Grilled Meats, Fish Linked to Hypertension

A new study indicates that high consumption of meat, poultry, or fish grilled, broiled, or cooked at a high temperature is associated with an increased risk for hypertension, independent of the overall amount consumed, and the risk is also increased with higher intake of well-done meat.

Lead author, Gang Liu, PhD, a postdoctoral research fellow in the Department of Nutrition at the Harvard T.H. Chan School of Public Health in Boston, Massachusetts, notes that among individuals who consume red meat, chicken, or fish regularly, our findings imply that avoiding the use of open-flame and/or high-temperature cooking methods, including grilling/barbecuing, broiling, and roasting, may help reduce hypertension risk.

The study of nearly 33,000 women in the Nurses' Health Study (from 1996 to 2012) and 54,000 men in the Health Professionals Follow-Up Study (also from 1996 to 2012) showed that consumption of red meat, chicken, or fish prepared with open-flame or high-temperature cooking more than 15 times per month was associated with a 17% higher risk for hypertension compared with the lowest category of consumption of the foods, defined as fewer than four times per month.

The study was presented at the American Heart Association EPI | Lifestyle Scientific Sessions 2018 in New Orleans, Louisiana.

Hazardous Chemicals

Grilled food is known to cause the formation of chemicals that can be carcinogenic, and Liu noted that while previous research has not shown a risk for hypertension, key mechanisms could explain the increased risk.

Although the exact reason remains unclear, accumulating evidence has suggested that cooking meats at high temperature can produce several hazardous chemicals, including heterocyclic aromatic amines (HAAs), polycyclic aromatic hydrocarbons (PAHs), and advanced glycation end products (AGEs), which could induce oxidative stress, inflammation, and insulin resistance in animal studies.

These pathophysiological pathways may also lead to an elevated risk of developing hypertension.

To take a closer look at the relationship, Liu and colleagues evaluated data on the 32,925 women and 53,852 men, excluding participants with hypertension, diabetes, cardiovascular disease, and cancer at baseline.

In the average follow-up of 12 to 16 years, 37,123 participants developed hypertension.

Among those who consumed two or more servings per week of red meats, chicken, or fish, participants who cooked with open-flame or high-temperature methods, including grilling, barbecuing, broiling, or roasting, more than 15 times per month, compared with those using those cooking methods fewer than four times per month, had an increased risk for hypertension.

In a further analysis of quartiles of meat doneness, those preferring the most well-done red or white meats, vs those preferring the least doneness, also had a pooled increased risk for hypertension.

The associations were observed even after adjustment for such factors as total consumption of red meats, chicken, and fish.

A closer analysis of specific food groups showed a higher risk for hypertension with the highest vs lowest consumption of open-flame or higher-temperature cooking for red meat, chicken and fish.

In terms of hypertension risk associated with meat doneness (well-done vs rare), the same trend was observed.

The authors also looked at estimated levels of intake of HAAs, the carcinogens associated with charred meat that are formed during high-temperature cooking of meats, as well as in the combustion of tobacco.

They found the highest quintiles of HAAs were indeed associated with an increased risk for hypertension compared with the lowest levels.

While the authors underscore that the study doesn't prove cause and effect, Liu said the findings nevertheless spotlight the potential role of grilled or high-temperature cooking in hypertension.

"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/barbequing and broiling," Liu said.

Limitations of the study

Important limitations of the study include that certain meats, including pork and lamb, and certain cooking methods, including stewing and stir-frying, were not included in the questionnaires. Furthermore, the study population largely comprised white health professionals and therefore may not be generalizable to all populations.

Liu noted that the study also did not look at the effects of grilled or open flame–cooked vegetables.

The future and real-life application

"In further studies, it would be interesting to look at the association for vegetables," he said.

The research may prompt a rethinking of some dietary recommendations for healthy proteins, said Penny Kris-Etherton, PhD, RD, a distinguished professor of nutrition at the Pennsylvania State University, University Park.

"This is a new finding," she told theheart.org | Medscape Cardiology. "It is surprising because we recommend grilling as a healthy cooking technique for protein foods. If we knew that it increased blood pressure, we would not make that recommendation."

She noted that the findings are nevertheless preliminary and leave many questions unanswered.

"This is a new finding, so it must be confirmed," Kris-Etherton said.

"Also, there are so many questions that relate to how this research should be applied in the real world, other than advising consumers to try to avoid (the kind of) unhealthy meat grilling that the authors describe. We need to know if any grilling of meat is okay."

As described in a Medscape slide show the cooking of meat, poultry, or fish over flames or very high temperatures has been linked to an increased risk for cancers, including colon, prostate, pancreatic, stomach, and breast cancers, particularly with well-done cooking.

The study was funded by the National Heart, Lung, and Blood Institute. Kris-Etheron has been involved in research involving plant mono-unsaturated fatty acids (canola oil, almonds, peanuts, and avocados) as well as animal mono-unsaturated fatty acids (lean beef).

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