Salad dressings and mayonnaise contain an essential fatty acid that may protect against fatal heart attacks, according to a new study by Harvard University researchers. The study, published in the May issue of the American Journal of Clinical Nutrition, found that salad dressings and mayonnaise contain alpha linolenic acid, an omega-3 fatty acid, that has protective effects against heart disease.
"Higher consumption of foods such as oil-based salad dressings that provide polyunsaturated fats, including alpha-linolenic acid, may reduce the risk of fatal IHD (ischemic heart disease)," the researchers wrote. A higher intake of oil and vinegar salad dressings, an important source of alpha-linolenic acid, was associated with reduced risk of fatal IHD when women who consumed this food more than five to six times a week were compared with those who rarely consumed this food, according to the researchers, led by Dr. Frank Hu, a research associate at the Harvard School of Public Health.
The intake of alpha-linolenic was derived from a 116-item food-frequency questionnaire completed in 1984 by 76,283 women without previously diagnosed cancer or cardiovascular disease. The report is the latest from the Harvard Nurses' Health Study, established in 1976, that examines the relationship between diet and heart disease.
"In the public's mind, fat has become public enemy number one," said Hu. "But the truth is that if you reduce your total fat consumption, you're also reducing the amount of good fats that you eatfats that have a protective effect against heart disease."
According to the Harvard study, the number one and two major contributors to the overall intake of alpha-linolenic acid based on the 1984 food-frequency questionnaire in the Nurses' Health Study were mayonnaise or other creamy salad dressing and oil and vinegar salad dressing (e.g., Italian). Approximately 70% of alpha-linolenic acid was from vegetable or plant sources (e.g., salad dressings and vegetable oils).
"In conclusion, this study provides support for the hypothesis that a higher intake of alpha-linolenic acid will reduce the risk of fatal IHD," the researchers noted. "Our findings suggest that a reduction in the consumption of foods such as oil-based salad dressings that contain polyunsaturated fats, including alpha-linolenic acid, may increase the risk of fatal IHD."