New Study Suggests Walnuts may Fend off Stress-related Negative Impacts in University Students

Being a university student is an especially stressful time in life. In fact, eight in 10 university students report experiencing frequent bouts of stress, and 61% of university students seek counseling for anxiety, depression or other needs.¹

California Walnuts

A novel study published in Nutrients from researchers at the University of South Australia found that eating two ounces of walnuts a day for 16 weeks in undergraduate university students improved self-reported mental health indicators, had a protective effect against some of the negative impacts of academic stress, and aided self-reported sleep quality in the longer term.²

"We've always known walnuts to be a health-promoting food, but because of the design and length of this study, the findings really paint a picture of how a simple food like walnuts can help combat stress," explains Mauritz F. Herselman, a PhD student who worked on this study.

In this randomized clinical trial, co-funded by the University of South Australia and the California Walnut Commission, the participant group who ate walnuts also experienced increased metabolic markers linked with protection against stress. Additionally, in females only, eating walnuts may have countered the negative effects of academic stress on the diversity of the gut bacteria.

"University students are a unique population of people who transition into their adulthood while completing university degrees which can be challenging and stressful. The pressure to complete and find attractive jobs is high and can impact on students' mental and physical health and overall well-being. Thus, managing academic stress is important, and various strategies can be adopted by students to get through their university journeys. Dietary intervention is one of such strategies that can boost students' brain health but is often neglected by students," states Larisa Bobrovskaya, Associate Professor, Clinical and Health Sciences at the University of South Australia and lead researcher on the study.

Study Overview: University students aged 18 to 35 were randomly selected to be in either a treatment group or a control group for 16 weeks of this study.The treatment group was provided with pre-portioned walnuts and asked to consume one portion (approximately 56 grams) per day. The control group was asked to refrain from consuming any type of nut or fatty fish for the same duration. Participants provided blood and saliva samples and completed a series of self-reported questionnaires on mental health, mood, general well-being, and sleep habits three times during the study. A subgroup of participants also provided fecal samples at each clinical visit. A total of 60 participants, 30 in each group, completed the study.

Promising Results for Walnuts: The group eating walnuts seemed to experience a protective effect against some of the negative impacts of academic stress on mental health compared to the control group. A summary of the study findings can be found below:

• Daily consumption of walnuts prevented significant changes in mental health-related scores and scores of stress and depression. Walnuts may alleviate the negative effects of academic stress on the mental health in university students.

• Daily consumption of walnuts increased total protein and albumin levels, thus may protect against the negative effects of academic stress on metabolic biomarkers.

• While academic stress did not change stress biomarkers such as cortisol and α-amylase, daily walnut consumption decreased α-amylase levels, further suggesting that walnuts may protect against the effects of stress.

• Academic stress was associated with lower gut microbial diversity in females. But, daily walnut consumption may alleviate the negative effects of academic stress on the diversity of the gut microbiota in females.

• Walnut consumption may improve sleep in the longer term.

Other emerging, but consistent evidence from observational and clinical research suggests eating walnuts is associated with:^3-5

• Lower prevalence and frequency of depressive symptoms in U.S. adults

• Improved mood in otherwise healthy young adults and

• A greater likelihood of achieving overall health at an older age, with mental health as a domain of healthy aging

In fact, walnuts have a unique matrix of bioactive nutrients and phytochemicals that may underlie the beneficial effects on mental health seen in these studies.⁶

"While more supporting research is needed, evidence is becoming clear that consuming walnuts as a healthy eating pattern may have positive effects on cognition and mental health, potentially owing to their abundance in omega-3 ALA content^*. Furthermore, research has shown that increasing dietary tryptophan, which the brain uses to make serotonin (a natural mood stabilizer), results in reduced symptoms of anxiety and depression.⁷ Thus, the presence of tryptophan in walnuts may have also contributed to these findings," explains Bobrovskaya.

Commenting on the study outcomes, Celebrity Nutritionist Ryan Fernando states, "The prevalence of stress among students in India cannot go unnoticed, and it may cause mental health issues, among other things. I recommend adding walnuts to daily eating patterns, a versatile, simple, and accessible dietary change to promote brain health and overall well-being in university-aged students."

These results are encouraging and support previous results found in similar populations, but there are limitations to the current study. Mainly, participants were not blinded to the walnut treatment. Additionally, the results could have been further influenced by the 2020 COVID-19 pandemic and stay-at-home orders, as clinical visits were disrupted during this period.

Further work is needed to improve the understanding of the complex pathways through which eating patterns that include walnuts, can influence the brain or affect mental health.

References:

1. Stress in college. The American Institute of Stress website. www.stress.org/college-students. Accessed November 30, 2022.

2. Herselman MF, et al. The effects of walnuts and academic stress on mental health, general well-being and the gut microbiota in a sample of university students: A randomised clinical trial. Nutrients. 2022;14:4776.

3. Freitas-Simoes TM, Wagner M, Samieri C, Sala-Vila A, Grodstein, F. Consumption of nuts at midlife and healthy aging in women. Journal of Aging Research. 2020;5651737.

4. Arab L, Guo R, Elashoff, D. Lower depression scores among walnut consumers in NHANES. Nutrients. 2019;11(2):275.

5. Pribis P. Effects of walnut consumption on mood in young adults - a randomized controlled trial. Nutrients. 2016;8(11):668.

6. Nutrients in one ounce of walnuts. California Walnut Commission website. walnuts.wpenginepowered.com/wp-content/uploads/2020/05/Nutrients-In-1OZ-Handout_Update.pdf. Accessed November 30, 2022.

7. Lindseth G, et al. The Effects of Dietary Tryptophan on Affective Disorders. Archives of Psychiatric Nursing. 2015; 29(2): 102-107.

*Walnuts are the only nut with an excellent source of the omega-3 alpha-linolenic acid, or ALA, per serving (2.5 g ALA/oz).

Peer-reviewed paper:

Herselman MF, et al. The effects of walnuts and academic stress on mental health, general well-being and the gut microbiota in a sample of university students: A randomised clinical trial. 2022;14:4776.

|Nutrients | DOI:10.3390/nu14224776.

Mauritz F. Herselman, Sheree Bailey, Permal Deo, Xin-Fu Zhou, Kate M. Gunn and Larisa Bobrovskaya

Funding Source:

This research was co-funded by the University of South Australia (UniSA) and the California Walnuts Board & Commission through the New Partner Research Scheme (UniSA). Walnuts for the study participants were provided by the California Walnuts Board & Commission. We thank Carol Sloan for her commitment to deliver walnuts to Australia without delays. We thank Walnuts Australia for providing walnuts to the control group (upon completion of the study). M.F.H. is a recipient of the University of South Australia Postgraduate Award (USAPA), Australia.

About California Walnut Commission

The California Walnut Commission, established in 1987, is funded by mandatory assessments of the growers. The Commission is an agency of the State of California that works in concurrence with the Secretary of the California Department of Food and Agriculture (CDFA). The CWC is mainly involved in health research and export market development activities.

For more industry information, health research and recipe ideas, visit www.californiawalnuts.in.