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HEALTH

The right diet can prevent strokes and heart attacks

Eat more fruits and vegetables and less animal fat, and avoid excessive alcohol consumption

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The Mediterranean diet has the strongest evidence for stroke risk reduction. It is low in sugar, high in fat (with 40 per cent of the calories from "good" fats such as olive and canola oil), high in plant-based foods (such as whole grains, vegetables and legumes), and favours fruits as desserts.

STROKE and heart disease (cardiovascular disease) remain the major causes of morbidity and mortality all over the world. The best way to prevent cardiovascular disease is to make the right choices for your health; prevention is better than cure. Smoking cessation and good control of your blood pressure are two measures that can be implemented if you want to reduce your risk of cardiovascular disease. Importantly, your food choices can make a major impact on your risk of cardiovascular disease.

Benefits of a healthy lifestyle

Lifestyle behaviour can determine your risk of cardiovascular disease. Studies, including the US Health Professionals study, the Nurses' Health Study, and the Swedish Primary Prevention Lifestyle Study (September 2014, Journal of the American College of Cardiology) showed that adherence to good lifestyle measures such as not smoking, maintenance of normal body mass index, daily exercise, healthy diet and avoidance of excessive alcohol can reduce cardiovascular disease by up to 80 per cent or more when compared to those who did not achieve any of these five healthy behaviours.

Impact of diet

The trend of decreasing whole grain, vegetable and fruit consumption and marked increase in meat and egg consumption in China over a 10-year period (2003 to 2013) has been associated with about a 27 per cent increase in stroke and more than 200 per cent increase in death from heart artery disease.

The current trend of many guidelines emphasises a reduced intake of animal fat and an increased intake of fruits and vegetables. Among the diets recommended, the Mediterranean diet has the strongest evidence for stroke risk reduction. The Mediterranean diet is low in sugar, high in fat (with 40 per cent of the calories from "good" fats such as olive and canola oil), high in plant-based foods (such as whole grains, vegetables and legumes), and favours fruits as desserts.

In a comparison of the impact of dietary patterns on risk of heart artery disease, the Seven Countries Study reported that the risk of heart artery disease for a Mediterranean diet was about 7 per cent of that in Finland and about 40 per cent of that in Japan.

Even if you consider yourself healthy and have not had heart disease or stroke, you can benefit from a healthy diet. Data from the Spanish Primary Prevention of Cardiovascular Disease with a Mediterranean Diet (PREDIMED) study showed a reduction of stroke by 47 per cent in five years when compared to a low-fat diet.

Benefit is seen also in those with a past history of heart attack or stroke. Interestingly, in the prevention of stroke and heart artery events for those with a past history of heart attack (secondary prevention), when comparing the results of the Lyon Diet Heart Study (using the Mediterranean diet) with the landmark Scandinavian Simvastatin Survival Study (using the cholesterol-lowering medication called simvastatin), those on a Mediterranean diet for four years had about a 70 per cent reduction in heart events and stroke as compared to about a 40 per cent reduction in recurrent heart events after six years of simvastatin.

Eggs and health

The question that is often asked is whether it is good to eat eggs. The view that regular egg intake is harmless is based on data from two USA studies which reported that there was no downside from egg consumption except for diabetics, for whom an egg a day doubled the risk of heart disease. However, this should be interpreted in the context that more than 90 per cent of US participants in the study had a poor healthy diet score and hence, it is difficult to assess the incremental effect of eggs alone as the baseline diet was unhealthy. In a population such as in Greece, where the predominant diet is the Mediterranean diet, it was reported that an egg a day increased the risk of heart artery disease fivefold among persons with diabetes.

Red meat and the gut

The latest US dietary guidelines published in 2016 emphasises the importance of reducing saturated fat intake. Compared to white meat (chicken, fish), red meat (beef) has more saturated fat, and has about four times as much carnitine. The yolk of a 65g egg contains about 237mg of cholesterol and 250mg of carnitine.

In humans, when gut bacteria digest foods containing carnitine (red meat and egg yolks) or choline (egg yolk), a metabolite called trimethylamine (TMA) is produced and this metabolite is then further processed in the liver to become trimethylamine n-oxide (TMAO). While the consumption of red meat has been linked to an increased risk of heart disease, diabetes mellitus, and premature death, recent studies on TMAO have shown that beyond the detrimental effects of saturated fat, there are other mechanisms which increase the risk of stroke and heart disease.

An article in the Journal of The American Association of Medicine published in June 2019 reported that studies have shown that people with higher blood levels of TMAO have more than twice the risk of heart attack, stroke, or other serious cardiovascular problems, as compared to those with low levels of TMAO.

What kind of bacteria you have in your gut is dependent on your diet. If more red meat is consumed, the gut will adjust to produce more "meat-eating" bacteria. For long term vegans who start eating red meat, the bacteria may initially not be able to produce TMA in the gut, and hence TMAO levels will not be high. If the vegans keep on consuming red meat, more "meat-eating" bacteria will be produced and more TMA will be produced and TMAO levels will increase.

Consumption of alcohol

While mild to moderate consumption of alcohol appears to reduce the risk of stroke and heart attack, heavy consumption increases the risk, especially for stroke, and in particular bleeding in the brain. Heavy drinking is also associated with sudden cardiac death, failure of the heart pump function, stroke, and disease of the lower limb arteries but a lower risk of heart attack. In particular the increase in stroke risk is likely to be due to the increase in blood pressure and the development of an abnormal heart rhythm, atrial fibrillation. Atrial fibrillation is an important cause of stroke.

Keeping the doctor away

Those at risk of cardiovascular disease should consider a mainly plant-based diet with plenty of whole grains, vegetables, fruits and legumes, more polyunsaturated oils (olive and canola), and consumption of fish and poultry rather than red meat or processed meat. Avoidance of deep-fried food and food with trans fats, reducing intake of sugar and potatoes, and eating fewer egg yolks will contribute to a more healthy diet. Hence, if you want to keep the doctor away, start making the right choices for food today.


This series is produced on alternate Saturdays in collaboration with Singapore Heart, Stroke & Cancer Centre