Vitamins are organic compounds needed 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 from eating a well-balanced diet. However, some people may need more of certain vitamins: women need extra folic acid during pregnancy, people with little exposure to sunlight may benefit from Vitamin D, and people on a plant-based diet can benefit from Vitamin B12 supplementation.
Since the advent of agriculture, some 12,000 years ago, many of the diseases of modern civilization, such as diabetes, heart disease, obesity, are linked to our shift from mostly herbivorous, plant-based diets to the high energy, low nutrient diets of westernized societies.
Is it then possible that our current diets are deficient in nutrients and thus, necessitating the need for vitamin supplementation? In the UK National Diet and Nutrition Survey (NDNS), blood analysis revealed Vitamin C depletion in 5% of men, 3% of women; B12 deficiency in 2% of men and 4% of women; folate deficiency in 4% of men and 5% of women; Vitamin D deficiency in 14% of men and 15% of women. Except for Vitamin D, the levels of deficiency seen here are quite small.
So why do roughly half of the American adults take a multivitamin or supplement regularly? In fact, there is a $12 billion per year marketplace for vitamins and supplements.
A 2016 study published in the Journal of the American Medical Association, showed the use of multivitamins has decreased from 37% in 1999-2000 to 31% in 2011-2012. Meanwhile, intake of Vitamin D supplementation 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 journey looking at the data to see what the evidence shows and whether we should be recommending regular multivitamin supplementation.
Multivitamins and Cognition
A study in 1995 discussed the role of Vitamin C, E, and Beta Carotene in protecting the brain from oxidative damage and thus could be involved in slowing down or preventing cognitive decline.
The 2007 Physicians Health Study II, looked at the effects of Beta Carotene supplementation (50mg on alternate days) versus placebo on cognition. There were 4052 participants with an average follow-up of 18 years. The study showed a significant improvement in Beta Carotene group.
In 2012, a meta-analysis of 10 studies with 3200 people looking at multivitamins and cognition, found multivitamins to be effective only in improving immediate memory recall. However, no effect on delayed memory recall.
In 2013, a randomized, double-blind, placebo-controlled study examined multivitamin supplementation and cognitive function in 5947 male physicians age 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 (500mg daily) versus placebo, on prostate and total cancer. This was a randomized, double-blind, placebo-controlled study of 14,641 male physicians, age 50 or older. After 8 years of follow-up, neither Vitamin C nor E had any effect on prostate or total cancer risk.
Another study in 2012, 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 mortality. This was a randomized, double-blind, placebo-controlled study involving 14,641 male US physicians with a 14-year follow-up.
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. Overall, there was no association between multivitamin use and diabetes risk.
A review article in 2015 examined the available evidence around multivitamins and diabetes and concluded that no real recommendation can be made.
Multivitamins and Heart Disease
A 2015 study looking at 37,193 healthy women age forty and over also found no association between multivitamin use and risk of heart attack, stroke, or death. This was a prospective cohort study with an average follow-up of 16 years.
In 2016, a study looked at multivitamin’s role in cardiovascular disease among 18,530 male physicians age forty and older. Among participants who reported taking multivitamins for longer than 20 years, there was a 44% reduction in major cardiovascular events. However, the study authors JM Gaziano and HD Sesso reported in their disclosures that they receive grants from the Council for Responsible Nutrition Foundation: the “leading trade association for dietary supplement and function food industry.”
Multivitamins and Mortality
In the prospective Multiethnic Cohort study involving 182,099 participants, there was no clear association between all-cause mortality and multivitamin intake despite an 11-year follow-up.
A meta-analysis from 2013 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 reviewing all these studies, what conclusions can we draw.? First, multivitamins are not a substitute for a healthy, whole foods plant-based diet, in any way. The evidence does not support taking multivitamins as insurance against poor eating habits or not exercising. Consider Vitamin D supplementation given a large number of Americans noted to be deficient. Vitamin B12 is necessary for people following a strictly vegan diet. Of course, folate is incredibly important for pregnancy.
The supplement industry has created all sorts of multivitamins with clever marketing. For families on limited incomes, spending money on fruits and vegetables will have a far greater return on investment than supplements.
At the end of the day, the same time tested, evidence-based advice, still is the best route to follow. Eat a healthy diet full of fruits, vegetables, legumes, nuts, seeds, and whole grains; limit your salt, red and processed meats, and sugar-sweetened beverages; make exercise a part of your daily habit; practice gratitude and meditation; get at least 7 hours of sleep.