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Nutrients 5

Unsaturated fats – monounsaturated and                Balancing omega 3 and omega 6 fats
polyunsaturated                                       in diets

Most vegetable oils, nuts and seeds contain more      The balance of these two groups of fats affects
monounsaturated and polyunsaturated fat than          health. Up until about 50 years ago our diets had
saturated fat.                                        about equal quantities of these omega 3 and omega
                                                      6 fats, but nowadays we eat a much higher
Essential fats: omega 3 and omega 6 fats              proportion of omega 6 fats and very little omega
                                                      3 fat. This change is thought to be one of the factors
Two key groups of essential polyunsaturated fats      causing increased rates of allergy, asthma and hay
that the body cannot make are omega 3 and omega       fever in children.
6 fats (Table 1.1.2). Plant foods provide these in a
shorter chain form and the body converts them to      Vitamins
a long-chain form to use in the cells in our body.
Food from animal sources provides these essential     Vitamins are chemicals that are needed for the
fats directly in the long-chain form.                 proper functioning of the human body but cannot
The long-chain form of omega 3 fat is particularly    be made within the body. They are made by certain
needed for the growing brain, the nervous system      plants, animals or bacteria and thus the vitamins
and for good vision. Infants can only make limited    are acquired by eating those plant and animal foods.
amounts of the long-chain form and rely on            Certain bacteria in the gastrointestinal tract provide
getting plenty of long-chain omega 3 in breast        two of the vitamins – vitamin K and vitamin B12.
milk or infant formula as well as some oily fish
during weaning. Children over 1 year of age              Vitamins A, D, E and K are fat-soluble vitamins
should be able to make adequate amounts of the        and are found within the oils and fats in some
long-chain forms even if they eat a vegetarian diet   foods. When an excess of these vitamins are eaten,
without fish. Some research shows, however, that      reasonable amounts of them can be stored in the
children who regularly eat oily fish a couple of      body. Vitamin C and the B vitamins are water-
times per week and have a good intake of omega 3      soluble and any excess amounts of them consumed
fat in the long-chain form are less likely to get     are excreted in urine. The stores of these vitamins
asthma.                                               that are built up are much smaller and it is thus
                                                      crucial to have a regular supply in the diet.

Table 1.1.2  Names and food sources of the various essential omega 3 and omega 6 fats

       Omega 3 fats                                                                 Omega 6 fats

Short-chain form – from plants

Names  ALA (alpha-linolenic acid)                                                   LA (linoleic acid)

Main food sources Walnuts, linseeds, and their oils                                 All nuts, seeds and vegetable oils
                            Rapeseed oil
                            Olive oil and soya oil have smaller amounts

Long-chain form – from animal foods

Names  EPA (eicosapentaenoic acid)                                                  GLA (gamma linolenic acid)
       DHA (docosahexaenoic acid)                                                   AA (arachidonic acid)

Main food sources Best source is oily fisha                                         Fish, meat and egg yolks
                            Other sources are red meat and egg yolks
                            depending how the animals and chickens are fedb

a Oily fish are: salmon, mackerel, trout, fresh tuna, sardines, pilchards and eel.

b Animals that have grazed on grass rather than been fed cereals have higher amounts of omega 3 in their meat. Egg yolks
from chickens fed a special feed high in omega 3 fat will be a good source of omega 3 fats.
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