In a recent study published in European Journal of Clinical Nutrition, researchers report that protein intake from plant sources may improve sleep quality. Conversely, increased intake of animal protein worsens sleep quality.
Study: Protein intake and its association with sleep quality: results from 3 prospective cohort studies. Image credit: sivaleela . v / Shutterstock.com
How does diet affect sleep?
High-quality sleep at night is essential for a healthy life. Changes in metabolic rate, blood circulation, hormone secretion, and immune regulatory functions occur during sleep, which are necessary to maintain homeostasis in the body.
An adult needs seven to eight hours of sleep daily to reduce the risk of chronic disease and mortality. However, a significant decrease in sleep duration in the general population has been reported in recent decades, with many individuals reporting difficulty initiating and maintaining sleep and waking multiple times during the night and early morning. The prevalence of both disorders and sleep disorders has also increased, which can lead to daytime functional impairment and an increased incidence of many chronic diseases.
Poor diet quality, characterized by a higher intake of saturated fat, refined carbohydrates and processed foods, can negatively affect sleep quality and duration. Studies have produced mixed results regarding the impact of protein intake on sleep quality, which could be due to different ratios of specific amino acids in different protein sources.
About the study
In the current study, scientists are investigating the effect of total protein intake and intake of different protein sources on sleep quality. For this purpose, dietary intake data and measures of sleep quality were collected from three ongoing prospective cohort studies among United States health professionals, including the Nurses’ Health Study (NHS), NHS2, and the Health Professionals Follow-up Study (HPFS).
In these cohort studies, participants’ dietary intake was assessed every four years using validated food frequency questionnaires. Sleep quality was assessed using the original or modified version of the Pittsburgh Sleep Quality Index.
Data obtained from a total of 32,212 and 51,126 women from the NHS and NHS2 studies, respectively, as well as 14,796 men from the HPFS, were analyzed to determine the association between protein intake and sleep quality.
Important observations
In all three cohorts, participants with the highest protein intake had higher body mass index (BMI) values and a greater prevalence of pre-existing health conditions than those with the lowest protein intake. More than 65% of study participants reported seven to eight hours of sleep each night.
Regular use of sleep medications was reported by 5-6% of study participants. The presence of sleep apnea was more common among participants with the highest protein intake, with the prevalence of this condition higher in men than in women.
Study participants with better sleep quality were associated with slightly lower BMI values, higher physical activity, better diet quality, higher alcohol consumption and fewer pre-existing health conditions. In comparison, those who reported higher consumption of animal protein were more likely to have a higher BMI, lower physical activity and more pre-existing health conditions. These factors were more favorable among participants with a higher intake of plant protein.
Association between protein intake and sleep quality
The current study found no relationship between total protein intake and sleep quality. Although total animal protein intake was not associated with sleep quality, higher plant protein intake was associated with better sleep quality.
Among different animal protein sources, dairy protein intake had divergent associations. While no association was observed between dairy protein intake and sleep quality in the NHS and HPFS cohorts, a positional association was observed in the NHS2 cohort.
Among different meat sources, intake of processed and unprocessed red meat and poultry was associated with worse sleep quality. This type of association was not observed for fish intake.
conclusions
The current study found no relationship between total protein intake and sleep quality between men and women. However, a positive correlation was observed between plant protein intake and sleep quality. After adjusting for potential confounders, this association was less pronounced in men and weak in women.
Protein-rich plant sources are often rich in carbohydrates and fiber, which have been shown to improve sleep quality. In comparison, processed red meat and poultry, which are higher in fat, may also lead to poorer sleep quality, as observed in the current study.
Journal Reference:
- Wirth, J., Lin, K., Brennan, L., et al. (2024). Protein intake and its relationship to sleep quality: results from 3 prospective cohort studies. European Journal of Clinical Nutrition. doi:10.1038/s41430-024-01414-y.
