Quote:
How is veganism ideal if it doesn't naturally provide an essential nutrient?
Same with iron-- isn't the iron from animal sources superior to that from plant sources?
(I have no bias for meat or vegan, simply exploring it myself too)
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Athena: You raise good points here, and I'd like to maybe help fill in some gaps here.
First, veganism as it stands today, does not provide a reliable source of B-12 unless it is supplemented in the diet. So on the surface, I can see why this might be an achilles heel in the vegan diet.
But, we would have to find a diet then that provides ample B-12. Meat has not been found to be a reliable source of B-12, at least according to extensive studies done by the USDA. The B-12 is too tightly bound within the protein to be adequately absorbed by our intestinal tracts. Even if meat were a good source, it is no longer a natural source of B-12. Unfortunately because of modern feeding practices of cattle, they no longer receive adequate B-12 in their diet and so they have to receive B-12 supplements (in other words, you are getting a supplement of B-12 second hand by eating meat).
Please refer to:
Am J Clin Nutr. 2000 Feb;71(2):514-22.
http://www.ars.usda.gov/...2000/000802.htm
So, if meat is not a bioavailable source of B-12, then what is? Well, according to the USDA only fortified foods (e.g. foods that are fortified with "supplemental" b-12) and dairy are reliable sources of B-12, other than actual supplements.
The question is, how much dairy to we have to consume then to get the adequate levels of B-12 in our diet. Well, you have to consume roughly 6 to 7 eight ounce glasses of milk a day. Since this is the only reliable source of B-12 in food, would it be ideal to include this much into our diets?
Well, unfortunately dairy is the single most polluted food in our diets. It often has levels of dioxin and other petrochemicals that are far in excess of limits set by the EPA. It is also a food that promotes anemia by not only have low levels of iron, but also has elements which prevent proper absorption of iron. It is a very low nutrient dense food, and is very high in preformed Vitamin A which is not a healthful nutrient according to studies. On top of that, high consumption of dairy leads to excessive levels of Insulin-like Growth Hormone 1 in humans, and high levels of this hormone have been linked with various cancers, including but not limited to breast, prostate and colon cancers. I could go on, but I guess you get the idea here. Again, too, the B-12 from the cow's is not native to their diets any more, so they are getting it supplemented in.
Yet, despite the high levels of consumption of foods high in B-12 in this country, it has been estimated by Harvard School of Public Health that B-12 is the most common nutrient deficiency in the US.
So, I guess it comes down to the fact that we are not getting sufficient B-12 from our diets, and even if we could, the food sources that would give us sufficient B-12 our too polluted and unhealthful to eat in the required quantities to be considered ideal.
In other words, in today's industrialized world where we wash fruits and veggies excessively (we used to get B-12 from the soil remnants on our produce), we are really best off taking a supplement for B-12. B-12 has found to be non-toxic in extremely high doses, so there is really no downside here (it is also relatively cheap).
Iron
Heme iron is indeed rich in meat, I do not believe this to be a particularly healthy component of beef. First, anemia is not generally a disease caused by lack of iron intake, it is more a disease of excessive blood loss (often through menstruation)(Br J Nutr. 2005 Oct;94(4):557-64.). The higher bleeding patterns are associated with higher hormone levels (J Reprod Med. 1999 Feb;44(2 Suppl):158-64.) Higher hormone levels are associated with lower intake of fiber, and higher intake of animal foods and fats.
So, unfortunately, while meat is a good source of dietary iron, it is also part of the cause of the anemia in the first place. Further, the ready absorption of heme iron is not necessarily a good thing anyway. Excess iron is stored in body tissues and is associated with later heart disease and brain degeneration. Excess iron is also an oxidant.
Because heme iron is so readily absorbed, the body takes it on whether it needs the extra iron or not. While nonheme iron is not as well absorbed, this is generally good because the sources of non-heme iron are loaded in fiber which is good for reducing hormone levels. When the body needs iron, non-heme iron is absorbed more readily, and if iron stores are good it is absorbed less readily (Again, a good thing since excess iron is bad).
Hope this is informative and/or helpful!
Joey