A diet soda a day may cost you dearly in the middle ages. A new Brazilian study has found that people who consumed certain artificial sweeteners equivalent to the amount in a can a day saw a 62 per cent decline in their ability to remember and recall words when compared to people who consumed the lowest levels. The effect was more pronounced in mid-lifers than in the 60-plus age group. Dr Claudia Kimie Suemoto, lead study author and director of the Biobank for Ageing Studies at the University of São Paulo’s Medical School in Brazil, was quoted as saying that people who consumed highest amounts of no-calorie sweeteners showed a 62 per cent faster global cognitive decline than those who consumed the lowest amount. “That’s the equivalent of 1.6 years of brain aging,” he said. Why is the study significant? “Sweeteners may contribute to oxidative stress, which refers to an imbalance between harmful free radicals and the body’s ability to detoxify them, which can damage brain cells. This, coupled with neuroinflammation— an inflammatory response within the brain — could impair brain function and promote cognitive decline over time,” says Dr Saptarshi Bhattacharya, senior consultant, endocrinology, Indraprastha Apollo Hospitals, Delhi. These sweeteners are found in many diet sodas, sugar-free gums, low-calorie desserts and various processed foods intended to reduce sugar intake and manage blood glucose levels. What did the study say? The study is observational and has found an association between use of artificial sweetener use and cognitive decline. People in the highest use category consumed an average of 191 milligrams, or about 1 teaspoon, of artificial sweeteners each day. A can of diet soda sweetened with aspartame, according to the WHO contains 200 to 300 milligrams. The middle category of people, who consumed an average of 66 milligrams of artificial sweeteners a day, reported a 35 per cent faster rate of global cognitive decline — which is about 1.3 years of ageing — than people who consumed the lowest amount of 20 mg. Researchers analyzed the diet and cognitive abilities of nearly 13,000 Brazilians between 35 and 75 over eight years. Diabetics had a more pronounced decline in memory as did consumers under 60. This finding did not apply to those over age 60. Which are the offending sweeteners? Researchers studied aspartame, saccharin, acesulfame-K, erythritol, xylitol, sorbitol and tagatose, all of which are “generally recognized as safe” by the US Food and Drug Administration (FDA), which has set limits for their use. However, the WHO had declared aspartame to be potentially carcinogenic in July 2023. Recent studies found erythritol to accelerate clotting of blood, leading to cardiovascular risks. How sweeteners affect the gut-brain axis? Artificial sweeteners have been linked to disruptions in the blood-brain barrier, a shield that prevents harmful substances from entering the brain. “Weakening of this barrier can leave the brain vulnerable to damage, which may accelerate aging-related changes and increase risks for neurodegenerative diseases. Changes in cerebral blood flow caused by these sweeteners can also impact cognitive function. Proper blood flow is essential to deliver oxygen and nutrients to brain cells, supporting memory, attention, and overall mental performance,” says Dr Bhattacharya. Artificial sweeteners, he adds, may also disturb the gut microbiome, the community of microorganisms in the digestive tract, which plays a vital role in brain health through the gut-brain axis. “Alterations in gut bacteria can affect inflammation and nervous system signalling, possibly worsening cognitive health,” he says. In addition to these effects, aspartame specifically can increase levels of certain amino acids, such as phenylalanine and aspartic acid, in the brain. “These compounds can interfere with the production of neurotransmitters like serotonin, dopamine and norepinephrine, which regulate mood, cognition, and pain perception. This interference may lead to symptoms like headaches, migraines, anxiety, and sleep disturbances,” says Dr Bhattacharya. How should artificial sweeteners be consumed then? While artificial sweeteners may offer short-term benefits like lower calorie intake and better blood glucose, their long-term impact on brain health raises caution. “Consumers may consider moderating their intake and exploring natural sweetener alternatives to support brain wellness,” suggests Dr Bhattacharya.
