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Good foods, bad foods

Confused about which foods are good and bad for your heart? Here’s the last word — for today — on heart-healthy meals.

india Updated: Feb 11, 2012 22:34 IST
Robert Davis
Robert Davis

If you’re trying to eat a heart-healthy diet, figuring out what to believe can be overwhelming. The advice we get on everything from eggs to olive oil is often confusing and maddeningly contradictory.

Ironically, this growing confusion comes at a time when scientists who study nutrition know more than ever. Too often, though, we hear about only the latest study (which may be poorly designed) or research that’s agenda-based. It’s like seeing one or two pieces of a jigsaw puzzle and trying to determine what the entire picture is.

To know what the science really shows, it pays to look at all the evidence, assigning greater weight to studies that are more rigorous. In many cases, this can give us a reliable indication of what’s really good or bad. Based on a thorough review of research, here’s what’s believable — and what’s not — regarding some familiar claims about heart health.

Oats lower cholesterol

TRUE: Oats contain a type of soluble fibre known as beta-glucan, which is also found in barley. It’s thought to lower cholesterol by binding to bile acids and removing them from the body. Bile acids are made from cholesterol, so when the body has to deploy more of its cholesterol to help replace the eliminated bile acids, there’s less of it in the blood.

The Cochrane Collaboration, an independent group that assesses the evidence for various treatments, conducted an analysis in which it pooled results from eight studies involving people with elevated cholesterol and other risk factors for heart disease. The studies lasted only four to eight weeks, so we don’t know about long-term effects.

Olive oil is the best oil

FALSE: Olive oil is often singled out as an especially heart-healthy vegetable oil because it’s high in monounsaturated fat. But it’s also lower in polyunsaturated fat than other oils. Both these fats are considered good fats that reduce the risk of heart disease.

Which of these fats is better is unclear but one analysis called it a draw, concluding that replacing saturated fat with either monounsaturated or polyunsaturated fat has an equally beneficial effect on cholesterol levels.

Another theory is that olive oil antioxidants known as polyphenols make it more healthful than its rivals. Preliminary research suggests that virgin and extra-virgin oils, which are high in polyphenols, may be more heart-healthy than refined olive oil.

Coffee is bad

FALSE: Cohort studies, which followed tens of thousands of people for many years, have found that coffee drinkers have no greater risk of heart attacks or strokes than those who abstain; indeed, they appear to have a slightly lower risk and appears to live longer. Though coffee can temporarily increase blood pressure, there’s little evidence that it causes hypertension.

One possible reason for the apparent benefits is that coffee is rich in antioxidants. Some studies suggest that as many as six cups a day are associated with benefits but many says that’s little too much because of the potential side effects of caffeine, which include insomnia, jitters and stomach upset.

Eggs cause heart disease

FALSE: Researchers have conducted a number of long-term cohort studies on eggs and heart disease, which have collectively followed several hundred thousand people. In general, the research has exonerated eggs: Eating up to six a week was not associated with a higher risk of heart attacks and strokes.

So how can this be if egg yolks are high in cholesterol? Most of our cholesterol is made by the liver, which ramps up production when we eat saturated and trans fats. But cholesterol from food appears to have little impact on most people’s cholesterol levels. And in people it does affect — so- called hyper-responders — studies show there can be an increase in good (HDL) cholesterol along with the bad kind, which offsets heart disease risk.

Eggs are relatively low in saturated fat, and they contain unsaturated fats, which may be beneficial. Plus, they’re a good source of protein and several vitamins and minerals.

Fish oil protects your heart

TRUE: Decades ago, scientists discovered that Greenland Eskimos rarely died from heart disease despite a diet high in fat from fish. Researchers theorised that the fish fat was somehow protective, an idea that subsequent research has largely supported. Several studies show that people who regularly eat fish are less likely to die of heart disease than those who don’t.

The key ingredients appear to be the omega-3 fatty acids EPA and DHA, which are found in most fishes but especially in oily ones such as salmon, mackerel, trout, sardines and tuna.

The American Heart Association recommends eating oily fish at least twice a week. People with heart disease are advised to get twice as much, or 1,000 milligrams per day of EPA and DHA combined.

Nuts are good for the heart

TRUE: Once regarded as high-fat nutritional villains to be avoided at all costs, nuts are now touted as a health food that can ward off heart disease. Several large cohort studies (the type in which people are asked about their dietary habits and then followed for years or decades) have consistently found lower odds of heart disease and heart-related deaths among nut eaters, regardless of sex, age, or occupation.

Nuts also appear to decrease inflammation in arteries, which may contribute to heart attacks. All nuts are relatively high in unsaturated fats, which are thought to be good for the heart. But overindulging can lead to extra pounds.

Chocolate is good

HALF-TRUE: Cocoa, a main ingredient in chocolate, is high in antioxidants known as flavanols, which are also found in red wine, tea and certain fruits. Though the evidence overall is mixed, some cohort studies have linked high flavanol intake with lower rates of heart-related deaths. Generally, dark chocolate is higher than milk chocolate in flavanols.

Small, short-term experiments show that chocolate (especially the dark variety) can lower blood pressure, reduce inflammation in arteries and reduce blood clotting. Even though it’s relatively high in saturated fat, studies show that chocolate doesn’t raise LDL cholesterol and may even lower it. Look for products that list cocoa or chocolate liquor — and not sugar — as the first ingredient.

The Washington Post

First Published: Feb 11, 2012 22:30 IST