There is some evidence that an increase of potassium, calcium and magnesium in the diet may help to lower blood pressure. But a great deal of research still has to be done into this subject and it is too soon to recommend that people take mineral supplements for the control of hypertension. Similarly, although it is thought that omega-3 and omega-6 polyunsaturated fatty acids may decrease blood pressure, further research is needed before recommendations can be made.
Alcohol as a risk factor
Excessive alcohol consumption - defined as more than two drinks daily - is linked to both high blood pressure and high cholesterol levels. HDL (cholesterol) levels tend to increase with an increase in alcohol intake, but the risks associated with a moderate alcohol intake (1-2 beers or 2 glasses of wine or 2 tots of whisky or brandy per day) appear to be no higher than those of abstainers; however, heavy drinkers have increased levels of most of the coronary risk factors.
Interestingly, results of the CORIS (Coronary Risk Factor) Study - which involved men as well as women - showed that blood pressure and cholesterol levels tended to be slightly lower in light drinkers than in both heavy drinkers and in those who don't drink at all. A moderate alcohol intake therefore seems to be associated with lower blood pressure levels and also appears to protect the individual from cardiovascular risk and mortality. However, the serious medical and social problems associated with alcoholism should discourage any increase in alcohol consumption.
Breaking new ground
As research into the causes of heart disease continues, additional factors come to light which appear to be relevant in the prevention of CHD. Sometimes, however, it can take years before a suspected link is proved scientifically.
The fat/fibre connection
Recent studies on the role of dietary fibre in lipid (fat) metabolism have shown that fibre can have a positive effect by interfering with the body's absorption of fat. It has also been proved that dietary fibre - and especially water-soluble fibre, which is found in dried legumes, oats, oat bran, apples and oranges - has a cholesterol-lowering effect. It is not yet clear what precise mechanism is involved. Because of its obvious benefits in this and other areas, we should all increase our intake of dietary fibre to at least 20-30 g a day. This can be achieved by eating unrefined cereals, more wholewheat bread, fruit and vegetables and by substituting dried legumes (such as beans or lentils) for animal protein at least once per week. An additional benefit of a high fibre diet is that it is also high in complex carbohydrates - a good substitute for fat in the diet.
The vitamin controversy
The role of vitamins in the prevention and treatment of coronary heart disease is controversial and much research is still being done in this area. It has been suggested - but not proved conclusively - that ascorbic acid (vitamin C) and vitamin E may have a protective effect in the early stages of atherosclerosis (blockage of the arteries). Niacin (one of the B-complex vitamins) is often combined with cholesterol- lowering drugs used to treat high blood cholesterol levels. However, there is not sufficient proof as yet to suggest that vitaminsupplementation will lower anyone's risk of developing coronary heart disease.
Cholesterol-lowering Eating Plan
The Heart Foundation has given the following guidelines for achieving the goals of the Prudent Dietand maintaining low blood cholesterol levels:
- Eat less fat and substitute unsaturated for saturated fats. One of the major goals of a cholesterol-lowering eatingplan is to eat less total fat, not only because this is an effective way to reduce the amount of saturated fat in your diet, but also because it helps to decrease your total daily kilojoule intake.
- Cut down on foods of animal origin. Dietary cholesterol found in these foods raises blood cholesterol levels significantly.
- Eat more complex carbohydrates, especially those rich in fibre. Good sources include wholewheat bread, brown rice, pasta, cereals, dried peas and beans, fruit and vegetables. (Fibre - especially the water- soluble type found in oats, oatbran, some fruit and legumes - may even help to reduce blood cholesterol levels.)
- Avoid being overweight. To achieve or maintain your ideal body weight, your kilojoule intake should not exceed the number of kilojoules your body needs.
- Use less salt (sodium). A high sodium intake may cause high blood pressure. Cut down on the salt you use at the table and in the preparation of food. Be aware of the 'hidden' salt in commercial foods.
- Limit your alcohol intake. A moderate intake is regarded as two drinks (2 glasses of wine, 2 x 25 ml tots of spirits or 1-2 beers) per day. If you are overweight, avoid alcohol entirely.