วันพฤหัสบดีที่ 23 เมษายน พ.ศ. 2558

Why Eggs And Other Cholesterol-Laden Foods Pose Little Or No Health Risk

Yesterday, the press and public health community confused consumers with the message that an advisory panel was urging the government to stop warning people off eggs despite high cholesterol content. Stories such as The return of the egg? New dietary guidelines may downplay cholesterol risks on Fox News left people guessing as to whether or not this change would be bad or good for human health. Here’s what the Fox News version of the story said:
“The recommendations from the Dietary Guidelines Advisory Committee, which are now under review, are expected to downplay the importance of lowering cholesterol intake.
The most recent set of guidelines in 2010 recommended consuming less than 300 milligrams per day of dietary cholesterol, which is about the amount in one egg.”
Are doctors backing off an important health warning? If cholesterol is indeed a “risk” why are they changing their tune?
The answer is pretty simple, though it flies the face of some longstanding prejudices. Scientists have known for years that most of the cholesterol in food gets broken down, discarded, or used to make bile acids, which you need to digest food. Some cholesterol is also needed to make hormones and cell membranes. The cholesterol in your blood – you make most of that yourself, said Dan Rader, a professor of molecular medicine at the University of Pennsylvania.
It may sound perverse – why would your body make something as evil as cholesterol? Well, because it’s not actually evil. Animals need cholesterol for various jobs, but as Rader explains, we also need to be able to clean up the excess. People get high cholesterol because the mechanism for cleaning up extra cholesterol isn’t working well. The main risk factors for poor cholesterol cleanup include genes and dietary factors other than cholesterol consumption. He cites trans fats (in processed foods) and saturated fats(from certain animal products) as risk factors.
“It’s counterintuitive,” he said, “But most of the cholesterol in our blood is not derived from our diets. Every cell in your body makes cholesterol.” The old guidelines, he said, were based on a wrong assumption. “We now know that cholesterol in the diet makes very little difference in terms of bad cholesterol in blood.”
The scandal here is that it’s taking so long for science to get incorporated into nutritional guidelines. The reason for the foot-dragging can be seen in some of the quotes from doctors, urging “caution” in lifting eggs from the bad list until they were sure beyond a shadow of a doubt that this food would not cause harm.
Their inertia reflects a common fallacy in nutrition – the ludicrous notion that you can just cut out foods without people reaching for other kinds of food. The reality is that many of us aren’t even fat and need to eat a whole lot of food every day to function. If you cut out eggs, you’ve got to add something else to substitute for it. A look around a supermarket or restaurant breakfast menu gives a pretty good idea what Americans are eating instead of eggs: Towers of syrupy pancakes, pop tarts, fruit loops, coco puffs, Fred Flintstone portions of pastries and bagels.
The food nannies had an easy time getting Americans to avoid eggs, since they represent effort to cook. It seemed like a win-win that we could feel good about feeding our families sugar corn pops, which are easier all around.

Unfortunately, there are risks to sugar and starch. Some people have tied them to the ongoing epidemics of obesity and type 2 diabetes.
Penn’s Rader said he agreed that going on a low fat, higher carb diet isn’t the right choice for many people. I followed Rader in his medical rounds a few years ago for a story about his pioneering approach to health care, which involved treating every patient differently. That idea is now catching on as personalized medicine, or more recently, “precision medicine” – recently cited by Obama in his State of the Union Address.
But there are some universals. Trans fats don’t appear to be good for anyone. Growing children need certain nutrients to thrive. There is a place for government guidelines. But the question that remains: If the government has been slow to incorporate the correct science on eggs, should we still take nutritional guidelines seriously on anything else?

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