Battling cognitive decline: Where do we stand?

Recent years have seen a flurry of scientific activity pushing to investigate the possible links between nutrition and cognitive impairments in the elderly.

Indeed, the market for ingredients linked to cognitive benefits is 'set to explode', according to Dr Mark Schauss of laboratory testing services firm Lab Interpretation.

While there is not yet a 'miracle pill' that can guarantee we will not lose our marbles, there is a growing body of data supporting the cognitive benefits of various nutrients including omega-3 fatty acids such as DHA, the Mediterranean diet, phosphatidylserine (PS), caffeine, vitamin E, and the B vitamins.

In this special edition article NutraIngredients take a look at some of the science backing these, and other, nutrients.

DHA omega-3​

Docosahexaenoic acid (DHA) is an omega-3 fatty acid that is a primary structural component of the human brain, cerebral cortex, skin, and retina. As such, there has been great interest in whether increased intakes of the fatty acid can aid in the development if the brain - and whether higher intakes can help to protect against cognitive declines in older age.

Several studies have suggested that omega-3 fatty acids are essential for keeping nerve cells in the brain healthy, whilst others have found people who regularly consume fish that are rich in omega-3 have a lower risk of developing memory loss or Alzheimer’s disease.

However, there have been few high quality clinical trials to back up these general observations.

Indeed, recent research published in the Nutrition Journal​​ demonstrated that daily supplementation with DHA-rich omega-3 fish oil significantly improved working memory capacity in healthy people.

Led by Professor Inger Björck of Lund University, Sweden, the research team gave healthy participants aged between 15 and 72 a daily supplement containing three grams of omega-3 PUFA fish oil or a placebo for five weeks before testing cognitive functions and metabolic risk markers including blood pressure, serum triglycerides, and fasting glucose measures.

In addition to finding a benefit on working memory, the team identified an inverse relationships  between cardiometabolic risk factors and cognitive performance, "indicating a potential of dietary prevention strategies to delay onset of metabolic disorders and associated cognitive decline.” ​

Such a relationship between outcomes in cognitive tests and metabolic risk factors highlights the importance of early dietary prevention to prevent cognitive declines that are associated with metabolic disorders, said Björck.

However a recent Cochrane review​ of the evidence in this area concluded that omega-3 supplements are 'unlikely' to prevent cognitive declines and dementia in the elderly.

In Europe DHA is the only nutrient to have received a positive opinion from the European Food Safety Authority (EFSA) relating to brain development and the maintenance of normal brain function.

Vitamins and minerals​

Supplementation with specific essential vitamins and minerals, or indeed multivitamins​, has also been long suggested to have benefits on our cognitive functions. From vitamin E to the B vitamins, there is vast research to suggest the benefits of essential vitamins and minerals on cognitive functions and memory.

Research has, for example, shown that people with decreased mental function and Alzheimer’s disease are more likely to have low blood levels of vitamin E tocopherols and tocotrienols. The research​ analysed data from 168 Alzheimer patients, 166 people with mild cognitive impairment, and 187 people with normal cognitive function - finding that people with both forms of cognitive decline were 85% less likely to have the highest average levels of total tocopherols and total vitamin E. In addition, they were 92% and 94%, respectively, less likely to have the highest average levels of total tocotrienols.

Indeed, researchers have suggested that screening levels of vitamin E​ could be a reliable biomarker for Alzheimer's disease risk.

But it is not all about vitamin E. Studies have also suggested that insufficient levels of vitamin D may increase the risk of cognitive decline, while a plethora of research has linked the B vitamins with slowing the declines in mental function​ associated with mild cognitive impairment.

Indeed recent research has even suggested that a high dose of B vitamins could stop the onset of Alzheimer’s​ by preventing shrinkage of the medial temporal lobe.

Meanwhile, research published last year suggested that regular consumption of silicon-rich mineral water​ could help to reduce the clinical signs of Alzheimer’s disease by removing excess levels of aluminium that are linked to the disease.

In parallel with this a reduction in aluminium levels, the research team reported some ‘remarkable’ effects on cognitive function in the individuals with AD – with eight out of 15 showing no deterioration in cognitive abilities over the period of the study. Three of these eight, showed clinically-relevant improvements in cognitive functions, the research team said.

Polyphenols and berry promise​

Early research has also suggested that a diet supplemented with berries could help to protect brain functioning​ during aging, with studies in older women suggesting that high intakes of flavonoid rich berries can delay memory decline​ and appear to delay cognitive aging by up to 2.5 years when compared to those consuming lower amounts.

The research team used data from the Nurses' Health Study – containing data from over 120,000 women - finding that increased consumption of blueberries and strawberries was associated with a slower rate of memory decline in older women – with a greater intake of anthocyanidins and total flavonoids also associated with slowing memory decline.

Resveratrol has also been shown to have potential in battling cognitive declines, with research in animals suggesting that supplementation of the polyphenol at doses achievable in the diet could boost mental functions.​ However the team behind the findings said that the studies need to be repeated in humans before any firm conclusions can be drawn.