Vitamins are organic compounds required for normal growth and development. So far we have identified four fat-soluble vitamins (A, D, E, K) and nine water-soluble vitamins (B1, B2, B3, B5, B6, B7, B9, B12 and C). All vitamins can be obtained by eating a balanced diet. However, some people may need more of certain vitamins: women need extra folic acid during pregnancy, those with little exposure to sunlight can benefit from vitamin D, and those on a plant-based diet can benefit from vitamin B12 supplementation.
Since the emergence of agriculture some 12,000 years ago, many of the diseases of modern civilization, such as diabetes, heart disease, and obesity, have been linked to our shift from predominantly herbivorous, plant-based diets to the high-energy and low-nutrient diets of Westernized societies. .
So is it possible that our current diet is nutrient deficient and therefore necessitates the need for vitamin supplementation? In the UK National Diet and Nutrition Survey (NDNS), blood analysis showed vitamin C depletion in 5% of men, 3% of women; B12 deficiency in 2% of men and 4% of women; folic acid deficiency in 4% of men and 5% of women; Vitamin D deficiency in 14% of men and 15% of women. Aside from vitamin D, the deficiency levels observed here are quite small.
So why do about half of American adults take a multivitamin or supplement on a regular basis? In fact, there is a $ 12 billion a year market for vitamins and supplements.
A 2016 study published in the Journal of the American Medical Association found that multivitamin use decreased from 37% in 1999-2000 to 31% in 2011-2012. Meanwhile, vitamin D supplementation intake has increased from 5.1% to 19% from 1999-2000 to 2011-2012. Fish oil supplementation has also increased from 1.3% to 12%.
Let’s take a look at the data to see what the evidence shows and whether we should recommend regular multivitamin supplementation.
Multivitamins and Cognition
A 1995 study discussed the role of vitamins C, E and beta-carotene in protecting the brain from oxidative damage and thus may be involved in slowing or preventing cognitive decline.
The 2007 Physicians Health Study II looked at the effects of beta-carotene supplementation (50 mg every other day) versus placebo on cognition. There were 4052 participants with an average follow-up of 18 years. The study showed significant improvement in the beta-carotene group.
In 2012, a meta-analysis of 10 studies involving 3,200 people looking at multivitamins and cognition found that multivitamins were only effective in improving immediate memory recovery. No effect on delayed memory recall.
In 2013, a randomized, double-blind, placebo-controlled study examined multivitamin supplementation and cognitive function in 5,947 male physicians aged 65 and older. After 12 years of follow-up, there was no significant difference between the multivitamin group and the placebo group.
Multivitamins and Cancer
In 2009, another study was published looking at the effects of vitamin E (400 IU every other day) and vitamin C (500 mg per day) versus placebo, on prostate cancer and total cancer. This was a randomized, double-blind, placebo-controlled study of 14,641 male physicians aged 50 or older. After 8 years of follow-up, neither vitamin C nor E had any effect on prostate cancer risk or overall cancer risk.
Another 2012 study, looking at the data from Physicians Health Study II, showed a small but statistically significant decrease in the risk of total cancers by 8% in men. However, there was no difference in the risk of cancer death. This was a randomized, double-blind, placebo-controlled study of 14,641 male US physicians with a follow-up of 14 years.
Multivitamins and Diabetes
A 2011 study looked at the relationship between multivitamin use and diabetes. The study looked at 232,007 participants from the National Institutes of Health-American Association of Retired Persons Diet and Health Study. In general, there was no association between the use of multivitamins and the risk of diabetes.
A 2015 review article examined the available evidence surrounding multivitamins and diabetes and concluded that no real recommendation can be made.
Multivitamins and heart disease
A 2015 study of 37,193 healthy women aged 40 and older also found no association between multivitamin use and risk of heart attack, stroke, or death. This was a prospective cohort study with a mean follow-up of 16 years.
In 2016, a study looked at the role of multivitamin in cardiovascular disease among 18,530 male physicians aged 40 and older. Among participants who reported taking multivitamins for more than 20 years, there was a 44% reduction in serious cardiovascular events. However, study authors JM Gaziano and HD Sesso reported in their disclosures that they receive grants from the Council for Responsible Nutrition Foundation, “the leading industry association for nutritional supplements and functional food industry.”
Multivitamins and Mortality
In the prospective Multiethnic Cohort study with 182,099 participants, despite an 11-year follow-up, there was no clear association between all-cause mortality and multivitamin intake.
A 2013 meta-analysis looked at 21 studies, 91,074 people with an average follow-up of 43 months, found no effect of multivitamins on all-cause mortality.
After looking at all these studies, what conclusions can we draw? First, multivitamins are in no way a substitute for a healthy, plant-based diet based on whole foods. The evidence does not support the use of multivitamins as insurance against poor eating habits or not exercising. Consider vitamin D supplementation, given a large number of Americans who are found to be deficient. Vitamin B12 is necessary for people on a strict vegan diet. Folate, of course, is incredibly important to pregnancy.
The supplement industry has created all kinds of multivitamins with clever marketing. For families with limited income, spending money on fruits and vegetables will yield a much greater return on investment than supplements.
Ultimately, the same tried-and-true, evidence-based advice is still the best course of action. Eat a healthy diet full of fruits, vegetables, legumes, nuts, seeds and whole grains; limit your salt, red and processed meats, and sugar-sweetened drinks; make exercise part of your daily routine; practice gratitude and meditation; sleep at least 7 hours.