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This paper is part of the 2018 NMJ Special Issue on Cognition and Mental Health. Download the full issue here.
Relation
Nilsson A, Salo I, Plaza M, Björck I. Effects of a mixed berry drink on cognitive functions and cardiometabolic risk markers; a randomized crossover study in healthy older adults.Plus one. 2017;12(11):e0188173.
Objective
To evaluate the effects on cognitive function and cardiometabolic risk markers after 5 weeks of consumption of a drink made primarily from dark berries.
Draft
Randomized Crossover Trial; 5-week intervention, 5-week washout, 5-week intervention
Participant
Forty healthy Swedish adults aged 50 to 70 (mean age 63), 30 women and 10 men, normal to slightly overweight (mean BMI ≤ 28), all non-smokers with no evidence of disease. All participants avoided alcohol, antibiotics, probiotics, and intake of berries or high-fiber foods during the study period.
intervention
Participants were randomized into either the BC group (n=20) or the CB group (n=20); For the first 5 weeks, the BC group consumed the berry drink while the CB group consumed the control drink. During the second 5-week intervention period (after a 5-week washout period), the BC group consumed the control drink and the CB group consumed the berry drink.
Although I must admit that I was amazed to learn about the ability of berry pigments (anthocyanins) to improve insulin response, I was not at all surprised to read about their neurological effects.
During each 5-week intervention period, participants consumed 600 mL of the berry drink or control drink per day (200 mL with each meal). The berry drink was made from 150 grams of frozen blueberries and 50 grams each of frozen blackcurrants, elderberries, cranberries and strawberries, all combined with 6 grams of tomato powder (from 100 grams of tomatoes). The control drink (water-based) was similar in carbohydrate content, volume and pH.
Study parameters assessed
Participants were assessed four times during the study, first at baseline and then again after each of the 5-week intervention segments. Working memory and selective attention were assessed using standard neurocognitive testing methods. Vital signs were recorded and blood was drawn and assayed for the following cardiometabolic risk markers: glucose, insulin, homeostatic model assessment of insulin resistance (HOMA-IR), free fatty acids (FFAs), cholesterol, interleukin (IL)-6, IL-18, malondialdehyde (MDA), and oxidized Low density lipoprotein (LDL).
Both the study and control drinks were examined for total phenolic content, antioxidant activity, carbohydrates, fiber, protein, fat and pH.
Primary outcome measures
Changes in the above parameters (cardiometabolic risk markers and cognitive performance) after 5 weeks of consumption of the berry drink compared to 5 weeks of consumption of the control drink.
Key insights
Participant
Based on cardiometabolic risk markers, all but 7 of the 40 participants who completed the study had one or more of the common diagnostic components of metabolic syndrome as defined by the International Diabetes Federation at baseline.
Analysis of berry drinks
The berry drinks contained an average of 1,300 mg of polyphenols per liter and showed good antioxidant effects. The control drink had no polyphenols and no antioxidant effect. Both the control and berry drinks contained 2.2% glucose and 3.4% fructose. The berry drink also had 0.6% protein, 0.3% fat, 1.35% insoluble fiber and 0.45% soluble fiber compared to 0% of all of those for the control drink.
Comparison of berries vs. control group
Five weeks of 600 ml of berry drink per day reduced total and LDL cholesterol, insulin and insulin resistance, while 5 weeks of the control drink increased each of these markers. The differences for all of these 4 findings were statistically significant.
Working memory, 30 minutes postprandial, was better after 5 weeks of the berry drink than after 5 weeks of the control drink.
Practice implications
This group of researchers contained some very nice references about the connection between type 2 diabetes mellitus and metabolic syndrome and cognitive decline.1.2Some have actually been found to have reduced cognitive function, which precedes changes in glucose tolerance.2.3Previous studies also found that berries improved insulin sensitivity in overweight adults and slowed cognitive decline in older people.4.5Although I must admit that I was amazed to learn about the ability of berry pigments (anthocyanins) to improve insulin response, I was not at all surprised to read about their neurological effects. Berry pigments can cross the blood-brain barrier and are highly effective in reducing neuroinflammation.6These compounds are able to reduce levels of nuclear factor kappaB (NF-kB) in the brain.7
The researchers used frozen berries rather than fresh ones for the study drink. Bill Mitchell, ND, an early proponent of berry pigments, often said that freezing destroyed cell walls and made more phenolic compounds available. While elderberries, blackcurrants and cranberries are not readily available, frozen blueberries are. You can buy a large bag of these at any Costco and grocery store. While some people were concerned that the Environmental Working Group (EWG) included blueberries on the "dirty dozen" list, according to the Pesticide Data Program website (where the EWG gets its list), frozen blueberries did not show the low levels of residues found on fresh blueberries.8I often recommend that individuals consume one cup of blueberries each day, but this study may suggest that 3 cups may be better if it can be tolerated.
The researchers used only 2 of the many neurocognitive testing methods available and found only a modest improvement in working memory after 5 weeks of the berry drink. Neurocognitive testing is available for clinicians to use in their practice. It is an inexpensive, rapid, and easy-to-use test that provides a quantitative assessment of executive functioning. This test allowed clinicians to easily track patients' cognitive improvement through naturopathic treatment.