah Schenker, a nutrition scientist at the British Nutrition Foundation, states: "Just because some is good doesn't necessarily mean more is better." Vitamin C tablets of up to 1,000mg a day have been widely on sale over the flu season, marketed alongside claims that these mega-doses will help us fight off sniffs and sneezes. Yet recent research at Leicester University suggested that a daily vitamin C dose of just 500mg raises levels of a substance which may cause DNA damage, possibly aggravating the risk of cancers and diseases like rheumatoid arthri- tis. Schenker notes: "It seems that there is a kind of U-shaped progression here, where not enough of a nutrient heightens potential health risks, the recommended amount is good and lowers the risk of possible problems, but taking mega-doses actually raises the risk of problems again."

One of the functions of the newly formed Expert Group on Vitamins and Minerals will be to consider the need for clearer labelling, better information and for indications of safe upper levels for nutritional supplements. The current government is also considering whether there should be legislation to fix upper limits for vitamins and minerals, as is the case in most other European countries.

Lyndel Costain, spokeswoman for the British Dietetic Association, says: "Taking many supplements can be an awful waste of money, particularly the water-soluble vitamins like B and C, which are often just peed out. You just end up making very expen-sive urine. There are some wealthy areas of London which must have very well-nourished gutters." More worryingly, it has been reported that prolonged high-dose use of water-soluble vitamins can increase the risk of kidney stones.

Vitamins A, D, E and K, all found naturally in fatty foods such as oily fish, margarine and butter, are fat-soluble, so the body finds them harder to excrete. Taking large doses of vitamin A is ill-advised, especially for women, as it builds up in the liver and presents serious risks to any future foetus. The worst-case scenario, if excessive amounts are taken over long periods, is liver failure. Gastro-intestinal and liver damage can also be caused by prolonged use of high-dose iron supplements.

Costain continues: "You can also suffer all sorts of imbalances if you take too much of any one supplement. For example, taking zinc is supposed to boost the immune system, but take more than 50mg a day and it can actually reduce your immunity and interfere with iron and copper absorption." Large doses of calcium can also inhibit iron absorption, and high doses of beta carotene can interfere with our ability to absorb other related nutrients.

In the area of novel health fads, as in others, the award for taking things to extremes goes to the US. America's favourite new health and happiness guru is the Harvard-educated Dr Weil, who, along with blockbuster books and his own television show, has his own website entitled "Ask Dr Weil". Visit the page and he will advise you, after a brief question-and- answer session, on which vitamins and minerals he thinks you should take. To test the system, I entered my details (with a couple of ultra-healthy tweaks) just to see what he would recommend. Dr Weil suggested eight high- dosage supplements: vitamins C, E and a B complex, selenium, mixed carotene, calcium citrate, magnesium and dong quai. This regime would cost around pounds 40 a month to keep up, and was described by Lyndel Costain as "pretty irresponsible". The saving grace is that people are notoriously bad at being consistent in taking pills; our weakness may, in this case, be an inadvertent strength.

And ironically, it is people who might benefit most from dietary supplements - those on low incomes - who can least afford them. It is the fact that they cannot afford a reasonable diet in the first place that generally creates the problem, and vitamin pills are unlikely to be first on the shopping list if there are bills to pay.

While research suggests that people who take a daily supplement are the healthiest, it is often those same people who are eating the best diets, so it's hard to tell which is the most important factor in their well- being. And as Costain says: "There's probably a lot of things in fruit and vegetables that we haven't even discovered yet that interact with each other and which you can't package in a pill. There are lots of questions that need answering through thorough clinical research. If you feel the urge to pop a pill, take a basic multi-vitamin and if it doesn't seem to change anything after three months, just stop taking it."