Comment by fasterik
2 days ago
Nutrition science has come up with acceptable macronutrient distribution ranges (AMDR). The recommendation for adults is 45-65% of total calories from carbohydrates, 20-35% from fat, and 10-35% from protein. That is definitely not low carb.
The sources of those macronutrients also matter. The ideal range for saturated fat is 5-10% of total calories. Meat consumption, especially red meat, is associated with higher risk of colorectal cancer. Dairy consumption is associated with higher risk of prostate cancer.
I haven't read the new guidelines in detail but if they're recommending red meat and whole milk as primary foods, then they are not consistent with the research on cancer and cardiovascular disease risk and I doubt that people following them would meet the AMDRs or ideal saturated fat intake.
To be fair, those macronutrient guidelines were established not because of any special properties of those macros (give or take the nitrogen load from protein) but because when applied as a population-level intervention they encourage sufficient fiber, magnesium, potassium, etc. You can have 50% of your calories be from fats and still live a long, healthy life, and you can do so as a population (see, e.g. Crete and some other Mediterranean sub-regions in the early/mid-1900s). You can have a much higher protein intake and have beneficial outcomes too.
Your point about the sources mattering isn't tangential; it's the entire point. The reason the AMDR exists is to encourage good sources. A diet of 65% white sugar and 25% butter isn't exactly what it had in mind though, and it's those sources you want to scrutinize more heavily.
Even for red meat though, when you control for cohort effects, income, and whatnot, and examine just plain red meat without added nitrites or anything, the effect size and study power diminishes to almost nothing. It's probably real, but it's not something I'm especially concerned about (I still don't eat much red meat, but that's for unrelated reasons).
To put the issue to scale, if you take the 18% increased risk in colorectal cancer from red meats as gospel (ignoring my assertions that it's more important to avoid hot dogs than lean steaks), or, hell, let's double that to 36%, your increased risk of death from the intervention of adding a significant portion of red meat to your diet is only half as impactful as the intervention of adding driving to your daily activities.
The new guidelines seem to be better than just recommending more steaks anyway. They're not perfect, but I've seen worse health advice.
Well, there are two factors that go into the recommendations. As you mentioned, one is adequate micronutrients. The other is chronic disease risk reduction. The 5-10% of total calories from saturated fat recommendation falls into the latter category. The risk of meat and dairy is not just cancer, but saturated fat.
I would agree that with proper knowledge and planning, it's possible to reduce carbs and increase protein/unsaturated fats while maintaining adequate fiber and micronutrients. But in practice, I think it's much more common to see people taking low-carb diet recommendations as a license to eat a pound or more of meat per day, drink gallons of milk per week, and completely ignore fiber intake, which is objectively not healthy.