Cholesterol is a waxy type of fat that is present in all animal tissues. Babies get it from their mother’s milk. We could not exist without cholesterol because it is a structural component of all body cells and also an important building block for the body to make some hormones, vitamin D and the bile acids needed to digest fats. We also need to look at a more sinister side of cholesterol. Because the body must have some cholesterol, we have a way to make it in the liver. This is essential for those who do not eat animal foods, but sometimes the body’s cholesterol-making mechanism goes into overdrive and produces too much. This excess cholesterol circulates in the blood attached to proteins called Low Density Lipoproteins (or LDL). LDL cholesterol (or “bad” cholesterol) can clog arteries and impede blood flow to vital organs such as the heart. Cholesterol can also be carried in the bloodstream attached to High Density Lipoproteins (HDL). This is ‘good’ cholesterol which is taken back to the liver for the body to recycle for essential purposes.
Some people inherit genes that encourage the body to make too much cholesterol, and if they eat too much saturated fat their ‘bad’ LDL cholesterol level increases. Most people in Western countries consume high levels of saturated fat and this is the major cause of excess cholesterol in the blood and cholesterol deposits in the arteries.
Adults normally produce about 1 gram (1000mg) of cholesterol a day to satisfy the body’s essential functions. If we eat foods containing cholesterol, the body should cut back on its own production. A breast-fed baby getting cholesterol from its mother’s milk, for example, makes very little cholesterol because the milk contains enough.
In theory, when we eat prawns, our body should reduce the amount of cholesterol it makes. However, if our diet is high in saturated fat and we have the ‘wrong’ genes, our cholesterol-production mechanism may not work effectively and the cholesterol from prawns or fish or any other animal food can add to what your body is making which may be several grams a day.
To put this into perspective, even if our body does make too much cholesterol, the quantity of ready-made cholesterol we would get from prawns will be only a fraction of the total. It is much more important to reduce the saturated fat in our diet than to fuss about foods containing ready-made cholesterol.
There are some problem combinations which provide high levels of saturated fat and cholesterol for example, fried bacon and eggs, or seafood battered or crumbed and then fried in saturated fat.
Prawns themselves have virtually no saturated fat, so as long as we have them grilled, barbecued, steamed or cooked with a ‘good’ unsaturated fat like olive oil, they should not cause problems.
Experimental evidence backs this. In spite of public confusion over prawns and cholesterol, there have been very few studies where people have been fed prawns and had their blood cholesterol levels measured. However, a study was conducted a few years ago in which researchers in the United States gave 18 volunteers 300g of shrimp every day for three weeks. Their total blood cholesterol levels rose slightly, but further examination showed there was a greater proportional increase in ‘good’ HDL cholesterol than in ‘bad’ LDL cholesterol. The subjects triglyceride levels, another type of undesirable fat fell with the shrimp diet.
The Japanese are the world’s greatest consumers of prawns. They also have the highest life expectancy and it is possible the two things could be connected. At the very least, it is fair enough to say that the cholesterol in prawns and other seafood is unlikely to damage the arteries provided the seafood is not battered or crumbed and cooked in saturated fat.
Like all seafood, prawns contain omega 3 fatty acids. These valuable fats lower triglyceride levels and have many other benefits for heart health. Prawns have less fat and therefore contain a lower level of omega 3s than some other seafood like Atlantic salmon, but the omega 3 content in prawns average of 120 mg/100g is well above the minimum 60mg/100g required for an official label of “good source of omega 3 fatty acids”.
Prawns are a good source of omega 3 fatty acids, an excellent source of protein
and a great way to get iron, zinc and vitamin E.
N u t r i t i o n I n f o r m a t i o n:
(one serving of prawns, 100g flesh)
energy 420kJ (100 cals)
saturated fat 0.1g
omega 3 fat 120mg
Vitamin E 2.9mg