Here's an article that shows how "scientific" studies are ineffective at proving some stuff. It can't say clearly if vitamin pills are effective or not to protect from illness/reduce risks of disease. Some studies say vitamin pills don't really have any positive or negative effect - but they're not sure... A few studies show that certain supplements could reduce the risks of certain health issues... but they're not absolutly sure. And some other studies say supplements could even be counterproductive and cause premature deaths - but they're not sure...
Some scientists are so incompetent that in one study they consider the vitamins from fruits and veggies to be the samething as vitamins from supplements !
Some studies have even shown a negative supplement effect. Analysis of data collected from some 70,000 postmenopausal nurses showed that over an 18-year period, those who consumed the most vitamin A from food or from supplements had the greatest risk of bone fractures.
I've read today that a 40 years-old man got seriously illed because of a Vitamin D overdose due to supplements. He had been taking those pills for like 2 years and then had to go to the hospital and it took 30 months for the vitamin D blood level to go back to normal. I've read this in a magazine, but here's some quotes from the article on Canadianliving.com which summarize vaguely a bunch of studies. And here's the link to the article.
Do Multivitamins Work ?
A typical survey-type, or "observational," study involved over 83,000 healthy American physicians who filled out questionnaires about supplement intake and dietary habits. Roughly 30 percent of the doctors regularly took vitamin supplements. After about six years, 1,000 or so had died of some form of cardiovascular disease. Were the deceased more or less likely to have been taking antioxidant supplements? As it turned out, there was no relationship between supplement intake and cardiovascular death. Of course, it is possible that physicians are more health conscious that others and pay more attention to their diet, so that they already had a sufficient intake of antioxidants.
low vitamin E intake during pregnancy has shown to increase the risk of childhood asthma, and women who take vitamin supplements during pregnancy appear to have a reduced risk of having infants who develop brain tumours.
How about studies of blood levels of vitamins? English researchers in one case found that among 20,000 people, those who had the highest level of vitamin C in the blood lived the longest. But was this because of the vitamin C, or was the vitamin C just acting as a marker for increased fruit and vegetable intake? Low levels of folic acid have been linked with breast cancer, heart disease and, most significantly, with giving birth to babies with neural tube defects. Still, such studies do not show cause and effect. You can never be certain that the observations are not due to some other dietary factor that happens to parallel folic acid in its presence. That's why intervention studies are the most meaningful. And in the case of folic acid in pregnant women, they certainly back up the observational studies. Supplementing the diet with 400 micrograms of folic acid daily significantly reduces the risk of neural tube defect.
Researchers in Oxford, England, enrolled over 20,000 adults with heart disease risk factors such as diabetes, high blood pressure or high blood cholesterol in a major study. Half received a daily supplement of 600 IU vitamin E, 250 milligrams vitamin C and 20 milligrams beta-carotene, while the others got a placebo. The supplements were certainly effective in increasing blood levels of vitamins, as tests clearly showed. But after five years there was absolutely no difference in any form of disease or in death rates between the groups. Maybe, though, these subjects already had the beginnings of cardiovascular disease that could not be reversed with the supplements and perhaps in a healthy group, supplements can prevent disease. Maybe …
To supplement or not?
As is evident, it is possible to support either side of the "to supplement or not" debate by looking at the scientific literature selectively. But what happens when scientists put all the data together in a meta-analysis? Sometimes they just add to the confusion! That's what Goran Bjelakovic and his colleagues at the University of Nis in Serbia and Montenegro apparently did when they examined the relationship between dietary antioxidants and the risk of gastrointestinal cancers. Free radicals can form in the gut and have been implicated in cancer, and fruits and vegetables have been shown to be protective, presumably because of the antioxidant content. So it certainly seemed reasonable to expect that antioxidant supplements should be beneficial in preventing cancer. Bjelakovic scoured the scientific literature and identified 14 rigorous placebo-controlled trials involving over 170,000 subjects. All the trials used oral supplements, although amounts varied, as did combinations. Vitamin C ranged from 120 to 2,000 milligrams a day, vitamin A from 1.5 to 15 milligrams, beta-carotene from 15 to 50 milligrams, selenium from 50 to 228 micrograms and vitamin E from 30 to 600 IU. The supplements were taken for years, either daily or every other day. Such doses are typical of what average consumers might take.
The results of the meta-analysis were unexpected. No protection against esophageal, gastric, colorectal, pancreatic or liver cancer was found. Selenium supplementation in a few of the trials did show some optimistic results. Now for the real shocker: in seven trials, all of high quality, involving over 130,000 subjects, the supplement takers had a higher rate of premature death! The researchers actually calculated that one premature death would be expected for every 100 people taking supplements. Little wonder that this work prompted sensational headlines like "Vitamins Only Take You Closer To Death." How do we interpret this surprising finding? The study was well executed and has statistical weight, but is it not possible that people who are ill are more likely to take supplements and that this explains the increased mortality? Or that supplements are most effective when taken for longer periods? And maybe they don't protect against cancer but have other benefits.
Supplements proved not helpful
Dr. Bjelakovic decided to look into this possibility by mounting a second meta-analysis. His team tracked hundreds of published trials on the health effects of beta-carotene, vitamin A, vitamin C, vitamin E and selenium supplements, and whittled these down to 68 that met the criteria for proper blinded, randomized, placebo-controlled trials. Some studies used low doses of supplements, some high; some lasted months, other many years. Some used single antioxidants, others used various combinations. But the strength of a anti-meta-analysis lies in pooling results from many studies, evening out variables and allowing an overall conclusion to emerge. As in his previous study, Bjelakovic found no benefit from the supplements, and as before, he noted an increase in mortality among supplement takers. The data appear to be robust. More than 230,000 participants were involved in the 68 trials, 21 of which focused on healthy subjects who were taking antioxidants to prevent disease.
Better to get our vitamins from food than from pills
While I do not think that vitamin supplements are killing us, there is mounting evidence that it is better to get our vitamins from food than from pills. It seems that there is an almost magical blend of antioxidants, minerals and probably unrecognized other ingredients in fruits, vegetables and whole grains that cannot be replicated in supplements. A 13-member expert panel of the National Institutes of Health in the United States concluded that there is insufficient evidence for or against recommending vitamin supplements except in three cases. Supplementation with B vitamins in women of child-bearing age is beneficial, as is supplementation with calcium and vitamin D in postmenopausal women to prevent bone fractures. And the progression of macular degeneration can be reduced with a mix of beta-carotene, zinc, vitamin C and vitamin E.