Cholesterol is a soft waxy substance like fat, which is produced mainly in the liver. It comes under the category of 'lipids'. It is important in the structure of the body cells, Hormones, Bile acid and Vitamin D. Hence some amount of cholesterol is good for the body. Even when we consume no cholesterol, liver manufactures cholesterol in sufficient quantity for normal body functions.
It is only the excess cholesterol generated in the body due to ill-planned diet which deposits in the lining of blood vessels and make them narrow and hardened resulting in high blood pressure and other heart diseases. The process of narrowing and hardening of arteries due to deposition of cholesterol is called as "Atherosclerosis'. Atherosclerosis also renders the blood vessels inelastic and brittle which makes artery easily susceptible to rupture. If a brittle brain artery ruptures, brain hemorrhage follows. This is termed as stroke. Stroke may lead to paralysis or instant death.
At the time of birth arteries are smooth, open and elastic conduits for blood circulation. They expand and contract as blood flows though them. With ageing and wrong life-style and eating habits they lose their flexibility and become brittle by deposition of cholesterol. Calcium deposition may harden the arteries further. By narrowing of the arteries, blood flow is compromised to various organs. When the lining of artery becomes narrow due to atherosclerosis, the chances of a blood clot or 'thrombus' being formed there becomes quite high. If such blood clot blocks a coronary artery, it may result in a heart attack or severe angina. If a blood clot is formed in brain artery, it may lead to brain hemorrhage or stroke. Blood clot is formed by platelets, red blood cells and other cells sticking together. Since the walls of the arteries also become roughened in atherosclerosis, the blood cells easily adhere there and form blood clots.
Fats and cholesterol are carried in the blood in the form of Lipoproteins. There are three kinds of Lipoproteins-
1. VLDL (Very Low Density Lipoprotein)
2. LDL (Low Density Lipoprotein)
3. HDL (High Density Lipoprotein)
HDL cholesterol is considered to be good cholesterol because it is protective and helpful. It rather reduces harmful LDL cholesterol from the blood and tissues and delivers it back to the liver where it is processed for excretion. It is the LDL cholesterol which is the main culprit promoting deposits in the arteries and gradually blocking the passage for blood. Hence it is desirable to have higher HDL and lower LDL cholesterol in blood.
Previously it was thought that unlike cholesterol, triglycerides (fats) don't deposit in the arteries. But new researches show that triglycerides also depositing in the arteries, if present excessively. Triglycerides are fats devoid of any cholesterol. The stored fats of both plants (nuts and oil seeds) and animals (depot fats) are triglycerides. That's why it is desirable to have regulated intake of unsaturated fats also (which is devoid of any cholesterol) since they will increase blood triglyceride level. Triglycerides and cholesterol together are called blood lipids. Ways to reduce triglyceride level:
- Reduce total fat intake.
- Reduce sugar, sweets and soft drinks (as excess sugar readily gets converted to triglyceride level of blood.
- Reduce alcohol intake. Alcohol increases triglyceride level of blood
- Do regular exercises. They help to reduce blood triglyceride level.
- Increase intake of Omega 3 PUFA rich foods (or Alpha linolinic acid) as they reduce blood triglyceride level. For the benefit of readers, sources of such foods as given below.
- Cereals and millets: wheat, bajr
- Pulses & legumes: Blackgram, Urad, Lobia, Rajmah, Soyabeen
- Vegetables: Green leafy vegetables
- Spices: Fenugreek (Methi) Mustard (Rai)
- Oils: Mustard, Soyabeen
- Animal food: Fish
6. Do occasional fasting. Fasting reduces blood triglyceride level.
Ways to increase HDL (good) cholesterol :
- Do regular exercises. Exercise increases HDL cholesterol.
- Reduce total fat intake. There is a reciprocal relationship between blood levels of triglycerides level and HDL cholesterol. Hence people with high blood triglycerides tend to have low HDL.
- Reduce intake of transfatty acids (Vanaspati ghee, Margarine). They reduce HDL cholesterol.
- Reduce excessive intake of PUFA rich oils. HDL levels nay decrease if PUF accounts for more than 10% of energy intake.
- Certain foods have found to improve HDL cholesterol e.g., Onion, soyabean, garlic, soluble fiber (Pectin) in apple, banana, Iasbgol powder etc.
Ways to reduce LDL (harmful) cholesterol:
- Reduce saturated fat intake and increase unsaturated fat (MUFA & PUFA) intake.
- Reduce intake of dietary cholesterol. Foods having high cholesterol should be avoided.
- Reduce intake of tea, coffee, soft drinks, chocolate etc. The caffeine in these products stimulates excess cholesterol production in the body.
- Reduce intake of tobacco (smoking, Pan chewing etc.)
- Reduce mental stress, has been found to increase LDL cholesterol.
- Avoid sedentary life and do regular exercises.
- Take measures to cure high blood pressure and diabetes if you have any of these diseases since these diseases tend to increase cholesterol in blood.
- Increase intake of food containing soluble fibres e.g. Apple, Banana, Carrot, Oat bran, pulses, Isabgol etc. Soluble fiber binds with dietary cholesterol and is excreted out of the body along with undigested food.
- Certain foods have been found to reduce LDL cholesterol, for example, onion, garlic, soybeans, Amla etc. It is observed that daily intake of 3-4 cloves of fresh garlic and Amla (in any form-Juice or raw or pickle) have substantial cholesterol lowering effect.
Why use vegetable oils?
1. Choose a variety of vegetable oils instead of single oil since most of the vegetable oils don't have an ideal mix of PUFA, MUFA and Omega 3 PUFA in them. (Note-oils with only PUFA are not desirable since they reduce HDL cholesterol)
2. Mix two or more oils of different composition. A good choice is equal mixture of PUFA rich sunflower, safflower or corn oil and MUFA rich groundnut oil. Vegetarians may supplement this mixture with occasional use of mustard oil to ensure omega 3 PUFA intake. Mustard oil alone is not a good choice since if contains erratic acid which is detrimental for heath equal amount of PUFA and MUFA.
3. Vegetable oils undergo chemical changes on exposure to air, high temperature and humidity, hence following precautions should be observed in their purchase and storage. Always purchase a fresh batch of the oil by checking the date of manufacture:
- Select a packing which is likely to be consumed within a month.
- Prefer aluminum or coloured glass packing over plastic or tin.
- Remove the oil from plastic or tin container at home and refill the oil in airtight and waterproof steel, aluminum or an opaque glass bottle.
- Don't leave the lid of the oil container open since it will tend to react with air.
- Keep the oil in refrigerator during peak summer and rainy season.
Some important facts regarding fats and cholesterol summarized:
1. Some amount of fat intake is necessary for the body. Zero fat is harmful for the body. It is the excess fat and wrong combination and type of fats which are harmful for the body.
2. Saturated fats increase blood cholesterol and triglycerides.
3. Transfatty acids increase blood cholesterol, reduce HDL cholesterol and increase blood clotting tendency.
4. Vegetable oils and all plant foods don't have cholesterol (except palm and coconut).
5. Monounsaturated fats (MUFA) decrease blood cholesterol.
6. Polyunsaturated fats (PUFA) decrease blood cholesterol.
7. Omega 3fatty acids present in some PUFA reduce triglycerides, prevent clot formation and reduce LDL cholesterol.
8. Excess of PUFA decreases HDL (good) cholesterol.
9. Fish and fish oils lower blood triglycerides, prevent clot formation and decrease LDL cholesterol.
10. Animal foods have saturated fats and have substantial cholesterol (except fish).
11. Carbohydrates particularly refined sugars have no cholesterol but they increase triglycerides.
12. Soluble firbres (found in cereals, pulses, vegetables, fruits) decrease cholesterol and triglycerides.
13. Daily intake of cholesterol for a normal person shouldn't exceed 300 mg/day and for persons with coronary
heart diseases (CHD), it should not be more than 200Mg/day.
14. Excess of PUFA increases blood triglyceride level
15. Alcohol increases blood triglyceride level. Its moderate amount increases HDL (good) cholesterol level also.
16. Some amount of cholesterol is needed by body for its functioning. Hence a limited intake of saturated fats is not harmful.