Saturday, February 28, 2015

Nutrition Confusionism

The new draft Dietary Guidelines were just released. I won't post the link here, because few people will read the dense document. The major take home points were: eat more whole fruits and vegetables, less sugar, less meat, less saturated fat, less salt, and don't worry about cholesterol too much.

I was just at the Partnership for a Healthier America conference, where lots of nutrition experts mingled with lots of food company executives. There was a lot of confusion and snickering amongst the group. Some decried the Committee for stating that how much cholesterol you eat is not that important. Others asked why saturated fat and salt were still emphasized, even though the best evidence does not support reducing these food ingredients to improve health.

The non-scientists asked the scientists why nutrition is so confusing. They made it sound like the science was constantly changing, but the guidelines committees ignored the science. I listened to this segment of NPR's Science Friday, where the host asks why the nutritionists, "have known that eggs are ok to eat, but the rest of us didn't."

Who is at fault here? I'm not sure. But I recently skimmed through my nutrition courses from when I was an undergraduate at Cornell. I went through my notes where I indicated that we were taught that is very difficult to find an association between salt and hypertension within a population. I also had copious notes stating that the connection between calcium intake and bone health was weak. (Thanks to Charles McCormick for this great class!)

I then went to my intro course table of contents and found our lecture titles: "Diet and serum cholesterol: environment or biology?", implicating that cholesterol in the diet doesn't matter that much. Another was, "Ambiguous connections: salt and hypertension". Thank you Dr. Levitsky for teaching us how to think about the facts without the hype.

The "new" news that we do not have great evidence dietary cholesterol, salt, and other nutrients are critical for health, is really not that new. I was learning it back in 1997.

So now people are telling us nutrition is confusing and that we said salt, cholesterol, and fat are bad and then good. I'm not sure where the confusion comes from. Is it from nutrition researchers who devote their careers to studying the role of one nutrient and its effect on health? Is it from journalists who love to sensationalize the latest food craze based on one study? Or is it from food companies who make so many claims about food and health, that we end up just buying whatever sounds good at the time?

I'm not going to blame one group. We are all part of the problem. But, one thing has been consistent throughout the years. This fact is summed up in this line in the new dietary guidelines report:
"Vegetables and fruit are the only characteristics of the diet that were consistently identified in every conclusion statement across the health outcomes."
So just follow the simple advice to eat more (whole) fruits and vegetables. (Sorry smoothies and vegetable juices don't count.) Avoid the processed junk. That advice is probably a few generations old.