Study highlights:
• High intake of omega-3 fatty acids was linked with a 59 percent reduction in heart attack risk in a Costa Rican study.
• High level of omega-6 fatty acids was linked to lower blood pressure among healthy people in an international study
• Both omega 3 and omega 6 fatty acids are essential acids but must be obtained from food.
 
DALLAS, July 8 – Consuming omega-3 fatty acids found in some vegetable cooking oils and fish was associated with reduced heart attack risk in a Costa Rican population study, and eating omega-6 fatty acids was linked to lower blood pressure for healthy people in an international study.

The studies were separately published respectively in Circulation: Journal of the American Heart Association and Hypertension: Journal of the American Heart Association.

Both omega-3 fatty acids (alpha-linolenic acids from plant foods, EPA and DHA from some fatty fish) and omega-6 fatty acids (mainly linoleic acid) are polyunsaturated essential fatty acids that must be obtained from food because the body cannot make them sufficiently. Omega-3 fatty acids are found in found in walnuts, soybean, canola and flaxseed oils and in fish such as salmon, tuna and sardines.

Omega-6 is plentiful in soybean, safflower, sunflower, and corn oils, as well as in tofu, nuts and seeds. The American Heart Association recommends eating omega-3 containing fish twice a week and eating your fats from polyunsaturated sources such as nuts, seeds and vegetable oils.

Replacing saturated and trans fatty acids with omega-3 and omega-6 fatty acids may reduce cardiovascular risks, according to previous research.

In the Circulation study led by Hannia Campos, Ph.D., intake of omega-3 from vegetable oils was associated with a 59 percent reduction in heart attack risk. Researchers studied 1,819 residents of Costa Rica who had survived a first heart attack and compared them to a similar group who had not had a heart attack. Participants completed a food and alcohol frequency questionnaire and researchers analyzed body fat samples to determine their alpha-linolenic acid content.

Compared to those with the least amount of alpha-linolenic acid in their body fat samples, those with the highest levels had a 59 percent lower heart attack risk – “a large and significant reduction.”

“Alpha-linolenic acid was associated with a very strong protective effect, and the relationship quickly reached a plateau with most of the effect achieved after just a small intake,” said Campos, senior lecturer in the nutrition department at Harvard School of Public Health in Boston, Mass.

These data suggest that the amount of dietary alpha-linolenic acid required to produce this relationship in this population study corresponded to two teaspoons of soybean oil or canola oil, half a teaspoon of flaxseed oil or six to 10 walnut halves.

If confirmed by further research, it might someday be possible to reduce the prevalence of cardiovascular disease by adding a little of this essential fatty acid to the diet in the many countries where intake of fish containing long-chain omega-3 fatty acids, and vegetable oils containing alpha-linolenic acid is low, as it is in Costa Rica, Campos added.

Compared to the United States, consumption of vegetable oils containing omega-3 and fish is very low in Costa Rica. Residents there also tend to eat tropical white fish, which is much lower in long-chain n-3 fatty acids than the cold-water species such as salmon and mackerel that are commonly eaten in North America, she added.

Fortunately, since the 1980s, the Costa Rican population has decreased consumption of palm oil, a vegetable oil that lacks alpha-linolenic acid and is high in saturated fatty acids. They’ve also increased consumption of other vegetable oils – especially soybean oil – that are rich in alpha-linolenic acid, she said.

Co-authors with Campos are Ana Baylin, M.D., D.Sc., and Walter C. Willett, M.D., M.P.H. The study received grants from the U.S. National Heart, Lung, and Blood Institute, National Institutes of Health.
The Hypertension study led by Katsuyuki Miura, M.D., Ph.D., found that a higher consumption of the most common plant-based dietary polyunsaturated fatty acids or omega-6s is associated with lower blood pressure.

The International Study of Macro/Micro-nutrients and Blood Pressure (INTERMAP) is the first comprehensive population-based investigation on linoleic acid and blood pressure and the first such study in eastern and western populations. It included 4,680 men and women ages 40 to 59 from the People’s Republic of China, Japan, the United Kingdom and the United States.

In an analysis of a subset of 2,238 individuals called the “non-intervened” participants: those who consumed no therapeutic diet or nutritional supplements, had never been diagnosed with cardiovascular disease, diabetes or high blood pressure and took no medication for those conditions, researchers found a statistically significant association between higher linoleic acid intake and lower blood pressure.

“Our findings indicate a favorable influence of linoleic acid on high blood pressure, a well-known cardiovascular disease risk factor,” said Miura, associate professor in the department of health science at Shiga University of Medical Science in Shiga, Japan. “These results lend support to current recommendations for increased ingestion of polyunsaturated fatty acids from vegetable sources, in place of saturated fatty acids from animal sources, for cardiovascular disease prevention.”

Study participants provided four in-depth 24-hour dietary recall surveys, eight blood pressure measurements at four separate office visits and two 24-hour urine collections so that researchers could determine nutrient intake.

“In the non-intervened group, with control for 14 variables, we found that a higher linoleic acid consumption of about 9 grams/day was associated with a 1.4 millimeters of mercury (mm Hg) lower average systolic blood pressure and a 1.0 lower average diastolic blood pressure,” Miura said.
Blood pressure is expressed as two numbers: the higher number (systolic) represents the pressure when the heart contracts to pump blood around the body; the lower number (diastolic) represents the pressure when the heart relaxes between beats.

Even the “small” decrease in average blood pressure in a whole population has a big effect on the risk of cardiovascular death and disability within that population, Miura said.

“Lowering the systolic blood pressure of a population by ‘small’ amounts, such as 2 mm Hg, is estimated to reduce mortality rates by 6 percent for stroke and by 4 percent for coronary heart disease,” he said.

Vegetable oil was the main food group supplying linoleic acid in the study (49 percent of the total consumed in the People’s Republic of China, 30 percent in Japan, 28 percent in the United States and 17 percent in the United Kingdom). Other significant sources included table spreads, salad dressings, vegetarian meat substitutes such as tofu, grains and flour, nuts/nut butters and breads/rolls/biscuits/related products.

Co-authors with Miura are Jeremiah Stamler, M.D.; Hideaki Nakagawa, M.D., Ph.D.; Paul Elliott, M.B., Ph.D.; Hirotsugu Ueshima, M.D., Ph.D.; Queenie Chan, M.Sc.; Ian J. Brown, Ph.D.; Ioanna Tzoulaki, Ph.D.; Shigeyuki Saitoh, M.D., Ph.D.; Alan R. Dyer, Ph.D.; Martha L. Daviglus, M.D. , Ph.D.; Hugo Kesteloot, M.D., Ph.D.; Akira Okayama, M.D., Ph.D.; J. David Curb, M.D.; Beatriz L Rodriguez, M.D., Ph.D.; Patricia J. Elmer, Ph.D.; Lyn M. Steffen, Ph.D.; Claire Robertson, Ph.D. and Liancheng Zhao, M.D.

This research is supported by a grant from the U.S. National Heart, Lung, and Blood Institute, National Institutes of Health (NIH) and by the NIH Office on Dietary Supplements, and by national agencies in Japan, China, and the United Kingdom.

Disclosures for individual authors are available on the manuscript.

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Statements and conclusions of study authors that are published in the American Heart Association scientific journals are solely those of the study authors and do not necessarily reflect association policy or position. The American Heart Association makes no representation or warranty as to their accuracy or reliability.

NR08-1084 (CIRC/Campos and HYP/Miura)