The impact of animal protein is probably part of a larger-picture lifestyle. Keeping a balance of calories eaten and calories burned through activity is essential for maintaining a healthy weight. The evidence is much stronger that being overweight is harmful to your health and is linked to a variety of health issues, including heart disease.
Whether you do or do not eat animal protein is a personal choice. Eating lean meats in a diet composed of whole grains, fresh fruits and vegetables and the right calorie intake coupled with regular physical activity is likely a small risk. However, most Americans do not get regular physical activity and consume a diet far from what would be considered healthy. In this scenario, then risk factors are allowed to exert their influence to a greater degree.
Animal protein does not in itself cause heart disease. However, consuming excess animal protein can increase the risk for heart disease because of its high saturated fat content. The other reason is that animal protein tends to be higher in sulfur containing amino acids such as methionine. Methionine is metabolized to homocysteine, which, if a person is not getting adequate folic acid, B12 and B6 in their diet could tend to accumulate to higher than normal levels. High levels of homocysteine may be a moderate risk factor for heart disease. The key is moderation. Animal protein is perfectly safe in moderation, but consumed in conjunction with plenty of plant proteins, vegetables and fruits. A balanced diet, as always, is the key to reducing one's risk for heart disease.
A high intake of animal protein is linked to heart disease, many cancers, high blood pressure, kidney disease, osteoporosis, and kidney stones. Heart disease and high blood pressure are associated with increased intake of animal fats as well as animal protein. Cancer can be caused by proteins that are altered in some cooking processes, such as grilling and blackening, and by the action of gut bacteria on undigested protein. The kidneys are responsible for eliminating the breakdown products of protein, too much of which can have a damaging effect. A high-protein diet increases the excretion of calcium in the urine. Simply raising the intake of protein from 47 grams per day to 142 grams per day doubles the excretion of calcium in the urine. A diet this high in protein, common in the U.S., is a significant factor in the increased number of people suffering from osteoporosis and kidney stones in this country. A vegetarian diet is associated with a reduced risk of developing these diseases.

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Encyclopedia of Healing Foods
The concern about eating meat used to focus on fat and cholesterol, but another factor is carnitine, which we ingest with animal proteins. Watch nutrition specialist Michael Greger, MD, explain how carnitine can increase the risk of heart disease.
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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.