Branched-Chain Amino Acids in relation to food preferences and insulin resistance in obese subjects consuming walnuts: A cross-over, randomized, double-blind, placebo-controlled inpatient physiology study

Abstract

Background&aims: To assess whether the concentrations of circulating Branched-Chain Amino Acids (BCAAs) change after walnut consumption and, whether these changes are associated with alterations in markers of insulin resistance and food preferences.

Methods: In a crossover, randomized, double-blind, placebo-controlled study, ten subjects participated in two 5-day inpatient study admissions, during which they had a smoothie containing 48 g walnuts or a macronutrient-matched placebo smoothie without nuts every morning. Between the two phases there was a 1-month washout period.

Results: Fasting valine and isoleucine levels were reduced (p = .047 and p < .001) and beta-hydroxybutyrate levels were increased after 5-days of walnut consumption compared to placebo (p = .023). Fasting valine and isoleucine correlated with HOMA-IR while on walnut (r = 0.709, p = .032 and r = 0.679, p = .044). The postprandial area under the curve (AUC) of leucine in response to the smoothie consumption on day 5 was higher after walnut vs placebo (p = .023) and correlated negatively with the percentage of Kcal from carbohydrate and protein consumed during an ad libitum buffet meal consumed the same day for lunch (r = -0.661, p = .037; r = -0.628, p = .05, respectively).

Conclusion: The fasting and postabsorptive profiles of BCAAs are differentially affected by walnut consumption. The reduction in fasting valine and isoleucine may contribute to the longer-term benefits of walnuts on insulin resistance, cardiovascular risk and mortality, whereas the increase in postabsorptive profiles with walnuts may influence food preference. TRIAL REGISTRATION CLINICALTRIALS.GOV: Number: NCT02673281, Website: https://ichgcp.net/clinical-trials-registry/NCT02673281.

Keywords: Appetite; BCAA; Functional foods; Leucine; Mediterranean diet; Superfoods; Walnuts.

Conflict of interest statement

Conflict of interests All other authors have no conflicts of interest to disclose.

Copyright © 2021 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.

Figures

Figure 1.

Correlation plots of HOMA-IR with fasting levels of valine (A) and isoleucine (B) after 5 days of walnut consumption. Circulating levels of BCAA (C) and leucine (D) after smoothie intake (placebo or walnut) on the 5th day of treatment. Correlation plots of AUCs of leucine after walnut smoothie intake with percentage of Kcal from carbohydrate (E) and protein (F) in an ad libitum lunch the same day (5th day of treatment). Means0020± standard error (SE) of the mean are demonstrated for (C) and (D); r = correlation coefficient. *, ** indicate p<.05 and <.01 respectively in Fisher’s LSD test for walnut vs placebo for each timepoint in C and D.