Can the role of food processing answer the age-old question?
The number of people living with dementia is rising as life expectancy increases worldwide. By 2028, almost 30,000 Australians will live with dementia. It has been estimated that 40% of dementia cases could be prevented by controlling modifiable risk factors such as dietary intake.
Extensive research has identified the role of specific foods in dementia. For instance, consumption of Brazil nuts has seen benefits for individuals with mild cognitive impairment and research suggests that regular consumption of different types of nuts may be protective against dementia. More recently, cognitive function is examined in relation to food intake in a study by Monash researchers.
The role of industrial processing of food in dietary patterns has gained interest, in particular, the effects of ultra-processed foods defined as foods that undergo several industrial processes that cannot be reproduced at home. They contain little or no whole food and typically include flavourings, colourings, emulsifiers and other cosmetic additives.
Globally, dietary patterns are shifting from traditional diets based on whole foods and minimally processed foods. Consumption of ultra-processed foods, such as packaged snacks, ready meals, sausages, instant soups and noodles, are becoming more dominant in diets.
In the US, the average overall consumption of ultra-processed foods ranges from 58% of the energy intake in older adults to 67% among children and adolescents. In Australia, it is estimated that ultra-processed foods contribute to around 35% of the daily energy intake amongst people above 2 years old.
Consumption of ultra-processed foods has been associated with several chronic diseases including hypertension, diabetes and cardiovascular diseases. However, we currently have little understanding of the potential effects of dietary patterns rich in ultra-processed foods on dementia and age-associated cognitive decline.
Dr Barbara Cardoso and team explored the association between ultra-processed food consumption and performance in cognitive tests in a representative sample of older adults in the US. It was hypothesised that higher intake of ultra-processed foods is associated with worse cognitive performance in older adults.
Dr Cardoso and team investigated dietary intake and performance in cognitive tests of 2,934 older American adults as part of the National Health and Nutrition Examination Survey (NHANES).
The foods reported by the respondents were classified into four groups according to the extent of industrial processing they have undergone. These groups are:
1) Unprocessed or minimally processed foods
2) Processed culinary ingredients
3) Processed foods
4) Ultra-processed foods
The research found that increased consumption of ultra-processed foods was associated with poorer performance in the Animal Fluency test. This cognitive test is used to assess language and executive function in people with Alzheimer's disease (AD) and other neurological disorders.
There are several possible reasons for these findings. The consumption of ultra-processed foods is associated with risk factors for dementia, such as diabetes, hypertension, and obesity. Further, it is hypothesised that the high intake of these highly processed foods may increase low-grade inflammation, impairment of the blood-brain barrier and contribute to neuroinflammation. It has also been speculated that ultra-processed foods - which are rich in food additives, advanced glycation end products and sugar, and low in bioactive compounds with anti-inflammatory and antioxidant properties - may contribute to an unbalanced gut microbiome, which can compromise the gut-brain axis and mediate cognitive dysfunction.
Given that this study is a pioneer in establishing the relationship between ultra-processed foods intake and cognitive decline, more research is required to further investigate the effects of ultra-processed foods intake on cognition in the long-term, as well as the mechanisms involved.
Publication information
R Cardoso, B., Machado, P. & Steele, E.M. Association between ultra-processed food consumption and cognitive performance in US older adults: a cross-sectional analysis of the NHANES 2011–2014. Eur J Nutr (2022). https://doi.org/10.1007/s00394-022-02911-1
Dr Barbara R Cardoso is a nutritional biochemist with a Masters and a PhD from the University of Sao Paulo (Brazil) and international experience attained from research appointments in Brazil and Spain. She is interested in investigating the role of foods and micronutrients in age-associated cognitive decline and dementia.
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