Types of fatty acids
Introduction to fats: types of fat
There are four main types of fat, each with different chemistry:
- Saturated
- Mono unsaturated
- Poly unsaturated
- Trans fat.
Fats are made up of fatty acids which are chains of carbon atoms.
These chains can be either fully saturated by hydrogen atoms as seen in saturated fats or can be partially saturated as seen in mono unsaturated (MUFA) and poly unsaturated (PUFA) types of fats.
When MUFA and PUFA are artificially hydrogenated, they form trans fat.
Saturated fat (SFA)
Saturated fats are usually in solid form at room temperature. SFA is found most in animal foods like meat, poultry, butter (which contain 66% SFA) , ghee and whole milk. Other sources of SFA include coconut, palm and palm kernel oils.
Mono unsaturated fat (MUFA)
At room temperature, MUFA is in oil and liquid form. MUFA is derived from plant sources, ground nut (49% MUFA) and olive (77% MUFA), til oil, mustard oil. It is also found in margarine and peanut butter. It is labelled as a ‘good’ fat because it lowers the oxidation of LDL cholesterol and thus slows down the process of plaque formation. It also lowers triglyceride levels and promotes high level of HDL cholesterol.
Poly unsaturated fat (PUFA)
At room temperature, PUFA is in liquid form. Most common vegetable oils such as soya (61% PUFA), safflower (77% PUFA) and sunflower (69% PUFA), corn oil, soya bean and fish oil are high in poly unsaturated fats.
Trans fat
Both vegetable and fish oils are hydrogenated to form trans fat. Dalda and vanaspati are everyday sources. It is commonly used in biscuits, cakes, pastries, chocolates, creamers, dairy foods, ice cream etc. Trans fat remains solid at room temperature. In the body, it acts similarly to saturated fats.
Trans fat is the worse kind of fat, and should be avoided as much as possible in the diet
Cholesterol
In addition to dietary intake, cholesterol is also produced by the liver.
Cholesterol is essential for coating of nerve cells, formation of certain hormones and for various activities of the tissues in the body. The body contains about 10 grams of cholesterol.
Cholesterol is carried around in the blood on carrier molecules called lipoproteins. The main lipoprotein categories are:
- Low-density lipoprotein (LDL)
- High-density lipoprotein (HDL)
- Apolipoprotein (a).*
Each of these can form a compound of cholesterol, which is carried in the blood stream. These compounds are as follows:
| VLDL | VLDL is LDL + cholesterol + sugar. It releases sugar to the tissues to become LDL. |
| LDL | LDL carries cholesterol to the cells. Excess LDL is deposited in the blood vessels resulting in the formation of an atheromatous plaque. |
| HDL | HDL removes excess cholesterol and carries it to the liver where it is destroyed. |
| Apolipoprotein(a)* | Some of the natural cholesterol produced by the liver in response to free-radical damage is converted into LDL cholesterol and its relative Apolipoprotein (a) {Lp (a)}. Lp (a) holds fast to damaged blood vessels, attracting other Lp (a) molecules and finally constituting atherosclerotic plaques. A high Lp (a) level (more than 30 mg/dL) has been revealed to carry a 10-times greater risk for heart disease than LDL cholesterol level. |
Triglycerides
They are derived from carbohydrates and also formed in the liver. Chylomicrons and triglycerides are metabolized to provide energy to tissues.
Essential fatty acids (EFAs)
PUFA contains essential fatty acids EFA: linoleic, linolenic and omega 6 (N6) fatty acids, and omega 3 (N3)fatty acids:
- Omega-6 (N6) EFA are found in safflower, sunflower and corn oils
- Omega 3 (N3) EFA is derived from fish oils
- The optimal N6 to N3 EFA ratio should be 4:1. Our diets commonly contain a lopsided ratio of N6 to N3. N6 to N3 ratio of some of the commonly used cooking mediums in India (Insert table)
- In the past, excessive and exclusive use of PUFA (sunflower oil) was advocated. Now it is no longer recommended as PUFA is known to lower HDL levels. Also, PUFA is susceptible to hyperoxidation leading to generation of tissue-damaging radicals in the body.
Fat recommendations
- The overall fat intake as a percentage of dietary calories should not fall below 30%.
- Saturated fat should be one-third of the 30%. It is necessary for good health.
- Diet should include plenty of “good” MUFA; for example olive oil, seeds, nuts, and cold-water fish that have high N3 content.
- ‘Bad’ trans fat and prolonged heating and frying of fats which acts like saturated fat should be avoided.