What should you eat?

Dr. Sarfaraz K Niazi (e-mail: niazi@niazi.com)

For years, the nutritional guidelines have been established to prevent malnutrition. Not much has changed in these recommendations except recently there has been a push to reduce fat in our diet However, an extremely important consideration now focuses on the role of diet in preventing and curing diseases. In the West, where nutritional deficiencies are not common, this new aspect about food has attracted much attention. Unfortunately, in our part of the world, malnutrition remains the primary focal point. But if we also pay attention to disease prevention effects of diet, we can do well in reducing our helathcare bill significantly. We are also fortunate because of our financial misfortunes not to have plunged in the expensive dietary trends of the West that are now proving damaging to health. There is still time, therefore, to take a proactive action..

Several specific dietary factors have been recognized to cause or prevent diseases as diverse as cancer, coronary heart disease (CHD), birth defects, and cataracts. For years, these recommendations remained restricted to scientific and consumer literature and much controversy existed regarding their validity. Finally, after years evaluation, the National Research Council of the US Government issued, for the first time in 1989, a comprehensive guideline to preventing disease through diet. This included ideal combinations for diet and emphasized the use of carbohydrates, fruits and vegetables. Unfortunately, like most government positions, this report was also heavily influenced by economic interests and included recommendations which should not have been there. Five years from its issuance of the report, much research has surfaced to establish the flaws in the US Government's recommendations. For us to make the best use of these recommendations, we must first understand the flaws in them and then apply them to our local social and cultural environment.

First, we must understand why do scientists differ in their opinions regarding the effects of diet? It is because of the tremendous difficulties in doing research of this type. Historically, experiments on animals and small studies in humans regarding how food is converted to energy have been used to make recommendations about the quantities of proteins, carbohydrates and fats in our diets. Whereas these studies are sufficient to understand the food-energy connection, the food-disease connection is difficult to decipher. These could not be confirmed from simple, small studies traditionally conducted to evaluate the nutritional value of food. It requires examining the eating habits of large populations of people and then correlating them with the incidence of disease. For example, why do the Japanese women seldom get breast cancer while the incidence of stomach cancer is very high in Japan?; or, why do the Pakistani Punjabi women have the highest risk of heart disease among women worldwide or why do Eskimos seldom succumb to heart disease?

The population studies reveal that the differences in diets across cultures can be correlated with different disease patterns. It was also discovered that as populations migrate and change their diet, the disease pattern follow the new dietary habits. For example, the Japanese women who moved to US and adopted the Western diets now have the same incidence of breast cancer as the Western women. The Pakistani émigrés to UK offer a classic study option. The first off-springs of these emigrants developed the same disease traits as that of Englishmen because their diets changed whereas their parents who stuck to their ethnic diets showed some but not a large change in the disease pattern.

To understand the mechanism of diet controlling disease we need specific studies to isolate the "complicating factors." For example, are there any cultural traits such as smoking, consumption of alcohol, family size, body structure, eating styles, or environmental conditions that can change the effect of food on our body. These specific studies are of two types. One that use patient interviews to correlate the history of conditions including diet to disease. It was discovered from these types of studies that the Norwegians, Finns and Punjabi women have a high risk of heart disease because they consume copious quantities of dairy products, more than the world average. However, these studies are often not very useful because the patients may not be able to relate all relevant events, may have changed dietary patterns during the life or may have different genetic susceptibility to disease.

The type of study that provides best answers is what the scientists call a prospective study where we find a large homogeneous population such as Eskimos, Norwegians, Asian Dravidians and then randomly divide them into two groups. To one group we give a specific diet while the other group is allowed to continue with their traditional diet for 20-30 years. As the members of this selected group begin to succumb to disease, the data begins to emerge--the connection between diet and health becomes apparent. Unfortunately, it takes a very large group of subjects to have sufficient number of diseases or deaths and a very careful and expensive monitoring to assure compliance. How would you like to go on boiled rice and fish diet for the next 20 years? It is also important to record changes in the lifestyles of people as they grow older. Have they begun or quit smoking? Have they married? Has their socioeconomic status changed? All of these parameters have to be analyzed simultaneously before we can make definite conclusions.

Now let us examine the recommendations of the US Government in the light of the current data and as it is applied to our culture and environment.

Fat

Fat in diet is the most favorite component worldwide; somehow things fattening taste good. This connection was inculcated by Nature because fat has high calories and we needed them to survive the Ice Age and the cycles of famine. Those who could not develop a taste for fat perished. Before the advent of cooking, we consumed fat raw (Eskimos still do it). Cooking not only converts fat to a tastier form, it also makes it more hazardous because of the "free-radicals." that form upon heating fats. Fat also gets spoiled easily; oxidation of oils gives a rancid odor. Vegetable polyunsaturated oils are more prone to oxidation and require special storage conditions. Vegetable oils must be stored in air-tight containers to keep them from getting rancid. If it smells bad, do not use it.

Fat is also an essential component of diet. A lot of our internal chemical laboratory depends on fats to provide the raw material to make such essential chemicals as hormones and enzymes. However, excess of fat or the wrong type of fat wreaks havoc.

Heart Disease

Blocking of arteries that supply blood to heart itself (coronary heart disease or CHD) has long been associated with elevated cholesterol in the blood. Saturated fats (the types of fats that typically solidify easily such as butter, ghee and margarine) and cholesterol in diet increase levels of cholesterol in blood and therefore the incidence of CHD. But if we take polyunsaturated fats such as olive oil or safflower oil, the cholesterol levels decrease. The use of monounsaturated oils has no influence on cholesterol. This discovery lead to a great rush to dump the saturated fats and adopt oils for cooking. Unfortunately, instead to improving our health, this trend caused greater damage because we began assuming that these oils are safe and increased our consumption. The advertising agencies are much to blame for it. It is illegal in the US to make any health claims for cooking oil. Also, all vegetable oils are cholesterol-free, there is no need to make this claim as if it were beneficial to health. The dubious practice to promote cooking oils continue in Pakistan.

More recently, the issue of two types of cholesterol (HDL, the heavy or LDL, the light cholesterol) was identified. The culprit was LDL and higher HDL levels even afforded protection against heart disease. If we restrict consumption of saturated fat (butter, ghee, etc.) then both LDL and HDL go down and as a result the effect on CHD may not as pronounced. The fat in meats is an integral part but its effect of LDL are less pronounced as observed from using cooking saturated fats. However, if we replace saturated fat with polyunsaturated fats, LDL is reduced without lowering HDL and this should have beneficial effects on heart. Monounsaturated fats besides causing a small decrease in LDL also reduce blood sugar and triglycerides (the free floating fats).

Several studies point that the HDL levels are a good marker of health but its level are altered not only by diet but also by such factors as use of alcohol, hormones, obesity, smoking, exercise and medications. We should not therefore rely on diet alone to cut down LDL and elevate HDL cholesterol.:

The beneficial effects of polyunsaturated fats have resulted in recommendations to increase their intake to about 10% of total calorie source. To obtain maximal benefit, we should not restrict ourselves to one type of cooking oil. This is necessary since some oils have the added benefit of increasing our resistance to heart attacks.

There is a general consensus that we should not receive more than 30% of our calories from oils (of this, one-third from polyunsaturated oils). However, this premise has come under fire. Studies show that not all high fat-consumers succumb to CHD. People living in Crete consume very high quantities of olive oil and have a very low incidence of CHD. Though communities consuming large saturated fat quantities are generally at higher risk, the connection is weakening in newer studies. Greeks who had historically used 40% of calories through fat show surprisingly low incidence of heart disease. But the fat they use is mostly monounsaturated type (olive oil); on the other hand Japanese who use only 10% calories from fat also have very low incidence of CHD as Greeks. The common factor being the low levels of saturated fat in their diets.

There is evidence that too low a consumption of fat can also be harmful since the resulting low levels of cholesterol can produce strokes, suicidal tendency and stomach cancers, as seen in the Japanese.

The use of fish diet to reduce CHD was based on studies in Eskimos, who seldom get heart disease despite large consumption of fat. This fat however, is quite different from the fat in the Western diet. It is what we call the Omega-3 fat, restricted to marine sources. The Omega-3 fats found in fish reduce aggregation of platelets, thin blood out, slightly reduce blood pressure and decrease triglycerides in blood. The connection between fish and CHD prevention however has not been consistently found. Since fish is a better meat than beef, we may continue to heed the advise to increase consumption of fish. The usual precaution about environmental contamination of fish must be considered also. In our environmental situation, deep sea fish is a safer bet.

Manufacturing of hydrogenated vegetable oils (margarine and vegetable shortening or banaspati ghee) has come under severe fire. The process of conversion changes the space orientation of fatty acids. (In technical jargon, it make high trans acids, up to 40%). Consumption of fats high in transfatty acids results in a marked reduction in HDL, the good cholesterol and a sharp increase in LDL and other fats clearly responsible for CHD. These converted fats also pose additional hazard of metallic contamination from the catalysts used for conversion. The bottom line is quite clear: Never use margarine or vegetable shortening. Even butter and ghee are preferred.

Vitamin E is long known to prevent conversion (oxidation) of LDL fats that results in blockage of arteries. Studies now confirm that the maximum benefits are gained at 100 mg per day dose of vitamin E but that can not be easily obtained from diet alone. An interesting connection reported is that if you take monounsaturated fats, vitamin E has lesser beneficial effect because these fats have a lesser chance of being oxidized in the body in the first place. So, if you are taking a lot of polyunsaturated fats, take 100 mg of vitamin E per day.

Cancer

It is generally believed that higher fat consumption increases incidence of cancer. Detailed analysis of studies now refute this blanket assumption. Breast cancer, now we know, is more related to total calorie intake than to fat in diet. Generally, in cultures where female children grow faster and have earlier menstruation, the incidence of breast cancer is higher; this indicates that when female body cells multiply faster, they also tend to become carcinogenic. Taller women with larger breast sizes have higher chances of developing breast cancer. In China where breast cancer remains low, age at menarche is still around 18 years and breast size is generally small. Multiple factors contribute to differences in incidence of breast cancer: reproductive patterns, physical activity, adiposity, alcohol intake and use of hormones. It is no longer just the fat in diet. In Pakistan, an alarming condition is emerging. The use of hormones in cattle to increase milk production contaminates the dairy products and as a result the consumers are getting a big dose of these hormones. The menstruation age is decreasing which means that at later age, the incidence of breast cancer will increase substantially.

Colon cancer remains connected to consumption of red meat and fat from animal sources. Components of red meat such as heat-induced carcinogens and readily available iron may be responsible. Though studies regarding prostate cancer are not conclusive, the connection with red meat and animal fat intake (which yields the culprit alpha linolenic acid) is considered established. Men over 40 remain at higher risk of prostate cancer if they continue to consume large quantities of red meat.

Obesity

Obesity clearly cuts down on life expectancy. If you reduce the amount of fat in your diet, you lose weight and live longer. No dispute about that. However, recent studies show that differences in fat intake do not always explain obesity in different populations. Southern Europeans take lower fat than the Northern Europeans, but nevertheless have higher rates of obesity. In China, where fat intake is customarily low, even to a level of less than 5% in some counties, the correlation among the various counties consuming different amount of fat and obesity does not exist. Use of low-fat diet does not assure a long-term weight modification. There seems to be no reason to reduce fat intake to below 20% of all calories consumed to accomplish weight loss. The long-term modification in overall caloric intake and exercise remain the firm advise.

The bottom line on the fat in diet is that we must restrict use of saturated fats particular those from dairy sources and those artificially hydrogenated. Monounsaturated intake seems to be favored in moderation along with polyunsaturates. Dietary fat does not, in the long-term, determine obesity, neither does it relate to cancer directly. Red meat animal fats should not be used at all.

Vegetables and Fruits

The role of vegetables and fruits is now well established in preventing all types of cancer; beta-carotene and vitamin C are considered supporting players. However, use of whole fruits and vegetables rather than their extracts or pills derived from them work better because there are yet unknown cancer preventing mechanisms which can not be provided in the isolated components. Relative merit of different types of fruits and vegetables in preventive disease is not yet established. Our best bet is to select them on the basis of total calories; lesser the better.

Dietary fiber lowers blood pressure and reduces risk of CHD. Vitamins B-6 and folic acid are now known to reduce risk of CHD by a unique mechanism of lowering a specific factor, homocysteine, in the blood.

Vegetarians and non-vegetarians who consume large quantities of vegetables and fruits have generally lower blood pressure. Dietary antioxidants, carotenoids and vitamin C, reduce the risk of cataracts by reducing accumulation of oxidized and denatured proteins in the lens.

Starches and Complex Carbohydrates

Increase in dietary carbohydrates, particularly in the form of starches and complex carbohydrates is recommended. Whole grain is preferred to retain the loss of vitamins, thiamine, riboflavin and folic acid in milling. Soluble fiber such as oat bran and psyllium (ispaghol) not only prevent constipation, they also lower cholesterol and reduces blood pressure.

Adults should get at least 800 mg of calcium per day not only to protect bones but also to reduce blood pressure and risk of cancer. Dairy products customarily thought to provide calcium are now known to be a poor choice. Calcium in dairy products is not absorbed effectively and the proteins in dairy product increase excretion of calcium from body creating calcium deficiency. It is now firmly established that adults should not use dairy products and calcium must be sought from supplements which are very cheap.

Proteins

Proteins have long been considered essential to the development of body muscles--totally untrue. Like other nutrients, proteins also provide the needed components of body's energy requirement We need proteins to supply the essential amino acids that our body does not synthesize. But then neither does the body of animals whom we eat. They get it from plant sources. Why not get to the source directly and cut the "middle-man "out. Legumes and beans are an excellent source of essential amino acids without the side effects associated with animal protein diets. If we must eat meat, it should only be poultry or fish. No red meat. There is absolutely nothing magical about red meat except its lethality..

[11 January 1995 The Daily Dawn; abbreviated version]