Background:
This important public health question was identified by the U.S. Departments of Agriculture (USDA) and Health and Human Services (HHS) to be examined by the 2020 Dietary Guidelines Advisory Committee.
The 2020 Dietary Guidelines Advisory Committee, Dietary Patterns Subcommittee conducted a systematic review to answer this question with support from the Nutrition Evidence Systematic Review (NESR) team.
The goal of this systematic review was to examine the following question: What is the relationship between dietary patterns consumed and sarcopenia?
Conclusion statements and grades:
Dietary patterns
Insufficient evidence is available to determine the relationship between dietary patterns and sarcopenia in older adults. (Grade: Grade not assignable)
Diets based on macronutrient distribution
Insufficient evidence was available to determine the relationship between diets based on macronutrient distribution and sarcopenia. (Grade: Grade not assignable)
Methods:
Two literature searches were conducted using 3 databases (PubMed, Cochrane, Embase) to identify articles that evaluated the intervention or exposure of dietary patterns consumed and the outcomes of sarcopenia. A manual search was conducted to identify articles that may not have been included in the electronic databases searched. Articles were screened by two NESR analysts independently for inclusion based on pre-determined criteria.
Data extraction and risk of bias assessment were conducted for each included study, and both were checked for accuracy. The Committee qualitatively synthesized the body of evidence to inform development of a conclusion statement(s), and graded the strength of evidence using pre-established criteria for risk of bias, consistency, directness, precision, and generalizability.
Summary of the evidence:
This systematic review includes 4 prospective cohort studies that examined the relationship between dietary patterns and sarcopenia, 2 of which also examined diets based on macronutrient distribution, that met inclusion criteria, and were published between January 2000 and October 2019.
Two of the studies reported macronutrient distributions in which the percent of energy from fat was higher than the AMDR.
Dietary patterns were defined as the quantities, proportions, variety, or combination of different foods, drinks, and nutrients (when available) in diets, and the frequency with which they are habitually consumed.
Diets based on macronutrient distribution were examined when at least one macronutrient proportion was outside of the acceptable macronutrient distribution range (AMDR) for carbohydrate, fat, and/or protein. When describing and categorizing studies included in this review, the Committee did not label the diets examined as “low” or “high,” because no universally accepted, standard definition is currently available, for example, for “low-carbohydrate” or “high-fat” diets. Instead, the Committee focused on whether, and the extent to which, the proportions of the macronutrients were below or above the AMDR
The studies were inconsistent, both in terms of which dietary patterns or macronutrient distributions that were examined, how dietary intake was assessed, assessment of sarcopenia, and results reported regarding the association between dietary patterns and risk of sarcopenia. In addition, the studies had relatively small sample sizes with few cases of sarcopenia.
The body of evidence had several risks of bias, including lack of adjustment for all potential confounders, and assessment of diet only once at baseline, and lack of accounting for possible changes in dietary intake that may have occurred over follow-up.
The studies were direct and generalizable, in that that the intervention, comparators, and outcomes of interest in the included studies are directly related to the systematic review question, and are applicable to the U.S. population. However, study participants may have been healthier than the average older adult.