Cholesterol decoded5 min read . Updated: 01 Jul 2015, 01:41 AM IST
Is cholesterol highly misunderstood? We debunk some myths
Earlier this year, the US dietary guidelines advisory committee announced that “cholesterol is not considered a nutrient of concern for overconsumption". Does this also hold true for Indians who are at a higher risk of having diabetes and heart disease?
Soumya Umesh, assistant professor, department of medicine, St John’s Medical College Hospital, Bengaluru, says, “We cannot tell Indians to relax the dietary cholesterol levels as we have a higher risk of coronary heart disease and diabetes than Americans."
Cholesterol, a lipid produced by the liver, is vital for many body processes, such as insulating nerve cells in the brain and providing structure for cells. It is also a precursor for the biosynthesis of vitamin D and steroid hormones cortisol, testosterone and estrogen.
Cholesterol has a bad reputation because its high levels are considered to be the cause for a host of illnesses, including heart disease, blood pressure and diabetes. But recent research says it’s not cholesterol per se that we need to worry about. According to a 2009 study published in the International Journal Of Clinical Practice, “The earlier purported adverse relationship between dietary cholesterol and heart disease risk was likely largely over-exaggerated." A 2010 study published in the journal Current Atherosclerosis Reports found that increasing levels of dietary cholesterol are not correlated to increased risk of cardiovascular disease.
Here’s the low-down on some of the myths and facts about cholesterol.
Cholesterol is linked to heart disease
Fact: Cholesterol is carried in the bloodstream by low-density lipoproteins (LDL) and high-density lipoproteins (HDL). HDL, or good cholesterol, scavenges cholesterol from the bloodstream and carries it to the liver for disposal, while LDL, or bad cholesterol, carries cholesterol from the liver to the rest of the body. Bengaluru-based dietitian Anupama Menon says: “HDL zips around the system and does not reside in the arteries, whereas LDL floats around, and forms deposits in the walls of the arteries, limiting blood flow, which may eventually cause cardiovascular disease."
It is higher LDL and lower HDL levels, and not the cholesterol they carry, that raise the chances of heart disease.
Dietary cholesterol affects blood cholesterol levels
Fact: Adarsh C.K., consultant gastroenterologist and hepatologist, BGS Global Hospital, Bengaluru, says: “Our blood cholesterol is derived from two sources. The majority is produced by the body (around 85%) and the rest by dietary cholesterol. One should note that usually food with high cholesterol also contains high saturated fats and trans fats, which can increase blood cholesterol levels and are bad for our health."
The body adjusts the synthesis of cholesterol according to the cholesterol in the diet. If the diet consists of high cholesterol, the body will make less and vice versa, says Dr Adarsh.
Dr Umesh adds: “Blood cholesterol depends on genetic make-up and familial disposition. Indians have a higher risk of coronary heart disease at lower BMI (body mass index) compared to the Western population. A combination of higher level of triglycerides (a type of fat), LDL cholesterol, higher proportion of small-dense LDL (one of the molecules in LDL) and low HDL levels, known as atherogenic dyslipidemia, are common in Indians." Atherogenic dyslipidemia is a typical characteristic of type 2 diabetes and obesity, and is also a risk factor for cardiovascular disease.
“For diabetics, the lipid profile and LDL cholesterol levels matter more than just cholesterol. A diet that contains good fatty acids, such as unsaturated fats, can reduce the risk of artherogenic dyslipidemia. Saturated fats and trans fats in diet result in the worst kind of lipid profile," says Belinda George, assistant professor, endocrinology department, St John’s Medical College Hospital.
A low-fat diet helps lower cholesterol levels
Fact: The types of fat in the diet affect blood cholesterol levels. A review of research on dietary carbohydrates and fats published in the American Journal Of Clinical Nutrition in 2010 showed that cutting back on fats, or a low-fat diet, has no health benefits. In a low fat-diet, you lose out on the fats that are good for the heart, and it is often compensated by switching to refined carbohydrates, which results in increasing the risk of heart disease and diabetes.
Menon says, “All fats are important in the body for certain functions. But saturated fats, such as red meat, whole milk products, ghee and coconut oil, can increase LDL and should be consumed in small quantities." Adds Dr Umesh: “Trans fats, found in hydrogenated vegetable oil, are the worst type of fat, as they are useless for the body, increase LDL and triglycerides, and decrease HDL. Many packaged foods, such as potato chips and bakery products, which use refined grains like maida (all-purpose flour), are low in fibre and contain trans fats. Reusing cooking oil also increases trans fat levels."
Nuts and eggs can affect blood cholesterol
Fact: Only animal cells can produce cholesterol, all plant-based foods, including nuts, contain zero cholesterol. Dr Umesh says, “Nuts contain unsaturated fats which improve cholesterol levels and are good for health." There are two types of unsaturated fats—monounsaturated and polyunsaturated—both of which are equally beneficial. Almonds, peanuts, hazelnuts and pecans are rich in monounsaturated fats, while walnuts are high in polyunsaturated fats.
A study published in 2010 in the Asia Pacific Journal Of Clinical Nutrition on consumption of nuts and its relation to heart disease found that frequent nut consumption lowered total and LDL cholesterol as well as the LDL:HDL ratio in healthy people as well as those with moderate hypercholesterolaemia (high levels of cholesterol in the blood).
The benefit of eggs has been controversial as the yolk contains 200-300mg of cholesterol, which is higher than the recommended daily limit (200mg, according to the Indian Council of Medical Research). But Dr Umesh says: “It would be unwise to cut out the yolk, as it is a good source of minerals, unsaturated fats and vitamins such as D and B12. Five-six whole eggs per week are okay for those who do not have a cholesterol problem."
MANAGE YOUR CHOLESTEROL
Some steps to follow for a healthy life:
u Eat wholegrains, unprocessed food, fruits and vegetables daily
u Exercise daily for 30 minutes
u Avoid trans fats and saturated fats; consume more lean meats
u Stick to the recommended daily allowance of 40-50g of total fat for adults
u Include nuts, flaxseed, sunflower seeds and fatty fish in the diet to increase HDL
u Replace high-fat dairy products with low-fat milk products.
By Anupama Menon , dietitian, Bengaluru; and Soumya Umesh, assistant professor, department of medicine, St John’s Medical College Hospital, Bengaluru.