Medscape Medical News
Nadine Eckert
September 11, 2024
A diet in which the primary source of fat is plant sources is associated with decreased mortality. Animal fat, on the other hand, is associated with an increased risk for death. These are the results of a study published in JAMA Internal Medicine that followed more than 600,000 participants over two decades.
Dr Bin Zhao of the National Clinical Research Center for Metabolic Diseases at the Key Laboratory of Diabetes Immunology in Changsha, China, and colleagues concluded from these data that consuming plant-based fats instead of animal fats could be beneficial for health and improve survival.
It may not be so simple, however. “We are one step ahead of the publication: We no longer just distinguish between animal and plant fats but mainly consider the composition,” said Dr Stefan Lorkowski, chair of biochemistry and physiology of nutrition at the Institute of Nutritional Sciences at the University of Jena, Jena, Germany, in response to inquiries from the Medscape German edition.
What’s in a Fat?
Although Zhao and colleagues studied the effect of different plant and animal fat sources (eg, grains, nuts, legumes, plant oils, red and white meat, dairy, eggs, and fish), they did not consider the composition of the fatty acids that they contained. “It matters which dairy products, which plant oils, and which fish are consumed,” said Lorkowski.
The data analyzed in the Chinese study come from a prospective cohort study (NIH-AARP Diet and Health Study) conducted in the United States from 1995 to 2019. At the beginning, the 407,531 study participants (average age, 61 years) filled out dietary questionnaires once. They were then followed for up to 24 years for total and cardiovascular mortality.
During this period, 185,111 study participants died, including 58,526 from cardiovascular diseases. Participants who consumed the most plant-based fats, according to the dietary questionnaires filled out in 1995, had a lower risk for death than those who consumed the least plant-based fats. Their overall mortality risk was 9% lower, and their cardiovascular mortality risk was 14% lower. This finding was especially noticeable when it came to plant fats from grains or plant oils.
Animal Fat and Mortality
In contrast, a higher intake of animal fat was associated with both a higher overall mortality risk (16%) and a higher cardiovascular mortality risk (14%). This was especially true for fat from dairy products and eggs.
A trend towards a reduced overall and cardiovascular mortality risk was observed for fat from fish. “The fact that only a trend towards fish consumption was observed may be due to the study having many more meat eaters than fish eaters,” said Lorkowski.
Another imbalance limits the significance of the study, he added. The two groups, those who primarily consumed plant fats and those who primarily consumed animal fats, were already distinct at the beginning of the study. Those who consumed more plant fats were more likely to have diabetes, a higher body mass index (BMI), higher energy intake, and higher alcohol consumption but consumed more fiber, fruits, and vegetables and were more physically active. “They may have been trying to live healthier because they were sicker,” said Lorkowski.
Potential Confounding
Zhao and his team adjusted the results for various potential confounding factors, including age, gender, BMI, ethnicity, smoking, physical activity, education, marital status, diabetes, health status, vitamin intake, protein, carbohydrates, fiber, trans fats, cholesterol intake, and alcohol consumption. However, according to Lorkowski, “statistical adjustment is always incomplete, and confounding cannot be completely ruled out.”
Nevertheless, these results provide relevant insights for dietary recommendations that could help improve health and related outcomes, according to the authors. “Replacement of 5% energy from animal fat with 5% energy from plant fat, particularly fat from grains or vegetable oils, was associated with a lower risk for mortality: 4%-24% reduction in overall mortality and 5%-30% reduction in cardiovascular disease mortality,” they wrote.
Fat Composition Matters
Animal fat, however, should not simply be replaced with plant fat, said Lorkowski. “Cold-water fish, which provides important long-chain omega-3 fatty acids, is also considered animal fat. And palm and coconut fat, while plant-based, contain unhealthy long-chain saturated fats. And the type of plant oils also makes a difference, whether one uses corn germ or sunflower oil rich in omega-6 fatty acids or flaxseed or rapeseed oil rich in omega-3 fatty acids.
“A diet rich in unsaturated fats, with sufficient and balanced intake of omega-3 and omega-6 fatty acids, that is also abundant in fiber-rich carbohydrate sources and plant-based protein, is always better than too much fat from animal sources.”
This story was translated from the Medscape German edition using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.
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