Overweight and Cholesterol intake in your diet

The effect of dietary cholesterol on cholesterol levels in the blood is less crucial and more variable among individuals than the effects of saturated fat - nevertheless, it plays an important contributory role and this is why the recommended limit for cholesterol consumption has been set at 300 mg per day. Of course, the average person has no means of measuring the amount of cholesterol in various foods, but what you can do is identify those which are rich sources and ensure that you eat them in moderation only (see below).

Foods high in cholesterol

Beef, butter, chicken, turkey, duck, cream, all full-cream dairy products, fish, lamb , mutton, pork, tongue

Foods very high in cholesterol

Brains, caviar, egg yolks, giblets, kidneys, liver, prawns, shrimps

These foods are also high in saturated fat and should be eaten only occasionally. (Saturated fats raise blood cholesterol levels far more than does dietary cholesterol in animal foods.)

Overweight and heart disease

The role of obesity or overweight as an independent risk factor for CHD has not been clearly established, but what is known is that it is associated with risk factors such as raised LDL (`bad') cholesterol and total blood cholesterol, lower HDL (`good') cholesterol, hypertension(high blood pressure) and diabetes mellitus. Hypertension is much more common in overweight people; moreover, when weight is reduced and then maintained at a lower level, blood pressure tends to drop as well - if the weight goes up again, so does the blood pressure. There is a particularly strong link between obesity and hypertension in children and for this reason, it is important that children and adolescents do not gain excess weight - in fact, maintaining an ideal body weight should be a goal for the population in general.

Obesity also seems to be a significant, independent predictor of coronary heart disease, especially in women. Although women generally have lower blood cholesterol levels than men, these tend to rise after the menopause. Smoking also seems to be on the increase in women and this can be an important contributory factor. It has been shown that if you are overweight, a cigarette smoker and you take oral contraceptives, your risk of having a heart attack increases significantly.

In summary, the maintenance of ideal body weight by means of a combined diet and exercise programme makes good sense because of the relationship between obesity and an increased risk of heart disease. Also, for a large number of people who suffer from hypertension, weight control can be an effective way of treating the problem and may prevent the necessity for drug treatment.

Hypertension - the 'silent' killer

Apart from being one of the three major risk factors for CHD, high blood pressure is also the single most important risk factor for cerebrovascular disease (strokes). Hypertension affects one in five people in South Africa - yet many are unaware that they suffer from it until a routine medical check-up reveals the problem.

The specific causes of 95% of hypertension cases are unknown, although it is clear that certain dietary factors are important contributors. These include obesity, stress and excessive intakes of sodium (salt) and alcohol. The danger of high blood pressure is that it adds to the workload of the heart and arteries and accelerates atherosclerosis (blocking of the arteries), causing structural changes in the arteries - the higher the pressure, the greater the amount of damage done.

The salt/hypertension link

Evidence that there is an important link between a high salt intake and hypertension is sometimes described as 'circumstantial', but it is nevertheless very significant. While it may be impossible to prove that sodium is a direct cause of the condition, the incriminating evidence seems sufficient to recommend a general reduction in the consumption of salt.

Sodium is an unnecessary supplement to our diet - many foods have a natural sodium content which is quite sufficient for our needs - but we acquire the taste for added salt simply because it is given to us from an early age and it becomes a habit to pour it onto our food. The average South African consumes 10-15 g of salt a day, which is well above the recommended amount of 7,5 g. This includes salt which has been added to processed foods, in home cooking and at the table.

Although many people have normal blood pressure levels in spite of a high sodium intake, the recommendation is that since a low intake has no ill effects - while too much salt clearly raises the blood pressure levels of a large number of people - it makes sense to be on the safe side and either throw out the salt cellar or at least restrict its use considerably.

Dieting Factors that Affect Hypertension

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.