By Ellen Feldman, MD
Altru Health System, Grand Forks, ND
Summary Points
- Dietary habits of 521,120 individuals enrolled in a national study for older Americans were collected. This group was followed for a mean of 16 years.
- Multivariate-adjusted all-cause mortality hazard ratios were:
- 1.09 (95% confidence interval [CI], 1.07-1.11) for frequent butter consumers;
- 1.01 (95% CI, 1.05-1.09) for frequent margarine consumers;
- 0.97 (95% CI, 0.95-0.99) for frequent canola oil consumers; and
- 0.96 (95% CI, 0.95-0.98) for frequent olive oil consumers.
- Hypothetically replacing corn oil, canola oil, or olive oil for equal amounts of butter and margarine correlated with lower all-cause mortality and cause-specific mortality from diabetes and cardiovascular, respiratory, and Alzheimer's diseases.
SYNOPSIS: This comprehensive prospective study reveals that, compared to non-consumers, individuals using butter and/or margarine have an elevated total mortality rate, while those incorporating canola and/or olive oil into their diets exhibit a reduced total mortality risk.
SOURCE: Zhang Y, Zhuang P, Wu F, et al. Cooking oil/fat consumption and deaths from cardiometabolic diseases and other causes: Prospective analysis of 521,120 individuals. BMC Med 2021;19:92.
“Good nutrition creates health in all areas of our existence. All parts are interconnected.”1
This tenet by nutritionist Dr. T. Colin Campbell underscores the multifaceted effect of diet on health, a principle that is especially relevant when examining dietary fat — a vital, yet frequently misunderstood component of nutrition.
Fats, derived from plant and animal sources, are not merely a caloric necessity. These compounds play an important role in cardiovascular health. There is robust, but nuanced, data indicating that the effect of fat extends beyond mere quantity but to the quality and types of fat consumed. This distinction is critical, and while the superior health benefits of polyunsaturated fats over saturated fats are widely recognized, the practical application in everyday dietary guidance remains inadequate, and the translation to dietary advice remains limited.2,3
The global and domestic trends in fat consumption mirror societal shifts; worldwide plant-derived fat, predominately oils, have seen a marked increase in production, from 198 million metric tons in 2019 to 208.8 million metric tons in 2022, signifying a greater awareness and preference for plant-based options.4
Meanwhile, in the United States, there has been a parallel uptick in animal fat intake, with butter consumption soaring from 4.5 to 6.5 pounds per person per year between 2000 and 2022, perhaps in part a reflection of a shift away from processed fats.5
Against this evolving nutritional backdrop, Zhang et al designed a long-term, prospective study designed to clarify the relationship between some commonly used dietary fats and oils and mortality outcomes — both for overall and cause-specific cases.
One overarching goal of the study was to translate theoretical nutritional guidance into practical and actionable recommendations that healthcare providers can confidently transmit to their patients.
Participants in this study were selected from a larger nationwide survey: the National Institutes of Health-American Association of Retired Persons (NIH-AARP) diet and health study, which began in the mid-1990s.
Working with broad exclusion criteria, such as persons with extreme (high or low) calorie intake, persons with proxy responders, and nonresponses, Zhang et al identified 521,120 <eligible individuals to participate in their investigation. All participants received a validated 124-item food frequency questionnaire focusing on the type and frequency of oil and fats consumed as well as other diet elements present over the past year.
Consumption patterns of three common types of solid fat (butter, lard, and margarine) and three widely used oils (olive oil, corn oil, and canola oil) were analyzed. To ensure rigor, results were adjusted for multiple variables, including race, socioeconomic status, education, overall diet healthfulness, body mass index, and intake of other oils and fats beyond those primarily studied.
Over a median follow-up of 16 years, the researchers documented the causes of death for 129,328 participants by integrating data from two national mortality databases.
Results
Participants were categorized into tertiles, reflecting their reported consumption levels for each type of fat.
Strikingly, higher consumption of both butter and margarine was associated with a marked increase in all-cause mortality relative to non-consumers. In contrast, subjects with a higher intake of olive and canola oils exhibited a lower risk. Corn oil usage did not display any significant association with all-cause mortality rate.
Table 1 presents a detailed view of all-cause mortality rates, stratified by the consumption frequency of the various cooking oils and solid fats, with adjustment made for multiple variables.
Table 1. All-Cause Mortality (Hazard Ratio and 95% CI) in Relation to Cooking Oil/Solid Fat Consumption Frequency with Multivariate Adjustment |
|||||
| Type of Fat/Oil | Non-Consumer | Lowest Tertile | Middle Tertile | Highest Tertile | P Value |
Butter |
1.00 |
0.98 (0.96-1.00) |
1.05 (1.03-1.06) |
1.09 (1.07-1.11) |
< 0.001* |
Margarine |
1.00 |
0.99 (0.97-1.01) |
1.03 (1.01-1.05) |
1.07 (1.05-1.09) |
< 0.001* |
Olive oil |
1.00 |
0.96 (0.94-0.99) |
0.97 (0.95-0.98) |
0.96 (0.95-0.98) |
< 0.001* |
Canola oil |
1.00 |
0.98 (0.95-1.00) |
0.97 (0.95-0.99) |
0.97 (0.95-0.99) |
< 0.001* |
Corn oil |
1.00 |
0.97 |
0.98 |
0.99 |
0.092 |
*Statistically significant value CI: confidence interval |
|||||
A parallel pattern emerges when looking at data from death caused by cardiovascular disease (CVD). High olive oil consumption correlates with a modest, yet significant 5% lower rate of CVD mortality compared with non-consumers. Conversely, the highest tiers of butter and margarine consumption are linked to 8% and 10% upticks in CVD mortality, respectively. Notably, the pattern deviates from overall mortality data, since neither canola oil nor corn oil intake shows a significant tie to CVD mortality. (See Table 2.)
Table 2. CVD Mortality (Hazard Ratio and 95% CI) in Relation to Cooking Oil/Solid Fat Consumption Frequency with Multivariate Adjustment |
|||||
| Type of Fat/Oil | Non-Consumer | Lowest Tertile | Middle Tertile | Highest Tertile | P Value |
Butter |
1.00 |
0.96 (0.93-1.00) |
1.04 (1.01- 1.08) |
1.08 (1.05- 1.12) |
< 0.001* |
Margarine |
1.00 |
1.01 (0.97-1.04) |
1.06 (1.03-1.09) |
1.10 (1.06-1.14) |
< 0.001* |
Olive oil |
1.00 |
0.93 (0.89-0.97) |
0.95 (0.92-0.99) |
0.95 (0.92-0.99) |
< 0.001* |
Canola oil |
1.00 |
0.99 (0.95-1.04) |
0.98 (0.94-1.02) |
0.97 (0.94-1.00) |
0.052 |
Corn oil |
1.00 |
1.01 (0.96-1.05) |
0.99 (0.95-1.03) |
1.00 (0.96-1.03) |
0.78 |
*Statistically significant value CVD: cardiovascular disease; CI: confidence interval |
|||||
Other Cause-Specific Mortality
In the realm of cause-specific mortality, butter and margarine consumers demonstrated increased risks of death from cancer, diabetes, and respiratory, kidney, and chronic liver diseases, among others. In contrast, lard consumption was associated with higher all-cause and respiratory disease mortality, but the respondent pool was limited, making conclusions difficult. Canola oil consumption was inversely associated with mortality from respiratory and infectious disease. Likewise, olive oil intake showed a protective association against mortality from Alzheimer’s disease and respiratory disease.
Exploring hypothetical scenarios, Zhang et al applied statistical models to estimate the effect of substituting a tablespoon of various oils for butter. Substitutions of corn, canola, or olive oil projected respective decreases in all-cause and CVD mortality (from 5% to 8%), reinforcing the potential health benefits of such dietary adjustments.
Commentary
This long-term, rigorous study is not without limitations, but it succeeds in bringing actionable and concrete information of value to providers and patients alike. These results point to a link between butter and margarine consumption and higher mortality rates as well as an association between consumption of olive oil, canola oil, and corn oil with lower mortality rates overall, underscoring the health implications of fat type in our diets.
There are details that still need to be understood and most likely will be tackled in future studies. For example, changes in diet over time was not considered in this study and neither were changes in the composition of dietary elements.
Margarine in particular has become much less popular over time, and it is likely that the avid margarine consumer of the 1990s changed this pattern in the 2000s as this product fell out of favor. One reason for the decreased use of margarine was that the older margarines contained trans-fats, which were beginning to be linked with an elevated level of heart disease in the 1990s (close to the start of this study).6
Other limitations of this study are the reliance on recall to document food consumption patterns. With the advances in technology today, the possibilities for a real-time analysis of diet and portion size are limitless. Such a methodologic change has the potential of adding valuable information in this field of study.
It is necessary to remember that this is a prospective study, and while correlation is strong, causation is not proven. There may be nonidentified confounding factors that are at work here that skew the data. Looking closely at further studies with subgroups of population may help with identification.
Furthermore, this study does not shed light on the underlying mechanisms at play. It is plausible that the health effects of fats and oils are influenced by how they are cooked, and that the health associations observed with canola and olive oils may be because of their relatively high levels of monounsaturated and omega-3 fatty acid oils.
These aspects remain subjects for ongoing investigation.7
The strengths of this study are numerous and include the large number of participants and long-term follow-up.
Clinically, this research bolsters the rationale for advising patients to favor non-hydrogenated vegetable oils over solid fats and offers providers a substantial basis for dietary recommendations.
References
- Campbell TC. Dr. T. Colin Campbell’s 8th principle of food and health. Center for Nutrition Studies. Updated Oct. 20, 2021. https://nutritionstudies.org/dr-t-colin-campbells-8th-principle-of-food-and-health/
- Liu AG, Ford NA, Hu FB, et al. A healthy approach to dietary fats: Understanding the science and taking action to reduce consumer confusion. Nutr J 2017;16:53.
- Nettleton JA, Lovegrove JA, Mensink RP, Schwab U. Dietary fatty acids: Is it time to change the recommendations? Ann Nutr Metab 2016;68:249-257.
- Shahbandeh M. Consumption of vegetable oils worldwide from 2013/14 to 2022/2023, by oil type. Statista. Published Sept. 20, 2023. https://www.statista.com/statistics/263937/vegetable-oils-global-consumption/
- Shahbandeh M. Per capita consumption of butter in the United States from 2000 to 2021. Statista. Published Nov. 2, 2023. https://www.statista.com/statistics/184011/per-capita-consumption-of-butter-in-the-us-since-2000/
- Silva T, Barrera-Arellano D, Ribeiro APB. Margarines: Historical approach, technological aspects, nutritional profile, and global trends. Food Res Int 2021;147:110486.
- Corteva Agriscience. Oils comparison chart. https://www.healthyoils.corteva.com/content/dam/dpagco/corteva/microsites/healthyoils/files/Healthy_Oils_Comparison_Chart.pdf
This comprehensive prospective study reveals that, compared to non-consumers, individuals using butter and/or margarine have an elevated total mortality rate, while those incorporating canola and/or olive oil into their diets exhibit a reduced total mortality risk.
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