"Eat a low fat, low cholesterol diet."
How many times have you heard that over the years? Simple isn't. It would probably have been followed up by claims that doing so would lead to weight loss, the prevention of cancer and a reduction in heart disease. Unfortunately, like most things, the truth is a lot more complicated.
Recent research has shown that the amount of fat that you consume isn't linked to disease. Results from a lengthy study called the Women's Health Initiative Dietary Modification Trail undertaken by Harvard showed that sticking to a low-fat diet for 8 years did not prevent breast cancer, colon cancer, heart disease or help with weight loss. Instead, what matters is the type of fat you consume. Put simply you must avoid bad fats and substitute them with good fats. Bat fats are saturated and trans fats, which increase the risk of certain diseases. Good fats, meaning monounsaturated and polysaturated fats, lower the risk. So far, so good.
But what about cholesterol? We all know that too much in your food is bad for you, right? In fact that's wrong too. Only 25% of cholesterol is absorbed from food, the rest of the cholesterol in your blood is created by your liver. So it's actually the mix of fats in your diet that influences on your blood cholesterol levels, not what you eat.
But what is cholesterol? Well it's a waxy substance that your liver links to carrier proteins called lipoproteins that let it dissolve into blood and be carried around the body. Cholesterol plays an essential part in the formation of cell membranes, hormones and vitamin D. Too much cholesterol in the blood can block arteries and lead to problems such as heart disease or strokes. Luckily, cholesterol levels can be reduced by changing the type of fats you eat.
However, you don't stop eating cholesterol to reduce its level. Unsurprisingly, it's more complicated than that. What's important isn't the cholesterol in your blood, but the type of lipoproteins that are carrying the cholesterol. There is a 'good' type and 'bad' type of lipoprotein.
Low-density lipoproteins (LDL) carry cholesterol from the liver to the rest of the body. When there is too much LDL cholesterol in the blood, it can be deposited on the walls of the coronary arteries. Because of this, LDL cholesterol is often referred to as the 'bad' cholesterol.
High-density lipoproteins (HDL) carry cholesterol from the blood back to the liver, which processes the cholesterol for elimination from the body. HDL makes it less likely that excess cholesterol in the blood will be deposited in the coronary arteries, which is why HDL cholesterol is often referred to as the 'good' cholesterol.
In general, the higher your LDL and the lower your HDL, the greater your risk of heart disease. So we should reduce LDL, and increase HDLs. And guess what can do that? Good fats can. Simple isn't. Still not clear? Well the table below should help. It shows you what good fats are, what bad fats are and what their effect is on HDL and LDL levels.