Essential Fatty Acids
The main components of all fats are the fatty acids which might be saturated,
monounsaturated or polyunsaturated. Fats containing a high proportion of saturated
fatty acids are solid at room temperature. These are commonly known as saturated
fats and are usually derived from animal sources e.g. lard, suet and butter.
Most plant fats are high in either polyunsaturated or monounsaturated fats except
palm and coconut fat which is highly saturated.
Saturated and monounsaturated fats are not necessary in the diet as they can
be made in the human body.
Two polyunsaturated fatty acids (PUFAs) which cannot be made in the body are
linoleic acid and alpha-linolenic acid. They must be provided by diet and are
known as essential fatty acids. Within the body both can be converted to other
PUFAs such as arachidonic acid, or eicosapentaenoic acid (EPA) and docosahexaenoic
acid (DHA).
In the body PUFAs are important for maintaining the membranes of all cells;
for making prostaglandins which regulate many body processes which include inflammation
and blood clotting. Another requirement for fat in the diet is to enable the
fat-soluble vitamins A, D, E and K to be absorbed from food; and for regulating
body cholesterol metabolism.
Polyunsaturated Fatty Acids - Dietary Sources
Food sources of the two main dietary polyunsaturated fatty acids (linoleic acid
and alpha-linolenic acid) are listed below.
Linoleic Acid (Omega 6 family)
Vegetables, fruits, nuts, grains & seeds.
Good sources - oils made from safflower, sunflower, corn, soya, evening primrose,
pumpkin and wheatgerm.
Alpha-Linolenic Acid (Omega 3 family)
(Please note - fish is not the only source of omega 3 acids. Flaxseed oil contains
twice as much as is found in fish oil!). Flaxseeds (linseeds), mustard seeds
and pumpkin seeds, soya bean, walnut & rapeseed (canola) oils. Green leafy
vegetables and grains. Spirulina.
Good sources - oils made from linseed flaxseeds (linseeds), rapeseed (canola)
& soya bean.
EPA's and DHA's
Alpha-linolenic Acid is converted in the body to EPA (eiocosapentaenoic acid)
usually found in marine oil and DHA (docosahexaenoic acid) usually found in
marine fish oil. Many factors affect the rate of conversion and one factor seems
to be a high food intake of linoleic acid which is typical of vegan diets and
may suppress the body's ability to convert alpha-linolenic acid to DHA. Vegans
can achieve a better balance of PUFAs in their body tissues by using less sunflower,
safflower and corn oils and more oils
containing alpha-linoleic acid such as rapeseed (canola) oil, or soya bean and
walnut oils. This would encourage their tissues to make more DHA.
Conclusions
Numerous expert committees have recommended a reduced consumption of total fat
by the general population. Only vegan diets generally comply with current guidelines
that fat should not contribute more than 35% of the total energy intake of adults
and older children.
Saturated fats contribute to high levels of cholesterol in the blood, a risk
factor for atherosclerosis and heart disease, while polyunsaturated fats (PUFAs)
have the opposite effect. Vegan diets, containing no meat and dairy fats, are
low in saturated fatty acids and high in beneficial PUFAs. Vegans consume considerably
more of the essential PUFA linoleic acid than do omnivores, and approximately
similar levels of the other essential PUFA, alpha-linolenic acid.
Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), two non-essential
PUFAs, do not occur in vegan diets. The human body can convert alpha-linolenic
acid into EPA and DHA but, even so some of the body tissues of vegans contain
less DHA and EPA than those of other dietary groups. The consequences of this
difference, if any, are not known.
Similarly, breast milks of vegans, vegetarians and omnivores contain differing
proportions of various polyunsaturated fatty acids, and these differences are
reflected in some body tissues of infants. It is not yet known what, if any,
effect these variations may have on the growth and development of infants.
Further Details
For more details on EFAs and the vegan diet in general see Vegan Nutrition by
Gill Langley. This book is the most comprehensive survey of scientific research
on vegan diets. It is ideal for vegans, would-be vegans and health care professionals.
It includes highlighted key points, easy-to-follow tables and chapter summaries.