The China Study - T. Colin Campbell and Thomas M. Campbell

Wide-Ranging Effects: Bone, Kidney, Eye and Brain Diseases

ONE OF THE MOST CONVINCING ARGUMENTS for a plant-based diet is the fact that it prevents a broad range of diseases. If I have a conversation with someone about a single study showing the protective effect of fruits and vegetables on heart disease, they may agree that it's all very nice for fruits and vegetables, but they will probably still go home to meatloaf and gravy. It doesn't matter how big the study, how persuasive the re- sults or how respectable the scientists who conducted the investigation. The fact is that most people have a healthy skepticism about one study standing alone-as well they should.
But if I tell them about dozens and dozens of studies showing that the countries with low rates of heart disease consume low amounts of animal- based foods, and dozens and dozens of studies showing that individuals who eat more whole, plant-based foods get less heart disease, and I go on to document still more studies showing that a diet low in animal-based foods and high in unprocessed plant-based foods can slow or reverse heart disease, then people are more inclined to pay some attention.
If I keep talking and go through this process not only for heart dis- ease, but obesity, Type 2 diabetes, breast cancer, colon cancer, prostate cancer, multiple sclerosis and other autoimmune diseases, it's quite pos- sible that people may never eat meatloaf and gravy again.
What has become so convincing about the effect of diet on health is the breadth of the evidence. While a single study might be found to sup- port almost any idea under the sun, what are the chances that hundreds, even thousands, of different studies show a protective benefit of plant- based foods and/or harmful effects of animal-based foods for so many different diseases? We can't say it's due to coincidence, bad data, biased research, misinterpreted statistics or "playing with numbers." This has got to be the real deal.
I have so far presented only a small sample of the breadth of evidence that supports plant-based diets. To show you just how broad this evi- dence is, I will cover five more seemingly unrelated diseases common in America: osteoporosis, kidney stones, blindness, cognitive dysfunc- tion and Alzheimer's disease. These disorders are not often fatal and are often regarded as the inevitable consequences of aging. Therefore, we don't think it's unnatural when grandpa gets blurry spots in his vision, can't remember the names of his friends or needs a hip replacement op- eration. But, as we shall see, even these diseases have a dietary link.
OSTEOPOROSIS
Did you ever have an elementary school teacher tell you that if you didn't have bones, you would just be a shapeless blob on the floor? Or maybe you learned about the human skeleton from that popular song, " ... the ankle bone is connected to the shin bone, the shin bone is con- nected to the knee bone," etc. At that same time in your life, you prob- ably were told to drink milk to build strong bones and teeth. Because none of us want to be shapeless blobs, and because our celebrities have been paid to advertise milk's presumed benefits, we drank it. Milk is to bone health as bees are to honey.
Americans consume more cow's milk and its products per person than most populations in the world. So Americans should have wonder- fully strong bones, right? Unfortunately not. A recent study showed that American women aged fifty and older have one of the highest rates of hip fractures in the world.l The only countries with higher rates are in Europe and in the south Pacific (Australia and New Zealand)l where they con- sume even more milk than the United States. What's going on?
An excess rate of hip fractures is often used as a reliable indicator of osteoporosis, a bone disease that especially affects women after menopause.  It is often claimed to be due to an inadequate intake of calcium. Therefore, health policy people often recommend higher calcium con- sumption. Dairy products are particularly rich in calcium, so the dairy industry eagerly supports efforts to boost calcium consumption. These efforts have something to do with why you were told to drink your milk for strong bones-the politics of which are discussed in Part IV.
Something is amiss, though, because those countries that use the most cow's milk and its products also have the highest fracture rates and the worst bone health. One possible explanation is found in a report showing an impressively strong association between animal protein intake and bone fracture rate for women in different countries.2 Au- thored in 1992 by researchers at Yale University School of Medicine, the report summarized data on protein intake and fracture rates taken from thirty-four separate surveys in sixteen countries that were published in twenty-nine peer-reviewed research publications. All the subjects in these surveys were women fifty years and older. It found that a very impressive 70% of the fracture rate was attributable to the consumption of animal protein.
These researchers explained that animal protein, unlike plant pro- tein, increases the acid load in the body.3An increased acid load means that our blood and tissues become more acidic. The body does not like this acidic environment and begins to fight it. In order to neutralize the acid, the body uses calcium, which acts as a very effective base. This calcium, however, must come from somewhere. It ends up being pulled from the bones, and the calcium loss weakens them, putting them at greater risk for fracture.
We have had evidence for well over a hundred years that animal pro- tein decreases bone health. The explanation of animal protein causing excess metabolic acid, for example, was first suggested in the 1880s4 and was documented as long ago as 1920.5 We also have known that animal protein is more effective than plant protein at increasing the metabolic acid load in the body.6.7,8
When animal protein increases metabolic acid and draws calcium from the bones, the amount of calcium in the urine is increased. This effect has been established for over eighty years5 and has been studied in some detail since the 1970s. Summaries of these studies were pub- lished in 1974,9 198po and 1990Y Each of these summaries clearly shows that the amount of animal protein consumed by many of us on a daily basis is capable of causing substantial increases in urinary calcium.