Effects of Consumption of Nut Components on Cognitive Function, Intestinal Microbial Communities and Markers of Health

Effects of Daily Tree Nut Consumption on Cognitive Function, Metabolomics and Intestinal Microbiota

Tree nuts (for example brazil nuts, almonds, hazelnuts, walnuts, cashew nuts etc) contain a wide variety of nutrients including fatty acids, polyphenols and micronutrients. The beneficial health effects ascribed to the consumption of tree nuts include improvements to cardiovascular outcomes and regulation of glucose levels and inflammation. Emerging evidence suggests that specific components of nuts may also contribute to brain health and function.

The aim of the present study is to assess the effects of four weeks' supplementation of nut components on cognition and subjective measures. Urinary metabolites and intestinal microbial communities will also be assessed allowing biomarkers of nut exposure to be highlighted.

To date, only two small human intervention trials have evaluated the effects of nuts as a sole intervention on cognition. One study reported a benefit verbal fluency and constructional praxis following daily consumption of 6 g brazil nuts for 6 months in older adults diagnosed with mild cognitive impairment. Eight weeks' consumption of 60 g/d walnuts in healthy young adults aged 18-25 years also resulted in improved inferential verbal reasoning scores compared to placebo.

The development of various 'omics' technologies has enabled researchers to investigate the influence of nutrients or dietary change on metabolic pathways at multiple levels with a view to developing biological markers of dietary intake.

Metabolomic approaches have been used successfully to study nut consumption; for example putative biomarkers of nut consumption have been revealed as metabolites associated with serotonin pathways. Furthermore, certain nut biomarkers identified using metabolomics appear to be negatively associated with health parameters which is suggested to be due to gut microbiota dysbiosis and provides an important link between nut consumption, the gut microflora and metabolic pathways.

This study will assess the effects of four weeks' supplementation with nut components on cognition. Metabolomic and metagenomic approaches will be utilised to analyse urinary metabolites and intestinal microbial communities allowing biomarkers of nut exposure to be highlighted. Metabolic and gut microbiota responses will then be correlated with changes in cognition in order to identify inter-individual differences in response, and further understanding of the mechanisms underpinning cognitive benefits of nut consumption.

Inclusion Criteria:

• Healthy
• Willing to abstain throughout the trial from any nutritional supplementation
• Willing to abstain throughout the trial from the intake of any nuts or nut containing products

Exclusion Criteria:

• Aged under 18 or over 49
• Relevant pre-existing medical condition/illness
• Current use of prescription medications (excluding contraception)
• Learning difficulties and dyslexia
• Visual impairment that cannot be corrected with glasses or contact lenses including colour blindness
• Currently suffer from migraines (> 1 per month)
• Smoking or use of any nicotine replacement products e.g. vaping, gum, patches
• History of or any current food intolerances/sensitivities, including nut/peanut allergies
• Never consumed nuts, or regularly consume nuts more than twice per week
• Irregular bowel function (less than one bowel movement per day)
• Body mass index (BMI) under 18.5 or over 30
• Pregnancy, seeking to become pregnant, or current lactation
• Inability to complete all of the study assessments
• Current participation in other clinical or nutrition intervention studies
• Not proficient in English equivalent to IELTS band 6 or above
• Have any known active infections
• Blood pressure >139/89mmHg
• Are employed in a job that includes night shift work
• Have habitually used supplements within the last month (defined as more than 3 consecutive days or 4 days in total)