Olive Oil Diet and Blood Pressure: Spanish Study Finds a Clue
A Spanish team led by Valentina Ruiz-Gutiérrez of the CSIC’s Instituto de la Grasa in Seville reports that a year on a Mediterranean diet with virgin olive oil or nuts changed the fat make-up of red blood cell membranes in people with high blood pressure, which they offer as one explanation for why the diet lowers blood pressure. This note covers what the study measured, how small it was, and what it means for the oil you buy.
What happened
The paper appears in the November issue of the American Heart Association journal Hypertension and was published online earlier this month. It was reported in the Spanish press on October 21. The first author is Francisca Barceló of the University of the Balearic Islands, and the team includes researchers from the Instituto de la Grasa and from groups in Seville, Málaga and Barcelona.
The work is a small offshoot of PREDIMED, the large Spanish trial testing whether a Mediterranean diet prevents heart disease in people at high risk. The trial has already reported that a Mediterranean diet rich in virgin olive oil or nuts reduces systolic blood pressure. This substudy looked at 36 of its participants with high blood pressure after one year on their assigned diets and asked what was happening at the level of the cell.
The answer, according to the authors, is in the membranes of red blood cells. After the year, the cholesterol content of those membranes fell and the phospholipid content rose in all the diet groups studied, a shift the authors link to more fluid membranes. Membranes rebuilt from the olive oil and nut groups also showed a greater tendency to form a particular structure, tied to a rise in one class of phospholipid. Ruiz-Gutiérrez summed it up to the press: the Mediterranean-style diet changes membrane structure and affects fat metabolism, which is badly disturbed in people with hypertension.
| Study detail | What was reported |
|---|---|
| Participants | 36 people with high blood pressure from the PREDIMED trial |
| Length | One year of dietary intervention |
| Diets | Mediterranean style, supplemented with virgin olive oil or nuts |
| Main finding | Less cholesterol and more phospholipid in red cell membranes |
| Journal | Hypertension, November 2009 |
Why it matters
The idea that olive oil is kind to blood pressure is not new; this site has carried earlier reports linking olive oil to lower blood pressure, and our plain summary of what olive oil can and cannot do for blood pressure still stands. What researchers have lacked is a clear mechanism. Showing a measurable change in cell membranes, in real patients on a real diet, gives the trial result some biological footing.
It is also good news for the Spanish sector, which has long pushed for health messages on olive oil. A mechanism published in a cardiology journal is worth more to that effort than any advertising slogan.
What it means for buyers
Keep the scale in mind. Thirty-six people is a small group, the nut group showed changes too, and the study measured membranes, not heart attacks. It supports the case for the diet as a whole, which is the case made in our piece on making extra virgin olive oil part of your diet. It does not turn any single bottle into a treatment.
- The oil in the trial was virgin olive oil, not refined “light” oil.
- The benefit comes from a whole diet, followed for a year.
- Olive oil works best as a swap for other fats, not as an extra.
Within weeks of a study like this, you will see bottles and brochures promising to “protect your heart”. The trial oil was virgin olive oil, but bottles labeled simply “olive oil” are mostly refined oil with some virgin oil added for color and taste. If the health story is why you are buying, read the grade on the label, and remember the nuts did much the same job in this study.
This is general information, not medical advice. High blood pressure needs a doctor’s care; do not change or stop any medication without talking to your doctor first.