Many of us for years now have been happily purchasing food products with labels proudly announcing that it has no fat or very little fat, believing that it is the root of all our unwanted weight problems. In reality fat is necessary for the optimal functioning of our bodies.
Dietary fat has many functions which can be classified as:
- metabolic;
- storage; and
- structural.[1]
In particular fat is responsible for transporting fat soluble vitamins around the body, as well as providing vital cushioing for the body's major organs.
When fat is consumed as dietary fat, the body can't absorb the fat directly. It needs to break down the fat into its parts. Essentially the fat is broken down by a substance known as lipase. There are many types of lipase, but those responsible for the breakdown and digestion of fat come in three flavours:
- Lipase present in food.
- Lingual lipase (manufactured in the mouth and present in the saliva);
- Gastric and pancreatic lipase (manufactured in the stomach and by the pancreas).[2]
It seems to be controversial as to whether or not, lipase is present in some foods or not. It is even more controversial as to whether or not eating such foods would be beneficial for your health and the digestion of fat.
A German study published in 2002, found that many raw meat products contained lipase, but the heated alternatives contained very little. "..... Heated sausage was largely lipase free ..... while raw sausages contained up to 283 micrograms/kg lipases ..."[3]
Another study completed by the Mahidol University in Thailand, isolated a yeast strain from milk that could produce lipase which was stable under 70 degrees centigrade.[4]
Dr Kennedy on his site The Doctors' Medical Library also comments that lipases can be found in foods high in fats such as avocado and nuts. He also comments that because the western diet is made up almost totally of cooked food, our bodies miss out on lipase found in raw foods.
Lingual lipase was thought to be instrumental in the breakdown of triaglycerides, while travelling down the esophagus, however, is now thought not to have a large affect on fat digestion.
While in the stomach, the fat goes through a process of slow breakdown and is mostly completed in the small intestine. [5]
The fat that enters the intestine is mixed with bile and churned up to form a soup-like consistency. The fat is then attacked by lipase secreted from the pancreas which breaks down the fat into glycerol and fatty acids. The fatty acids then, depending on their chain length, will be absorbed by the body through the portal vein or the lymphatic system and into the liver [5].
[1] Barasi (1997) Human Nutrition A Health Perspective Oxford University Press Inc. P. 88
[2] Kenessaw State University Chemcases
[3]
Braun P, Buchner S, Fehlhaber K. Quantitative determination of lipases and their heat stability in food of animal origin Berl Munch Tierarztl Wochenschr. 2002 Jan-Feb;115(1-2):24-9.Abstract
[4] Dharmsthiti S, Ammaranond P. Purification and characterization of lipase from a raw-milk yeast (Trichosporon asteroides). Biotechnol Appl Biochem. 1997 Oct;26 ( Pt 2):111-6. Abstract
[5] Aspects of Fat Digestion and Metabolism
