For the longest time, medicine has considered that vitamins and certain supplements are a “might help, can’t hurt” kind of proposition, the idea being that they might benefit people whose diet is poor, those with medical conditions, or for those looking for “super-health”.
Science is continuing to suggest that many vitamins and supplements not only do not have the benefits of the foods they are derived from, but may be toxic in their own right.
Let’s start with fish and fish oil/omega 3 supplements. There is good evidence which suggests mothers who eat fish at least once per week have babies who have higher tests on every measure of neurological development, including IQ, during the first 2 years of life. However, it is uncertain if this benefit extends to mothers who take Omega 3 supplements. Health Canada even has some information on the subject. http://www.hc-sc.gc.ca/fn-an/pubs/nutrition/omega3-eng.php
The topic gets more interesting with beta carotene (the most studied of a group of pigments in peppers, squashes, carrots etc.) which is converted into vitamin A in the human body. It is known that smokers who eat a diet rich in carotenoids, get less lung cancer than smokers who don’t eat much of these vegetables. 2 very large studies, the ATBC study in Finland in 1994 with 29,000 male smokers, taking 20 mg of beta-carotene over 6 years had more lung cancer. In the US, the CARETS study in 1996, a study of more than 18,000 male and female smokers and male asbestos workers, 30 mg beta-carotene supplements taken daily over 4 years was linked to a 28% higher risk of lung cancer and a 17% higher risk of death from all-cause in smokers taking placebo.
Both studies were stopped early due to the negative health outcomes of smokers taking beta-carotene. However, even in follow-up 4 years after exiting the study, the relative risk of lung cancer remained elevated in the smokers, with higher risk seen in female smokers.
The AREDS trial, which ended in 2001, showed that a specific formula of nutritional supplements containing 500 mg of vitamin C, 400 IUs of vitamin E, 50 mg beta-carotene, 2 mg of copper, and 80 mg of zinc slowed the risk of age-related macular degeneration in those who already had intermediate age-related macular degeneration and advanced age-related macular degeneration in only one eye. Interestingly, copper was added to the formula only to compensate for the propensity of zinc supplements to reduce copper levels in the body, giving more weight to the idea that taking supplementary vitamins might have unknown or little-known consequences.
A follow-up study called the AREDS2 study was published in 2013. This used a different formula, avoiding the use of beta-carotene in response to the evidence for a possible cancer-promoting effect as per the ATBC and CARETS studies above. This formula contained 500 mg vitamin C, 400 units vitamin E, 2 mg of copper again, 10 mg of lutein, 2 mg of zeaxanthin, and 80 mg of zinc. However, although the long-term effects and possible toxicities of lutein or zeaxanthin supplements are considered low, there is little data on long-term use.
Other studies have shown: vitamin E supplementation may increase all-cause mortality, high dose vitamin B6 is neurotoxic, green tea extract has caused liver toxicity requiring liver transplant, and that high dose calcium supplementation may cause vascular calcification in certain populations.
Last, but not least, an article in the January 20, 2022 issue of the Western Producer page 17 has a headline “Black Beans May Control Diabetes”. The article notes that the US Department of Agriculture has undertaken some research that shows one serving of black beans per day reduced insulin resistance in obese mice by 87%.
The article also notes that: “Scientists found that whole and cooked black beans, combined with a high fat diet, seemed to have the greatest impact on the mice in the study”.
“We also tested if supplementing the high-fat diet with individual components from black beans would have the same beneficial impacts on the obese mice. [We] didn’t find the same effects at all. It was only adding whole black beans which had the benefits.” Said Wallace Yokoyama, the USDA scientist who led the research.
The research in mice and men is clear: get your nutrients and vitamins from whole foods and not supplements whenever possible and exercise a modest amount of caution with vitamins and supplements.