“Good” and “bad” fats: Study reveals that the types of saturated fats you consume may affect your heart health
06/03/2019 / By Evangelyn Rodriguez
The latest Dietary Guidelines for Americans recommends that people reduce their intake of saturated fats and shift to eating foods rich in healthier polyunsaturated and monounsaturated fats. In particular, Americans are urged to stay away from meats, poultry, and dairy products that contain high amounts of solid fats as much as possible, as both solid fats and saturated fats are linked to a higher risk of coronary heart disease (CHD). However, a recent large-scale study involving British and Danish cohorts suggests that not all saturated fats are equally harmful with respect to the development of CHD. Some have minimal to no contributory effect at all. And the difference lies in their molecular structure, specifically, the length of the chains these fatty acids have.
Different types of saturated fats have different effects on heart attack risk
More than 50 years ago, people made the connection between diets high in saturated fat, elevated low-density lipoprotein (LDL) cholesterol, and CHD. It was then that dietary guidelines began to change and urge people to restrict their consumption of saturated fatty acids to reduce their risk of heart disease. But in recent years, conflicting findings have raised questions about whether or not these guidelines have got it right. In particular, the results of several meta-analyses suggest that the type of saturated fat (and there are many) may, in fact, be the determining factor that makes a certain fatty acid a contributor to heart disease or a preventive aid.
For their study, researchers from the Netherlands, the U.K., and Denmark looked into the molecular composition of fatty acids to determine if the variations in their length (4 to 18 carbon atoms) affect their association with the risk of myocardial infarction (MI, heart attack). They enlisted almost 75,000 people from Denmark and the U.K. and conducted a follow-up 13 years and 18 years later for each cohort, respectively. Of the nearly 75,000 individuals involved, the researchers reported that about 3,500 experienced a heart attack between the start of the study and the follow-up.
“We found that eating relatively little of the longer chained saturated fatty acids and consuming plant-based proteins instead was associated with a lowered risk,” said Ivonne Sluijs, the corresponding author of the study. “Substitution of those saturated fats with other energy sources such as carbohydrates did not affect the risk to develop myocardial infarction,” she added.
Long-chain saturated fatty acids, such as palmitic acid with 16 carbons and stearic acid with 18 carbons, are abundantly present in meats. They can also be found in palm oils, coconut oils, and other vegetable oils. Plant-based proteins that, according to the study, could be used as healthy substitutes to long-chain saturated fatty acids may be sourced from chickpeas, almonds, lentils, and spirulina. (Related: Spirulina explained: Here’s what you need to know about this healing superfood.)
On the other hand, shorter-chained saturated fatty acids with four to 10 carbons showed an inverse correlation with MI risk. These fatty acids are produced by good bacteria in the gut while they ferment dietary fibers. These fibers come from fruits and vegetables, as well as whole grains, rice, beans, and legumes.
Food sources of saturated fats also make a difference
Upon comparing their results with other cohort studies, such as those done in the U.S., Sluijs and her team said that the differences in their results could be due to the food sources involved. For instance, in one American cohort study, researchers reported that saturated fatty acids with 18 carbons are strongly associated with MI risk, whereas most European cohort studies, including the present, found a slightly different relationship. Sluijs and her colleagues reported that saturated fats with 16 and 18 carbons might be adversely associated or not associated with MI risk, depending on where they were sourced. According to them, the main sources of long-chained saturated fats in American diets are meat and mixed meals, while in most European countries, the majority of long-chain saturated fats come from dairy products.
“These observations could reflect a difference in the underlying dietary pattern, e.g. the difference in consumption of dairy versus meat, but could also reflect actual differences of SFAs (saturated fatty acids) effects on CHD risk markers,” they wrote. “Because of the high correlations between the SFAs, observational cohort studies alone will not suffice in answering the question whether individual SFAs have different associations with MI or CHD.”
“Therefore, for further examination of the effects of the short-to medium-chain SFAs on MI risk, evidence from intervention studies is needed,” the researchers concluded.
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