Already healthy people take supplements while those most in need of them don't, researchers conclude

Researchers Christiane Schroeter, California Polytechnic State University, San Luis Obispo and Sven Anders, University of Alberta, Canada, wrote a paper titled “The Impact of Nutritional Supplement Choices on Diet Behavior and Obesity Outcomes”​ that was accepted for presentation at the meeting of the Allied Social Sciences Association’s annual meeting in San Francisco in early January. The paper uses data gleaned from the data from the National Health and Nutrition Examination Survey (NHANES) to estimate the impact of nutritional supplements intake on respondent’s body weight outcomes, while controlling for diet quality based on individual Healthy Eating Index (HEI-2010) scores.

The authors said they used a Propensity Matching Score (PSM) statistical analysis technique to correct for potential selection bias and closed-loop nature of the self-reported behavior and diet-health outcomes.

Schroeter and Anders’ paper begins with a cautionary note on dietary supplementation as a health-promoting strategy. “Little is known about the role and impact of nutritional supplements as an input into consumer diet quality and health status. Furthermore, existing evidence is mixed with regard to the economic impact of nutritional supplements and how the intake thereof could influence a person’s dietary behavior. The 2010 DGAs state that nutrients should come primarily from food, and recommends that specific supplementation might be needed for at-risk populations, such as postpartum women, as well as older Americans,”​ they wrote. They went on to note that the 2015 Dietary Guidelines Advisory Committee recommended that nutrient needs should be met by food alone.

Cart first, or horse?​

Through that filter, the pair said that their parsing of the NHANES data led them to conclude that dietary supplementation was one behavior chosen by people most likely to already be doing most things right in terms of choosing a high quality diet with enough fruits and vegetables, getting enough exercise and maintaining a healthy weight.

“Our study shows that nutritional supplements intake decisions are affected by diet quality, health, demographic and lifestyle factors. This study also suggests a possible link between diet-health behavior (supplement intake) and obesity as measured by BMI. . . . individuals of normal weight (individuals with a lower BMI) and individuals who consume more fruits were found to hedge against health risks by frequently consuming nutritional supplements,” ​they wrote.​

The pair’s conclusions raise the question of whether any positive influence of the use of dietary supplements could be more appropriately attributed to the higher demographic status of the typical supplement user. These people are more likely to come from situations that auger well in general for their health status. 

“The results of the study suggest that several health indicators, demographics, and lifestyle variables significantly affect the selection into the treatment group of nutritional supplements takers. Nutritional supplements intake is positively associated with a significantly lower BMI when all other observable characteristics between supplement takers an non-takers are controlled for. We also found that supplement takers are likely to be white, highly educated, of higher household income, non-smokers and of overall higher health status. Nutritional supplements consumers differ from non-takers in terms of diet quality, “ ​Schroeter and Anders concluded.

But the pair said that lower demographic populations, those who have poor diets that are most likely to be deficient in essential nutrients and therefore the consumers with the biggest demonstrable need for dietary supplements, are less likely to be taking them.

“These results suggest that at-risk populations who need to supplement their diets with [dietary supplements] are not those currently taking them. . . one way to encourage consumption of nutritional supplements among at-risk groups would be to establish a health policy on consumption, especially with regards to fruits and vegetables and nutritional supplements, in order to target specific at-risk populations,”​ they wrote.

Source:​
“The Impact of Nutritional Supplement Choices on Diet Behavior and Obesity Outcomes”
Allied Social Sciences Association Annual Meeting, San Francisco CA Jan. 3-5 2016
Authors: Schroeter, Christiane; Anders, Sven.