Interest in health and wellness is higher than ever among Americans; and that interest translates into interest in boutique fitness, alternative medicine, and eating patterns perceived to be more healthful. Dietary supplements also fit into the new wellness profile of Americans, with “improving” or “maintaining” health as the most commonly reported reasons for taking dietary supplements.
Data collected in the nationally representative National Health and Nutrition Examination Survey (NHANES) asked Americans whether or not they take any dietary supplement products. Since 1999, 52 percent of Americans have reported using dietary supplements, though levels of use of specific products have shifted. An analysis of the NHANES data completed in 2016 and published in the Journal of the American Medical Association found that use of multivitamin/mineral supplements decreased between 1999 and 2012 while use of vitamin D and fish oil supplements increased most dramatically. Indeed, in 1999, 5.1 percent of Americans reported using vitamin D and 1.3 percent of Americans reported using fish oil supplements. By 2012, 19 percent of Americans reported using vitamin D and 12 percent reported use of fish oil supplements.1
Research has been mixed on the effects of dietary supplements, but it is noteworthy that only 23% of dietary supplement use is under the supervision, recommendation, or direction of a healthcare provider.2 Other analysis from the NHANES survey found that “supplement users are more likely to report very good or excellent health, have health insurance, use alcohol moderately, eschew cigarette smoking, and exercise more frequently than nonusers.”1 Whether or not dietary supplements are responsible for the better health of their users, adherence to supplements does play a role in maintaining health and other health-conscious behaviors. Healthcare providers can play a major role in guiding safe and effective use of dietary supplements through reminders, collaboration, and improved education on nutrition, depending on the needs and interests of individual patients and their conditions.
While it is tempting to associate adherence to pharmacological drugs with adherence to dietary supplements, they are very different products and can be associated with different behavioral patterns. Adherence to pharmacological drugs can vary immensely as well, depending on the drug and the condition, but tend to be lower than one might expect. For example, even clinical trials in which patients receive frequent attention and reminders about taking their medications, average adherence ranges only from 43-78 percent among patients receiving treatment for chronic conditions.3 Adherence rates may be higher for acute or serious conditions like HIV or organ transplant, for example. The research on adherence to dietary supplement regimen is quite paltry, but one might assume that adherence rates are closer to those for drugs used for chronic, rather than acute conditions.4
Individuals who are conscious of their health and diet demonstrate better adherence to dietary supplements. For example, a recent Finnish study found that people who follow a vegan diet are more adherent to their supplement regimen. The cross-sectional study found that 91 percent of vegans included in the study used dietary supplements, compared to 78 percent of non-vegetarians.5 Both rates of supplement use are very high, but reconfirm the finding that health-conscious people are likelier to use supplements regularly. Among diabetes patients, survey research has shown that patients who were younger and had higher education and career achievement were likelier to use supplements.6
For people who are less health conscious, live in more resource-poor settings, or have less health literacy or education about supplements, reminders and support can be crucial to adherence. A long-term, placebo controlled trial of over 5,000 women of reproductive age was conducted in Vietnam in which women received preconception supplements and, if they became pregnant, they received prenatal supplements. Over the course of the study, health workers visited participant women every two weeks. Overall adherence to the supplement regimen ranged from 78-82 percent, but lower adherence was observed in individuals who were of minority ethnicity, lived in more rural areas, and were of lower socioeconomic status. Increased contact with health workers was associated with better adherence.
In an ideal world, all supplement users would be completely compliant with their supplement plans and would check in regularly with a healthcare provider about their health behaviors. Unfortunately a variety of factors contribute to poor adherence. Healthcare providers can identify those patients who are at risk of low adherence, such as lower socioeconomic status, and tailor behavioral interventions like text message or email check-ins to support their supplement use. They may also identify those patients who are likely to be compliant and encourage them to support their diet with nutritional supplements, such as patients who demonstrate a high level of interest in their health status.