Matt Stone is doing an interesting series on the damage to the thyroid caused by eating too much muscle meat instead of the gelatinous materials found in the other half of the animal.
Muscle meats and eggs are very rich in methionine, which increases our need for homocysteine-neutralizing nutrients (vitamins B6, B12, folate, betaine, and choline), and also increases our need for the amino acid glycine, found most abundantly in skin and bones.
Thus, although having a PEMT gene that Uncle Buck would surely envy might lower our choline requirement, consuming lots of methionine won't help us at all. In fact, extra methionine just gives us more homocysteine and thereby increases our need for choline, betaine, folate, B12, and B6.
Glycine is depleted in the detoxification of excess methionine, another amino acid. Eggs and meat are the main sources of methionine—it not only constitutes a greater percentage of their total protein but these foods are also higher in total protein than plant foods (see Figure 9).56 It is important, therefore, for the expectant mother to liberally match her eggs and muscle meats with glycine-rich skin and bones and folate-rich liver, legumes and greens.
While the metabolism of methionine uses up glycine, betaine and folate can generate glycine in addition to neutralizing homocysteine, although the effect of betaine is restricted primarily to certain tissues such as the liver and kidney.
But where's all the folate? Liver and beans. You can get lots of folate if you eat liver, and you can get lots by eating lentil soup, but if you're eating a bean-free diet and you can't stand the taste of liver, you're going to have to eat the quantities of green vegetables that Joel Fuhrman recommends in order to obtain a comparable amount of folate.
Thus, while many people may improve their digestion and other symptoms by removing wheat and beans, the fact that they may consider these foods “evil” does not automatically deliver them from the need to make up these nutrients from some other source. Muscle meats will always increase the need for glycine from skin and bones, but this effect could be greatly exaggerated if one eliminates legumes (and fortified bread?) without also increasing one's intake of organ meats and green vegetables.
This gives me a lot to think about, as I've really slacked on making stocks since starting grad school, and I often find myself in the office or lab too often to steam many vegetables.