Meat-and-potatoes types may want to pay attention to research from Italy. An amino acid found abundantly in meat dramatically damages blood vessels. Methionine is an amino acid that turns into homocysteine during metabolism. Homocysteine is deadly to blood vessels. Researchers gave volunteers a big dose of methionine, and then measured the effects.
Homocysteine levels almost tripled after methionine (100 mg/kg of weight). Dramatic increases in substances that damage blood vessels were also evident, including prothrombin and plasminogen activator.
Normally, the amino acid L-arginine has a beneficial effect on blood vessels. But in the presence of so much homocysteine, L-arginine could not protect vessels. Instead, it actually turned foe and made things worse. Researchers believe that homocysteine interferes with L-arginine’s ability to create nitric oxide, a blood vessel-friendly substance that reduces oxidative stress inside arteries.
Antioxidant vitamins C and E can reverse the negative effects of homocysteine if given at the same time as the methionine is ingested. One thousand milligrams of C plus 800 IUs of vitamin E are required. Researchers believe that homocysteine overwhelms arteries with free radicals that damage their inner lining. Years of damage may lead to heart attacks and strokes.
Vitamins that break down homocysteine were not tested in this study which looked solely at damaging substances generated by oxidative stress.
Nappo, F, et al. 1999. Impairment of endothelial functions by acute hyperhomocysteinemia and reversal by antioxidant vitamins. JAMA 281:2113-118.