The new research was led by Gang Liu, Ph.D., of the Department of Nutrition at the Harvard T.H. Chan School of Public Health in Boston, MA.
High blood pressure, or hypertension, will occur when the force of blood that pushes against the wall of the arteries becomes too high. This can increase the risk of stroke, heart attack, and heart disease.
Since updated blood pressure guidelines came into play in the United States last year, it is now estimated that almost half of adults across the country have hypertension.
An unhealthful diet is known to be a major risk factor for hypertension. The new study, however, suggests that it's not just the type of food that we eat that influences blood pressure; how we prepare our food can also play a part.
Previous studies have documented the many potential harms of consuming meats cooked at high temperatures. One study reported by Medical News Today last year, for example, linked a high intake of grilled, smoked, or barbecued meats to a 23 percent greater risk of death for breast cancer survivors.
Research has also associated foods cooked at high temperatures with a greater risk of heart disease.
For this latest study, Liu and colleagues sought to determine whether the cooking temperature or doneness of meat and fish — that is, how well they are cooked through — might influence blood pressure.
Cooking methods and blood pressure
To reach their findings, the researchers analyzed the data of 32,925 women who were a part of the Nurses' Health Study, 53,852 women who took part in the Nurses' Health Study II, and 17,104 men who participated in the Health Professionals Follow-Up Study.
For each study, information was collected on how much meat and fish the subjects consumed each month, as well as how these foods were cooked and their levels of doneness.
At baseline, none of the participants had high blood pressure, diabetes, cardiovascular disease, or cancer. Over an average follow-up period of 12–16 years, a total of 37,123 participants developed hypertension.
The team found that subjects who ate grilled, broiled, or roasted beef, chicken, or fish at least 15 times each month were 17 percent more likely to develop high blood pressure than those who consumed these foods fewer than four times per month.
Among participants who reported preferring their meat well-done, the risk of hypertension was increased by 15 percent, compared with those who preferred their meat rarer.
HAAs and hypertension
The scientists also estimated the levels of heterocyclic aromatic amines (HAAs) consumed by each subject. HAAs are potentially harmful compounds that are produced when meats are cooked at high temperatures.
The study reveals that participants who consumed higher levels of HAAs were at 17 percent greater risk of high blood pressure, compared with those who consumed lower levels of the compounds.
Notably, the study revealed that the links between hypertension, cooking method and temperature of cooking, and doneness of meat were independent of the type of foods that subjects consumed and how much they ate.
Explaining the possible mechanisms behind their findings, Liu says that HAAs and other chemicals produced by high-temperature cooking may lead to oxidative stress, inflammation, and insulin resistance, which can raise the risk of hypertension.
While this research cannot prove cause and effect, the team says that to lower blood pressure, it might be worth revising our cooking methods for meat and fish.
"Our findings suggest that it may help reduce the risk of high blood pressure if you don't eat these foods cooked well-done and avoid the use of open-flame and/or high-temperature cooking methods, including grilling/barbecuing and broiling."
Gang Liu, Ph.D.