Saturated fat is a heterogeneous group of chemicals. Fatty acids have hydrocarbon tails and these hydrocarbon tails are concentrated sources of energy which makes them highly efficient fuels. The hydrocarbon chains of fatty acid vary in length and are classified based on this chain length into short chain fatty acids (2 to 4 carbons), medium chain fatty acids (6 to 12 carbons in length), or long chain fatty acids (14 to >20 carbons). Dietary saturated fatty acids tends to be groups as a single entity, and this relates partly to the fact that most dietary saturated fat is in the form of the C16 palmitic acid and C18 stearic acid, and partly due to laziness and ease of classification. However, saturated fatty acids of different chain lengths can have quite different physiological effects and so this homogeneous grouping of a heterogeneous group leads to inaccurate statements about the effects of saturated fats. This is particularly true for the effects of saturated fatty acids on the development of cardiovascular disease.
Saturated fatty acids are a heterogenous group of chemicals, albeit with a similar hydrocarbon chain (fatty) structure bonded to a terminal carbon containing a carboxyl group (acid). In saturated fats, the carbon chain is saturated with hydrogens, meaning that no double bonds are present. However, the chain length of the hydrocarbon chain varies, and these differing lengths may allow each saturated fat to exert different physiological effects. For example, short and medium chain saturated fatty acids (up to 12 carbons in length) are absorbed differently to the longer chain (>14 carbons) fatty acids. Evidence shows that once absorbed these two different absorption routes produce quite different metabolic fates for the relevant fatty acids. In addition, the types of foods that these fatty acids are present in should be considered. We do not eat saturated fats in isolation, but within foods. If these foods contain other accessory or essential nutrients that promote health, these sources of saturated fats may become healthy. Evidence suggests for example that saturated fat from dairy foods are beneficial, partly for this reason. Picture from Erasmus, U. 1993. Fats that Heal, Fats that Kill. Alive Book, Burnaby. 9th edition.
A recent study investigated the association between different saturated fatty acids and the risk of ischaemic heart disease based on a large scale food questionnaire from the Netherlands. The results of the study showed that total saturated fat intake was associated with a lower risk of ischaemic heart disease in the participants, and substituting saturated fat for polyunsaturated fat, carbohydrate, monounsaturated fat or animal protein was associated with an increased risk of ischaemic heart disease. Consumption of the short chain fatty acids butyric acid (4 carbons, found in butter) through to caproic (10 carbons), myristic (14 carbons) and saturated fats from dairy foods were associated with a lower risk of ischaemic heart disease. These results confirm that differences in the associations between saturated fats and ischaemic heart disease exist and that suggest that if cause and effect is proven, care should be taken to treat each saturated fat as an isolated chemical, and temptation to group the together for ease of study should be avoided.
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