Greater plant fat intake associated with lower overall and cardiovascular disease mortality

By Pooja Toshniwal PahariaReviewed by Danielle Ellis, B.Sc.Aug 13 2024

In a recent study published in JAMA Internal Medicine, researchers determined the relationship between animal and dietary plant fat intake with mortality from cardiovascular disease (CVD) and other causes.

Background

Dietary fats are crucial to maintaining cell membranes and metabolic fuel, absorbing and transporting fat-soluble vitamins, modulating ion channel activities, and regulating signal transduction. Plant-based fats contain more monounsaturated and polyunsaturated fat, while animal fats have a higher saturated fat content. There is increased scientific interest in the effects of consuming dietary fats on health outcomes, which depend on food sources.

However, limited data exists determining associations between dietary fat intake from various sources and human health. Although previous experimental and cross-national studies suggest that lowering dietary fat consumption is advantageous, recent cohort-based research, meta-analyses, and clinical trials provide conflicting results.

About the study

In the present prospective cohort-type study, researchers investigated whether consuming fat from animal or plant sources could increase all-cause and CVD-specific mortality in the United States.

The researchers obtained data from the National Institutes of Health (NIH)-AARP Diet and Health Study participants between 1995 and 2019 and analyzed data between February 2021 and May 2024. They used questionnaires to collect demographic, anthropometric, lifestyle, and dietary data, including specific fat sources.

The researchers obtained dietary data using the National Cancer Institute's (NCI) Diet History Questionnaire (DHQ). They ascertained the cause of death through follow-up linkages with the Social Security Administration Death Master File. They followed the participants until 31 December 2019 or death, whichever occurred first.

The researchers used multivariate-adjusted Cox proportional hazard regressions to estimate the hazard ratios (HR) and absolute risk differences (ARD) over 24 years. Study covariates included age, biological sex, body mass index (BMI), ethnicity, race, physical activity, smoking status, educational attainment, marital status, health status, diabetes, vitamin supplements, protein intake, carbohydrates, trans fat, cholesterol, fiber, and alcohol intake at baseline.

The researchers performed subgroup assessments to investigate whether the relationships differed by age, sex, BMI, diabetes, smoking, alcohol intake, Healthy Eating Index 2015 (HEI-2015) scores, vitamin supplements, health status, postmenopausal hormone treatments, and follow-up. To reduce confounding effects from other nutrients, they conducted stratified analyses by low and high intake of proteins (plant, animal, or total), fiber, carbohydrates, total vegetables, and fruits. They also performed a leave-one-out analysis to determine the relationship between replacing 5.0% of calories from plant fats with an equivalent decrease in animal fats from varied sources with any cause and CVD-specific mortality risks.

Results

Among 407,531 participants, 231,881 (57%) were male, with a mean age of 61. The median values for the daily intake of dietary fats from animal and plant sources were 29 grams and 25 grams, respectively. Individuals consuming more plant-based fats tended to be physically active, have diabetes, and have an increased BMI, with an elevated intake of calories, alcohol, fiber, vegetables, and fruit and fewer supplemental vitamins.

Over 8,107,711 individual years, the team recorded 185,111 fatalities, of whom 58,526 were due to cardiovascular disease. After multivariate adjustments (including adjustments for relevant dietary sources), increased plant fat intake (HR, 0.9 and 0.9; ARD reductions, 1.1% and 0.7%), especially from grains (HR, 0.9 and 0.9; ARD reductions, 1.0% and 0.7%) and vegetable-based oils (HR, 0.9 and 0.9; ARDs, 1.4% and 0.7%) was related to decreased risks of any-cause and CVD-specific fatalities, respectively.

Contrastingly, increased intake of animal fat (HR, 1.2 and 1.1; ARDs, 0.8% and 0.3%) from dairy products (HR, 1.1 and 1.1; ARD reductions, 0.9% and 0.2%) or eggs (HR, 1.1 and 1.2; ARD reductions, 1.4% and 0.8%) was related to an elevated risk for all-cause and CVD-specific mortality, respectively. Replacing 5.0% of calories from animal fats with 5.0% from plant fats, particularly fats from vegetable oils or grains, reduced the risk of any-cause mortality by 4.0% to 24% and CVD-specific mortality by 5.0% to 30%. They also performed sensitivity analyses, adjusting for the total calorie intake and excluding diabetes patients and the initial two to five years of follow-up.

The inverse associations of plant-based fat intake with any-cause mortality were statistically significant among individuals aged below 60 who consumed one to three alcoholic beverages per day. Conversely, the positive animal fat-mortality associations were more robust for males between 60 and 65 years of age with lower BMI. The association of animal fat consumption with cardiovascular disease mortality was stronger among younger individuals. Stratified and sensitive analyses yielded similar findings.

Conclusion

The study findings showed that increased plant fat intake, especially fats from vegetable oil and grains, lowered any-cause and CVD-specific fatalities. In contrast, increased animal fat intake, especially from eggs and dairy products, was related to increased mortality risk. The findings could inform dietary choices and guidelines to enhance human health.