Welcome to the April 2022 issue of Research Extracts. “The Extracts” is designed to keep busy practitioners and savvy consumers up to date on the latest research on diet, nutrients, botanicals, the microbiome, the environment, and lifestyle approaches to good health. Our medical team, which includes NDs, MDs, PhDs, RDs, an MS, and an LAc, has summarized the essence of several interesting recent studies.

In this issue you will find two studies on the effect of diet on cognitive function. In this issue: (1) this month’s Mental Health Moment – a study on the MIND diet, obesity, and brain function, (2) the effect of pesticide residues on mortality risk, and (3) the effect of dietary fiber on dementia risk.


Thorne Mental Health Moment: Diet, Brain Health, and Obesity

Cognitive function is a term used for a collective set of mental abilities – learning, thinking, memory, focus/attention, problem solving, and reasoning. Much data now suggests that diet has a direct impact on cognitive function over the course of a lifetime – but less on how diet directly impacts specific populations.

Overweight and obesity are known to have negative impacts on measurements of cognitive function.1 This is particularly linked to metabolic dysfunction. Some studies show a direct impact on brain structure – particularly a reduction in brain volume.2 Given that more than 40 percent3 of U.S. adults are affected by obesity, finding lifestyle interventions that can mitigate or reverse these effects is important. For example, calorie restriction like intermittent fasting has been studied from this perspective.

The MIND diet (Mediterranean-DASH Intervention for Neurodegenerative Delay) is an established dietary intervention that benefits cognitive performance. Based on the Mediterranean diet and dietary guidelines studied in high blood pressure, the MIND diet now has a decade of research showing it slows or prevents – and in some cases even reverses – cognitive decline in aging.4

A new study5 now suggests the MIND diet might be a valuable intervention for obese women. Forty adult obese women were randomly assigned to follow the MIND diet or a control diet for three months. Both groups were matched for calories and macronutrients (protein, fat, carbohydrate). The MIND diet group showed statistically improved measurements of memory and attention at the study’s end. They also had an increase in grey matter volume as measured by MRI, along with improved weight, body composition, and lower levels of inflammatory biomarkers.

Although weight loss itself has been shown to benefit cognition,6 this trial might indicate advantages for the MIND diet over other approaches. More data – and longer studies – are needed to understand the full impact of this intervention.

Contributed by Jacqueline Jacques, ND

References

  1. Farruggia MC, Small DM. Effects of adiposity and metabolic dysfunction on cognition: A review. Physiol Behav 2019;208:112578. doi:10.1016/j.physbeh.2019.112578
  2. Raji CA, Ho AJ, Parikshak NN, et al. Brain structure and obesity. Hum Brain Mapp 2010;31(3):353-364. doi:10.1002/hbm.20870
  3. Defining Adult Overweight and Obesity | Overweight & Obesity | CDC. Published September 17, 2020. https://www.cdc.gov/obesity/adult/defining.html [Accessed 4.8.22]
  4. Morris MC, Tangney CC, Wang Y, et al. MIND diet slows cognitive decline with aging. Alzheimers Dement 2015;11(9):1015-1022. doi:10.1016/j.jalz.2015.04.011
  5. 5. Arjmand G, Abbas-Zadeh M, Eftekhari MH. Effect of MIND diet intervention on cognitive performance and brain structure in healthy obese women: a randomized controlled trial. Sci Rep 2022;12(1):2871.
  6. Veronese N, Facchini S, Stubbs B, et al. Weight loss is associated with improvements in cognitive function among overweight and obese people: A systematic review and meta-analysis. Neurosci Biobehav Rev 2017;72:87-94. doi:10.1016/j.neubiorev.2016.11.017

Pesticide Exposure in the Diet, Disease, and Mortality

Pesticide use in the United States is regulated by the Environmental Protection Agency (EPA)  to ensure certain products don’t pose unreasonable risk to humans, animals, and the environment.1 Conventionally grown fruits and vegetables in the diet are the main exposure route for pesticides.2 Although it is well documented that fruit and vegetable intake is an important part of an overall healthy diet and has beneficial effects on chronic diseases, such as cardiovascular disease, the question remains: Does dietary pesticide exposure impact mortality?

Cohorts in the ongoing Nurses’ Health Study, Nurses’ Health Study II, and Health Professionals Follow-up Study were assessed by reviewing self-reported questionnaires of demographics, lifestyle, medical history, and habitual food consumption patterns.2 Data from the USDA Pesticide Data Program classifies pesticide residues on fruits and vegetables according to the Pesticide Residue Burden Scale, which was used to evaluate the fruit and vegetable intake in food frequency questionnaires that were completed every four years throughout the cohort studies. 

The primary outcome measured was all-cause mortality. Causes of death were categorized by cardiovascular disease, cancer, respiratory diseases, and others, as well as premature deaths calculated as before age 70. On initial analysis, both high- and low-residue fruits and vegetable consumption decreased mortality risk. However, when other variables that could impact results were factored in, only low-pesticide-residue fruit and vegetable intake was inversely associated with mortality, while produce with higher levels of pesticides did not decrease mortality risk. This suggests that high-pesticide residue offsets some of the benefits from those foods. Of note, participants who consumed more than four servings of either high- or low-pesticide residue fruits and vegetables daily were also more frequently active, never smokers, had lower BMIs, and had a higher consumption of total flavonoids, antioxidant nutrients, and fiber. 

Contributor note: These beneficial lifestyle behaviors and diet patterns provide a foundation for healthy living regardless of the impact of pesticide exposure. If feasible, then consider purchasing organic produce, which is less likely to have pesticide residues due to the organic food standards that prohibit synthetic pesticide use. Properly washing fruits and vegetables before consumption can also reduce pesticide residue exposure in the diet.

The Environmental Working Group just published their 2022 Dirty Dozen – a list of the 12 fruits or vegetables with the highest pesticide levels. 

Contributed by Carly Duffy, MPH, RD

References

  1. Regulation of pesticides with public health uses. Epa.gov. Updated June 16, 2021. https://www.epa.gov/pesticides/regulation-pesticides-public-health-uses  [Accessed April 6, 2022]
  2. Sandoval-Insausti H, Chiu YH, Wang YX, et al. Intake of fruits and vegetables according to pesticide residue status in relation to all-cause and disease-specific mortality: Results from three prospective cohort studies. Environ Int 2022;159:107024. doi:10.1016/j.envint.2021.107024

Is Dietary Fiber Intake Related to Dementia Risk?

Dietary fiber promotes health by modulating the gut microbiome and enhancing bacterial species associated with positive health outcomes. Gut-brain interaction, which is affected by the presence of various bacterial species, also influences cognitive function and brain plasticity. Knowing that consumption of soluble fiber promotes healthy bacterial species in the gut, researchers recently studied whether dietary fiber intake is associated with dementia risk.

The study cohort included 3,739 primarily healthy individuals ages 40-69. Each participant was evaluated annually from 1985-1999. Participants completed a 24-hour dietary recall for one day at each annual exam. The foods consumed were assessed for nutrient intake, including total, soluble, and insoluble fiber. Dementia risk factors were assessed annually by physical exam, lifestyle interviews, and blood labs.

Overall, men consumed less total fiber than women. Lower total fiber intake was associated with higher systolic and diastolic blood pressures. Both total fiber intake and soluble fiber intake were inversely associated with dementia risk. The authors proposed several possible mechanisms for the beneficial effect of fiber intake on dementia risk. As noted, fiber intake positively impacts the gut microbiome, leading to a more favorable bacterial composition for gut-brain health. In addition, along with lower blood pressure, fiber intake is also associated with healthy body weight, serum lipids, and fasting blood sugar – metabolic measures associated with dementia – as well as decreased risk of stroke and diabetes, two conditions that increase dementia risk.

In addition to fiber in your diet, consider adding supplemental fiber.

Looking to support cognitive function? Check out Thorne’s new Brain Factors.

Contributed by Jennifer L. Greer, ND, Med

Reference