Sugar is NOT toxic: Scientific perspectives on an unfounded hypothesis

Robert Lustig, a pediatric endocrinologist at the University of California, has garnered significant media and public attention by promoting his controversial view that sugar (or more specifically fructose) is “toxic” and responsible for obesity and other serious chronic diseases. He is best known for his lecture posted to YouTube in May 2009 (1) and subsequently his “Comment” published in the journal Nature, "The toxic truth about sugar" (2). He claims that fructose intake from sugars is excessive, and that like alcohol, it has toxic effects on the liver and the potential for abuse. These radical views as well as those in his new book, “Fat Chance: beating the odds against sugar, processed food, obesity and disease”, are not supported by the wealth of scientific evidence with regards to sugar consumption and health. These opinions have not been subject to the peer review process normally expected of meaningful contributions to the scientific literature. Instead he has chosen to base his dramatic assertions on misinformation and a misinterpretation of data, often used out of context (1-3).

Below is a brief summary of the peer-reviewed scientific evidence in relation to some of these controversial claims:

Sugars consumption in the Western World has remained stable, or even declined. Published data from national dietary surveys show that in the US (where Lustig is based), intakes of sugars have declined 23% between 1999 and 2008 (4). This declining trend has also been documented in the UK and Australia where intakes have fallen over the last 25 years (5-7). Lustig fails to clarify that the figures he quotes are values for sugar supply on the global market, and do not correspond to people's actual intakes (8).These values greatly overestimate actual sugar consumption as they do not account for waste at the retail, institutional and household levels. Global increases in sugar availability over the last 50 years reflect global population growth and development. To use this data as Lustig has, to state that consumption has tripled in the last 50 years is factually incorrect and misleading. In fact, at the individual level, the absolute and relative (%energy) availability of refined sugar has remained relatively stable during a period where total food energy available for consumption has steadily increased (8,9). In Canada, consumption of refined sugar has declined over the past 4 decades (10) and consumption of total added sugars is estimated to be stable or modestly declining as a percentage of total Calories (11).

Sugar is not associated with adverse health effects at the levels consumed by the general population. The totality of the scientific evidence concludes that sugar does not have a negative influence on behaviour, cancer, risk of obesity or heart disease (12-16). Even with respect to dental caries, the evidence concludes that it is the frequency of consumption of all fermentable carbohydrates that is the key issue as opposed to the absolute amount of sugars eaten. A number of major Expert Committees, such as the World Health Organization, Food and Agriculture Organization, European Food Safety Authority, and the US Institute of Medicine have considered all of the issues addressed by Lustig and his colleagues on a number of occasions, and have all concluded that there is no evidence of harm attributed to current sugar consumption levels (12-16).

Sugar consumption is not the cause of rising obesity rates. Current scientific reviews do not support the opinion that sugars are more likely to contribute to weight gain than any other source of Calories (17). The Canada - US DRI report (14), the basis for Canada’s dietary guidance, found “no clear and consistent association between increased intake of added sugars and body mass index (BMI)”. In fact, higher intakes of sugars are associated with lower body weights (17). Trends in sugar consumption plotted against obesity rates in Canada support this inverse correlation (10,18,19). Analysis of Canadian Community Health Survey data found that total energy intake significantly increased the odds of obesity for men and women, but the composition of their diets, meaning the relative percentages of carbohydrates, protein and fats was not a factor (20). These observations are consistent with the critical analysis of numerous high quality studies, which also do not support a link between sugars intake and the development of obesity (17). Obesity is a complex issue, which involves a combination of factors including but not limited to overconsumption of total Calories and physical inactivity.

Sugar and foods containing sugar are not addictive. A recent review of the literature on food addiction did not find convincing evidence to characterize foods as “addictive” because foods do not exhibit the criteria of substance abuse, such as tolerance, withdrawal, and intoxication (21). Although the sweet taste of sugar is pleasurable, studies do not support a specific role for sugar in increasing food cravings and sugar does not cause a physical dependence characteristic of addictive substances (22,23). The lack of any credible scientific support for the claim that sugar is addictive is detailed in the findings of a comprehensive review on sugar addiction, which concluded that “there is no support from the human literature for the hypothesis that sucrose may be physically addictive” and “on no occasion was the behaviour predicted by an animal model of sucrose addiction supported by human studies” (22).

The focus on the fructose component of sugars having toxic effects is not supported by the vast majority of credible scientific evidence. Findings from a limited number of animal studies and human studies involving abnormally high consumption of fructose do not reflect the role of fructose in the normal diet or its normal metabolism. It is only when excess energy is given as fructose at extreme levels of intake that increases in body weight and other abnormal health effects can be seen (24). Fructose does not cause biologically relevant changes as consumed in the general population, even at the highest levels of intake approaching the 95 percentile of intakes (25). Excessive consumption of any energy source is associated with excess body weight and metabolic changes, and fructose is no exception.

Critiques from other Health Professionals and Associations

A number of health professionals, Associations and academics all over the world have responded to the misleading claims stemming from the commentary "The toxic truth about sugar". Included among these are critiques from The British Nutrition Foundation, The Dietitians Association of Australia and The Australian Diabetes Council (see excerpts below). Several follow-up responses challenging the commentary were also published in the journal Nature, including a Canadian response from John L. Sievenpiper, Russell J. de Souza and David J.A. Jenkins (St. Michael's Hospital, Toronto, Ontario) (26).

British Nutrition Foundation: "Sugar is a source of energy in our diet and it is certainly not 'toxic' in the amounts on average consumed in the UK and other European countries... Overall, the commentary by Lustig and colleagues, published in Nature, does not reflect the current state of evidence around sugar and its association with chronic disease, as shown in some recent major systematic reviews." See: Facts behind the headlines - Is sugar really toxic?

Dietitians Association of Australia: "The Dietitians Association of Australia (DAA) believes it is simplistic and unhelpful to blame sugar alone for rising rates of obesity and other related health problems across the world. Labelling sugar as 'toxic' and 'addictive' and placing it in the same boat as alcohol is incorrect and misleading." Also see: DAA - sugar and obesity; and DAA - letter to media. 

Australian Diabetes Council: "This commentary is a provocative piece intended to encourage debate...'Sugar' is not the issue, it is far more complicated than that. The average Australian can do a lot to improve their diet, but casting sugar as the ultimate villain and calling for regulation is misleading, unfounded and unnecessary." Also see: Australian Diabetes Council's position on sugar - Australian Diabetes Council calls for balanced eating, not fad diets. 

References:

1. Lustig, R. H. Sugar: The Bitter Truth. UCSF Mini Medical School for the Public 7/2009, Health and Medicine, Show ID: 16717. 2009.
2. Lustig RH, Schmidt LA, Brindis CD. Public health: The toxic truth about sugar. Nature 2012;482:27-9.
3. Lustig RH. Fat Chance: Beating the Odds Against Sugar, Processed Food, Obesity and Disease. USA: Hudson Street Press, 2012.
4. Welsh JA, Sharma AJ, Grellinger L, Vos MB. Consumption of added sugars is decreasing in the United States. Am J Clin Nutr 2011.
5. Gregory J, Foster K, Tyler H, Wiseman M. The Dietary and Nutritional Survey of British Adults (1986-87). Her Majesty's Stationery Office, London 1990.
6. Department of Health. National Diet and Nutrition Survey: Headline results from Years 1,2 and 3 (combined) of the rolling programme 2008 - 2011. UK 2012.
7. Barclay AW, Brand-Miller J. The Australian Paradox: A Substantial Decline in Sugars Intake over the Same Timeframe that Overweight and Obesity Have Increased. Nutrients 2011;3:491-504.
8. FAOSTAT. Food and Agriculture Organization. http://faostat.fao.org 2012.
9. United Nations Population Fund. State of World Population 2011. UNFPA, New York 2011.
10. Statistics Canada. Food Statistics. 2012.
11. Canadian Sugar Institute. Estimated Intakes of Added Sugars in Canada and Relationship to Trends in Body Weight. Carbohydrate News 2011.
12. European Food Safety Authority. Scientific Opinion on dietary reference values for carbohydrates and dietary fibre. The EFSA Journal 2010;8:1462
13. World Health Organization and Food and Agriculture Organization. Diet, nutrition and the prevention of chronic diseases. Report of a Joint FAO/WHO Expert Consultation. WHO Technical Report Series 916. WHO Geneva, Switzerland 2003.
14. Institute of Medicine. Dietary Reference Intakes (DRI) for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, D.C.: The National Academies Press, 2005.
15. Food and Agriculture Organization. Report of a Joint FAO/WHO Expert Consultation. Carbohydrates in Human Nutrition. FAO Food and Nutrition Paper No 66, 1998.
16. Department of Health. Dietary Sugars and Human Disease. Committee on Medical Aspects of Food Policy. Report on Health and Social Subjects. Her Majesty's Stationery Office. 37. 1989. London.
17. Ruxton CH, Gardner EJ, McNulty HM. Is sugar consumption detrimental to health? A review of the evidence 1995-2006. Crit Rev Food Sci Nutr 2010;50:1-19.
18. Health Canada. Canadian Community Health Survey, Cycle 2.2, Nutrition. 2004.
19. Statistics Canada. National Population Health Survey. 1994-1999.
20. Langlois K, Garriguet D, Findlay L. Diet composition and obesity among Canadian adults. Health Rep 2009;20:11-20.
21. Ziauddeen H, Fletcher PC. Is food addiction a valid and useful concept? Obes Rev 2012.
22. Benton D. The plausibility of sugar addiction and its role in obesity and eating disorders. Clin Nutr 2010;29:288-303.
23. World Health Organization. Neuroscience of psychoactive substance use and dependence. WHO Geneva, Switzerland 2004.
24. Sievenpiper JL, de Souza RJ, Mirrahimi A et al. Effect of Fructose on Body Weight in Controlled Feeding Trials: A Systematic Review and Meta-analysis. Ann Intern Med 2012;156:291-304.
25. Dolan LC, Potter SM, Burdock GA. Evidence-based review on the effect of normal dietary consumption of fructose on development of hyperlipidemia and obesity in healthy, normal weight individuals. Crit Rev Food Sci Nutr 2010;50:53-84.
26. Sievenpiper JL, de Souza RJ, Jenkins DJ. Sugar: fruit fructose is still healthy. Nature 2012;482:470.