Fuel for the carb-protein wars!

Be warned: these studies will start getting cited in the nutrition wars. Okay that’s the this side of the wall summary of the summary of the studies in last week’s Science. From their other side of the wall synopsis:

The actual mouse study.

Th actual human study.

The mouse study in my mind is pretty poor. Studying protein levels up to 60% of caloric intake?? That is more than most think of as high protein. Typical American gets, as noted, about 16% of calories from protein. For most high protein means 25 to 30%. The supplemental information pg 8 gives the actual mortality numbers for the different diet plans. The highest median lifespan was actually a 42% protein diet and it was not far off from the top numbers for longest lifespan. On page 7 of that supplement it is noted that the animals in 3 the low protein groups wer dropped from analysis early because they were too unhealthy (lost too much weight or develped other health issues) to continue. Not quite a fair analysis.

The human study seems a bit better. From its summary:

This is not enough yet to convince me honestly and for my own sake I am planning to keep up with my relatively high protein high fiber (heavy on the plant derived proteins) nutrition approach. (Not low carb mind you.)

But I am sure that these studies will get cited in the nutrition wars and felt that those who are combatants should get a heads up!


Hmm. I don’t have any studies to cite, but hey, we aren’t in GQ or GD here. Here’s my guess:

There’s a segment of the population who run well on a high-carb, low-protein diet, and they happen to also have a much lower risk of diabetes precisely because their bodies handle carbs so well.

Then there’s another segment of the population (of which I am one) whose bodies can’t handle carbs and who become insulin-resistant early in life. This segment finds, consciously or unconsciously, that it feels better on a higher protein diet. Unfortunately our bodies are so whacked that we tend to come down with diabetes and obesity-related diseases much more frequently than the people in the other group.

For anyone interested in this topic, The Hundered Year Diet is a fascinating history of how thinking about the best approach to diet has see-sawed back and forth over the past 100 years.

Digging more into the article I am less impressed with the second one as well.

Not even any real attempt to control for confounders.

Just as a layman there’s also (IMO) a significant difference in people who get lots of protein by being big consumers of fatty meats in fast food (especially beef and pork) and other sources and those who have a higher protein ratio diet with the protein being mostly lean meats and other low fat protein sources.

Plus if following a high protein diet is keeping 20-50 lbs off you would have with a more carb centric diet I would think the overall health benefits of being less heavy would swap the protein risk issues in importance.

Your first point and Sattua’s are both wondering about confounders - some tendency of those who will later develop diabetes to be in the higher protein group even if they do not have diabetes at baseline just based on who knows how they feel when they eat lots of carbs, what other specifics travel with being in those groups, amount and type of fat, fiber, what sort of carbs … ? And very valid comments I think.

The second point though is exactly the point they are claiming is not true. Thinner with higher protein, in particular animal protein, and lower carb, they claimed, was not healthier in terms of the outcomes measured in the 50 to 65 year old group.

I particular though get cracked up by the fact that they, like the low carb zealots, see insulin as a likely culprit … “Our study indicates that high levels of animal proteins, promoting increases in IGF-1 and possibly insulin, is one of the major promoters of mortality for people age 50–65 in the 18 years following the survey …”

Poor insulin. It gets no respect. :slight_smile:

Even more odd to my read is their raising mTOR and IGF-1 as potential evils. The IGF-1/mTOR pathway is requisite for building muscle and mTOR in particular increases with exercise, which obviously is well associated with improved outcomes.