There is growing consensus among experts that eating high-cholesterol food has little impact on blood cholesterol levels
For years, doctors and dietitians counselled that eating food high in cholesterol was unhealthy and linked to heart disease.
Nutrition advisory boards weighed in on the negative effects of eating gastronomic goodies, such as eggs, seafood and red meat. For decades, cutting back on dietary cholesterol was a mainstay of nutritional recommendations.
Now, the dissenting voices are gaining ground.
There is growing consensus among doctors and nutrition experts that cholesterol in food has little effect on the amount of cholesterol in the bloodstream which contributes to the plaque that clogs artery walls.
A United States nutrition advisory panel that helps to shape the country's official dietary guidelines is now recommending the lifting of previous caps on fat and cholesterol and instead, is advising cutting down on how much added sugar Americans should consume.
This is in line with what major health groups, such as the American Heart Association, have advocated in recent years.
The panel for the US Dietary Guidelines Advisory Committee, which meets once every five years, said Americans were eating too much salt, sugar and saturated fat, and not enough foods that fit a "healthy dietary pattern", such as fruit, vegetables, nuts, whole grains, fish and moderate levels of alcohol.
Members of the panel said there should be less focus on individual nutrients, and more on overall patterns of eating, such as adopting a Mediterranean-style diet, with lots of olive oil, unrefined cereals, fruit and vegetables; moderate to high consumption of fish, cheese, yogurt, and wine; and low consumption of meat and meat products.
Studies have shown that such a diet is linked to lower rates of heart disease and stroke.
The new recommendations are expected to be in the soon-to-be-released 2015 Dietary Guidelines for Americans.
This development is similar to the Health Promotion Board's (HPB) current stance.
And it is also in line with emerging scientific consensus that the type of fat consumed is more important than the amount of cholesterol you eat, said an HPB spokesman.
REDUCE SATURATED FAT
Consuming dietary cholesterol does not increase blood cholesterol as much as consuming high levels of saturated fat, he said.
In June, HPB launched an updated healthy eating tool called My Healthy Plate, which has no specific recommendations on cholesterol consumption.
For most people, the amount of cholesterol eaten has only a modest impact on the amount of cholesterol circulating in the blood, said the HPB spokesman.
Instead, one key area of focus is on encouraging Singaporeans to raise the overall quality of the fat consumed by substituting saturated fat with "healthier" unsaturated fat where possible, he said.
Excessive consumption of saturated fat is linked to an elevated risk of cardiovascular diseases, especially when it displaces the beneficial effects of unsaturated fat, he added.
The visual for My Healthy Plate shows half a plate of vegetables, a quarter of whole grains and another quarter of meat and proteins.
The larger serving of vegetables aims to correct unhealthy eating habits as people here do not eat enough greens, but consume too much refined carbohydrates, such as white rice.
It also reminds people to opt for healthier oil, choose water instead of sugary drinks, and to stay active.
The push to consume healthier fat here is timely as a 2010 national nutrition survey showed diet trends tipping into the unhealthy range.
The overall saturated fat intake for Singaporeans has increased, the survey showed.
One of the main reasons is the growing trend in eating out.
Six in 10 people here usually eat out, up from five in 10 in 2004, according to survey findings.
Those who eat out tend to have worse diets compared with those who eat at home. For example, people who eat out six or more times a week typically consume 12 per cent more calories, 15 per cent more saturated fat and 34 per cent less whole grains than those who eat out less than six times a week.
DISEASE LINK HARD TO PROVE
The relationship between the consumption of large amounts of cholesterol and higher levels of serum cholesterol (cholesterol in the blood) has been hard to prove, said Assistant Professor Chin Chee Tang, senior consultant at the department of cardiology at National Heart Centre Singapore (NHCS).
Similarly, it has also been difficult to prove that consuming less cholesterol would lead to lower serum cholesterol levels.
Though some studies have shown a link between dietary cholesterol and coronary heart disease - one of which showed that the Mediterranean diet reduced one's level of low-density lipoprotein (LDL) or "bad" cholesterol, as well as the risk of cardiovascular events - most could not confirm the link on a large scale, said Dr Kenneth Ng, a consultant cardiologist at Novena Heart Centre.
Other studies, especially one from Finland, showed no correlation between the consumption of foods high in cholesterol and coronary deaths, he added.
A Canadian Health Report in 2000 found that cutting out 100mg of cholesterol from one's diet translated only to a tiny reduction in blood cholesterol levels.
In 2005, the US Institute of Medicine Report stated that in a review of 15 studies, only six showed a positive link between dietary cholesterol and cardiovascular disease. But those studies also had small sample sizes, making them statistically weak, added Dr Ng.
ESSENTIAL FOR HEALTH
Despite its bad reputation, cholesterol is necessary for good health.
It is a type of fat, or lipid, that is an essential building block for cell membranes and other crucial structures. Examples include the protective sheath that surrounds nerve fibres, as well as in the making of sex hormones, such as testosterone and oestrogen.
Cholesterol is made in the liver from fats, sugars and proteins.
In an average person, the body's own production of cholesterol far outstrips any contribution from cholesterol found in food.
Thirty per cent of LDL cholesterol is obtained from the diet, while 70 per cent is produced by the liver.
The amount that is produced is genetically determined, said Dr Ng.
Some researchers have found that the origin of the cholesterol found in the walls of the arteries is actually from the liver, he added.
Therefore, the more significant source of LDL cholesterol comes from the body's own production, which can get out of control either due to disease or genetic factors.
WHY IT IS BAD FOR YOU
The trouble with blood cholesterol is that too much of it, especially the wrong kind of particle, can cause serious problems inside the blood vessels.
LDL particles carry cholesterol to artery walls while high-density lipoprotein (HDL) particles pull cholesterol out of circulation and deliver it to the liver for destruction.
That is why LDL is "bad" and HDL is "good".
That high levels of LDL cholesterol is bad for health has been conclusively proven in the Framingham Heart Study, said Dr Ng.
This is a long-term, ongoing cardiovascular study on residents of the town of Framingham, Massachusetts in the US.
The same study has shown that people with low HDL cholesterol have a higher risk of heart disease. But researchers have not defined how much HDL cholesterol one should have to enjoy health benefits.
It usually takes time for blood cholesterol to build up in the arteries and cause coronary artery disease or stroke, said Dr Lim Ing Haan, consultant cardiologist at Mount Elizabeth Medical Centre.
From the late teens, the build-up can be seen as fatty streaks. As it progresses, fatty plaque forms throughout the artery to cause narrowing of these vessels.
When the narrowing is severe, blood flow and oxygen supply is affected and chest pain occurs.
Sometimes, the plaque ruptures and attracts a blood clot that chokes up the artery, causing a heart attack or stroke. This is dangerous, said Dr Lim.
Cholesterol is considered a culprit that works hand in hand with high blood pressure and diabetes, but it is no less harmful on its own, she added.
An example is the genetic disorder called familial hypercholesterolmia that results in super high levels of cholesterol.
Those affected by it have been known to need heart artery bypass operations in their teenage years, said Dr Lim.
THE NEW BAD GUY
Evidence now points to trans fat as having the strongest correlation to damaged blood vessels and coronary deaths.
Cutting down on saturated or trans fats in the diet has been shown to lead to lower serum cholesterol levels, said Prof Chin.
The US panel also singled out added sugars as one of its major concerns.
Previous dietary guidelines included warnings about eating too much added sugar but, for the first time, the panel is recommending that Americans eat no more than 12 teaspoons of sugar a day - or 10 per cent of daily calories - due to its link to obesity and chronic disease.
The best ways to lower one's serum cholesterol and LDL cholesterol, and raise HDL cholesterol, are to be physically active and to have a balanced diet.
HPB recommends eating a diet high in vegetables, fruit, whole grains and healthier proteins, such as lean meat, fish and tofu; and low in saturated fat, sugar and salt.
While there is no longer a specific limit on cholesterol consumption for most people, those with chronic diseases, especially diabetes, can still benefit from a low-cholesterol diet, said the HPB spokesman.
"We would advise them to check with their doctors," he said.
This is happy news for someone like Mr George Huang, an engineer in his 40s. He has a family history of high cholesterol and is taking statins, a medication that is a powerful inhibitor of LDL cholesterol production by the liver.
"I feel a little better about having my favourite lobster or crab noodles once in a while, as diet cholesterol does not play a big role in my blood cholesterol level," said Mr Huang.
Source: The Straits Times © Singapore Press Holdings Limited. Reproduced with permission.
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