Prawns have slightly longer legs than shrimps and their gills are different, but they are very similar.
Crayfish are bigger. Although they contain zinc, iodine and selenium, they are also high in cholesterol. Very low in fat and calories - around 100 calories per 100g.
Expert says: Fresh prawns are super high in Vitamin B12 - which is necessary for cell division and the lack of which is a problem in many countries.
B12 has to be obtained from the diet and is only available from animal sources, such as meat or fish, so can be an issue for vegetarians.
Beware of the creamy sauces accompanying these - which are high in fact and salt. Frozen prawns as they are often high in salt. The freezing process often uses sodium as part of storage process.
Selenium has highly protective properties and supports immune system function as well as being vital for optimal thyroid function.
What’s a portion? A large handful is a good sized amount and there are only about 76 calories in 100g.
When to avoid: If you have high cholesterol, eat only as an occasional treat