Is sugar a toxin?

[AllieParticipant]

Can added sugar and fructose be considered a toxin because of the way your body digests it?

[MeganParticipant]

Sugar, specifically fructose, has received a lot of attention lately after the viral video lecture and articles by Robert Lustig in 2006. Many researchers have tried to evaluate the role of fructose and its possibly toxicity in the human body. Some researchers are claiming like Lustig that increased fructose consumption mainly from sugar and high fructose corn syrup in the American diet, is the cause for the obesity epidemic and rise in metabolic syndrome. Fructose is thought to potently stimulate lipogenesis (1). The conversion of fructose to the glucose takes place almost exclusively in the liver and therefore is believed to cause non-alcoholic fatty liver disease (NAFLD) when done in high amounts (1) (thus Lustig comparison of fructose to alcohol). In a study by Ouyang et al. Participants with NAFLD were compared to controls matched for gender, age, and BMI. Those with NAFLD consumed 2-3 times more fructose than their control counterparts, which indicated that excessive fructose consumption, may play a role in the mechanism underlying the development of NAFLD (2).
There is a large body of evidence to show the possibility that a high fructose diet leads to obesity, diabetes, and dyslipidemia in rodents (3). In humans, these same effects are seen with high calorie diets, but not fructose exclusively (3). High fructose consumptions has been shown to increase plasma triglycerides in some studies, however further effects of this are unknown (3). Another study looked at daily fructose consumption of over 17,000 American subjects age 19-80 years and found that fructose was rarely consumed alone, only contributed to about 37% of total sugar intake and 9% of energy intake. They also found that it was not positively associated with serum triglycerides, HDL, cholesterol, glycohemoglobin, uric acid, blood pressure, waist circumference or BMI. (4)
In a recent Questions and Answer article with BMC, renowned sugar expert Luc Tappy stated that, “Given the substantial consumption of fructose in our diet, mainly from sweetened beverages, sweet snacks, and cereal products with added sugar, and the fact that fructose is an entirely dispensable nutrient, it appears sound to limit consumption of sugar as part of any weight loss program and in individuals at high risk of developing metabolic diseases. There is no evidence, however, that fructose is the sole, or even the main factor in the development of these diseases, nor that it is deleterious to everybody, and public health initiatives should therefore broadly focus on the promotion of healthy lifestyles generally, with restriction of both sugar and saturated fat intakes, and consumption of whole grains, fresh fruits and vegetables rather than focusing exclusively on reduction of sugar intake” (5).

1: Varman ST. Fructose induced lipogenesis: from sugar to fat to insulin resistance. Trends in Endocrinology & Metabolism. 2011; 22(2): 60-65.

2: Ouyang X, Cirillo P, Sautin Y, et al. Fructose consumption as a risk factor for non-alcoholic fatty liver disease. Journal of Hepatology. 2008; 48(6): 993-999.

3: Tappy L, Lê KA, Tran C, Paquot N. Fructose and metabolic disease: New findings, new questions. Nutrition. 2010; 26(11): 1044-1049.

4: Sun SZ, Anderson GH, Fickinger BD, Williamson-Hughes PS, Empie MW. Fructose and non-fructose sugar intakes in the US population and their associations with indicators of the metabolic syndrome. Food Chem Toxicol. 2011; 49(11); 2875-2882.

5: Tappy L. Q&A: “Toxic” effects of sugar: should we be afraid of fructose? BMC Biology. 2012; 10(42) Available at: http://www.biomedcentral.com/1741-7007/10/42.

[AllieParticipant]

​Thanks for your response, Megan! I actually spent some time watching a lecture by Robert Lustig, which is what really piqued my interest in this topic. The biochemistry of the way in which fructose is digested, as opposed to other sugars, such at glucose, is very convincing evidence on the harmful effects fructose could have. However, as I have examined various studies in my research, the evidence becomes quite a bit more foggy.​ For example, I found NHANES data that observed women from 1991-1999 and found that there was no association between fructose intake and cases of metabolic syndrome, uric acid levels, and BMI (1). I really hope that more research is done on this topic, because I find it quite fascinating!

1. Sun, S.Z., Anderson, G.H., Flickinger, B.D., et. al. ” Fructose and non-fructose sugar intakes in the US population and their associations with indicators of metabolic syndrome.” Food and Chemical Toxicity. Vol. 49(11): 2875-2882.

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