Fatty acids taken in the dietary form have a significant influence on serum cholesterol levels and the development of various cardiometabolic diseases. A new research study has suggested that the intake of saturated fatty acids (SFA) present in the diet (such as in cheese and butter) have similar effects to carbohydrates, monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) on high-density level (HDL) cholesterol but have different activity on low-density level (LDL) cholesterol.
Cardiovascular disease (CVD) involves abnormalities in the function of heart or blood vessels (veins, arteries, and capillaries) and encompasses a broad range of pathological symptoms (heart attack, chest pain or stroke). Most commonly, abnormal levels of lipids are the cause of morbidity and mortality associated with cardiometabolic risk (coronary artery disease (CAD), heart attack and coronary death). Therefore, nutrition has a powerful influence on improving lipid levels of CVD by either switching to diets that contain either mono or polyunsaturated fatty acids. Following a suitable healthy diet brings physiological changes such as a decrease in plaque formation, endothelial vasomotor dynamics, oxidation of low-density lipoproteins (LDL, bad cholesterol) and thrombolytic activity. Naturally, a diet high in saturated fats (e.g. cheese) raises the levels of cholesterol in the blood, while unsaturated fats, polyunsaturated fatty acids (PUFAs) and monounsaturated fatty acids (MUFAs), contribute beneficial effects on heart health. Especially, dietary saturated fatty acids play a key role in regulating the risk of CVD. Most literature studies have established the association between SFAs and risk of cardiovascular disease (CVD) while some studies reported controversies. A new research approach by Lamarche and his co-researchers at Laval University, Quebec, Canada not only established a relationship between SFAs and CVD but also analyzed the impact of SFA intake on cardiometabolic risk by comparing different dairy sources to other forms of fat sources. The interesting findings of the study were published in the American Journal of Clinical Nutrition, 2017.
In order to understand the impact of SFAs on CVD, a randomized controlled trial (RCT) was carried out by researchers in Canada on 92 individuals. The study subjects, which were diagnosed with obesity and had low levels of high-density lipoprotein (HDL, bad) cholesterol, were assigned to have five different diets lasting 4 weeks each, separated by a 4-week washout period. The diets were: two diets high in SFAs obtained from diets of either cheese or butter, a MUFA rich diet, a PUFA rich diet and a low-fat, high-carbohydrate diet. When comparing the impact of SFAs from cheese and butter on cardiometabolic risk factors, it observed that serum HDL-cholesterol concentrations were similar after the cheese and butter diets in comparison to the MUFA- and PUFA-high diets, but the concentrations were significantly higher than those seen in the carbohydrate diet. Interestingly, after the cheese diet, LDL-cholesterol concentrations were lower than after the butter diet but were still higher than after the carbohydrate, MUFA, and PUFA diets. An LDL-cholesterol concentration after the butter diet was also shown to increase significantly – from 16.1% to 116.2% – when compared with the carbohydrate, MUFA, and PUFA diets. This change in LDL cholesterol by dietary SFAs is mostly attributed to polymorphisms in genes of cholesterol metabolism. Moreover, no difference exists between all diets on inflammation markers, blood pressure, and insulin-glucose homeostasis.
In summary, dietary intake of SFAs has a varying effect on LDL cholesterol concentrations but had similar effects on HDL cholesterol when compared with carbohydrates and control nutrients such as MUFAs and PUFAs. As well, SFAs present in food sources such as cheese and butter have no effect on several non-lipid cardiometabolic risk factors. In addition, nutrient and non-nutrient components of the food matrix had a significant role on the impact of SFAs on lipid content of blood, indicating the importance of whole food sources rather than single nutrient components. Some of the limitations of the study include a report which was based on self-assessment and a high drop rate of individuals in the trials.
Written By: Manche Santoshi, PhD