CHD affects more than 2.5 million people in the UK and comes in two main forms - angina and heart attack.
Angina is a pain in the chest and is caused by a narrowing of the blood vessels that supply the heart (atheroscelerosis). If one of these vessels becomes blocked by a blood clot (thrombosis) a heart attack results.
CHD, although largely preventable, remains the single most common cause of death in the UK. Every year, one in six female and one in four male deaths are due to CHD.
A number of factors are associated with an increased risk of developing CHD – the main ones are smoking, high blood pressure, high blood cholesterol, and obesity. However, other lifestyle factors - particularly diet and exercise - also have an important role to play.
Diet and CHD
Eating for heart health simply follows the principles of a healthy balanced diet. There is extremely good evidence that moderately low-fat diets, especially low in saturated fats, but high in carbohydrates, reduce the risk of CHD by inducing favourable blood lipid (fat) profiles.
Furthermore, despite the speculation in the media, it is important to add that there is no persuasive scientific evidence that sugary sources of carbohydrates - including sugar - behave any differently to starchy carbohydrates in terms of CHD risk. In fact the old idea that sugar causes CHD was dismissed as long ago as 1989 by the UK government's COMA Committee (Committee on Medical Aspects of Food) and the scientific evidence, both clinical and epidemiological, available since that date has been thoroughly assessed but does not merit any revision of that opinion.
The key dietary component to focus on in terms of CHD is fat. However, we do need some fat in our diet to provide us with our essential fatty acids and the fat soluble vitamins - A, D, E, and K. The official guideline daily amounts (GDAs) for fat are 95g for men and 70g for women per day. The GDAs for saturated fat are 30g and 20g for men and women respectively.
Reducing dietary fat intake - particularly saturated fats - improves the levels of fats in the blood, promotes weight loss, and so reduces CHD risk. Although high blood cholesterol is a risk factor for CHD, it in-turn is more affected by the amount and type of fat in the diet than the amount of dietary cholesterol eaten. So, for most people, it is much more important to monitor the intake of saturated fat than cholesterol.
The cornerstone of dietary advice concerning reducing CHD risk is to increase the intake of carbohydrate-rich foods as this will help reduce fat intake. Plus many fruits and vegetables rich in carbohydrates are also rich in antioxidants and soluble fibre, and so consumption should be encouraged.
Eating fish - especially oily fish like salmon, mackerel, and sardines - at least twice a week is also recommended. This is mainly because oily fish are a good source of an essential fatty acid - omega-3. Omega-3 fatty acids have been shown to be beneficial for the heart by helping to improve blood fat levels and reducing blood clotting. Other sources of omega-3 fatty acids are: rapeseed oil; pumpkin seeds; and walnuts.
Moderate alcohol consumption, about one or two drinks per day, is associated with reduced risk of CHD. But, high intakes – particularly ‘binge drinking’ - increases CHD risk.
Eating lots of salt can increase blood pressure in people who are susceptible to high salt intakes, so it’s also wise to keep an eye on salt intake.
Exercise and CHD
Getting, and keeping, physically active is the single most important thing for preventing CHD. In fact, being inactive doubles a person's chances of developing CHD. The current recommendation is that everyone should aim to accumulate 30 minutes or more of physical activity over the course of most days of the week. However, a recent study has reported that it doesn't matter whether the exercise is broken-up into three lots of 10 minutes a day or one continuous session of 30 minutes for it to improve cardiovascular health. In addition, research shows us, that the exercise does not need to be strenuous to confer a benefit to the cardiovascular system. Gentle ‘aerobic’ exercise such as walking, cycling, swimming and dancing, can be effective in reducing the risk of CHD.
Taking part in regular physical activity improves the levels of fats in the blood, lowers blood pressure, and can contribute to the maintenance of a desirable body weight - all helpful for protecting against CHD. Exercise also has a key role to play in improving survival following a heart attack. In addition to weight loss, exercise can substantially further enhance the beneficial effects of dietary modification and thereby optimises the protection from CHD.
Metabolic syndrome and carbohydrates
There have been many misleading articles in the media concerning carbohydrates and the development of Metabolic Syndrome or Syndrome X. The majority of these articles have focused on sugary, in particular fructose, sources of carbohydrates. It has further been postulated that the Metabolic Syndrome is a common underlying cause of CHD. Certainly a number of the clinical features of the Metabolic Syndrome are known risk factors for CHD, but this does not imply that the cluster of symptoms is necessary for CHD to occur.
The existence of this Syndrome and its underlying causes are the subject of working hypotheses, not fully established fact. It is postulated that a range of metabolic disturbances, including high blood pressure and high blood levels of fat and glucose, arise from a common underlying disorder of insulin 'resistance'. Insulin resistance is characterised by a reduced physiological response to the presence of the hormone insulin in the blood. The most common clinical consequence of insulin resistance is an impaired ability to control blood glucose levels leading to diabetes.
Most informed scientists consider that the major causes of insulin resistance, and therefore the likely causes of the Metabolic Syndrome, are obesity and low levels of physical activity. There is no persuasive evidence that the consumption of carbohydrates, including sugars, contribute appreciably to either insulin resistance, the Metabolic Syndrome, the onset of diabetes, or CHD. Nor is there evidence to suggest that reducing sugar consumption is a useful manoeuvre to ameliorate any of these conditions.
Substantial reductions in the risk of developing diabetes have been shown to occur in glucose intolerant subjects who take regular moderate physical activity, lose some weight and modify their diet to include less saturated fat and more fibre. There is some evidence that a diet that mainly consists of foods that release glucose more slowly into the blood stream - the so-called 'low glycaemic' foods - may improve glucose control, presumably by reducing insulin resistance. However, there is also research that shows no link between the glycaemic index of the food and CHD risk (even in people with diabetes). Sugar is a moderate carbohydrate food, comparable to pasta, and gives a rise in blood glucose more slowly than many common starchy foods such as bread (white or wholemeal), potatoes, cereals, or the commonly eaten varieties of rice.
Further information on CHD can be found on the British Heart Foundation's Website