After re-analyzing unpublished data from the 1960s, researchers found that replacing saturated fats with vegetable oil may not lead to a longer life, according to a recent paper published in the British Medical Journal.
Conducted from 1968–1973, the Minnesota Coronary Experiment tested whether replacing saturated fats with vegetable oil helps lower cholesterol and risk of death. The trial included more than 9,500 adults from a nursing home and mental hospitals in Minnesota, where diets can be strictly regulated. During the study, half of participants were fed meals that included milk, cheese and beef, all of which are rich in saturated fats. The other half received meals enriched with corn oil, which contains polyunsaturated or “good” fats.
The trial was designed to show that reducing saturated fats would help lower cholesterol and reduce risk of both heart disease and death. But analysis of unpublished data suggests the opposite.
After following participants for an average of 15 months, researchers found that unsaturated fats did help lower cholesterol levels. In fact, participants on the low saturated fat diet reduced their cholesterol by 14% compared to those on the standard diet. However, this drop in cholesterol did not reduce mortality risk. Results actually suggest that the greater the drop in cholesterol, the greater the risk of death.
Of course, authors advise caution when interpreting results. Although the trial was one of the most rigorous dietary trials on vegetable oil and cholesterol, there are many explanations for findings.
It’s possible that participants were not followed long enough to show any significant cardiovascular benefits. It’s also possible that participants who saw the greatest drops in cholesterol also had the highest cholesterol to begin with, putting them at increased risk for heart disease and death. Experts also suspect that the intervention was too rich in omega-6 fatty acids, which in excess can promote inflammation.
Therefore, experts stand by current dietary guidelines, which recommend replacing saturated fats with polyunsaturated fats like vegetable and olive oils. More than 1/3 of Americans have high cholesterol, which increases risk for heart disease, heart attack and even death. Many studies show that saturated fats raise “bad” cholesterol levels, which is why experts recommend limiting saturated fat consumption. As part of a heart-healthy diet, choosing healthier fats and eating plenty of nutrient-rich foods can help reduce risk for heart disease and improve health.