Saturated fat from your diet increases your LDL and total cholesterol, but stating that this puts you at an increased risk of cardiovascular disease, as we have done for many years, is too simplistic.
Most fats in your food and in your body are triglycerides, which consist of 3 fatty acids. Whether these fatty acids are saturated or unsaturated varies with your diet, as triglycerides can be made up of fats that you have eaten or fats made by your liver from other energy sources such as carbohydrates.
Cholesterol is another kind of fat that you can get from food or produced by your liver.
As fat cannot dissolve in blood, most of it is moved around your body in small particles, called lipoproteins. The most important ones are the low density lipoproteins (LDL) and the high density lipoproteins (HDL). LDL carries cholesterol and fat from the liver to the rest of your body, where they are needed by your cells for energy production and to make essential substances such as hormones. HDL picks up the surplus of LDL from your blood and brings it back to your liver.
How exactly atherosclerosis plaques develop is still not well understood, but as far as we know LDL particles get trapped in the vessel wall, where they become oxidized by free radicals. This creates an inflammatory reaction which leads eventually to the formation of a plaque.
Too much saturated fat in your blood can also cause an inflammatory reaction, and can therefore start and/or aggravate the situation.
Studies have shown that too much low density lipoprotein or LDL puts you at a higher risk of cardiovascular disease, and that high density lipoprotein or HDL protects you. LDL is therefore often called “bad” cholesterol and HDL “good” cholesterol, and clinicians use the LDL/HDL ratio or the total cholesterol/HDL ratio to estimate your risk. The amount of triglycerides in your blood is also important.
To keep your vessels healthy, you want a diet that is anti-oxidant and anti-inflammatory, improves the LDL/HDL ratio and lowers the amount of triglycerides.
Everybody agrees that industrial trans-fats are bad for your health. They are made by hydrogenating vegetable oils and, as they are more stable than other fats, are ideal for frying and making processed food. However, they increase LDL and lower HDL, and you should therefore avoid them. Some whole foods such as milk contain small amounts of trans-fats, but there is evidence that these are different from the industrial ones and do not harm you.
Saturated fats are typically found in red and processed meat, butter and other forms of animal fats. Previously, scientists thought that eating too much saturated fats increases your risk of cardiovascular disease, as they raise your LDL. However, studies do not confirm this.
Their effects on your health vary depending on which food they come from. Red meat contains cholesterol and heme iron that probably increase the risk, and processed meats contain preservatives that are bad for your health. Milk and milk products on the other hand, are a good source of nutrients such as calcium, potassium, phosphorus and vitamin D. As a result, they lower your risk of cardiovascular disease.
Different foods contain different proportions of specific saturated fats, combined or not with other fats, and affect therefore your risk factors in different ways. Unfortunately, we do not understand this fully yet and we need more research.
Most scientists agree that you should try to limit your intake to about 10% of your energy, but it is very controversial that limiting it even further is helpful. Moreover, an important question is by what you replace it.
Mono-and poly unsaturated fats
Replacing saturated fats by mono-unsaturated fats improves the LDL/HDL ratio slightly. A Mediterranean diet is good for your heart and blood vessels, but modern studies could not proof that this was due to its high mono-unsaturated fat content.
Many studies have shown that replacing saturated fats by polyunsaturated fats is beneficial. Unfortunately, they did not differentiate between trans-fats and saturated fats and some scientists think that the beneficial effects were due to the fact that the trans-fats were taken out of the diet, and had nothing to do with reducing the saturated fats.
This is a controversial and rapidly evolving subject, and it is therefore a good idea to keep informed about the latest findings. As yet, it is prudent to reduce the amount of saturated fats in your diet to about 10%, and to favour polyunsaturated fats.
Sources of mono-unsaturated fat include nuts, olives, vegetable oils and avocados, but also beef and milk. You will find polyunsaturated fats in food such as seeds, nuts and fish.
In practice, fats are often replaced by carbohydrates. Unfortunately, this increases the risk of cardiovascular disease, because your liver transforms the surplus of carbohydrates into saturated fats. These interact then with your immune system, which leads to a chronic, low-level inflammation and stimulates the formation of atherosclerotic plaques.
The situation is especially bad when you are eating high glycemic index foods.
The glycemic index ranks carbohydrate-containing foods according to how quickly they increase the glucose levels in your blood. Foods such as white bread, pretzels or sugary drinks are high glycemic, as they have a score of more than 70, while carrots, lentils or apples are low glycemic (their score is less than 55). You can find lists in books or online, for example here.
We should therefore reduce the amount of carbohydrates with a high glycemic index, eliminate industrial trans-fats from our diet and consume more vegetables, fruit and fish.
Saturated fats are not the only cause of chronic inflammation: sleep deprivation, smoking, inactivity and stress are also important factors. It is not enough to have a healthy diet; you need to have a healthy lifestyle.
Disclaimer: this article is for general information only, and does not replace medical advice. It cannot be used to diagnose or guide treatment. If you have any concerns or questions, you should talk to a qualified health provider.
M de Oliveira Otto, D Mozaffarian, D Kromhout et all. Dietary intake of saturated fat by food source and incident cardiovascular disease: the multi-ethnic study of atherosclerosis. Am J Clin Nutr. 2012; 96(2): 397-404.
R Kuipers, D de Graaf, M Luxwolda et al. Saturated fat, carbohydrates and cardiovascular disease. Neth J Med. 2011; 69(9): 372-378.
K Kingsbury and G Bondy. Understanding the essentials of blood lipid metabolism. www. medscape. com; accessed 13/10/2013.