Conventional Dietary Management of Cholesterol
While the development of plant sterol-enriched spreads is a very significant advance in the dietary management of cholesterol, it does not replace conventional dietary therapy. Rather, a plant sterol-enriched spread is an adjunct to conventional advice, which substantially increases the potential of diet to lower serum total and LDL-cholesterol.
What is conventional diet therapy?
Since the 1960s dietary advice to lower blood cholesterol has revolved around the manipulation of dietary fatty acids. This advice was based on the work of two series of experiments conducted independently by Keys et al (1) and Hegsted et al (2). Both found saturated fatty acids raised blood cholesterol and polyunsaturated fatty acids lowered it.
The potency of polyunsaturated fatty acids in lowering blood cholesterol was about half that of saturated fatty acids in raising it. Fats rich in monounsaturated fatty acids had a neutral effect on cholesterol. Dietary cholesterol was found to have a small, but significant, blood cholesterol-raising effect.
Based on these studies for healthy eating the key dietary advice for reducing became the replacement of dietary saturated fat with polyunsaturated fat, with some reduction in dietary cholesterol. More recently, monounsaturated fats and carbohydrates have also been considered good substitutes for saturated fat, which remains the key dietary determinant of blood cholesterol.
What are the main sources of saturated fat?
In western industrialised countries most sources of fat in the diet are rich in saturated fats. These include:
1. Dairy fats – butter, cheese, cream and full-fat dairy foods
2. Meat fat, sausages and luncheon meats
3. Baking fats used in commercial cakes, biscuits and pastries
4. Commercial frying fats used for takeaway foods and snack foods
The saturated fatty acid content of the fats in these foods is 50-60 per cent. Consumption of all these foods needs to be curtailed in order to reduce dietary saturated fat intake. Dairy fats are the most cholesterol-raising and special attention needs to be paid to reducing dairy fat in the diet for a healthy eating lifestyle. Low and reduced-fat milks and yoghurts are recommended.
What are the main sources of unsaturated fats? Margarine spreads and unsaturated vegetable oils are the only major source of fat in the diet not dominated by saturated fats. Polyunsaturated and monounsaturated fats comprise 75-90 per cent of fatty acids margarines and oils. These foods also serve as the major sources of the essential fatty acids,, Vitamin E and Vitamin D in the diet.
The most freely available vegetable oils are sunflower, canola and olive oils. These are also used in margarine spreads. Although all three oils are recommended, sunflower and canola have an advantage over olive oil with respect to cholesterol-lowering. Advice for people is to:
1. Use table margarine instead of butter
2. Use sunflower, canola or olive oil in for frying and in salads
Nuts are also high in unsaturated fats and low in saturated fats. They may be recommended for people on cholesterol-lowering diets.
What does the Heart Foundation recommend?
The Heart Foundation recently made the following dietary recommendations for healthy eating that will lower blood cholesterol:
1. Use margarine spread instead of butter or dairy blends.
2. Use a variety of oils for cooking – some suitable choices include canola, sunflower, soybean, olive and peanut oils.
3. Use salad dressings and mayonnaise made from oils such as canola, sunflower, soybean and olive oils.
4. Choose low or reduced fat milk and yoghurt or ‘added calcium’ soy beverages. Try to limit cheese and ice cream to twice a week.
5. Have fish (any type of fresh or canned) at least twice a week.
6. Select lean meat (meat trimmed of fat and chicken without skin). Try to limit fatty meats including sausages and delicatessen meats such as salami.
7. Snack on plain, unsalted nuts and fresh fruit.
8. Incorporate dried peas (eg split peas), dried beans (e.g. haricot beans, kidney beans), canned beans (eg baked beans, three bean mix) or lentils into two meals a week.
9. Make vegetables, and grain based foods such as bread, pasta, noodles and rice the major part of each meal.
10. Try to limit take-away foods to once a week.
Take-away foods include pastries, pies, pizza, hamburgers and creamy pasta dishes.
11. Try to limit snack foods such as potato crisps and corn crisps to once a week.
12. Try to limit cakes, pastries and chocolate or creamy biscuits to once a week.
13. Try to limit cholesterol-rich foods such as egg yolks and offal e.g. liver, kidney and brains.