The sea around Cornwall is amongst the cleanest in the UK. It's also home to some of the healthiest food available with over 40 native fish species.

Fish, so essential to a balanced diet, can help with weight loss, complexion and brain development. Thanks to sustainable fishmongers like The Cornish Fishmonger it can also be enjoyed with a clear environmental conscience.

With two types, white and oily, it helps to know which is which. Salmon, tuna, sardines and mackerel are all oily fish so called because the oils (fats) are distributed throughout the flesh. Mackerel is one of the most plentiful and nutritious. Like all oily fish it's high in Omega-3 which is good for the heart, brain, eyes and immune system. It's also a rich source of protein, amino acids, vitamin and minerals, particularly those for healthy bones, teeth, skin and metabolism. Mackerel gets the green tick too as a highly sustainable fish that offers great value for money.

White fish like cod, haddock and flat fish share many of the benefits of oily fish. The difference is their oil is stored in the liver. It makes them lower in fat and perfect for weight loss. Lemon sole is an ideal choice at this time of year; it's wild, fished sustainably and with only 135 calories per 150g fillet it's both low in fat and high in vitamins that support healthy bones, teeth, skin and metabolism.

The government recommends two 150g portions a week one of which should be oily. For Cornwall's best, The Cornish Fishmonger which offers over 30 species ready filleted or whole sent from quayside to doorstep in 24 hours.