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The end of the year and accompanying holidays are often tied to food. Perhaps that explains why increased interest in recent findings related to nutrition and cognition resulted in this week's top trending clinical topic. A recent study has added to a growing body of evidence regarding the impact of flavonols on memory and brain health (see Infographic).
Flavonols are a subclass of flavonoids, which can be found in vegetables (eg, onions, kale, lettuce, tomatoes) and fruits (eg, apples, grapes, berries), as well as some teas and wines. Evidence had previously demonstrated that some flavonol components reversed histologic hallmarks of Alzheimer's disease in mice. This new research shows the potential for benefit in humans as well. The study included around 960 participants (average age, 81 years). Most were female (75%) and White (98%). Over an average of 7 years of follow-up, they filled out an annual nutritional questionnaire and completed cognitive and memory tests.
To determine rates of cognitive decline, researchers used an overall global cognition score summarizing 19 cognitive tests. After adjusting for various factors, researchers found a significant difference in cognitive decline between those with the highest vs the lowest intake. The group with the lowest flavonol intake consumed about 5 mg/d, whereas the group with the highest consumed an average of 15 mg/d. The average amount of flavonol intake in US adults is about 16-20 mg/d. Participants with the highest intake of kaempferol had a 32% slower rate of cognitive decline than those with the lowest intake. Those with the highest intake of quercetin had a 30% slower rate. Those with the highest intake of myricetin had a 31% slower rate.
On the opposite side of the food-brain connection, a recent study found that a diet high in ultraprocessed foods (UPFs) increases the risk for dementia. Researchers analyzed UPF consumption in more than 70,000 individuals free of dementia at baseline (mean age, 61.6 years). Over 10 years of follow-up, these conditions developed:
Dementia: 518 participants
Alzheimer's disease: 287 participants
Vascular dementia: 119 participants
Unspecified dementia:1 12 participants
In the lowest consumption group, UPFs comprised 9% of the daily (an average of 225 g/d). In the highest consumption group, UPFs accounted for 28% of the daily diet (814 g/d). Compared with those who consumed the least UPFs, the dementia risk among those with the highest consumption was increased by 50% (hazard ratio [HR], 1.51; 95% CI, 1.16-1.96; P < .001). Vascular dementia risk was increased more than twofold (HR, 2.19; 95% CI, 1.21-3.96; P < .01).
Beverages were the main contributors to UPF intake, accounting for 34%, followed by sugary products (21%), dairy products (17%), and salty snacks (11%). Researchers concluded that substituting 10% of habitually consumed UPFs with unprocessed or minimally processed foods would result in a 19% lower risk for all-cause dementia (HR, 0.81; 95% CI, 0.74-0.89; P < .001) and a 22% lower risk for vascular dementia (HR, 0.78; 95% CI, 0.65-0.94; P < .01).
Perhaps cranberries would be a good substitution, as a recent study showed that they may boost memory and brain function in healthy middle-aged and older adults, in addition to lowering low-density lipoprotein cholesterol. Results from a randomized, placebo-controlled trial of adults aged 50-80 years showed that consuming freeze-dried cranberry extract — equal to one cup of fresh cranberries — for 12 weeks was associated with improved episodic memory. Increased regional perfusion was observed in the right entorhinal cortex, the accumbens area, and the caudate of patients who consumed cranberries. This was accompanied by significantly improved visual memory. However, cranberry intervention did not improve other neurocognitive domains, such as working memory and executive functioning.
Even some dietary fats may boost cognitive function in older adults. A study from earlier in 2022 found that dietary intake of polyunsaturated fatty acids (PUFA), particularly omega 6, may be beneficial. The analysis used combined data from the 2011-2012 and 2013-2014 cycles of the National Health and Nutrition Examination Survey. To assess cognitive function, researchers used total and delayed recall scores of the Consortium to Establish a Registry for Alzheimer's Disease (CERAD), the animal fluency test, and the digit symbol substitution test (DSST).
The study included 2253 adults aged 60 years or older (mean age, 69.4 years) and 51% non-Hispanic White persons. After adjusting for various factors, dietary intake of PUFA and omega 6 fatty acid was positively associated with DSST. The DSST score increased about 0.06 standard deviation (SD) (about 1 score) with each SD increase in fatty acids (8.8 g/d for PUFA and 7.9 g/d for omega 6; P values were 0.02 for PUFA and 0.01 for omega 6). The animal fluency score increased about 0.05 SD (around 0.3 score) with each SD (1.1 g/d) increase in dietary intake of omega 3. Although further research is needed, experts stressed the importance of balancing fat intake.
With cranberries, flavonol-containing foods, and certain dietary fats potentially helping, and UPFs possibly hurting, the impact of nutrition on cognition is of interest to those trying to slow declining cognition. As more evidence becomes available, it will almost certainly be quickly "eaten up," as it was this week.
Learn more about cognitive impairment.
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Cite this: Ryan Syrek. Trending Clinical Topic: Memory-Boosting Foods - Medscape - Dec 09, 2022.