The World Health Organization (WHO) has released a significant new guideline that advises against the use of non-sugar sweeteners (NSS), commonly referred to as artificial or low-calorie sweeteners, for controlling body weight or reducing the risk of noncommunicable diseases. This recommendation stems from a comprehensive review of available scientific evidence, which concluded that substituting sugar with NSS does not lead to long-term weight loss in either adults or children. While some short-term clinical trials indicated a reduction in calorie intake when NSS replaced sugar in foods and beverages, this effect did not translate into sustained weight management. Furthermore, the evidence regarding NSS’s impact on hunger and satiety was mixed, with some studies suggesting reduced hunger and others pointing to an increased appetite with higher NSS consumption.
The WHO’s extensive review, which synthesized data from a multitude of studies, paints a complex picture of the role NSS play in public health. The guideline, officially titled "Use of non-sugar sweeteners: WHO guideline," was published in July 2023, marking a notable shift in how international health bodies are advising on these widely consumed food additives. These sweeteners, including well-known examples such as aspartame, acesulfame potassium (Ace-K), saccharin, sucralose, and stevia glycosides, are present in a vast array of food and beverage products globally, from diet sodas and sugar-free yogurts to tabletop sweeteners. The organization explicitly excluded sugar alcohols, such as maltitol, xylitol, and sorbitol, from this particular guideline, as their metabolic effects and research profiles differ.
Understanding the WHO’s Evidence Review
The WHO’s recommendation is rooted in a systematic review of evidence, which included a meta-analysis of randomized controlled trials (RCTs) and observational studies. The RCTs, which are generally considered to provide stronger evidence due to their controlled nature, consistently showed no long-term benefit for body weight reduction when NSS replaced sugar. While participants in these trials sometimes consumed fewer calories in the immediate term, this did not appear to lead to a significant difference in body weight over extended periods.
However, the observational cohort studies within the review presented a more concerning picture. These studies, which track large groups of people over time, revealed an association between the long-term consumption of NSS-containing beverages and an increased risk of cardiovascular disease and premature death in adults. Similarly, higher overall NSS intake, whether from beverages or added to foods, was linked to a greater risk of developing type 2 diabetes.
It is crucial to acknowledge the WHO’s nuanced interpretation of these observational findings, particularly the potential for "reverse causation." This phenomenon suggests that individuals who are already at higher risk for chronic diseases, such as those with higher body mass index (BMI), obesity, or metabolic risk factors, may be more inclined to choose NSS as a perceived healthier alternative to sugar. Therefore, the observed association between NSS and disease risk might, in part, reflect pre-existing health conditions rather than NSS directly causing these issues. The WHO also noted the absence of a significant association between NSS intake and cancer or cancer-related deaths in their review.
A Call for Reduced Sweetness in Diet
The overarching message from the WHO is a clear call for a global reduction in the overall sweetness of the diet, starting from early life. The organization emphasizes that NSS, despite their non-caloric or low-caloric nature, do not offer any nutritional benefits. This perspective encourages a fundamental shift in dietary habits, moving away from a reliance on sweet tastes, whether from sugar or its artificial substitutes, towards a palate that appreciates less intensely sweet foods and beverages. The rationale is that by reducing the overall preference for sweetness, individuals are more likely to choose healthier, nutrient-dense options.
Divergent Perspectives: Harvard Chan School’s Critique
While generally aligning with the WHO’s sentiment to curb excessive sweetness, experts from the Harvard T.H. Chan School of Public Health have raised specific criticisms regarding the WHO’s meta-analysis. Their concern centers on the exclusion of several large-scale observational cohort studies from the WHO’s review. These omitted studies, which collectively involved over 100,000 participants, reportedly found that substituting sugar-sweetened beverages with artificially sweetened ones was associated with less weight gain over time. This finding, according to the Harvard experts, is more consistent with the outcomes observed in smaller, short-term randomized controlled trials.
Based on statistical modeling of these excluded studies, the Harvard Chan School estimates that replacing one serving of a sugar-sweetened beverage with an artificially sweetened alternative could be linked to a 4% lower risk of all-cause mortality, a 5% lower risk of cardiovascular disease-related mortality, and a 4% lower risk of cancer-related mortality. This suggests that, from their perspective, NSS might indeed offer some transitional benefits for individuals seeking to reduce their sugar intake, particularly for those accustomed to high levels of sugar consumption.
Optimal Beverage Choices for Long-Term Health
The discussion surrounding NSS naturally leads to a consideration of optimal beverage choices for sustained health. Frank Hu, Chair of the Department of Nutrition at the Harvard T.H. Chan School of Public Health, offers a pragmatic perspective. He suggests that for individuals who are habitual consumers of sugar-sweetened beverages, artificially sweetened beverages can serve as a "temporary replacement." However, he unequivocally states that the "best choices would be water and unsweetened coffee or tea." This highlights a hierarchy of beverage preferences, with water and unsweetened beverages at the pinnacle of healthfulness.
Spotlight on Aspartame: A Closer Look
The WHO’s broader stance on NSS is further contextualized by recent assessments of specific sweeteners, most notably aspartame. In July 2023, the International Agency for Research on Cancer (IARC), a specialized agency of the WHO, along with the Joint FAO/WHO Expert Committee on Food Additives (JECFA), released a risk assessment of aspartame and cancer. The IARC classified aspartame as a Group 2B carcinogen, meaning it has "limited evidence" of carcinogenicity in humans, specifically citing liver cancer.
However, it is crucial to note that this classification does not equate to a direct causal link or a recommendation to avoid aspartame. JECFA reaffirmed its previously established acceptable daily intake (ADI) for aspartame, which remains at 40 milligrams per kilogram of body weight per day. For an average 150-pound (68 kg) adult, this translates to a daily limit of approximately 2,727 mg of aspartame. This amount is equivalent to roughly eleven 12-ounce cans of diet soda, as a typical can contains about 250 mg of aspartame. JECFA concluded that the available evidence from animal and human studies was not convincing enough to alter this guideline, affirming that consumption within this range is safe. The agencies emphasized the need for more comprehensive research, including longer-term studies with follow-up and randomized controlled trials, to further elucidate any potential cancer risks.
Broader Implications and Public Health Strategy
The WHO’s guideline on NSS carries significant implications for public health policy, food labeling, and consumer guidance. By advising against their use for weight management and disease prevention, the organization is signaling a move towards promoting dietary patterns that inherently reduce the demand for intense sweetness. This could influence regulatory bodies, food manufacturers, and public health campaigns worldwide.
The contrasting views between the WHO’s primary guideline and the analysis from Harvard Chan School underscore the ongoing scientific debate and the complexity of interpreting nutritional research. While the WHO’s broad recommendation leans towards caution and a fundamental dietary shift, the Harvard perspective suggests potential transitional benefits of NSS for certain populations. This highlights the importance of personalized dietary advice and the need for individuals to consult with healthcare professionals.
Ultimately, the WHO’s guidance encourages a proactive approach to health, emphasizing the long-term benefits of cultivating a preference for less sweet foods and beverages. This aligns with broader public health goals of combating obesity, diabetes, and cardiovascular diseases, which are major global health challenges. The organization’s stance serves as a potent reminder that while NSS may offer a temporary solution for reducing sugar intake, they are not a sustainable strategy for achieving optimal health and well-being. The emphasis remains on whole, unprocessed foods and beverages that provide essential nutrients without contributing to an overreliance on sweetness. The ongoing research into specific sweeteners like aspartame further underscores the dynamic nature of nutritional science and the continuous effort to provide the most accurate and beneficial guidance to the public.
