Pesticides, heavy metals, and other toxins like mercury accumulate in the fat tissues of animals (including human animals). When people consume meat, poultry, and fish, they consume these accumulated toxins in much higher doses than would be possible if they consumed only plant foods.
The danger is serious: The US government advises pregnant woman and young children to avoid eating fish due to the high accumulation of mercury. Diet for a New America reports that:
- Fewer than 1 out of every 250,000 slaughtered animals is tested for toxic residues
- 99% of average American mother's milk contains significant levels of DDT
- Only 8% of average American vegetarian mother's milk contains significant levels of DDT
(PS "organic meat" doesn't necessarily mean the meat is pesticide-free. The US organic certification for meat, dairy, and eggs refers more to hormones and antibiotics than to pesticides. Organic meat can come from a cow who has been fed some pesticide-coated grains or even mercury-filled fish. Also please note, the word "natural" has no legal definition.)