If you currently limit your intake of butter, full fat dairy produce and meat, and carefully check food labels for the amount of saturated fat they contain, you’re not alone. For decades we have been told by health experts to cut back our intake of saturated fats to reduce our risk of cardiovascular problems and instead choose foods rich in unsaturated fats such as vegetable oils, nuts, seeds, avocados and oily fish. However, new research, published in the Annals of Internal Medicine, has cast some doubt on the benefit of limiting the amount of saturated fat in our diet.
Considering the evidence
The analysis, which looked at close to 80 quality studies, involving over half a million participants in total, found that people who ate most saturated fat were no more likely to develop heart disease than people who had the least amount of saturated fat in their diet. Equally, those people who ate a diet higher in unsaturated fat were just as prone to heart disease as those who consumed far less unsaturated fat. The research did, however, confirm that a higher intake of trans fats, found in certain soft margarines, fried foods and commercially baked goods like cakes, cookies, pastries, pizza, chips and frozen meals, increases your risk of coronary artery disease. While saturated fats may not be as unhealthy as previously thought, before you start adding steak, cheese and chocolate to your weekly shop, it’s important to consider the reasons for these findings. Saturated fats may offer some benefits, but this study doesn’t necessarily give you the go-ahead to up your intake of saturated fat, as your diet as a whole is also important.
Impact of saturated fat on cholesterol levels
Firstly, although saturated fats raise levels of LDL cholesterol, the type of cholesterol associated with narrowing of the arteries, it turns out that saturated fats increase a subset of larger LDL particles known as type-A, which are less likely to damage your arteries than small, dense type-B LDL particles. This is because the larger LDL molecules are less reactive, so less likely to trigger inflammation, which usually contributes to the formation of plaques on the coronary arteries. Certain saturated fats may even lower levels of LDL cholesterol, with the saturated fat stearic acid, which accounts for around half the saturated fatty acids in beef, rapidly converted into heart-healthy monounsaturated fat. The positive impact of heptadecanoic acid, a saturated fat found in dairy produce, may also explain why dairy consumption is not associated with heart disease risk.
Saturated fats additionally boost levels of protective HDL cholesterol, which removes cholesterol from the arteries, with a higher level of HDL associated with a reduced risk of coronary artery disease. This contrasts with trans fats, which raise harmful LDL cholesterol, while lowering beneficial HDL cholesterol. In view of the impact of trans fats on your cholesterol profile and the fact that many processed foods are high in both trans and saturated fat, consuming a diet high in saturated fat may indirectly increase your risk of future heart problems.
Low-fat, high carbohydrate diets are not beneficial
Another consideration is that no cardio-protective benefit was seen among those people who cut back on saturated fat because other aspects of their diet were not considered in these studies. People often swap high fat savory foods for extra bread and simply change from having chocolate, cookies and cakes to sweet foods that might be low in fat, but are just as high in sugar. This is relevant, as if saturated fats are replaced with extra carbohydrate in the diet, particularly sugary foods, this will not benefit cardiovascular health, as the amount of carbohydrate in your diet can also adversely affect your cholesterol profile.
For instance, high carbohydrate diets are linked to increased levels of damaging type-B LDL cholesterol and lower levels of HDL, as well as raised levels of triglycerides, which are another type of fat in the blood that increase your risk of heart disease. From this it seems that it is a carbohydrate rich diet that will do more damage to your arteries, so current advice from the American Heart Foundation is not to replace saturated fats with carbohydrates, but instead to replace them with monounsaturated and polyunsaturated fats. Indeed, research shows that both types of unsaturated fats lower LDL cholesterol, but monounsaturates, which are found in good quantities in olive and canola oil, avocados, nuts and seeds, have the advantage that they do not lower HDL cholesterol, unlike polyunsaturates, which are sourced from the likes of soyabean, corn and sunflower oil. While it is inadvisable to follow a low carbohydrate diet, including moderate portions of whole grains, such as oats, grainy bread and brown rice, which release their sugars more slowly will help to keep your lipid profile healthy.
Aim for a Mediterranean diet
The points above show why considering nutrients in isolation does not work particularly well when aiming to lower your risk of heart disease. Rather than aiming to eat less than a certain amount of saturated fat each day, you should consider the overall nutritional value of the foods you eat. This might be why a Mediterranean diet, which is rich in olive oil, fish and nuts, as well as including plenty of fruit, vegetables, pulses and whole grains, was shown to lower the risk of heart attacks and strokes more effectively than simply a low-fat diet.
The Mediterranean diet doesn’t exclude saturated fats, as after all cheese, yogurt, eggs and small amounts of meat are all included, but it is high in monounsaturates. It also offers fiber, antioxidants and other micronutrients beneficial to heart health in good supply and a Mediterranean approach to eating generally means a lower intake of refined carbohydrates than with low-fat diets. This recent study comparing a Mediterranean and low-fat diet in relation to cardiovascular disease was unfortunately not included in the analysis of different dietary fats on coronary heart disease risk. However, owing to the widely accepted benefits of the Mediterranean diet for cardio-protection, we should all aim to follow the Mediterranean food pyramid for better heart health.