C&B Notes

Sugar’s Turn on the Stand

Lost from the discussion about healthy diets is the thermodynamic fact that the ‘marginal’ calorie is the most important consideration.  Fats and carbs have had their unfortunate turns as the cause of obesity, and now sugar is in the crosshairs.

…if there is a problem in all of this, it’s that speaking definitively before definitiveness is due can spread more confusion.  Some find the “sugar is the enemy” message to be an oversimplification that makes the same mistake as the “fat is the enemy” message it is replacing: Advocating nutrient-focused eating instead of a holistic approach to eating nutritious foods, and less of it.  In “Is Sugar Toxic?,” a popular 2011 feature story in The New York Times Magazine, brigade member Gary Taubes offered the provocation, “If what happens in laboratory rodents also happens in humans, and if we are eating enough sugar to make it happen, then we are in trouble.”  Reasonable people disagree on the magnitude of those ifs.

“To say that fructose is toxic is a total misconception of the nature of the molecule,” Fred Brouns, a professor of Health Food Innovation at Maastricht University in the Netherlands, recently told me. “If you have too much oxygen, it is toxic. If you get too much water, you have water intoxication. That doesn’t mean we say oxygen is toxic.”  In March, Brouns published a challenge in the journal Nutrition Research Review titled “Misconceptions About Fructose-Containing Sugars and Their Role in the Obesity Epidemic.”  It took the fructose story to task, noting the integral role that popular media plays in science: “Since the recent publications of Lustig and co-workers, in which it was suggested that fructose is toxic and should be ‘treated as alcohol,’ the daily news all over the world highlighted fructose in sugar-sweetened beverages as a potential poison. …  The metabolic effects of fructose presented in ordinary human diets remain poorly investigated and highly controversial. …  One may rather aim at reducing the consumption of energy-dense foods.”   Brouns makes a call for skepticism, not absolution. “There have been studies that show fructose, when consumed in isolation, can be toxic,” he told me, “but we never consume fructose in isolation. It is eaten with glucose.”

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A recent review of many large meta-analysis studies did find that calories from sugar are all the same in terms of obesity outcomes.  Be it bread, pasta, or pixie sticks, the researchers found that at least when it comes to carbs and weight, a calorie is a calorie.  “Intake of sugars is a determinant of body weight in free living people consuming ad libitum diets,” authors led by Jim Mann, professor of human nutrition and medicine at the University of Otago in New Zealand, write, referring to the fact that people advised to eat less sugar all seem to lose an average of two pounds.  The study’s conclusion corroborated the traditional wisdom about calories and weight loss: “Change in body fatness that occurs with modifying intake of sugars results from an alteration in energy balance,” not from metabolic consequence of particular sugars.  They found that replacing sugars with other carbohydrates “did not result in any change in body weight.”  Roughly translated, for body weight, a calorie of carbs is a calorie of carbs.  Though, this didn’t take into account fatty liver or heart disease that Lustig notes can well be present in the skinniest of people.

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Brouns, similarly, says that industry can help by cutting down on added sugars, but “blaming added sugar as the main cause of obesity is totally wrong.  I think that is misleading the public. Pretty soon everybody will be focusing on sugars in the same way that, years ago, everybody was focusing on fat.” The glycemic index concept told us that foods high on the scale (high in glucose or anything that quickly breaks down into glucose) cause our blood sugar to spike and fall, to ill effect. It was this same glycemic-index that led Oz to recommend agave nectar to Oprah.  The glycemic index has proven to be a very rough indicator of a food’s quality — for example, carrots have a high glycemic index, and lard has a glycemic index of zero.  Isolated metrics can justify one way of eating or another, to make claims on packages and in commercials.  Trends in nutrient-based eating come and go.

Yesterday agave was in, and today it’s out.  “Natural” has little meaning for health outside of produce aisles.  Eliminating sugars from a diet can’t constitute playing it safe, in that it means getting calories elsewhere — just as the advice to cut out fat in the 1980s is blamed for making people increase their consumption of sugar.  Too much fat is bad, too much protein is bad, and too much starch is bad.  Everything is good, and everything is bad.  Even looking back, the basic tenets of the original 1980 USDA nutrition guidelines really do seem to hold up: “Eat a variety of foods; avoid too much fat, saturated fat, and cholesterol; eat foods with adequate starch and fiber; avoid too much sugar; avoid too much sodium.”  And, of course, “Food alone cannot make you healthy.”