Dietary fats, also known as lipids, are a major source of energy for your body. Your body also uses fats to make other chemicals, including prostaglandins, which are important signalling chemicals, and steroid hormones such as testosterone and estrogen. Fatty acids are classified based on their length as molecules, and this determines how your body digests them.
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Dietary fats are made up of three fatty acids attached to a glycerol backbone. These fatty acids consist of chains of carbon and hydrogen. These chains can be as short as one carbon atom long, or in the case of the essential fatty acids, 18 carbons long. Short-chain fatty acids are four to ten carbons long and are found in significant quantities in milk, according to the textbook, “Biochemistry.” The main short-chain fatty acids are butyric acid and capric acid. These are digested largely in the stomach.
Digestion is the process by which enzymes break down the food you eat into a form your body can absorb. The digestion of fats begins in your stomach and ends in your small intestine. It involves the work of several enzymes, which originate in your mouth, stomach and pancreas. Most fats travel to your small intestine. There, they are emulsified by bile from your liver and broken down by enzymes from your pancreas so that your body can absorb them. In contrast, shorter-chain fatty acids, which are a minority of dietary fats, are digested mainly in the stomach and do not require bile.
When short chain fats enter your stomach, an enzyme known as lingual lipase, which is secreted from glands at the back of your tongue, breaks them down into smaller molecules your body can absorb. This process is continued by gastric lipase, an enzyme released by your stomach. These enzymes can survive the acidic environment of the stomach and are therefore known as “acid lipases.” They are especially important for babies, for whom milk fat is the primary source of calories.
Milk products are the major source of short-chain fats in the diet. For example, 1 cup of whole milk contains 8 g of fat, 750 mg of which is in the form of short-chain fatty acids. These fats can be synthesized from other fats found in your body and are not required in the diet, so if you avoid milk products you need not worry about deficiencies. Short-chain fats are saturated fats, which makes foods such as butter solid at room temperature.