Food for Life: How the New Four Food Groups Can Save Your Life (7 page)

Source: J. A. T. Pennington,
Bowes and Church’s Food Values of Portions Commonly Used
(New York: Harper and Row, 1989).

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Table 3     
The Baron All-Stars

High protein intakes have been found to contribute to progressive kidney damage. The kidneys are the bloodstream’s filter, and high-protein diets push the kidneys to work extra hard. Protein breaks down in the body to amino acids and then to urea, both of which cause the kidneys to excrete more water. Thus, a high-protein diet raises the fluid pressure in the nephrons, which are the filter units of the kidney. The result is progressive destruction of kidney tissue.

Researchers have suggested that the human kidney may not be able to cope with frequent, large protein loads. Early humans ate meat rarely, if at all, and so they did not generally have to deal with large amounts of protein. With the current daily high intake of protein, though, the kidneys are called upon to constantly overwork in an effort to rid the body of the by-products from the breakdown of protein.
⁶¹

This is of particular concern for people who have a history of kidney infections or other kidney problems. But evidence suggests that excessive protein also causes a gradual decline in kidney function for those who are otherwise healthy, while lower protein intake helps preserve kidney function.
^61–
64
Already, physicians recommend protein restrictions for people who have lost some kidney function, but that is good advice for everyone else as well.

The average American diet contains far more protein than anyone needs. The reason is that meats, poultry, and fish are simply combinations of protein and fat. They contain virtually no carbohydrates and no fiber. It is difficult to include these foods in the diet without the protein content climbing rapidly. And as problems of osteoporosis and kidney disease indicate, it is important not to overdo your intake of protein.

Average years of life have not been dealt out fairly. A mouse gets only two years. A dog lives about a dozen years, or as long as eighteen in some exceptional cases. On the other hand, a turtle can easily outlive a human.

Human life expectancy in America is now about seventy-five years. This is an average, and includes not only those who live a full lifespan but also
those who die in childhood or early adulthood. For people who have already cleared enough hurdles to make it to fifty, the average lifespan is longer—about seventy-nine.

Women live longer than men, and lifespan is not currently the same for all races. African-Americans have a shorter life expectancy than whites, in part owing to higher rates of cardiovascular disease, stroke, and cancer. And the gap in mortality figures between African-Americans and Caucasians is widening. Yet neither African-Americans nor Caucasians in America live as long as most Asians.

The good news is that our bodies do not carry an expiration date. Lifespan can be altered. The foods we chose for breakfast, lunch, and dinner can not only help keep us free from life-threatening illnesses but can affect a more basic part of our body’s timetable. For instance, diet influences how fast children grow up and the age at which they reach puberty. Diet also influences the speed with which we race toward maturity, and may, in turn, influence how quickly the whole race ends.

A puppy reaches maturity in a matter of months, much earlier than a human baby. But growing up quickly may not be such a blessing. The slowly maturing human child will far outlive his or her canine companion.

During my medical education I worked for a time at an inner-city clinic in Washington, D.C. There, girls of twelve and thirteen often came in asking for birth control pills. Many had already given birth to their first child. Some had been sent in by their mothers, who did not want them to become pregnant again. I wondered why nature was so cruel as to design the human body to become sexually mature at an age when a boy or girl is not old enough to care for a child or even to sustain a long-term relationship.

Well, perhaps nature was not to blame. Evidence suggests that the body is designed to reach puberty much later. The World Health Organization has for many years gathered statistics on the age of puberty worldwide. In 1840, the average age of puberty in girls in Western countries was not 12.5 years of age, as it is today; it was 17. The age of puberty has been measured in the United States, England, Norway, Denmark, Finland, and other Western countries, where it has slowly but surely been dropping in every instance.
⁶⁵

Researchers have gathered much more information on girls than boys
because the onset of menstruation is much easier to pinpoint in time than is any biological change in boys. Nonetheless, there are suggestions that boys are maturing earlier, too. Researchers in England have observed that it is harder to fit children on bus seats than it was a generation ago, and, in fact, recent measurements showed that the average thirteen-year-old English boy is about two inches wider across the shoulders than in the 1950s.
⁶⁶
It is believed that the difference is not the adult size they will reach, but the speed with which they will reach it. Other researchers have found that both boys and girls in Norway are reaching physical maturity earlier than they were in the 1920s.
⁶⁷

The most likely explanation has to do with diet. Puberty in girls depends on female sex hormones called estrogens, of which the principal one is
estradiol
. The level of estrogens in the blood is affected by the foods we eat. The customary Western diet of meat, poultry, dairy products, and fried foods increases the quantity of estrogens in the blood.
^68–
70
The results are seen in the accelerated pace of puberty and in the likelihood of cancer in organs that are sensitive to sex hormones, as we will see in
Chapter 3
.

What part of the diet is to blame? It may be the large amount of fat we tend to eat. About 37 percent of our calories come from fat. That is much higher than it was in the 1800s, when high-fat diets were limited to a small, wealthy portion of the population. But the low age of puberty may also be due to something that is missing. Grains, vegetables, fruits, and beans have lots of fiber, but when they are displaced by high-fat foods, the fiber content of the diet is reduced.

One way the body rids itself of estradiol is through digestion. The liver pulls estradiol from the blood, chemically alters it, and sends it down the bile ducts into the intestinal tract. There, the fiber from grains, vegetables, fruits, and beans escorts excess estrogens through the intestine and finally out the door as waste. At least that is how the system is supposed to work. But chicken breasts, beef, eggs, cheese, and all other animal products contain not even a scrap of fiber. As these products have assumed a larger and larger portion of the American plate, they have pushed off the grains, vegetables, beans, and fruits. Without adequate fiber to hold them in the digestive tract, estrogens are reabsorbed into the bloodstream, where they once again become biologically active. Recycling programs are a great thing for bottles and newspapers. But recycling hormones adds to human problems, apparently contributing to a lower age of puberty.

If a woman changes her diet to favor grains and vegetables, her estradiol
level drops noticeably in short order. For instance, if you were to measure the amount of estradiol in the blood of vegetarians, it would be less than in meat-eaters. But this is just the beginning of the story, because what is important is not just the level of estradiol in the blood but also whether it can affect the reproductive organs. Estradiol, like testosterone, is carried around in the bloodstream on the special carrier protein,
sex hormone binding globulin
, whose job is to keep the hormone inactive until it is needed. Vegetarians have less estradiol to start with, and they also produce more of this carrier molecule. So more of their estradiol simply waits politely on its carrier protein rather than jumping in and directing the development of the breasts and other organs at inappropriate times.
⁷¹
Precisely the same thing happens with testosterone in males.

Certain foods have special effects. The soybean, for example, is a mainstay of Asian diets. It is sprouted, or steamed and eaten right out of the pod. It is turned into tofu and tempeh, and also into simulated hot dogs, burgers, and cold cuts, not only in Osaka and Tokyo, but also in Asian groceries and natural foods stores in America. Soybeans contain natural chemicals called
phytoestrogens
. These are very weak estrogens that can compete with and blunt the effect of normal estrogens. Estrogens attach to special receptors on the cells of the breasts and reproductive organs, like boats docking at a port. But if all the “docks” have been taken by phytoestrogens, there is nowhere for the estrogen to attach, and it will not affect its target organ. When the diet is rich in soybeans or soy products, phytoestrogens moderate the effect of estrogens.

If a change in diet is responsible for the drop in the age of puberty, then we would expect that, in countries that still follow a predominantly vegetable diet, puberty would occur at a later age. The Chinese diet, for example, is centered on rice and vegetables, with little meat and virtually no dairy products. I recently asked Dr. T. Colin Campbell, a biochemist at Cornell University who directs the massive China Health Study, about the age of puberty there. His findings confirm the theory. In China, puberty in girls occurs at an average age of about seventeen, ranging between fifteen and nineteen. And they not only have a higher age of puberty but also enjoy phenomenally low rates of heart disease, obesity, and cancer. In Japan, Westernization of the Japanese diet has been accompanied by a drop in the age of puberty in girls from 15.2 to 12.5 in the past four decades.
⁷²

Dr. Denis Burkitt, the surgeon whose research discoveries established the value of fiber in the diet, confirmed this in his years of research in Africa.
In rural African villages, the average age of puberty in girls is seventeen. In Johannesburg, it is thirteen, and the chief suspect is the Westernized diet in the urban setting.
⁷³

Further confirmation comes from the Netherlands, in a recent study involving sixty-three girls. Researchers recorded the amount of grains, vegetables, and other foods the girls ate. They took blood samples so that hormones could be measured, and they noted the age at which puberty began. Again, the results were unequivocal. The girls who ate more vegetables and grains had a later age of puberty. Those who ate less of these foods had more estradiol coursing through their veins, and, not surprisingly, an earlier onset of puberty.
⁷⁴
The Dutch researchers also noted that, while they saw a definite effect of different vegetable intakes in the girls they studied, none ate nearly the amount of fiber that vegetarians do. The Dutch girls who ate the most vegetables still only got about 20 grams of fiber per day, while typical vegetarians average about 30.
⁷⁰
So the rather subtle differences in diet between the girls in the Dutch study did affect the age of puberty, but not to the extent that a vegetarian diet would be expected to.

Not long ago, after a college lecture I gave on this subject, a woman from the audience told me that she had always wondered why she and her sister, who had grown up in Asia, had reached puberty in their mid-teens while their youngest sister, who had been raised in the United States, reached puberty at nine. In the third sister’s case, the rice-based Asian diet had been abandoned for roast chicken and fried foods.

In addition to diet itself, there is also the questionable effect of ingesting hormones from other sources. Many people remember news stories about children in Puerto Rico reaching puberty at age four or five because of hormones fed to chickens to make them grow more quickly. Hormones are routinely used in the United States, too. If you were to look behind the ears of cattle raised on America’s farms, you would find a small implant about the size of the end of a sharp pencil. The implant contains hormones that are used to make cattle grow faster. Ranchers actually use five different hormones. Three occur in the body normally: estradiol, testosterone, and progesterone. Two are synthetic: trenbolone acetate, which is a synthetic testosterone; and zeranol, which is a synthetic estrogen. In 1989, the European Economic Community banned imports of U.S. beef from cattle given hormones. But American farmers use these hormones routinely, contending that, while the hormones affect the animals, they are not concentrated enough in animal products to affect your health.

The effect of the hormone implants is probably minor compared to the effect of the beef itself in your body. Even the most chemical-free meats have enough fat in them to cause your hormone levels to rise measurably. Coupled with the fact that meats have no fiber, and actually displace fiber-rich foods from the plate, they give a predictable and unnatural boost to hormones.