These days, you can easily find a plethora of nutritional supplements on shop shelves aimed at promoting cardiovascular health.
You might be tempted to get one of these cholesterol-lowering supplements if you are worried about your cholesterol level.
Here's a look at three common ones:
Fish oils contain essential omega-3 fatty acids, of which the active components - eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) - have been shown to have anti-inflammatory and anti-thrombotic effects.
While some people may take it with the aim of preventing heart attacks, there isn't any strong evidence of protection for those who have not suffered from heart disease, said Dr Kenneth Ng, consultant cardiologist at Novena Heart Centre.
It does, however, have a protective effect in patients who have had heart attacks or vascular disease.
The main effect of fish oils is that they lower triglyceride levels.
However, the lowering of triglyceride levels by drugs or other means has not been shown to reduce the risk of cardiac events, said Dr Ng.
So far, clinical trials have shown evidence of secondary prevention, that is, in people who already have heart disease, he said.
Two clinical trials involving patients who had suffered a heart attack found that treatment with 850mg of omega-3 fatty acids per day led to a 45 per cent risk reduction in sudden cardiac death, said Dr Ng.
The only side effect is fishy breath if you burp after taking a pill with omega-3 fatty acids.
For high-risk patients, such as those with known heart disease or elevated triglycerides, one to two servings of oily fish (salmon, halibut, sardines and anchovies) per week is recommended, said Dr Rohit Khurana, a cardiologist at Gleneagles Hospital Singapore.
The American Heart Association, which recommends eating at least two servings of fish (particularly fatty fish) a week, said each cooked serving is 99g.
"For those who are unable or unwilling to consume this much fish, we suggest prescribing a daily fish oil supplement (about 1g-2g per day)," he added.
Dr Ng recommends taking at least 800mg of DHA and EPA combined. Always check the label as the actual amount of omega-3 oils to take depends on the concentration of EPA and DHA in each capsule, he said.
"Some brands of fish oils have very low levels of EPA and DHA in each 1g capsule. The good brands will have about 400mg of DHA and EPA in each capsule, so you would probably end up taking two to three capsules a day," he said.
RED YEAST RICE
This is a substance extracted from rice that has been fermented with a type of yeast. The active ingredient in red yeast rice is Monacolin K, which is chemically identical to lovastatin, a prescription drug which blocks the liver from producing bad cholesterol.
It can cause the same side effects as lovastatin, such as muscle pain.
Red yeast rice is marketed and found in varying doses in supplements such as Xuezhikang, Cholestin and Hypocol.
Three placebo-controlled studies have shown that red yeast rice can reduce total cholesterol by up to 16 per cent and LDL cholesterol by up to 24 per cent, said Dr Ng.
This is equivalent to a lovastatin dose of 20mg-40mg, he said.
There is no data as yet showing its benefit in reducing the incidence of heart attacks over the longer term, said Dr Khurana.
Nevertheless, red yeast rice could still be an alternative for those who do not want to take statins as it does have proven cholesterol-lowering effects, said Dr Ng.
In 2007, the United States Food and Drug Administration asked for some red yeast rice products to be withdrawn from the market because they contained more than trace amounts of lovastatin.
It said that the products cannot be marketed as supplements as they are unapproved new drugs.
"However, Hypocol, which is available in Singapore, has monacolins in the ingredients label... I would presume that the red yeast rice sold in Singapore is still effective," said Dr Ng.
There is a risk that lovastatin can cause severe muscle problems leading to kidney impairment but this complication is extremely rare, said Dr Ng.
"I have not encountered a single case in my years of practice. So theoretically, if someone takes a very high dose of statin and is susceptible to this complication, they can suffer from kidney failure."
If we stick to the manufacturer's dose, it is probably safer, he said.
CO-ENZYME Q10 (COQ10)
This is a natural anti-oxidant that is needed for basic cell function. People produce less of it as they age and disease can also deplete its levels.
However, there is no firm evidence that taking CoQ10 supplements can reduce cholesterol levels. So far, only about six randomised controlled studies of CoQ10 in the prevention of heart disease have been done and they were very small, with an average of 25-50 subjects, said Dr Ng.
"The outcomes were varied and nothing firm can be concluded on their effects on hypertension or cholesterol levels," he said.
"We cannot make any firm conclusions about the benefits of CoQ10 in this respect."
Instead, the main use of CoQ10 is now in treating heart failure, said Dr Ng, citing a trial called the Q-Symbio study.
It showed that the intake of CoQ10 resulted in a significant reduction in the death rates among those with heart failure and a lower rate of hospital admissions.
Heart failure happens when the heart cannot pump enough blood to meet the body's needs.
CoQ10 may also be used to reduce the common side effects of taking statins such as muscle pain, although the evidence is inconsistent, said Dr Khurana.
He said the ideal dose from supplements is 100mg once daily and natural dietary sources are mainly from meat and fish.
There is limited research on CoQ10 toxicity from long-term use of this supplement, he added.