Friday, September 11, 2009
Image by AdamSelwood.
In the past, I have written several posts about sugar (mainly fructose and high fructose corn syrup, aka HFCS), and how it is a driving force behind the current obesity epidemic. The evidence is compelling - the intake of added sugars (especially HFCS) has dramatically increased over the past 30 years, an increase which is mirrored by the increased prevalence of obesity. Further, these added sugars are "empty" calories, which tend to displace other foods that contain more nutrients. Then there are the many ways that sugar (again, especially HFCS) disrupts both metabolism and the hormones that signal satiety, resulting in increased health risk as well as increased food intake (outlined wonderfully in this powerpoint presentation by Dr Robert Lustig of the University of California at San Fransisco). That's right - sugar can actually make you more hungry! The insulin response to sugar and resulting lethargy may result in decreased energy expenditure as well. In short, sugar does many bad things to the human body, and it should be limited to a very small portion of our daily diet.
Now is any of this really a shock to anyone? Probably not. Even the food industry agrees that both sugar and HFCS should only be consumed in moderation. Don't believe me? Check out this commercial for HFCS (email subscribers will need to visit our main page to see the clip):
Ok, so they reverse the statement to say that HFCS is fine in moderation, but the natural implication is that it's not ok to consume in excessive amounts.
But what amount of sugar is moderate, and what amount is excessive? One can of pop? A half-litre of chocolate milk? Without a concrete value attached to it, "moderation" is pretty useless as a public health message. Thankfully, the American Heart Association has stepped in to fill the gap, with an excellent new review paper that outlines all of the arguments against sugar intake, and then gives concrete recommendations on the amounts that we should be consuming on a daily basis.
The paper, which will be published next week in the journal Circulation, was written by Rachel Johnson and other experts in the fields of nutrition, physical activity, metabolism, and epidemiology. They make an incredibly strong (and readable) argument that sugar and fructose have toxic effects on the human body, and that people should limit their intake accordingly, just as they would for other toxic substances. What is that upper limit? As the authors put it:
"A prudent upper limit of intake is half of the discretionary calorie allowance that can be accommodated within the appropriate energy intake level needed for a person to achieve or maintain a healthy weight based on the US Department of Agriculture food intake patterns".
I know that's a bit wordy, so I'll give a concrete example. Let's say that you're an average male, and thus require 2,200 calories per day to maintain body weight. It is assumed that it will take roughly 1900 calories to meet your nutrient needs (e.g. vitamins, minerals, etc), which leaves you with 300 "discretionary" calories that do not contribute to your nutrient needs. This report suggests that no more than half of these discretionary calories should be in the form of sugar.
Thus, men should limit their intake of added sugars to roughly 150 calories/day (9 teaspoons) while women should limit themselves to 80 calories (5 teaspoons). For reference, a normal can of pop has 8 teaspoons of sugar and 130 calories. In other words, try to limit your sugar intake to very low levels.
Now the authors go out of their way to say that these limits apply only to "added" sugars, and not to those found naturally in fruits and vegetables. The word juice is never mentioned in their report, but the sugars in juice are no different from those in pop, and there is no reason to think that they have any different effect on the human body. So best to limit your juice intake as well - eat your fruits and veggies instead.
The American Heart Association report is freely available, and it is excellent reading for anyone interested in the health effects of sugar consumption. It can be found here.
Have a great weekend,
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Johnson, R., Appel, L., Brands, M., Howard, B., Lefevre, M., Lustig, R., Sacks, F., Steffen, L., Wylie-Rosett, J., & , . (2009). Dietary Sugars Intake and Cardiovascular Health. A Scientific Statement From the American Heart Association Circulation DOI: 10.1161/CIRCULATIONAHA.109.192627
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