The No. 1 nutritional bad guy of the early 1990s still will be fat as people worry about how much they consume and how it affects their health.
The surgeon general, with the support of almost every mainstream health organization, has branded dietary fat as the most problematic nutrient. Not only is it the prime contributor to heart disease and obesity, and a longstanding national health obsession, but also current research indicates that fat may figure prominently in colon, breast and prostate cancer as well as high blood pressure.
Researchers long have known that a diet high in fats can elevate blood cholesterol levels in many individuals, beginning with young children; but fat nutrition is not that simple. Saturated fats-those found in abundance in animal products such as milk, cheese, butter and meats as well as in tropical fats such as palm kernel and coconut oil-tend to be the nastiest contributors to raising levels of low-density lipoproteins (LDLs) in the blood, or what some call bad cholesterol.
Compared to saturated fats, the polyunsaturated fats-those found in soy, corn, safflower, sunflower and walnut oils-tend to lower LDLs. But they also lower high-density lipoproteins (HDLs), the ”good” cholesterol.
Lest you believe that solves everything, consider that some research indicates that the polyunsaturates also may contribute to the development of cancer-prone cells in the stomach and elsewhere in the digestive system.
Monounsaturated fats-found in high amounts in olive, canola and peanut oils-tend to lower LDLs without effecting HDLs and thus have a somewhat positive effect on blood cholesterol. But remember, they still are fats, with all the other attendant consequences.
Other types of fats, introduced by technology, are processed vegetable oils that contain chemically altered fatty acids to adapt them for modern food products. These are made by adding hydrogen atoms to molecules of unsaturated fatty acids (a process known as hydrogenation) to make the molecules more saturated and thus more viscous and stable for use in products such as margarine, shortenings, baked goods and peanut butter.
These hydrogenated oils are called trans-fatty acids and constitute about 2 to 4 percent of our fat intake. Though still sparse, research is showing that trans-fatty acids can raise LDLs while having little or no effect on HDLs, although not to the extent of the saturates.
Because they contribute strongly to flavor and texture, fats turn up in much of our food, especially processed foods. Many current labels list the fat, and proposed regulations by the Food and Drug Administration will require almost all foods to put fat content on the label.
The National Research Council, a government-appointed agency that sets the recommended dietary requirements, states that fats should be limited to less than 30 percent of total calories.
There is a growing trend among heart and cancer researchers, however, to recommend stricter limits. Many now believe that holding fat to less than 20 percent of calories might be a better goal for good preventive nutrition.
For a person whose daily calorie intake is 2,200, about that of a typical woman 19 to 50 years old, a 20 percent fat diet is about 48 grams of fat daily.
To calculate fat limitations for your diet, determine your daily calorie intake, multiple by 30 or 20 percent, then divide by 9, the number of calories per gram in fat. The result will be the number of grams of fat you should consume in a day.
Carbohydrates and sugar
If fats are America`s nutritional culprits, carbohydrates are the good guys, especially those complex carbohydrates found in grains, legumes, fruits and vegetables. Though relatively low in calories, they are the preferred source of energy for the body and convey fiber, vitamins and other nutrients through the system.
Carbohydrates do not increase cholesterol, contribute to cancers or cause obesity (unless used to great excess). Most nutritionists recommend that at least 50 to 55 percent of calories come from carbohydrates, about 10 percent more than the 45 to 47 percent most Americans now consume.
One of the primary simple carbohydrates that has been abused by some consumers and vilified unjustly by others is sugar.
Unlike many of the complex carbohydrates, sugars contain few other nutrients and thus sometimes are considered ”empty” calories. For people who require few calories, sugar may not be a good source because its calories can replace necessary nutritients from other foods. But for people whose energy requirements are large, sugar can help fulfill them.
In the past sugar has been blamed for obesity, but nutritionists now know that sugar provides no more calories than pasta, potatoes, bread or broccoli. Some studies show that obese people actually eat less sugar than those whose weight is normal or below normal.
However, sugars frequently are accompanied by high-calorie fats in foods such as ice cream, chocolate and pound cake, so the idea of avoiding
”sweets” to stay lean still may have validity.
Several years ago it was widely thought that hyperkinesis (overactivity)
in children resulted from eating sweets. Similarly, some researchers alleged that aggressive, antisocial behavior in adults, mostly imprisoned males, could be traced to unbalanced diets heavily loaded with sugar. Because sugar easily is converted to energy in the body, it was thought to be the culprit.
This theory now has been shown to be wrong. Several controlled scientific studies have failed to establish any link between sugar consumption and hyperactivity or aggressive behavior.
The main problem with sugar, according to modern research, appears to be dental. Clinical studies over the last 40 years consistently have established that many carbohydrates, but particularly sticky, chewy forms of sugars, contribute to oral plaque and tooth decay. Thus, Mom`s advice to brush after meals, or at least rinse vigorously, was on the mark.
Because diabetes is characterized by high blood-sugar levels, there is a popular belief that sugar causes the diabetes. Sugar is not to blame, though people with the disease do need to monitor their sugar intake as well as the rest of their diet.
Authorities believe that the most common form of diabetes, which usually affects people over age 40, is caused by genetic factors, obesity, too little insulin or resistance to insulin.
Another type of diabetes, which strikes young people, has been attributed to an immune-system disorder. Neither is caused by consuming sugar.
Dietary fiber
Recently, dietary fiber has been viewed as more than something to ward off constipation. Research shows it may provide an important defense against heart disease and cancer.
All dietary fiber comes from plants. Unlike fats, carbohydrates and proteins, fiber is resistant to digestion, so some passes through our digestive system essentially unchanged while some is partially fermented by naturally occurring bacteria in the colon, producing, among other things, gas. Insoluble dietary fiber is that which does not dissolve in water. It comes mostly from foods such as whole grains and cereals, potatoes, cauliflower and green beans. Sometimes referred to as roughage, it has been shown to play a positive role in preventing constipation and hemorrhoids.
Soluble dietary fiber, found in beans, lentils, peas, barley, oat bran and fruit pectins, does dissolve in water and sometimes is pictured as a kind of thin glue or gum. It has been shown to help lower blood cholesterol when combined with a low-fat diet, although the FDA so far will not allow such a claim on food labels.
Studies of diabetics indicate that high-fiber diets or diets supplemented by soluble fiber result in lower blood-glucose levels and, in some cases, eliminate the need for insulin.
Some researchers believe that dietary fiber may help prevent colon and other types cancer in two general ways: Soluble fiber helps to dilute potential cancer-causing agents, typically in fats, and insoluble fiber helps speed up the passage of those potential carcinogens through the intestines.
Both kinds of fiber sometimes are used in the treatment of diverticulitis with good results.
Sodium
Whether from common table salt, salt added in processed food or from other compounds, sodium continues to be a controversial nutrient in the country`s food supply.
It has been well-established that for about 15 percent of the population, sodium can have an effect on blood pressure and hypertension. Also, it is generally agreed that people in this country eat much more salt than is necessary for good nutrition. For these and other reasons the NRC has recommended limiting intake to about 2,200 to 2,500 milligrams a day.
The American Heart Association says that consumption should be less than 3,000 milligrams. The body requires only 180 to 500 milligrams a day.
Even the Salt Institute, which is trying to change a negative public attitude toward salt, says that consumption should be somewhat limited-less than 5,000 milligrams.
The American Dietetic Association, although it also recommends a reduction of salt intake, states in a pamphlet, ”Since only about half the population is sensitive to sodium, though, lower sodium intake may not be helpful for everyone.”
Perhaps more significant is the relationship between sodium and potassium, said Alicia Moag-Stahlberg, a registered dietitian and an ADA spokesperson. Studies show that people should consume at least the same amount of potassium as salt, but because people are eating fewer fresh fruits and vegetables, the primary sources of potassium, most get only slightly more than half as much potassium as sodium.
The relationship is important because the lastest research shows that potassium can have a counterbalancing effect on higher sodium intake and can protect against hypertension and stroke, Moag-Stahlberg said.
”If everyone would increase potassium consumption by just 400 milligrams a day (about two servings of potassium-rich fruits or vegetables), stroke incidence would decrease by 40 percent, according to some studies,” she said. Calcium
There is a delicate balance between sodium, potassium, calcium, iron and other minerals in the system, including some of the trace elements such as selenium, zinc and magnesium. Cutting out one or boosting consumption of others without regard to the relationship may be counterproductive.
Calcium, for instance, if taken in large doses is less absorbed than when taken in moderate amounts, studies show. Diets high in sodium increase the loss of calcium. Calcium and iron compete with each other for absorption in the body. Calcium absorption is influenced negatively by the consumption of caffeine, alcohol, phosphorus and protein. (Americans` phosphorus intake is especially high because of their huge consumption of soft drinks.)
Most people do not get enough calcium, especially women, much recent research is showing. Calcium has been found to have a significant and sustained preventative effect on bone loss, especially in post-menopausal women, one study indicates.
Calcium also has been shown to have a role in guarding against colon cancer and is essential for blood-pressure control. The latest research indicates it also may be helpful in preventing symptoms of premenstrual syndrome.
Anti-oxidant vitamins
The latest nutritional research indicates that some vitamins found in foods, especially vitamin A/beta carotene, vitamin C and vitamin E, can help prevent the formation of free radical molecules, unstable particles that can attack and damage cell membranes and lead to a precancerous condition.
Free radicals also are thought to affect LDL cholesterol and help cause the formation of the plaque that clogs arteries and can lead to heart attacks and strokes.
Vitamins A, C and E, especially when consumed in foods, prevent this
”oxidation” process that creates the free radicals, and thus are labeled anti-oxidants.
Nutritionists emphasize that the exact process by which the anti-oxidants work is complex and that getting the vitamins from vegetables, fruits and other foods is preferable to taking supplements for two main reasons: Foods contain many other chemicals which may aid in the absorption and effectiveness of the anti-oxidants, and there can be some risk in taking too much.
For most nutrients there is a saturation curve: You require a certain amount, and intakes beyond that amount are ineffective. For some nutrients, such as selenium and vitamin A, too much can be toxic.
Eating fruits and vegetables high in vitamin C daily boosts the amount of that vitamin and also provides complex carbohydrates, fiber and other nutrients, Moag-Stahlberg said.
One of the best things about the sources of anti-oxidants is that it is good to eat vegetables, fruits and grains anyway. The fact that they may guard against cancer and heart disease is an added advantage, she said.
