November 13, 2021
Higher intake of vegetable fats from foods such as olive oil and nuts is associated with a lower risk for stroke, whereas people who eat more animal fats, especially processed red meats, may have a higher stroke risk, observational findings suggest.
In a study of more than 117,000 health professionals who were followed for 27 years, those whose diet was in the highest quintile for intake of vegetable fat had a 12% lower risk for stroke compared with those who consumed the least amount of vegetable fats.
Conversely, having the highest intake of animal fat from non-dairy sources was associated with a 16% increased risk of stroke.
Fenglei Wang, PhD, presented these results at the virtual American Heart Association (AHA) 2021 Scientific Sessions.
"Our findings support the Dietary Guidelines for Americans and dietary recommendations by AHA," Wang, a postdoctoral fellow in the Department of Nutrition at Harvard University's T.H. Chan School of Public Health in Boston, Massachusetts, told theheart.org | Medscape Cardiology.
"The main sources of vegetable fat have a large overlap with polyunsaturated fat, such as vegetable oils, nuts, walnuts, and peanut butter," Wang noted, adding that fish, especially fatty fish, is a main source of polyunsaturated fat and is recommended for cardiovascular health.
"We would recommend that people reduce consumption of red and processed meat, minimize fatty parts of unprocessed meat if consumed, and replace lard or tallow (beef fat) with nontropical vegetable oils, such as olive oil, corn or soybean oils in cooking, to lower their stroke risk," she said.
Moreover, although the results from this study of dietary fat are informative, Wang continued, "there are other dietary factors (fruits, vegetables, salt, alcohol, et cetera), and lifestyle factors (physical activity, smoking, et cetera), that are associated with stroke risk and worthy of attention as well."
"Many processed meats are high in salt and saturated fat, and low in vegetable fat," Alice H. Lichtenstein, DSc, an AHA spokesperson who was not involved with this research, noted in a press release.
"Research shows that replacing processed meat with other protein sources, particularly plant sources, is associated with lower death rates," added Lichtenstein, the Stanley N. Gershoff professor of nutrition science and policy at Tufts University in Boston, and lead author of the AHA's 2021 scientific statement, Dietary Guidance to Improve Cardiovascular Health.
"Key features of a heart-healthy diet pattern," she summarized, "are to balance calorie intake with calorie needs to achieve and maintain a healthy weight, choose whole grains, lean and plant-based protein and a variety of fruits and vegetables; limit salt, sugar, animal fat, processed foods, and alcohol; and apply this guidance regardless of where the food is prepared or consumed."
Replace Processed Meat With Plant Proteins
The focus on stroke in this study "is important" because, traditionally, studies of diet and cardiovascular health have focused on coronary heart disease, Andrew Mente, PhD, who also was not involved in this research, said in an email to theheart.org | Medscape Cardiology.
"Overall, the take-home message from the study is that replacing processed meat with plant sources of protein in the diet is probably beneficial," Mente, associate professor, health research methods, evidence, and impact, Faculty of Health Sciences, McMaster University, Hamilton, Ontario, Canada, said.
The finding that people who ate the most vegetable fat had a modest 12% lower risk of stroke than those who ate the least vegetable fat "points to protective effects of foods like seeds, nuts, vegetables, and olive oil, which has been shown previously," he continued.
The highest quintile of total red meat intake was associated with an 8% higher risk for stroke, but this was driven mainly by processed red meat (which was associated with a 12% higher risk for stroke). These findings are "generally consistent with cohort studies showing that processed meat, as with most highly processed foods for that matter, are associated with an increased risk of cardiovascular events," Mente noted.
"Surprisingly, dairy products (such as cheese, butter, or milk) in the study were not connected with the risk of stroke," he added. This finding differs from results of meta-analyses of multiple cohort studies of dairy intake and stroke and the recent large international PURE study, which showed that dairy intake was associated with a lower risk for stroke.
"What is needed to move the field forward," according to Mente, "is to employ new methods that use cutting-edge technology to study nutritional biomarkers and health outcomes."
"When dealing with modest associations as usually encountered in nutrition, it is a challenge to make causal connections based on dietary questionnaires, which are fraught with measurement error," he added. "The use of novel methods is where the field is headed."
Total Dietary Fat, Different Types, and Different Food Sources
Wang and colleagues investigated how total dietary fat, different types of fat, and fats from different foods were associated with incident stroke in 73,867 women in the 1984-2016 Nurses' Health Study and 43,269 men who participated in the 1986-2016 Health Professionals Follow-up Study.
The participants had an average age of 50 years; 63% were women, and 97% were White. They replied to food-frequency questionnaires every 4 years.
Total red meat included beef, pork, or lamb (as a main dish or in sandwiches or mixed dishes) as well as processed red meats (such as bacon, sausage, bologna, hot dogs, and salami).
Animal fat sources included meat, beef tallow, lard, and full-fat dairy products, such as full-fat milk and cheese.
The median percentage of total daily calories from different sources of fat ranged from 10% to 20% for vegetable fat, 3% to 10% for dairy fat, and 7% to 17% for nondairy animal fat (for lowest to highest quintiles).
The median percentage of total daily calories from different types of fat ranged from 5% to 8% for polyunsaturated fat, 4% to 7% for n-6 polyunsaturated fat, 9% to 15% for monounsaturated fat, 8% to 14% for saturated fat, and 1% to 2% for trans fat.
During follow-up, there were 6189 incident strokes, including 2967 ischemic strokes and 814 hemorrhagic strokes.
The researchers found that intake in the highest quintile of vegetable fat was associated with a lower risk for total stroke compared with the lowest quintile (hazard ratio [HR], 0.88; 95% CI, 0.81 - 0.96; P for trend < .001).
Similarly, the highest intake of polyunsaturated fat was also associated with lower total stroke (HR, 0.88; 95% CI, 0.80 - 0.96; P for trend = .002).
Highest intake of nondairy animal fat, however, was associated with an increased risk for total stroke (HR, 1.16; 95% CI, 1.05 - 1.29; P for trend < .001). They observed "similar associations" for ischemic stroke, but the only positive association for nondairy animal fat was with hemorrhagic stroke, the abstract notes.
The risk for stroke was lower by 9% per serving per day for vegetable oil but increased by 8% and 12%, respectively, per serving of total red meat or processed red meat.
The association for vegetable oil was attenuated after adjustment for vegetable fat or polyunsaturated fat, whereas adjustment for nondairy animal fat rendered the association for total red meat and processed red meat nonsignificant.
The study was funded by the National Heart, Lung, and Blood Institute of the National Institutes of Health. Wang has no relevant financial disclosures. Mente has received research funding from the Dairy Farmers of Canada and the National Dairy Council to analyze data on dairy consumption and health outcomes in the PURE study, which is funded by the Population Health Research Institute, Hamilton Health Sciences Research Institute, and more than 70 other sources (government and pharmaceutical).