Ideas about eating have changed over the years. Many people say, “I’ll eat what I like, because what is allowed today may be bad for you tomorrow.” To some extent “we become what we eat”, so it is foolhardy to ignore the latest discoveries.
During the holiday season it is easy to eat with abandon. But our usual eating habits can have great impact on our future life; for example, less fat may prevent future development of diabetes or a premature death. Some footballers and other athletes still mistakenly believe that a diet high in protein, such as steak and eggs, develops muscles and gives energy.
Such a diet will reduce performance and increase the risk of a heart attack. Active people do need more protein than couch potatoes, but a normal diet usually has enough. Athletes need high amounts of carbohydrate so they can store muscle glycogen to generate energy.
The Japanese, the longest-living people in the world, have low rates of heart disease, and Japanese women have low rates of breast cancer and few menopausal symptoms. The Japanese eat plenty of fish and plants, including soy products, and have a diet low in saturated fat.
Soy beans contain good supplies of all food groups, including soluble fiber, and they may help prevent breast and prostate cancer. They are one of the richest sources of plant oestrogens (phytoestrogens), which seem to be anti-cancer agents that stop or slow cancer-cell growth, particularly hormone-dependent cancers.
Plant oestrogens may bind to receptor cells, preventing the body’s more powerful natural oestrogens from attaching to them. Soy beans can also boost oestrogen supplies to menopausal women and so stop hot flushes. A Melbourne study showed that a diet with 45g of soy flour daily resulted in a 40 percent reduction in hot flushes.
Good sources of plant oestrogens are:
- wholegrain cereals
Many researchers believe that dietary fat is related to cancer and that a high-fiber diet lowers the risk, as has been shown for bowel cancer.
The risk of future cancer also increases if children consume so much high-energy food as to cause obesity and rapid growth. Cholesterol and triglycerides are normal components of blood and the higher their levels the greater the risk of a heart attack, but we need cholesterol for growth and for cell membranes to function.
The discovery that there are two types of cholesterol complicated ideas about diet. Scientists found that total cholesterol did not necessarily predict the risk of heart disease in an individual. The kind of cholesterol was important. Good, or high-density lipoprotein (HDL), cholesterol protects against heart and artery disease, but about 70 percent of cholesterol in the blood is usually in the form of bad, or LDL (low-density), cholesterol which increases the risk.
If your HDLs are low, an increased triglyceride level becomes a risk factor for heart disease. Researchers have found that, for people with relatively high cholesterol, eating at least 30g of soy protein daily can produce significant reductions in both bad and total cholesterol. Some other substances, such as omega-3 polyunsaturated fatty acids in fish, canola, walnut and linseed oils also seem to protect against heart attacks.
Some researchers think high amounts of vitamin E protect against heart attacks, but this is still controversial. It is hard to maintain supplies of fat-soluble vitamin E on a low-fat diet but vitamin pills are available. The cholesterol levels of US children are among the highest in the world. Eating too much saturated fat, not enough exercise, smoking and drinking will all put up your cholesterol level.
Americans typically have a diet containing about 33 percent fat. Our food contains about 13.5 percent saturated fat, found in cakes, chocolates, pastries and snack foods. The other fats in our diet are typically 5.5 percent polyunsaturated fat and 14 percent monounsaturated fat. Olives and some margarines made from canola or sunflower oil are high in monounsaturated fat. These lower total and LDL cholesterol but do not alter HDL cholesterol.
For best health we need to cut our saturated-fat intake by about a quarter, to about 10 percent. To reduce fat many people limit their use of spreads or use low-fat spreads and reduce meat and dairy products. However, this often reduces polyunsaturated and monounsaturated fat, but hardly changes saturated fat.
To reduce cholesterol level, butter and most margarines are best avoided since both may contain more than 80 percent fat. Butter contains about 60 percent saturated fat and increases total cholesterol in the blood as well as the LDL cholesterol. Both polyunsaturated and monounsaturated margarines will lower LDL cholesterol provided they don’t contain too much saturated fat.
During the manufacture of margarine, the hydrogenation of vegetable oils produces trans-fatty acids. A Harvard study showed that these fatty acids were harmful, but more recent studies have shown that at worst they are a minimal risk factor, though they do act like saturated fats and increase LDL cholesterol. But we eat only small quantities.
Fruit and Vegetables
Results from the large Framingham study show that fruit and vegetables help protect against stroke as well as heart disease. Vegetables give the greater protection and the more eaten the less the risk. Antioxidant vitamins may provide the protection or perhaps people who eat lots of fruit and vegetables eat less of harmful foods.
The wide variety of biologically active substances in fruit and vegetables may give the protection. A good strategy is to eat five different vegetables daily. Fast foods, which are high in saturated fat, are difficult to eliminate from teenagers’ diets. Having one or two fast-food meals a week is acceptable but minimize fat by avoiding fried foods.
To achieve weight loss avoid fat, rather than sugars. It was previously thought that excess of protein, carbohydrate or fat would be stored as fat. We now know that dietary fat is essentially the only one that ends up in the body’s large fat stores. Excess carbohydrate and protein is readily used for energy and we store only small amounts. Our appetite is mainly controlled by carbohydrate and protein because they produce a feeling of fullness. Fat has little influence on appetite.
A vegetarian diet seems to be a healthy one but it is essential to make sure your diet is balanced, otherwise there is a distinct risk that you will become anemic because of iron deficiency and your bone strength may fall because of calcium deficiency. Vegetarian children under five need to get sufficient energy foods or growth will be impaired.
Vitamin B12 needed by adults and by babies for nerve development is normally only in animal foods, though the body normally stores enough to last three years. Vitamin D needs to be adequate. Milk can supply these vitamins.
Women who expect to get pregnant need to make sure they get sufficient folic acid, contained in citrus fruit, leafy green vegetables and fortified breakfast cereals. Lack of folic acid produces serious neural-tube defects such as spina bifida in babies.
For a healthy diet, eat a wide range of foods, including bread, cereals, vegetables and fruit, remove skin from chicken and visible fat from meat, eat fish at least once or twice a week, use low-fat dairy products, use either polyunsaturated or monounsaturated margarines, avoid butter, use polyunsaturated or monounsaturated cooking and salad oils and reduce your salt intake.