The World Health Organization (WHO) has released a significant new guideline on the use of non-sugar sweeteners (NSS), a category often referred to as artificial or low-calorie sweeteners. After a comprehensive review of available scientific evidence, the WHO is advising against the long-term use of NSS for controlling body weight or reducing the risk of noncommunicable diseases. This recommendation marks a notable shift in public health messaging surrounding these ubiquitous food additives, which have been widely adopted by consumers seeking to reduce sugar intake.
The WHO’s research review, which synthesized data from numerous studies, concluded that substituting sugar with NSS does not lead to significant long-term weight loss in either adults or children. While some clinical trials indicated that replacing sugar with NSS could result in a lower calorie intake when consumed in place of sugar-sweetened foods and beverages, the overall impact on body weight management was found to be negligible over extended periods. Furthermore, the guideline highlighted inconsistencies in NSS’s effect on hunger and satiety. Some studies reported reduced feelings of hunger, while others observed a stronger appetite in individuals consuming higher quantities of NSS-containing products. This mixed evidence underscores the complexity of NSS’s physiological effects.
Beyond weight management, the WHO also examined the association between NSS consumption and the risk of chronic diseases. Observational cohort studies included in the review suggested a potential link between long-term intake of NSS-containing beverages and an increased risk of cardiovascular disease and premature death in adults. Similarly, higher consumption of NSS, whether in beverages or added to foods, was associated with an elevated risk of developing type 2 diabetes.
However, the WHO cautioned that these observed associations might be influenced by "reverse causation." This phenomenon suggests that individuals who are already overweight, obese, or possess metabolic risk factors may be more inclined to choose NSS as a perceived healthier alternative to sugar, thereby predisposing them to chronic diseases. In essence, the higher consumption of NSS might be a consequence of existing health conditions rather than a direct cause. Importantly, the WHO’s analysis did not find a significant association between NSS intake and an increased risk of cancer or cancer-related deaths.
Based on these findings, the WHO is recommending a proactive approach to dietary habits, advocating for a reduction in the overall sweetness in the diet, beginning from an early age. The organization emphasizes that NSS do not offer nutritional benefits and therefore should not be seen as a healthy alternative to sugar in the long run. Common examples of NSS that were included in the review are acesulfame K, aspartame, saccharin, sucralose, and stevia. It is important to note that sugar alcohols, also known as polyols, such as maltitol, xylitol, and sorbitol, which are frequently added to foods and beverages, were not part of this specific analysis.
Expert Reactions and Criticisms
Experts at the Harvard T.H. Chan School of Public Health largely concurred with the WHO’s core recommendation to reduce overall sweetness in the diet. However, they also offered constructive criticism regarding the methodology of the WHO’s meta-analysis. Notably, they pointed out that certain large-scale cohort studies were excluded from the review. These omitted studies, which collectively involved over 100,000 participants, had indicated that increasing the consumption of artificially sweetened beverages at the expense of sugar-sweetened beverages was associated with less weight gain over time. This finding was consistent with the results of smaller, short-term randomized controlled trials.
Statistical modeling based on the findings of these excluded studies suggested that replacing just one serving of a sugar-sweetened beverage with an artificially sweetened beverage could be linked to a reduced risk of total mortality (by 4%), cardiovascular disease-related mortality (by 5%), and cancer-related mortality (by 4%). These projections highlight a potential divergence in conclusions depending on the scope of studies included in an analysis.
Frank Hu, Chair of the Department of Nutrition at the Harvard T.H. Chan School of Public Health, provided further perspective on beverage choices. He stated, "for habitual consumers of sugar-sweetened beverages, artificially sweetened beverages can be used as a temporary replacement, although the best choices would be water and unsweetened coffee or tea." This nuanced view acknowledges the potential utility of NSS as a transitional tool for individuals trying to break away from sugar but reiterates the primacy of water and unsweetened beverages for optimal long-term health.
Background and Chronology of Guidance
The release of the WHO’s guideline on NSS follows a period of increasing scrutiny of these sweeteners. For decades, NSS have been marketed as a healthier alternative to sugar, particularly for individuals managing diabetes and seeking to reduce calorie intake. Their development and widespread adoption can be traced back to the mid-20th century, with aspartame, for instance, being approved for use in the United States in the early 1980s.
The scientific understanding of NSS has evolved over time, with ongoing research examining their metabolic effects, potential impacts on the gut microbiome, and long-term health consequences. Regulatory bodies worldwide have established acceptable daily intake (ADI) levels for various NSS, based on extensive toxicological studies. However, the interpretation and application of this research in public health recommendations have sometimes varied.
The WHO’s decision to issue a new guideline stems from a systematic review of evidence published up to late 2022. This review aimed to consolidate the latest findings on the efficacy and safety of NSS for weight management and the prevention of noncommunicable diseases. The process involved rigorous evaluation of randomized controlled trials, cohort studies, and meta-analyses to draw robust conclusions.
Focus on Aspartame: A Recent Risk Assessment
The recent guideline on NSS is complemented by separate assessments of individual sweeteners. A notable example is the risk assessment of aspartame, conducted by the International Agency for Research on Cancer (IARC), a specialized agency of the WHO, in collaboration with the Joint Expert Committee on Food Additives (JECFA). In July 2023, this assessment classified aspartame as a Group 2B carcinogen, indicating "limited evidence" of carcinogenicity in humans, specifically for liver cancer.
Despite this classification, the WHO and JECFA reaffirmed their previously established acceptable daily intake (ADI) for aspartame, which is 40 mg per kilogram of body weight. They stated that their research review did not provide evidence to alter this guideline, affirming that intake within this range is considered safe. For a 150-pound (68 kg) woman, this translates to a daily limit of approximately 2,727 mg of aspartame, equivalent to about eleven 12-ounce cans of diet soda, given that a single can typically contains around 250 mg of aspartame.
The expert committees acknowledged that the evidence on cancer risk in humans, based on both animal and human studies, was not yet convincing. They emphasized the need for more extensive research, including longer-term studies with follow-up and randomized controlled trials, to provide a more definitive understanding of aspartame’s potential long-term effects. This nuanced approach to aspartame highlights the ongoing scientific debate and the challenges in definitively linking specific food additives to health outcomes.
Broader Implications and Future Directions
The WHO’s new guideline on NSS has significant implications for consumers, food manufacturers, and public health policymakers. For consumers, it suggests a reevaluation of their reliance on NSS as a primary strategy for weight control or disease prevention. The emphasis shifts towards reducing overall sweetness in the diet and prioritizing nutrient-dense foods and beverages.
Food manufacturers may need to reconsider their product formulations and marketing strategies. While NSS have been a popular tool for creating "diet" or "sugar-free" options, the WHO’s guidance may encourage a greater focus on reformulating products with less intense sweeteners or promoting naturally unsweetened alternatives.
From a public health perspective, the guideline underscores the importance of comprehensive dietary approaches. It reinforces the value of promoting healthy eating patterns that are rich in whole foods and water, rather than relying on specific ingredient substitutions. The call to reduce sweetness in the diet from an early age is particularly crucial, as taste preferences are often established in childhood.
The divergence in findings between the WHO’s meta-analysis and some of the excluded large cohort studies also highlights the ongoing need for robust and transparent scientific inquiry. Continued research, particularly long-term observational studies and well-designed clinical trials, will be essential to further clarify the complex relationship between NSS consumption and human health. The WHO’s stance encourages a more cautious and holistic approach to dietary choices, prioritizing whole, unprocessed foods and reducing reliance on artificial interventions for health management. The ultimate goal, as advocated by public health experts, remains the cultivation of sustainable, healthy eating habits that contribute to long-term well-being.
