Diet as a potential risk factor for cognitive impairment
Maintaining a healthy dietary pattern is crucial for the prevention or delay of cognitive impairment.
SINGAPORE | 8 November 2019
From street food to heritage dining spots to our beloved hawker centres, options for tasty food abound. Resisting the urge to fill our stomachs with platters of satay and rojak can be tough, but understanding the benefits of a well-balanced diet can make navigating around this food paradise in search of a healthy meal much more bearable.
A local study known as the Singapore Chinese Health Study has shown that adherence to a healthy diet, defined by a lower proportion of animal foods such as red meat and higher proportion of plant foods such as vegetables, fruits and whole grains can potentially reduce the risk of cognitive impairment.
With one of the most rapid ageing populations in the region, the possibility of more individuals suffering from mild cognitive impairment (MCI) is no longer a problem of if, but when. MCI is the transitional stage between the expected cognitive decline of normal aging and the more serious decline of dementia. It is usually associated with physiological changes such as the shrinking of the hippocampus (the part of the brain that is responsible for memory storage), a lowered rate of glucose metabolism, as well as the gradual formation of beta-amyloid deposition and neurofibrillary tangles that lead to loss of synapses and neurons.
On first thought, there seems to be an unlikely connection between dietary patterns and brain health, and you might find yourself wondering how the food one eats can possibly prevent the brain of MCI patients from progressing towards its current trajectory – gross atrophy of the brain tissues. The connection between these two separate systems are not as simple we think. Advances in molecular biology have revealed the ability of food-derived signals to influence energy metabolism and synaptic plasticity. Raising the example of a widely coveted fatty acid – omega-3 – it provides plasma membrane fluidity at synaptic regions, improving synaptic function and neuronal excitability, thus mediating the effects of food on cognitive function.
“Food intake is a multi-dimensional exposure, where high consumption of some foods is typically associated with lower intake of other foods.” Said Dr Annie Ling, Group Director of the Policy, Research and Surveillance Division of Health Promotion Board (HPB), Singapore. Diverse foods consumed together produce synergistic effects, causing epidemiological studies which aimed to investigate the impact of individual food choices on cognitive health to be inconclusive. Instead, scientists have shifted their focus to studying the overall dietary exposures of related foods consumed together, and accounting for the possible interactions among them.
The studies have shown that dietary patterns that are rich in plant-based foods, including whole grains, vegetables and fruits, nuts and legumes, and low in red meat and sugar-sweetened beverages can be associated with reduced risk of cancer, diabetes and cardiovascular diseases. These five high quality dietary patterns are the alternative Mediterranean diet (aMED), the Dietary Approaches to Stop Hypertension (DASH), the Alternate Healthy Eating Index 2010 (AHEI-2020), the plant based diet (PDI), and the healthful plant based diet (hPDI).
In a separate study also conducted under the Singapore Chinese Health Study, 16,946 participants, aged 53 years on average at recruitment from 1993 to 1998, were scored on how similar their diet patterns were to the aforementioned high quality diets. Twenty years later, their cognitive function was evaluated once again. It was determined that in all five high quality dietary patterns, participants in the top 25 percent of scores for similarity to these dietary patterns had a significant reduction of 18 percent to 33 percent in risk of cognitive impairment compared to those who were in the lowest 25 percent. The results to this study conclusively proved that adherence to high quality diets in midlife was associated with a lower risk of cognitive impairment at older age.
“Previous studies have shown mixed results when it comes to diet and the risk of cognitive impairment, with few studies conducted in Asian populations,” Said Prof Koh Woon Puay, Principal Investigator of the Singapore Chinese Health Study, and Professor at Duke-NUS Medical School and the National University of Singapore’s Saw Swee Hock School of Public Health. “Our study suggests that maintaining a healthy dietary pattern is important for the prevention of onset and delay of cognitive impairment. Such a pattern is not about the restriction of a single food item but the composition of an overall pattern that recommends cutting back on red meats, especially if they’re processed, and including lots of plant-based foods and fish.” Prof Koh Woon Puay continues.
As a general guideline, HPB’s recommendation is to maintain a balanced and varied diet, and to eat across all food groups. A simple way to adhere to this guideline would be to fill half of their plates with fruit and vegetables, a quarter with wholegrains such as brown rice or whole meal bread, and the last quarter with protein foods such as bean products, seafood and meat.
The research paper was published in August 2019 on The American Journal of Clinical Nutrition.
This article was contributed by Michelle Tan Min Shuen, an editorial intern at World Scientific Publishing Co. and a contributing writer for Asia-Pacific Biotech News. She is from Nanyang Girls' High School, has a keen interest in chemistry and the life sciences, and pursues taekwondo in her free time.