Eating meat linked to poorer health

By Dr. Liji Thomas, MDFeb 3 2020

The seesaw continues with respect to the benefits of meat eating. The latest large new study published in February 2020 in the journal JAMA Internal Medicine reveals that eating red and processed meat is associated with a small but significantly higher risk of heart disease and death. Says researcher Norrina Allen, “It's a small difference, but it's worth trying to reduce red meat and processed meat like pepperoni, bologna and deli meats.”

Last November, a large meta-analysis of multiple studies concluded that there was no need for most people to reduce the amount of red and processed meat that they ate, due to the lack of a documented association between this and the risk of heart disease. The study raised much controversy as most previous research has consistently recommended lowering the intake of red meat.

Allen explains: “Everyone interpreted that it was OK to eat red meat, but I don't think that is what the science supports.” And it’s not just about heart disease or stroke: red and processed meat has repeatedly been associated with multiple negative health outcomes, including cancer. Current NHS recommendations are that the intake of red and processed meat be 70g or less a day.

Deli meats. Image Credit: Tyler Olson / Shutterstock

Red meat

Red meat includes beef, lamb, mutton, venison, veal and pork. And it is popular in the West primarily because it tastes good in many forms, while also being rich in protein and some vitamins like Vitamin B6, and minerals like iron, zinc and selenium. However, it is suspected that eating a lot of it raises the risk of colorectal (bowel) cancer. The problem is that the actual level at which the intake becomes “high” has not been defined so far.

Processed meat

Processed meat is a term that refers to meat that has been cured, smoked, salted or chemically preserved. A high intake of this has also been linked to bowel cancer. The various preservatives and additives in these meats, as well as the high salt content in some forms, are also reasons for their negative health impact.
There are various forms of processed meat, including:

• Sausages
• Bacon
• Ham
• Corned beef
• Other canned meats
• Sliced luncheon meats
• Deli meats
• Pates

The study

The researchers carried out an analysis of the data pooled from 6 cohorts, including almost 30 000 participants in all. Some of them had been followed up for 30 years. The data in all cases came from self-reported food intake over the last year or month, charted by the participants according to a detailed proforma. The average age of the participants was 54 years, about 44% being men and 31% non-whites.

The data came from different study populations, so the researchers adjusted for several parameters to make it more homogeneous. They also corrected for multiple factors that could influence the health outcomes, such as exercise and smoking. After their analysis, they also carried out several sensitivity analyses. All these measures were intended to confirm that the data was correctly interpreted and the conclusions were sound.

The findings

The current study shows that eating 2 servings of red or processed meat, or poultry, a week increased the risk of cardiovascular disease – disease of the heart and blood vessels – by 3% to 7%. There was no associated risk with fish intake, however.

Two or more servings of red or processed meat increased the risk of overall mortality by 4%, but this was not seen with fish or poultry.

The researchers are confident that their findings will stand up to scrutiny. Says investigator Victor Zhong, “Our study shows the link to cardiovascular disease and mortality was robust.”

The study has its limitations, of course. For one, the food data was gathered only once, at the beginning of the trial, which leaves out the possibility that food habits could have changed significantly over time. Secondly, cooking methods were not considered at all. However, it is known that fried chicken, especially when it is deep-fried, and fried fish, both push up the risk of chronic disease. These could have affected the risk of heart disease and mortality, but their impact cannot be evaluated from the present data.

Implications

The researchers say the small increase in cardiovascular risk but not in mortality, with poultry, is seen but is not sufficient to recommend either increasing or decreasing poultry intake. The association could be due to the mode of cooking or because the skin is also consumed, and not because of the chicken meat itself.

In the light of these findings, Zhong says, “Modifying intake of these animal protein foods may be an important strategy to help reduce the risk of cardiovascular disease and premature death at a population level.”

Fish intake was not related to any increased risk for either cardiovascular disease or mortality. Co-researcher Linda Van Horn says, “Fish, seafood and plant-based sources of protein such as nuts and legumes, including beans and peas, are excellent alternatives to meat and are under-consumed in the U.S.”