Our preference for sweet tastes represents an elegant evolutionary adaptation. The ability to detect sweet substances is thought to have evolved to identify energy-rich sources, primarily sugars found in fruits, plants, and breast milk, that provide essential metabolic fuel. This evolutionary pattern varies by species. Although some carnivores, such as cats, have lost functional sweet taste receptors, the ability to recognize and seek carbohydrates is still important for our survival and helps us identify suitable food sources for cultivation.
People cultivated sugar cane in Papua New Guinea about 8,000 years ago, and by about 5,000 years later, Indian producers had developed a way to extract solid sugar.
From the 16th to the 18th centuries, sugar transformed from a rare luxury to a ubiquitous commodity, becoming central to European and American markets as large-scale production on colonial plantations, an expansion heavily dependent on slave labor, became the norm. The unprecedented availability has led to a corresponding increase in consumption.
According to a study published in nutrientsusing NHANES data from 2015-2016, found that Americans consume about 17 teaspoons (68 grams) of added sugar per day, about one-third more than the WHO recommendation. Many people are adopting non-caloric sweeteners (NCS) as meal replacements due to established links with excessive sugar intake, obesity, and other diet-related chronic diseases.
International regulatory bodies have classified NCS as safe when consumed within established acceptable daily intake (ADI) limits. However, over the past decade, researchers have questioned the long-term effects of NCS on gut microbiota, metabolic regulation, and cardiovascular health. Observational studies have reported an association with elevated insulin, dysbiosis, paradoxical weight gain, and cardiovascular problems. Importantly, these findings reflect correlations rather than causation, highlighting the need for cautious interpretation.
Recent public concerns are Neurologyreported an association between noncaloric sweetener intake and cognitive decline in a large cohort of Brazilian adults. international media coverage was predictably sensational, with headlines such as “Sweeteners can have an impact on cognitive health equivalent to 1.6 years of aging, study finds”. However, beneath its sensational aspects, this study represents a methodologically robust effort that deserves careful consideration.
Elsa’s research
ELSA-Brazil is a cohort study of 15,105 civil servants aged 35 to 74 from six institutions across Brazil. Researchers follow participants over time to examine how exposures (such as diet, pollutants, and activities) are associated with outcomes (such as health outcomes). This research resulted in numerous publications including: Neurology A paper examining the incidence and progression of diabetes and cardiovascular disease.
At baseline, participants completed various tests and interviews, including cognitive tests. One assesses memory (word learning and retention) and two assesses executive function (attention, concentration, psychomotor speed). The researchers repeated these tests in a follow-up study to track changes in cognitive performance. Researchers assessed dietary intake using a semi-quantitative 114-item food frequency questionnaire (FFQ). The FFQ included items regarding sweetened beverages (“sugar-filled,” “sweetened,” “no sugar”) as well as dietary habits, such as fast food and sweet food intake.
The final sample included 9,226 people. The researchers defined regular NNS consumption as daily consumption of at least one NNS-sweetened product. Overall, 25.7% of participants reported using it regularly, primarily for coffee (20.9%). In adjusted models, higher education and income increased the likelihood of regular NNS use by about 80%, and moderate-to-vigorous leisure-time physical activity by about 30%.
This analysis Neurology study. However, despite our best efforts, some limitations remain. Observational studies preclude causal inferences, dietary assessment tools are prone to bias, and confounding can persist despite statistical ‘adjustment’.
Do sweeteners accelerate cognitive decline?
Published in Neurologythis study investigated whether intake of seven types of low- or non-caloric sweeteners (LNCS) was associated with decline in cognitive function over an eight-year period, hypothesizing that higher intakes would accelerate decline.
. Participants were categorized into two groups according to the frequency of LNCS use: less than once a day and “daily consumption,” and consumption was categorized into three increments (tertiles). The study included three waves of cognitive performance, each four years apart, with a baseline of 12,772 people.
Analyzes were adjusted for sociodemographic, lifestyle factors, metabolic variables, and diet quality, measured using the MIND dietary pattern, which emphasizes green leafy vegetables, red fruits, and olive oil while avoiding fried foods, sweets, and red meat.
After 8 years, participants in the highest tertile of LNCS consumption showed faster cognitive decline than those in the lowest tertile.
- Memory decreases 32% faster
- Verbal fluency decreased by 110% in the second tertile and 173% in the third (highest) tertile.
- Global cognition declined by 35% and declined 62% faster. This corresponds to approximately 1.3 to 1.6 years of “excessive cognitive aging.”
- Among the participants
- Saccharin and xylitol affected memory and global cognition, and tagatose affected executive function in diabetics. In non-diabetic participants, higher LNCS intake was associated with faster decline in verbal fluency and global cognition.
- Aspartame was associated with the fastest decline in all domains, and acesulfame K and erythritol were associated with declines in memory and global cognition. Tagatose showed no significant association.
The authors concluded that LNCS intake was associated with accelerated cognitive decline over 8 years, suggesting possible long-term adverse effects. Proposed mechanisms include neurotoxicity, neuroinflammation caused by toxic metabolites, and changes in the gut microbiota. The researchers highlighted two limitations specific to their study. That is, nearly 75% of participants were lost in completing all cognitive tests, and that diet was only assessed at baseline and did not reflect subsequent changes.
This graph shows that the highest tertile of total sweetener intake was more strongly associated with cognitive decline in participants with diabetes than in participants without diabetes. This pattern suggests that the observed association is not directly attributable to sweeteners but may reflect the effects of diabetes, especially when poorly controlled.
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Another noteworthy point concerns the relationship between tagatose and cognitive decline in diabetic participants. Although tagatose had no statistically significant negative effects in most tests and may have had a neutral or even potentially beneficial effect on global cognition, the diabetic subsample showed a faster decline in executive function. This observation seems to contradict the researchers’ conclusion that more natural sweeteners may serve as a suitable replacement for LNCS.
Overall, evidence suggests that nonnutritive sweeteners are generally safe given these limitations. This is reassuring news, especially for those who prepare for the holiday season with diet guarana (arguably the best soda in Brazil) to wash down their turkey with.
source: Brazilian Adult Health Longitudinal Study (ELSA-Brazil): Objectives and design. AM J. Epidemiol. Doi: 10.1093/aje/kwr294.
Exploring patterns of non-nutritive sweetener use in non-diabetic patients: Insights from the Longitudinal Study of Adult Health (ELSA-Brazil). nutrients. DOI: 10.3390/nu15224785.
Association between consumption of low- and zero-calorie artificial sweeteners and cognitive decline. Neurology. Doi: 10.1212/WNL.0000000000214023
