Studies on meat from mammals and processed meats continue to show increased risk for heart attacks and certain cancers (Crit Rev Food Sci Nutr, Jul 20, 2021; International Journal of Epidemiology, Feb, 2020;49(1):246–258). The largest review ever of the prospective studies, including thirteen cohort studies involving over 1.4 million people and followed for up to 30 years, found that:
• Each 50 g/day higher intake of processed meat (such as bacon, ham or sausages) increased the risk of coronary heart disease by 18 percent
• Each 50 g/day higher intake of unprocessed red meat (such as beef, lamb and pork) increased the risk of coronary heart disease by nine percent
There was no link shown between eating poultry (such as chicken and turkey) and an increased risk of coronary heart disease.

A study from Harvard School of Public Health showed that when people replace five percent of calories from saturated fats with the same amount of calories from:
• polyunsaturated fats, they gain a 25 percent reduction in heart disease,
• monounsaturated fats, they gain a 15 percent reduction in heart disease, and
• carbohydrates from whole grains, they gain a nine percent reduction in heart disease.
However, if they replaced the saturated fats in meats and dairy products with refined carbohydrates in bakery products and sugar added foods and drinks, they still were at the same high risk for heart attacks (Journal of the American College of Cardiology, September 28, 2015). The lead author of the study, Dr. Frank Hu, said, “In terms of heart disease risk, saturated fat and refined carbohydrates appear to be similarly unhealthful.”

Why Are Red Meat and Dairy Products Associated with Heart Attack Risk?
Eating red meat (Am J Clin Nutr, August 2012;96(2):397-404) or drinking milk (JAMA Pediatrics, July 2013) have been associated with increased risk for heart attacks and strokes. The evidence that eating mammal meat daily is harmful to your health is so strong that several factors have been proposed to explain the increase risk. Saturated fats may not be the culprits, they may just be markers for some other factor from these foods such as TMAO or Neu5Gc, or their lack of fiber, which is found only in plants.  In dairy products, the culprit may be galactose.

• TriMethylAmine Oxide (TMAO): TMAO is made by bacteria in the intestines from carnitine, choline, lecithin, creatine and creatinine, found in red meat, eggs, milk and dairy products, liver, poultry, shellfish, fish, sports supplements and protein drinks. Stanley Hazen at the Cleveland Clinic has shown that feeding humans carnitine can increase blood levels of TMAO (TriMethylAmine Oxide), a chemical that can punch holes in arteries and increase the formation of arteriosclerotic plaques (Nature Medicine, published online April 7, 2013 and N Engl J Med, 2013;368:1575-1584). More on TMAO

• Neu5Gc: Dr. Ajit Varkey discovered Neu5Gc, a sugar chain that is found in meat from mammals but not in the cells of humans (Proceedings of the National Academy of Sciences, published online April 7, 2014). Your immunity attacks all cells that have different surface sugar proteins than you do. So when you eat red meat, you absorb Neu5Gc and your immunity attacks it just like it attacks germs that are trying to invade your body. These same antibodies and cytokines that are supposed to kill germs can stay active to cause inflammation that punches holes in arteries to start plaques forming there. More on Neu5gc

• Galactose: The component in dairy products that may increase heart attack risk is a sugar called galactose. Whole milk, skim milk, butter and other non-fermented milk products contain galactose. High blood levels of sugars can cause cell damage. Only four sugars can be absorbed from your intestines into your bloodstream. Of the four, galactose appears to be the strongest cause of inflammation that punches holes in arteries to start plaques forming there. Fermenting milk breaks down galactose, so fermented dairy foods such as yogurt and cheese do not contain much galactose and therefore may be more healthful. More on Galactose

My Recommendations
It really doesn’t make much difference whether or not saturated fat or cholesterol in foods increase heart attack risk. It appears that there is an association between heart attacks and both red meat (meat from mammals) and dairy products, so researchers are looking for other factors that may be the cause. I will continue to report on their work, and meanwhile, I recommend limiting or avoiding these foods and basing your healthful diet primarily on plants. These studies support the diet I have recommended for many years: heavy on plants and light on animal products.