Mediterranean Diet and Fatigue among Community-Dwelling Postmenopausal Women

Abstract

Background Fatigue is one of the most common yet unexplained complaints in the primary care setting. Fatigue was related to an accelerated decline in mobility and cognitive function and the risk of hospitalization. Declined function and hospitalization were among the strongest predictors of transitioning from the community to residential care settings or nursing homes. Yet, fatigue in community-dwelling older adults has been underrecognized because of poor assessment and management. Physiologically, fatigue is the result of increased inflammation, increased oxidative stress, lack of essential nutrients, and altered metabolism. The Mediterranean diet has the benefits of decreasing inflammation, decreasing oxidative stress, providing multiple nutrients such as photochemical nutrients, and improving metabolism such as increasing insulin sensitivity and lowering LDL. Thus, a Mediterranean diet offers a possible avenue to lower fatigue, but the role of the Mediterranean diet pattern has yet to be examined in relation to fatigue, especially while leveraging well-powered cohorts with validated dietary measures. Besides, due to the low awareness of methods used to study nutrition, advanced and novel perspectives might offer additional tools for researchers in nursing science. One method that provides such a unique perspective is the isocaloric substitution method. Using this method, nursing researchers can look holistically at the relationship between fatigue and Mediterranean diets considering ecologically sensible tradeoffs rather than general associations. Objectives First, we reviewed definitions, measures, related factors, and consequences of fatigue in community-dwelling older adults. Second, we introduced the isocaloric substitution method to nursing research with both food and nutrient substitution as exemplars. Third, we 1) explored how the Mediterranean diet uniquely relates to fatigue and 2) examined how substituting Mediterranean diet recommended foods for Mediterranean diet not recommended foods relate to improvements in fatigue by using the isocaloric substitution method. Methods The study used an observational cross-sectional design with participants from two ancillary studies of the Women’s Health Initiative Long Life Study (WHILLS): Objective Physical Activity and Cardiovascular Disease Health (OPACH) Study and WHI-Food Intake (WHI-FI). The final analytical sample size is 4563. Four types of isocaloric substitution methods were demonstrated to examine the tradeoffs between different food choices/macronutrients. Finally, isocaloric substitution models were estimated to quantify the tradeoff in substituting foods recommended by the Mediterranean diet for foods not recommended by the Mediterranean diet (i.e., fish for red and processed meat, whole grain for non-whole grain, and whole fruit for fruit juices). Results The results showed alternate Mediterranean Diet (aMED) Quantile 5 (Q5, the highest adherence) was associated with 2.99 (95% CI: 0.88, 5.11), 4.01 (95% CI: 1.51, 6.53), and 2.47 (95% CI: 0.24, 4.70) point improvements in fatigue, energy, and weariness scores, respectively, compared with aMED Q1. Substituting fish for red and processed meat and whole for non-whole grains were associated with more favorable fatigue scores, whereas substituting whole fruit for juice was not. Conclusions 1) Fatigue-related factors mapped into biological, psychological, social, and behavioral factors. 2) Researchers in nursing can benefit from using isocaloric substitution methods. 3) The aMED was associated with improvements in fatigue. Substituting certain Mediterranean diet featured foods for non-Mediterranean diet foods was related to fatigue improvement.