For years, scientists have been trying to figure out if people who eat red meat are more likely to die prematurely of heart disease. In 2019, a series of research papers published in the Annals of Internal Medicine concluded that they are not. This news stirred up a hornets’ nest of controversy. It flew in the face of established dogma that red meat, especially processed meat, in the diet is risky. Many nutrition experts rejected those analyses.
How Safe Is It to Eat Red Meat?
The following year, an analysis of six studies produced conflicting information (JAMA Internal Medicine, online Feb. 3, 2020). The investigators collected data from nearly 30,000 participants. These people provided baseline diet data and then were followed for almost 20 years.
The authors found a small association between eating more red meat, processed meat and poultry with cardiovascular disease. Fish had no impact on mortality, either positive or negative. Unlike some previous studies (Journal of Internal Medicine, Oct. 2018), this analysis detected no protective effect from eating fish.
The absolute risk difference was almost 2 percent for people who ate two servings of processed meat weekly compared to those who ate none. In other words, what researchers call the effect size was small over 30 years. People eating processed meat such as salami, bologna, bacon or ham had a higher risk of cardiovascular complications, however.
Why Could Red Meat Put Your Heart in Danger?
Most researchers trying to understand how red meat raises the risk of cardiovascular disease have blamed fat and cholesterol. But new research suggests that gut microbes may also play a role (Arteriosclerosis, Thrombosis and Vascular Biology, Aug. 1, 2022).
Investigators from Tufts University and the Cleveland Clinic recruited 3,931 healthy adults over 65 years old. They collected the participants’ data for an average of 12.5 years. Those who ate more animal source foods were 18 percent more likely to experience a heart attack, stroke or death from a cardiovascular cause. In fact, total meat consumption, in particular, was linked to a 22 percent greater chance of such a disaster. Fish, poultry and eggs did not contribute significantly to the risk.
How Do Gut Microbes React to Meat?
The scientists also examined the chemicals produced by participants’ gut microbes. Specifically, trimethylamine-N-oxide (TMAO) and its metabolites, γ-butyrobetaine and crotonobetaine, were strongly linked to cardiovascular risk. Microbes in the intestinal tract create these compounds when they have a source of L-carnitine found in muscle. This may add to the explanation of why a diet rich in processed or unprocessed red meat seems to be hazardous to the heart.
The authors note that these compounds may play a more important role than cholesterol levels or blood pressure. Instead, the effect on blood sugar and insulin appear to be critical factors.
Diabetes Risk Rises When You Eat Red Meat:
This is not the first study to link insulin and blood sugar to red meat consumption. Years ago, results from the Health Professionals Follow-up Study and the Nurses’ Health Study showed that increasing meat consumption raises the risk for type 2 diabetes (JAMA Internal Medicine, July 22, 2013). The investigators analyzed detailed reports of food consumption from the volunteers at the beginning of the study and every four years thereafter.
Those who increased their consumption of processed meat products such as bacon, hot dogs, sausages or deli meats saw their risk of diabetes rise by around 48 percent over the next four years. Unprocessed meat consumption also had an impact, with the risk elevated around 30 percent over that time span. People who lowered their meat intake by about half a serving a day had a slight decline over the course of the 20-year study, though there was no significant change within four years.
The researchers are not quite sure what it is about red meat that might be the culprit. Some suggest saturated fat, while others blame it on sodium, preservatives, heme-iron or just extra calories. At that time, they were not looking at the possible effect of TMAO. Although people with type 2 diabetes are more likely to suffer cardiovascular complications, the connection with red meat seems a bit more complex.
If you’d like more advice on what you should eat for better health instead of warnings on what not to eat, you might like our book, The People’s Pharmacy Quick & Handy Home Remedies. In it, we describe three different diets that have been shown in studies to have health benefits.