Is Sugar Really Sugar?

   

     Last week an article published by Nature proposed that sugar be regulated in much the same way as tobacco and alcohol. Citing the UN, deaths caused by “chronic non-communicable diseases such as heart disease, cancer and diabetes pose a greater health burden worldwide than do infectious diseases, contributing to 35 million deaths annually.” The authors go on to describe the connection between increased rates of sugar consumption and the rising cases of metabolic syndrome worldwide.  These disorders are characterized by, but not limited to, obesity, hypertension, cardiovascular and liver disease.

     This has prompted the American Beverage Association to respond, “There is no evidence that focusing solely on reducing sugar intake would have any meaningful public health impact. Importantly, we know that the body of scientific evidence does not support that sugar, in any of its various forms – including fructose, is a unique cause of chronic health conditions such as obesity, diabetes, hypertension, cardiovascular disease or metabolic syndrome.” The Sugar Association largely concurs and adds that the use of beet or cane sugar has decreased over the same time period that the obesity epidemic has increased. Conveniently, the Sugar Association fails to mention that the use of high-fructose corn syrup (HFCS) filled in the gap:

     Why would the Sugar Association not mention HFCS? That’s because they don’t represent the HFCS industry–that’s the job of the Corn Refiner’s Association. And they have remained relatively silent on this front. Maybe they’ve been humbled by all the irony wrapped up in this episode. It’s no secret that HFCS has taken a few bumps over the last few years. The growing natural, health food trend has seriously impacted HFCS’s image and has affected sales. In response, the CFA has spent the last 2 years on a marketing campaign to rebrand their product as corn sugar, stating that, “Health and nutrition experts, including doctors, dietitians, researchers and professional organizations, are in agreement that whether it’s corn sugar — by which we mean HFCS, a sugar made from corn — or cane sugar, your body can’t tell the difference. Sugar is sugar.” Further muddying the waters is that corn sugar has long been the FDA-approved name for dextrose, which is corn-derived glucose (confused yet?). No love has been lost between the two competing industries as sugar growers have accused the corn industry of deceptive practices and a national false advertising campaign. If you ask me, looking at the graph above, the Sugar Association missed an opportunity to stick it to the Corn Refiner’s Association and lay the obesity blame at the feet of HFCS through the power of correlation!

Many shapes, one flavor

     Sugar is a loose term used to describe a class of molecules known as carbohydrates (organic compounds consisting of carbon, hydrogen and oxygen) characterized by a sweet taste. Dietary sugars typtically come in two forms known as monosaccharides and disaccharides. For instance sucrose, otherwise known as table sugar, is a disaccharide consisting of the monosaccharides glucose and fructose chemically linked together. Another example of a monosaccharide is lactose.

     Which brings me back to the premise that HFCS is a sugar. If A=B and B=C, then sugar must be sugar. Or is it? The authors of the Nature article explain, HFCS “is manufactured from corn syrup (glucose), processed to yield a roughly equal mixture of glucose and fructose.” However, there are chemical differences. Sucrose is extracted primarily from sugarcane or sugar beets, whereas HFCS is produced by a multistep process that starts with milling corn into corn starch, processing that corn starch into glucose syrup followed by enzymatic conversion of glucose into fructose. HFCS (55) is a blend of 55% free fructose and ~42% free glucose, while table sugar (sucrose) is 1 molecule of fructose chemically linked to 1 molecule of glucose.

Dangers of Fructose?

     Although sugar has long been thought of as “empty calories” that contributes to obesity, a growing body of evidence points to the connection between sugar, in particular fructose, and chronic illness such as high blood pressure, liver disease, and cardiovascular disease. Whereas glucose metabolism mostly yields the cell’s main fuel, ATP (adenosine triphosphosphate), fructose is primarily shunted into replenishing the body’s stored energy in the form of glycogen and fat. Chronic exposure to a high fructose diet may lead to elevated levels of fats (triglycerides) and cholesterol in the bloodstream which in turn increases the risk of metabolic syndrome. This has prompted researchers to target either the composition or bioavailability of fructose in HFCS as a potential difference between sucrose and HFCS. Bioavailability is the amount of or rate at which a substance or drug is accessible to the body. Scientists hypothesize that the higher % composition of free(unlinked) fructose in HFCS may in fact make HFCS more unhealthy than sucrose because more fructose is immediately available. In the case of table sugar, the bioavailability of fructose would be limited by the rate at which sucrose is cleaved into glucose and fructose.

     Two recent studies have suggested that sucrose and HFCS are not equivalent. Research conducted at Princeton revealed that mice fed water sweetened with HFCS gained more weight than mice fed water sweetened with equal amounts of sucrose. Furthermore, the researchers monitored rats fed a HFCS-diet for 6 months and observed signs of “ metabolic syndrome, including abnormal weight gain, significant increases in circulating triglycerides and augmented fat deposition, especially visceral fat around the belly.” In a study published in December 2011, healthy individuals who drank HFCS-sweetened Dr. Pepper had higher systolic blood pressure and higher amounts of fructose and uric acid in their blood serum (the blood fraction without blood cells and clotting factors) when compare to individuals who drank sugar-sweetened Dr. Pepper shortly after exposure.

    Dr. Pepper Throwback: I got 23 flavors but high-fructose corn syrup ain’t one…

     High uric acid is known to increase blood pressure and is associated with cardiovascular disease, type 2 diabetes and metabolic syndrome. However, the authors could not make definitive conclusions regarding the the relative bioavailability of fructose from HFCS vs sucrose. The amount of sucrose in the sugar-sweetened Dr. Pepper at the start of the study had already partially broken down into glucose and fructose and by the end of the study had completely converted into equal parts glucose and fructose. That being said, the total amount of fructose in the HFCS-sweetened Dr. Pepper was still higher at the start and end of the study than the amount in the sugar-sweetened Dr. Pepper. This suggests that the higher fructose content led to an increase in blood pressure, and higher fructose and uric acid serum levels. Needless to say, as with much of science, more work needs to be done.

You say tomato, I say tomahto…

     Perhaps this may all seem like a bit of semantics. After all, it is difficult to exactly pinpoint the causes of metabolic syndrome given that the overall eating habits of Americans have trended up and is confounded by a sedentary lifestyle. But from a public and health policy standpoint it is important that clear definitions and distinctions be made regarding added sweeteners– whether it be sugar or HFCS. Otherwise, it allows for claims like these to be made by the Heritage Foundation, “will higher-priced sugar lead to less consumption? If this logic held, America would already be healthier. Here’s why: The price of sugar is artificially high thanks to federal sugar subsidies and other regulations that, yet Americans still have a sweet tooth,” without acknowledging that the food industry more often than not turns to using HFCS, the price of which is kept artificially low through federal subsidies to corn growers.
Is it fair to say that Americans need to eat less? Yes. Is it fair to say that Americans need to exercise more? Yes. Is it fair to single-out one industry (well really 2, 3 if you count the food industry as a whole as well)? Maybe not. I don’t pretend to know whether added taxes or regulations on added sweeteners would stem the metabolic disease tide but we surely can’t ignore it and its public cost. And in that light, I commend the authors of the Nature article for kick starting a very important conversation, one in which I’ve heard very little in terms of alternatives from the targeted industries. Maybe we should start with re-examining the ways in which we subsidize our foods…

Le, M.T. et al. Effects of high-fructose corn syrup and sucrose on the pharmacokinetics of fructose and acute metabolic and hemodynamic responses in healthy subjects. Metabolism: Clinical and Experimental (2011). DOI:10.1016/j.metabol.2011.09.013

Lustig, R.H., Schmidt, L.A. & Brindis, C.D. Public health: The toxic truth about sugar. Nature 482, 27-29 (2012). DOI: 10.1038/482027a

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