Meat

I sure am glad it's not my job to come up with the best eating plan for all Americans, let alone the world.¹ (The World Health Organization has my sympathy.) The choices and defenders of those choices are numerous and polarized.

Regarding carbohydrates, it may be that a low-carbohydrate diet, around 10% of calories, is the best eating plan for overall health for everyone. Alternatively, it may be that a high-carbohydrate diet, above 45% of calories, is. Research has not sufficiently compared and contrasted the two.

From my reading, I do think that the type of carbohydrate plays a role in health. Carb from lentils is probably better than carb from Twinkies. Carb from an apple is probably better than carb from a bagel.

One reservation I have is the amount of meat, poultry, and fish a low-carbohydrate diet necessitates eating.

• Cooked and processed meat contains compounds than have been linked to cancer in humans (heterocyclic amines (which are estrogenic), polycyclic aromatic hydrocarbons, etc.). Many are known animal carcinogens.
  
  
• Hormones in meat, especially those administered in an industrial setting, have not been fully investigated for long-term effect, and have been linked to hormone-dependent cancer in humans.
  
  
• Heme iron, a highly bioavailable form of iron found in red meat, has been linked to hormone-dependent (and other) cancers and diabetes, through a possible mechanism of increased oxidative stress. Its long-term impact on health is not known.
  
  
• All fish contains mercury.
  
  
• To recommend this change for public health would require a spectacular increase in livestock production, especially given the UN's predictions of population growth in the next few decades. I am skeptical this increase can occur without an increase in factory farming ... and its attendant problems of antibiotic use (developing resistant strains), bacterial infection (e.g. E. coli), and environmental damage.

None of the above is to imply that an alternative high-carbohydrate diet, one that relies on seeds (wheat, rice, soy, corn, beans, etc.), doesn't come without components linked to disease, or without environmental impact.

It may very well be that the public health benefit of increased global meat and fish production, and consumption, outweighs hypothesized risks to health and the environment. Certainly, the increase of global grain production has not had a benign impact on those variables. As far as I can tell, this cost-benefit analysis has not been done.
________¹ Marion Nestle, author of "Food Politics", "Safe Food", and recently "What To Eat" addressed this how-best-to-feed-the-planet issue on her blog post: Today's Question: Feed Efficiency.
Her recent post addresses the renewed interest in low-carbohydrate diets: Sorting Out Low-Fat Vs. Low-Carbohydrate.