Results from a randomized preclinical trial suggests that adopting a Mediterranean diet may ease psychological stress and promote healthy aging. The findings of this study were published in Neurobiology of Stress.
Researchers from Wake Forest School of Medicine randomized adult female (N=38) macaques aged 8.2 to 10.4 years to receive a Western (n=21) or Mediterranean (n=17) diet for 31 months (~9 human years) following a 7-month standard diet baseline observational phase. The monkeys were assessed for behavior, blood pressure, heart rate, cortisol levels, adrenocorticotropin (ACTH), and by a stress test.
Both diets were balanced for protein, fat, and carbohydrate macronutrients. The Western diet contained protein and fats derived primarily from animal products, was high in saturated fats and sodium, and low in monosaturated and n-3 fatty acids. The Mediterranean diet protein and fats were derived primarily from plants, lean fish, and dairy, was high in monounsaturated fatty acids, complex carbohydrates, and fiber, and low in sodium and refined sugars.
At 29 months, a significant interaction between diet and heart rate fluctuation throughout the day (F[23,766], 2.5; P =.0001) was observed. Animals on a Mediterranean diet had elevated heart rates at mealtimes which returned to normal between feedings (adjusted mean difference, 17 bpm; P <.0001). The monkeys on the Western diet had less pronounced peaks during mealtimes and more sluggish recoveries (adjusted mean difference, 3 bpm; P =.264).
Animals on the Mediterranean diet exhibited 2.7% more frequent low frequency (0.01-0.2 Hz) heart beats (mean difference, 1.54; F[1,34], 4.322; P =.045) and less frequent very low frequency (<0.01 Hz) heart beats (F[1,34], 3.453; P =.072) compared with the Western diet group.
The overall age-related changes of heart rate patterns were delayed among animals fed the Mediterranean diet, in which at 12 months the Western group exhibited a 28.8% higher proportion of very low frequency heart beats (mean difference, 3.92; P £.004) and a 4.9% less frequent low frequency heart beats (mean difference, 2.86; P £.004). No difference was observed at 29 months.
Similarly, the cortisol response over time was delayed among the Mediterranean diet group (F[2,68], 4.84; P =.01), exhibiting a comparatively reduced response to acute stress of 15.6%. The investigators observed the Mediterranean diet reduced the adrenal cortisol response to ACTH by 18% (adjusted mean difference, 119.3; F[1,33], 9.0; P =.005).
At study conclusion a significantly different response to the stress test was observed for each treatment group (F[24,739], 1.87; P =.007). Monkeys on the Mediterranean diet had a greater increase of heart rate from baseline (60 bpm) compared with Western diet animals (38 bpm). At 240 minutes following the stress test, monkeys on the Mediterranean treatment had decreased heart rates by 23 bpm but the monkeys on the Western diet did not recover (+1.4 bpm).
This study was limited by only including female animals, it remains unclear how male macaques would respond.
These data indicated that a Mediterranean-like diet successfully modified the physiological stress responses during aging and may have important clinical implications for human health.
According to the study authors, “Our findings suggest that population-wide adoption of a Mediterranean-like diet pattern may provide a cost-effective intervention on psychological stress and promote healthy aging with the potential for widespread efficacy.”
Shively CA, Appt SE, Chen H, et al. Mediterranean diet, stress resilience, and aging in nonhuman primates. Neurobiol Stress. 2020;13:100254. doi: 10.1016/j.ynstr.2020.100254