The end of last year brought a perennial scientific argument: research in a reputable medical journal showing that vitamin and mineral supplementation was as helpful to health as sawdust – and possibly harmful.
And the new year is ushering in growing reaction from experts, who say the research is fatally flawed.
The studies, in the Annals of Internal Medicine in December, by scientists at the Johns Hopkins University School of Medicine in the US, and British scientists at Warwick University, include a meta-analysis of 24 trials involving 450 000 people.
It found no beneficial effect on mortality from vitamin supplementation. Another paper examined cognitive decline in 6 000 elderly men and found no improvement, despite 12 years on multivitamins.
A third paper looked at the effects of multivitamins on heart disease in 1 700 men and women over five years, and similarly concluded supplementation was unhelpful.
In a journal editorial, the researchers said vitamin use is not justified as it can cause harm, and should be avoided. They said vitamins should not be used for chronic disease prevention.
A common response to such views is of the conspiracy theory variety: that “Big Pharma” is behind the research. Drug maker Pfizer funds one of the studies.
US professor of biochemistry and biophysics Balz Frei believes there is no conspiracy, since pharmaceutical companies, including Pfizer and Bayer, make and sell vitamin products.
However, the research is terminally ill, he says. He and other experts have found a litany of design faults, including a high dropout rate, low adherence, use of low-potency, low-quality vitamin products, and “massaging” and “cherry-picking” of data.
An aggravating factor is ignorance by doctors who know little about nutrition, he says.
They are not trained in it, and do not understand how vitamins and minerals work in the body.
“Doctors don’t prescribe vitamins because they are trained to prescribe pharmaceutical drugs only, and to treat disease, not prevent it,” he says.
Ignorance also makes scientists reach the right conclusions for the wrong reasons: “It is correct to say vitamins shouldn’t be used to prevent chronic disease, not because they don’t work, but because that’s not their function,” says Prof Frei.
“Vitamins are necessary for life, for normal biological functions, not to prevent chronic disease. They support the function of cells for normal metabolism, immune function, and growth development – all basic processes related not to prevention of chronic disease, but to optimum health.” Most doctors do not know the difference between vitamin deficiencies and inadequacies, he says.
Most people have inadequate levels of vitamin C, but are not deficient; if they were, they would have deficiency diseases such as scurvy or pellagra.
Vitamin inadequacies prevent optimum functioning of biological processes, he says.
Inadequacies are common, and easily resolved by eating the recommended five to nine servings daily of fruit and vegetables. Most people do not eat sufficient quantities of these.
Whether a multivitamin and mineral can protect against cognitive decline, cancer and heart disease is controversial, but the evidence is “fairly good” for some of these diseases, Prof Frei says.
Findings last year from the most comprehensive, longest and largest study on multivitamins, the Physicians Health Study II, which followed more than 14 000 doctors over 11 years, show that a daily multivitamin lowers total cancer rate by a significant 8%, and 13%, when prostate cancer is discounted, Prof Frei says.
Solid data on cognitive function and eye disease show a significant 13% total reduction in cataracts. The study shows no effects on cognitive function or heart disease. Other studies over five years (“the minimum required in such research”) show beneficial effects on heart disease from vitamin and mineral supplements.
None shows harmful effects, because unlike pharmaceutical drugs, vitamins have never killed anyone, Prof Frei says.
When taken appropriately, according to recommended daily allowances (RDAs) and “tolerable upper intake limit”, vitamins are proven safe and beneficial in properly designed studies, he says.
The standard design of scientific research, the “gold standard” – randomised, placebo-controlled control trials – does not work for essential nutrients (vitamins and minerals).
“It would be unethical to make people deficient or inadequate in a micronutrient to test for an effect,” Prof Frei says.
“Doctors end up doing research on people who already have (varying) levels of vitamins and minerals. The placebo group is not the same as in a pharmaceutical group, and statistical power to see something significant is small,” he says.
British nutrition specialist Patrick Holford, founder of the Institute for Optimum Nutrition, says the latest research is “pure prejudice”, and another “long-standing scientific tradition – regular publication of poorly conceived studies that don’t clarify anything”.
“No one who knows about nutrition, or is interested in adding to our knowledge of what does and doesn’t work, would have conducted these studies,” says Mr Holford,
“Why try to prevent dementia with a fairly low-dose multivitamin when there is already a good randomised trial (by Oxford University scientists) showing it is possible to slow down brain shrinkage and memory loss, the two hallmarks of Alzheimer’s, with high doses of B vitamins to those at risk,” he says.
“That’s about half the population over 65.”
Giving multivitamins to heart disease patients who are also on a range of powerful drugs is “equally ignorant”.
The informed approach is to use specific supplements known to benefit heart disease on patients who are deficient, Mr Holford says.
Other specialists, among them Dr Geert Verhelst, a Belgian medical doctor and phythotherapy (plant medicine) specialist, who visited SA last year to talk about diabetes and cholesterol control, say the use of inferior, synthetic vitamin products with low levels of essential micronutrients that are likely to be poorly absorbed, is another major study weakness.
Cape Town nutrition consultant Vanessa Ascencao says the research findings are “reductionist, closed-minded thinking”.
In an ideal world, we would get all nutrients needed from food, but people are eating food almost totally devoid of nutrients, and they are not exercising, Ms Asencao says. “That’s a fatal combination.”
Ms Asencao says 56% of women in South Africa are overweight, 33% of men are overweight, and 22% of children aged 2–5 years are obese. ” We have a rise in diabetes, heart disease, hypertension and cancer, many of which are preventable,” she says.
Vitamin and mineral supplements are not a “cure-all”.
They help to “bridge the gap between what our diets supply nutrient-wise, and what we need for optimal health”, she says.
In an editorial, the researchers said vitamin use is not justified as it can cause harm, and should be avoided.
Source: Business Day
Last Updated on 9 July 2014 by HPCSA Corporate Affairs