Will a Multivitamin Reduce the Risk of Deficiency?

By: Julia Bird, Senior Associate Scientist, Human Nutrition and Health, dsm-firmenich

Multivitamins may help decrease the risk of vitamin deficiency.

One of the reasons why I chose to study nutrition science was so that I could understand a subject that would have a direct impact on my own life. Having a healthy diet is important to me, and it has been fascinating to learn about what goes into a healthy diet and the reasoning behind the dietary recommendations. An important lesson for me has been that there are many dietary patterns associated with good health. Even so, it seems like everyone has an opinion about nutrition.

One controversial aspect of nutrition is whether dietary supplements are worthwhile. On the one hand, scientists and the media have published critical commentary over the inappropriate use of dietary supplements. On the other, there are many people who suffer from malnutrition worldwide. Even in high-income countries such as the U.S., comprehensive studies report that the diets of many people are poor and dietary supplements can help people attain adequacy. For example, less than 10% of U.S. adults meet fruit and vegetable recommendations and 45% had a diet considered to be “poor” when compared to dietary guidelines¹. Intakes of calcium, magnesium, and vitamins D, A, C, E, and K were low for a “considerable percentage” of U.S. adults, and supplements can help make up the micronutrient gap^.2 Adding to the confusion, more than half of adults use dietary supplements³, and the dietary supplement industry is large and still expanding. I realized that there were several questions that I wanted to ask that did not seem to be answered in the current literature: 

• What is the risk that someone has any nutrient deficiency?
• Who is at risk of any deficiency?
• Does dietary supplementation reduce the risk of deficiency?
• How do dietary supplements affect deficiency risk in people with a poor diet compared to those with a largely adequate diet?

The Centers of Disease Control and Prevention in the U.S. has provided an excellent resource for nutrition researchers by surveying the health and nutritional status of the population for many years with the National Health and Nutrition Examination Survey (NHANES), the data from which is publicly available. Using the survey years 2003-2006, which contains the broadest range of biochemical markers of nutrient status, my colleagues and I drew up a research plan to answer these questions, then set about crunching the numbers.

We found that almost one in three people living in the U.S. are at risk of deficiency, and the most common deficiencies are for vitamins B6, B12, C and D. When looking at age and gender groups, women aged 19-50 years old are at greatest risk (41%), as are people of lower socio-economic status, non-Hispanic Blacks, and underweight or obese adults. We found that using a dietary supplement reduced risk of deficiency, particularly multivitamins that contain a wide range of different vitamins and minerals. Specifically, 44% of people not taking a dietary supplement were at risk of deficiency, compared to 16% taking a multivitamin, or 40% taking any other dietary supplement. When we looked at diet, it’s clear that meeting the dietary recommendations helps to reduce risk of deficiency. People who met the EAR for all the vitamins and minerals in our analysis had a risk of deficiency of only 16%, compared to people with the poorest diets, who had a risk of deficiency of 58%. Also here, dietary supplements could reduce risk of deficiency. Using a multivitamin could reduce risk of deficiency from 70% to 30% in people with the poorest diets, when compared to people not taking a dietary supplement. In people with adequate diets, risk of deficiency was reduced from 28% to 5% when comparing dietary non-users with multivitamin users. It seems that the risk of any deficiency is quite common in the U.S., and particular groups in the U.S. are at greater risk of deficiency. Having a good diet helps reduce risk of deficiency, as does taking a multivitamin, and in combination, the risk of deficiency is the lowest.