Diets rich in plant- vs animal-based monounsaturated fatty acids show significantly lower rates of total and cardiovascular disease (CVD) mortality, particularly when the plant-based fatty acids replace other notoriously unhealthy fats, including saturated or trans fats, as well as refined carbohydrates.
“Our study is the first large prospective cohort study with more than 20 years of follow-up, and more than 90,000 participants, and more than 20,000 deaths, looking at monounsaturated fatty acids from plant and animal sources,” coauthor Marta Guasch-Ferré, PhD, from the Harvard School T.H. Chan of Public Health in Boston, Massachusetts, told theheart.org | Medscape Cardiology.
In the study of more than 63,000 women in the Nurses’ Health Study and nearly 30,000 men in the Health Professionals Follow-Up, an average of 22 years of follow-up showed that a higher intake of monounsaturated fatty acids from plants was associated with a 16% lower risk for death from any cause.
A higher intake of monounsaturated fatty acids from animals was meanwhile associated with a 21% higher risk for death from any cause.
The findings were presented this week at the American Heart Association EPI | Lifestyle Scientific Sessions 2018 in New Orleans, Louisiana.
While monounsaturated fatty acids in general are linked to improved lipid profiles and reductions of cardiovascular disease risk factors, including hypertension and obesity, particularly compared with saturated or trans fats, prospective evidence on the association has been limited and inconclusive, Guasch-Ferré said.
“One possible reason is that dietary monounsaturated fatty acids can come from both plant and animal sources, with divergent nutrient components that may potentially obscure the associations for total monounsaturated fatty acids,” she said.
To take a closer look at the differences between plant- and animal-based monounsaturated fats, Guasch-Ferré and colleagues turned to the Nurses’ Health Study, including 63,412 women evaluated between 1990 and 2012, and the Health Professionals Follow-up Study, including 29,966 men from 1990 to 2010.
Intake of types of monounsaturated fatty acids were calculated according to validated food-frequency questionnaires that were collected every 4 years, in addition to food composition databases reflecting changes in food choices over time.
The study showed leading food sources of plant-based monounsaturated fats included olive oil, Italian salad dressing, peanuts, peanut butter, and other nuts.
Top food sources of animal-based monounsaturated fatty acids were beef, cheddar cheese, butter, bologna and other processed meats, and pork.
In evaluation of the 20,672 deaths that occurred during the study, including 4599 cardiovascular deaths, the authors adjusted for a wide range of demographic, lifestyle, and dietary factors, including age, ethnicity, smoking status, alcohol intake, family history of disease, menopausal status, physical activity, aspirin use, multivitamin use, baseline hypertension, baseline hypercholesterolemia, body mass index, total energy intake, and intake of fruits and vegetables.
They found that after the adjustments, higher intake of plant-based monounsaturated fatty acids was associated with reductions in total mortality (hazard ratio [HR], 0.84 [95% CI, 0.79 – 0.89]; P < .01), while higher consumption of animal-based monounsaturated fatty acids was associated with higher risk for mortality (HR, 1.21 [95% CI, 1.07 – 1.37]; P < .01).
In addition, mortality significantly improved when plant-based monounsaturated fatty acids replaced saturated fatty acids (15% lower risk for mortality), refined carbohydrates (14% lower risk), or trans fat (10% lower risk for mortality), in an equivalent number of calories the diet.
Furthermore, a model suggesting replacement of animal-based with plant-based monounsaturated fatty acids showed a total mortality risk reduction of 24%, while the replacement of a combination of animal-based monounsaturated fatty acids and saturated fatty acids with plant-based monounsaturated fatty acids showed a reduced total mortality risk of 20%.
Reductions specifically of cardiovascular mortality were similar with the same substitutions (HR, 0.74 and 0.83, respectively).
“In general, our findings support a beneficial role of monounsaturated fatty acids for the prevention of cardiovascular and total mortality, when plant-based foods such as vegetable oils, nuts, and related products are the primary sources,” Guasch-Ferré said.
Important limitations of the study include the study’s reliance on self-reporting of dietary details and the assumption that a higher consumption of plant-based foods would suggest a generally healthier lifestyle.
The findings are nevertheless consistent with the recommendations of the US Department of Health and Human Services’ 2015–2020 Dietary Guidelines for Americans, which have underscored the importance of dietary fat quality instead of quantity, Guasch-Ferré added.
“Specifically, the intake of vegetable fats, oils and other fats from plant sources has been encouraged while the intake of animal fats, and particularly red and processed meat, has been discouraged,” she said. “Our results are in accordance with these recommendations.”
Previous research has shown the Mediterranean diet, which notably emphasizes plant-based food sources and recommends low intake of red meat, to indeed be associated with a reduced cardiovascular risk, in addition to a wide array of other health benefits.
That study, which was published in BMC Medicine and included about 23,000 UK residents, showed lower cardiovascular disease and mortality rates among those who adhered to the Mediterranean diet.
“We estimate that 3.9% of all new cardiovascular disease cases or 12.5% of cardiovascular deaths in our UK-based study population could potentially be avoided if this population increased their adherence to the Mediterranean diet,” the study’s senior author, Nita Forouhi, MRCP, PhD, from the Medical Research Council Epidemiology Unit at the University of Cambridge, United Kingdom, said in a journal news release.
The new study offers important further insights underscoring the potentially different health effects within the class of monounsaturated fatty acids, Penny Kris-Etherton, PhD, RD, a distinguished professor of nutrition at the Pennsylvania State University, University Park, told theheart.org | Medscape Cardiology.
“It is very interesting to see adverse associations between animal sources of monounsaturated fatty acids and cardiovascular disease risk,” said Kris-Etherton, who is a spokesperson for the American Heart Association.
“We have always thought that monounsaturated fatty acids were a neutral fatty acid class,” she said. “The new research is now showing that plant monounsaturated fatty acids are beneficial, whereas animal monounsaturated fatty acids are not — and in fact, they are adversely associated with cardiovascular disease risk.”
With existing challenges in conveying the risks and benefits of the various types of fats, additional efforts to underscore the differences between plant- and animal-based monounsaturated fatty acids may not help matters, Kris-Etherton added.
“This could be very confusing to consumers,” she said. “A simple message is that consumers should follow current dietary guidelines and substitute saturated fats with unsaturated fats, both monounsaturated fatty acids and polyunsaturated fatty acids.”
“Major sources of saturated fat are animal foods and major food sources of monounsaturated fatty acids and polyunsaturated fatty acids are plant foods,” she added. “So, in substituting unsaturated fatty acids for saturated fatty acids, people will be eating more plant-based and less animal monounsaturated fatty acids.”
The study was supported by a research grant from Unilever R&D. The study was also funded by research grants from the National Institutes of Health. Geng Zong and Qi Sun, from the Harvard School of Public Health, also contributed to the study. Coauthors Anne Wanders and Peter L. Zock are employees of Unilever Research and Development. Unilever is a producer of food consumer products. No other authors have disclosed conflict of interest. Kris-Etherton has been involved in research involving plant monounsaturated fatty acids (canola oil, almonds, peanuts, and avocados) as well as animal monounsaturated fatty acids (lean beef).
American Heart Association EPI | Lifestyle Scientific Sessions: Epidemiology and Prevention | Lifestyle and Cardiometabolic Health 2018.