Findings from two large cohort studies and 9797 incident cases of cardiovascular disease (CVD) showed that higher olive oil intake was associated with a lower risk for coronary heart disease (CHD) and total CVD in US men and women.
Replacing about 1 teaspoon per day (5 g/day) of margarine, butter, mayonnaise, or dairy fat with an equivalent amount of olive oil was associated with a 5% to 7% lower risk for total CVD and CHD, reported Marta Guasch-Ferre, PhD, from the Harvard T. H. Chan School of Public Health, Boston, Massachusetts.
"The main message of our results is that we provide further support for the recommendation to replace saturated fat from animal fat with more unsaturated plant oils, such as from olive oil, for the prevention of cardiovascular disease," said Guasch-Ferre in an interview.
The researchers reported their results March 5 at the American Heart Association Epidemiology, Prevention, Lifestyle and Cardiometabolic Health Scientific Sessions in Phoenix, Arizona. The study was simultaneously published in the Journal of the American College of Cardiology.
After adjusting for other dietary and lifestyle factors, those with higher olive oil intake (>½ tablespoon per day or >7 g/day) had a 14% lower risk for CVD and an 18% lower risk for CHD compared to those who did not consume olive oil.
No significant association was noted between olive oil consumption and total or ischemic stroke.
However, asked to comment on the findings, Salim Yusuf, DPhil, McMaster University Hamilton, Ontario, Canada, said the study was well done, "given the limitations of the methods," but is "entirely unconvincing" and provides no basis on which to make any changes to dietary recommendations.
"When you change one thing in diet, you don't expect to see big changes, so the 5% to 7% lower risk they found is within what's plausible, but it's also within the limits of error of the method, so it's really neither here nor there," said Yusuf in an interview with theheart.org | Medscape Cardiology.
"There's lots of confounding in observational data, so it just cannot robustly tell you differences of 5% or 10% or 20%. You need much bigger differences to believe it," he added.
Yusuf also noted that the results of this study contradict those of a recent meta-analysis that showed a benefit from olive oil consumption regarding the risk for stroke.
"In this study, it's coronary heart disease that was lower, and in the meta-analysis, it was strokes that were lower, so it's not consistent," he said.
Bringing Mediterranean Diet Research to US Shores
The associations between olive oil intake and the risk for CVD have never been evaluated in a US population. Given that olive oil intake has increased in recent years, the researchers wanted to see whether the associations seen in Mediterranean populations might also be seen here.
Guasch-Ferre and colleagues pooled data from 61,181 women from the Nurses' Health Study (1990–2014) and 31,797 men from the Health Professionals Follow-up Study (1990–2014) who were free of cancer, heart disease, or stroke at baseline. Diet was assessed using a validated semiquantitative food frequency questionnaire at baseline and every 4 years.
"Over the last 30 or 40 years, we've seen several observational studies that have indicated that olive oil is beneficial for heart disease in European populations, but there were no studies to show this association in the US population," said Guasch-Ferre.
To theheart.org | Medscape Cardiology, Guasch-Ferre noted that the results were similar when olive oil was compared with other plant oils combined (eg, corn, safflower, soybean, canola).
"A limitation of this study was that the intake of olive oil was not as high as in Mediterranean populations, so we were not able to see an association between the different types of healthy oils," said Guasch-Ferre. The researchers could not distinguish between different varieties of olive oil because that information was not recorded.
Mean olive oil consumption increased from 1.30 g/day in 1990 to 4.2 g/day in 2010. Mean intake in the highest using group was 12 g/day, or about 2.5 teaspoons, compared to a mean intake of 40 g/day at baseline in the Spanish participants of the PREDIMED study.
"As observational studies go, this is as good as they get, done by one of the best groups in the world, but it’s still an observational study, and the differences seen are so small," Yusuf said.
Yusuf was a member of a group of leading scientists who released a consensus statement detailing the findings from the latest research regarding the intake of saturated fats and heart disease.
After reviewing the evidence, the expert group agreed that the most rigorous current science fails to support a continuation of the government's policy of limiting consumption of saturated fat.
Members of the group sent a letter to the secretaries of the US Department of Agriculture and the US Department of Health and Human Services — the two agencies responsible for issuing the Dietary Guidelines for Americans — suggesting they give "serious and immediate consideration to lifting the limits placed on saturated fat intake for the upcoming 2020 Dietary Guidelines for Americans."
Asked whether he would have any qualms about using butter instead of olive oil in a recipe, Yusuf replied, "No qualms at all, but like with everything, the key is moderation and diversity. I wouldn't have any qualms eating a moderate amount of different types of natural foods."
The study was supported by research grants from the National Institutes of Health. Guasch-Ferre has disclosed no relevant financial relationships.
J Am Coll Cardiol. Published online March 5, 2020. Full text
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