fish & omega-3 oils
A study involving 99 healthy older adults found that levels of monounsaturated fatty acids were associated with cognitive performance and the organization of the brain's attention network.
MUFAs are found in olive oils, nuts and avocados, and are a component of the Mediterranean diet, which has been associated with slower cognitive decline and lower dementia risk.
Data from 915 older adults (mean age 81.4) participating in the very long-running Rush Memory and Aging Project, has found that those who reported eating seafood less than once a week showed greater cognitive decline compared to those who ate at least one seafood meal per week.
A largish Chinese study, involving 541 9-11-year-olds, has found that those who ate fish at least once a week slept better and had higher IQ scores, on average, than those who ate fish less frequently or not at all.
The study suggests that sleep may be a reason for the association previous research has found between the consumption of fish / omega-3 oils and better cognition.
Analysis of data from the Age-Related Eye Disease Study (AREDS) and AREDS2, involving a total of around 8,000 older adults, has found that those with the greatest adherence to the Mediterranean diet had the lowest risk of cognitive impairment. High fish and vegetable consumption appeared to have the greatest protective effect. At 10 years, AREDS2 participants with the highest fish consumption had the slowest rate of cognitive decline.
A study involving 116 healthy older adults (65-75) has found that higher levels of several key nutrients in the blood were associated with more efficient brain connectivity and better cognitive performance. In fact, the findings suggest that the level of nutrients governs the strength of the association between functional brain network efficiency and cognitive performance.
A mouse study has found that canola oil in the diet was associated with worsened memory, worsened learning ability, and weight gain in Alzheimer's mice.
Canola oil-treated animals also had greatly reduced levels of amyloid beta 1-40 (the “good” version), leading to more amyloid-beta plaques (made from amyloid beta 1-42), and a significant decrease in synapses.
The mice were given the equivalent of about two tablespoons of canola oil daily. The mice began their enriched diet at 6 months of age, before they developed any signs of Alzheimer's.
A pilot study involving 106 participants of the Rush Memory and Aging Project who had experienced a stroke followed participants for an average of 5.9 years, testing their cognitive function and monitoring their eating habits using food journals. It was found that those whose diets scored highest on the MIND (Mediterranean-DASH Diet Intervention for Neurodegenerative Delay) diet score had substantially slower rates of cognitive decline than those who scored lowest.
A mouse study has found that fish oil, which contains high levels of omega-3 polyunsaturated fatty acids, significantly helped clear amyloid-beta peptides (involved in the development of Alzheimer’s) from the brain.
https://www.eurekalert.org/pub_releases/2016-10/foas-abo102616.php
Huixia Ren, Chuanming Luo, Yanqing Feng, Xiaoli Yao, Zhe Shi, Fengyin Liang, Jing X. Kang, Jian-Bo Wan, Zhong Pei, and Huanxing Su. Omega-3 polyunsaturated fatty acids promote amyloid-β clearance from the brain through mediating the function of the glymphatic system. FASEB J. doi:10.1096/fj.201600896 ; http://www.fasebj.org/content/early/2016/10/07/fj.201600896.abstract
Initial findings from the Walnuts and Healthy Aging (WAHA) study indicate that daily walnut consumption positively impacts blood cholesterol levels without adverse effects on body weight among older adults.
The study involved 707 healthy older adults of whom some were told to add significant daily amounts of walnuts (~15% of caloric intake) to their usual diet. They were not given any advice on what they should be eating, apart from that.
After a year, a comparison of the two groups found that those eating the walnuts were not any heavier than those who hadn't included walnuts in their diet, but the walnut-diet resulted in significant reductions in LDL cholesterol. There was minimal effect on triglycerides and HDL cholesterol.
Another study reported at the conference found that daily consumption of 1.5 ounces of walnuts significantly affected the bacteria in the human gut in a way that was favorable to decreasing inflammation and cholesterol. This was a small study involving only 18 healthy adults. However, a 2015 study with rats similarly found that a diet with walnuts had a significant effect on gut bacteria communities.
Walnuts are unique among nuts in being primarily composed of polyunsaturated fat. This includes alpha-linolenic acid (ALA), the plant-based omega-3 fatty acid, which is known to reduce inflammation. Walnuts are the only nut that contain a significant amount of alpha-linolenic acid.
Walnuts are also said to be an excellent source of antioxidants — indeed, second only to blackberries.
http://www.eurekalert.org/pub_releases/2016-04/es-nri040116.php
Ros E, Rajaram S, Sala-Vila A, et al. Effect of a 1-Year Walnut Supplementation on Blood Lipids among Older Individuals: Findings from the Walnuts and Healthy Aging (WAHA) study [abstract]. FASEB J. 2016;30(Supp 1)293.4. Available at: http://www.fasebj.org/content/30/1_Supplement/293.4.abstract
Guetterman HM, Swanson KS, Novotny JA, et al. Walnut Consumption Influences the Human Gut Microbiome [abstract]. FASEB J. 2016;30(Supp 1)406.2. Available at: http://www.fasebj.org/content/30/1_Supplement/406.2.abstract
Vinson, JA & Cai, Y. (2012) Nuts, especially walnuts, have both antioxidant quantity and efficacy and exhibit significant potential health benefits. Food & Function, 3(2), 134-140 . http://pubs.rsc.org/en/Content/ArticleLanding/2012/FO/C2FO10152A#!divAbstract
A new meta-analysis supports the link between intake of EPA and DHA omega-3 fatty acids, and reduction in major depressive disorder (MDD).
The meta-analysis only included studies in adult patients with MDD assessed using standardized clinical interviews, and excluded studies that specifically studied perinatal/perimenopausal or comorbid MDD, in order to get a more homogenous population. Studies not applying a randomized placebo-controlled trial design were also excluded. This criteria resulted in 13 studies with a total of 1233 participants (out of an original pool of 1955 studies).
The analysis of these studies showed a benefit for these omega-3 acids that was comparable to effects reported in meta-analyses of antidepressants. The effect was greater in studies supplementing higher doses of EPA and performed in patients already on antidepressants.
http://www.eurekalert.org/pub_releases/2016-03/g-nss031716.php
Mocking, R. J. T., Harmsen, I., Assies, J., Koeter, M. W. J., Ruhe, H. G., & Schene, A. H. (2016). Meta-analysis and meta-regression of omega-3 polyunsaturated fatty acid supplementation for major depressive disorder. Transl Psychiatry, 6, e756. Retrieved from http://dx.doi.org/10.1038/tp.2016.29