Lessons from China.

Lessons from China

It's been called the most comprehensive study of diet and disease ever conducted. The China Project has collected 367 items of information each on over 6,000 people, generating more than 100,000 correlations between lifestyle and about 45 different diseases.

And it may have some important lessons for Americans.

"In my opinion, making a few cosmetic changes, like trimming the fat off meat, drinking lowfat milk, and using vitamin-fortified foods and nutrient supplements, isn't necessarily going to accomplish that much," says principal investigator T. Colin Campbell of Cornell University.

"The data from this and other sources suggest that we're going to need major dietary changes to significantly alter the prevalence of diseases like cancer, heart disease, and diabetes."

Q: What led you to study the diets and diseases of China?

A: In China, cancer is a local disease. The rates range from very high in some regions to virtually nothing in others, unlike here, where we see about the same amount of cancer everywhere.

That's because in China, each region has different habits and foods, and people don't move all over the place. And the diseases that are common in the U.S. are beginning to occur in some regions. So we're able to take a look at the factors that are causing these diseases to emerge.

Q: What's in a typical Chinese diet?

A: It varies a lot, but rice is part of almost every meal in most of China. They might have fish or some other soup for breakfast, or, in Beijing, some steamed bread.

The Chinese always consume vegetables in season and in some regions they eat tubers like sweet potatoes in generous quantities. In some areas, people eat fish almost every day. Others don't get any at all. Eggs, pork, and chicken are mostly delicacies.

Milk products are hardly known, except in the far north among the Moslems in the Inner Mongolia and Xinjiang regions where they eat goat, yak, horse, and camel milk and cheese.

Q: What's the most important lesson we can learn from China's diet?

A: We've got a lot of analysis yet to do, but we've seen some interesting results and they all point in the same direction: That a diet made up of at least 80 to 90 percent plant materials may be optimal. Our diet averages only about 30 percent plant materials.

Q: Are you including vegetable oil? That's a plant material.

A: I'm talking about whole plants--the roots, flowers, leaves, stems, and buds. Call them vegetables, fruits, and grains if you like.

Some parts of the plants are high in starch so we get lots of energy. Other parts have the fiber or minerals. And plants also have a whole array of antioxidants--such as vitamins C and E and the carotenoids--so they protect against cancer, heart disease, and other diseases common to the U.S.

Q: Are you recommending a diet that's low in fat?

A: Yes. Fat intake is much lower in China. Fat provides only about 15 percent of the average person's calories--less than half what it is here.

Preliminary analysis indicates that the lower the fat intake within their already low range--6 to 24 percent of calories--the lower the breast cancer rates.

That's exciting because I've always thought that the recommendation to get the fat down to 30 percent of calories is too narrowly focused. It shouldn't focus just on fat, and it doesn't go low enough. We ought to be making major changes in our diet if we're really interested in reducing risk.

Q: Are you encouraged by the recent trend towards eating lower-fat foods, such as fat-free cheese and ice cream and trimmer meats?

A: What we've been doing for the last 10 to 15 years in this country is really cosmetic. I'm not against using low-fat products, because nothing is really lost. On the other hand, I don't think we're accomplishing much. Because we should really be focusing on consuming far fewer foods of animal origin.

Q: Why is that?

A: As we put animal foods into our diet, we increase the caloric density and the intakes of animal protein and saturated fat. And in the process, we decrease the intake of fiber and variety of antioxidant nutrients. Nutritionally, we're doing everything wrong.

Q: What diseases are linked to animal foods in China?

A: As people in urban areas get money, there's a new enthusiasm for meat that's seen in every society in the world. And people who eat more meat have higher blood cholesterol levels and higher blood albumin levels, which is a function of protein intake.

As blood levels of albumin and cholesterol go up, the diseases we tend to get in the West--cancer, heart disease, and diabetes--also start going up. It's quite remarkable.

Q: But aren't some cancers, like liver cancer, more common in China?

A: Yes. In recent years, many people have thought that the major cause of liver cancer is either persistent infection with hepatitis B virus or aflatoxin, a mold that grows on foods such as peanuts, corn, and dried milk. We found no association between aflatoxin and liver cancer in China.

We did find a highly significant association between persistent infection with hepatitis-B and liver cancer, but what was really striking was the association with blood cholesterol.

As cholesterol goes up, so does the risk of liver cancer. And the higher the blood cholesterol level, the more meat and fat, and the less fiber and legumes people consumed.

Q: What does cholesterol have to do with liver cancer?

A: In China, liver cancer is associated with the consumption of animal nutrients--both fat and protein. These human data coincide beautifully with the animal studies done by Linda Youngman in our lab. We can give as much aflatoxin as we like to animals, and whether or not they get tumors depends on how much protein they're fed.

Q: Does it matter if it's plant or animal protein?

A: Yes. In our animal studies on aflatoxin, if we switch from animal to plant protein, we basically turn off the further growth of liver tumors.

Q: How high does blood cholesterol go among the Chinese?

A: Average cholesterol levels at our survey sites in China ranged from about 100 to 200, although other data show much higher levels for Chinese individuals living in urban areas.

But even in the 100-to-200 range, the higher their cholesterol, the greater their risk of heart disease and other diseases common in the U.S.

Q: Was cancer more common at very low blood cholesterol levels?

A: No. Some studies in the U.S. have shown that when cholesterol gets much below 160, we see an increase in colon cancer rates.

In China, the reverse was true. The lower the cholesterol levels, the lower the risk of colon cancer.

Q: Do fruits and vegetables reduce the risk of cancer among the Chinese?

A: One of the analyses shows that people who consume more fruit--and have higher levels of vitamin C in their blood--have a lower risk of cancer of the esophagus. That's one of the few relationships that's been examined so far.

Q: You said a diet rich in plant materials is also rich in carotenoids, which the body can convert to vitamin A. Are you talking about beta-carotene?

A: Beta-carotene has had an enormous amount of publicity, much of which I think is too narrowly focused. Fruits and vegetables contain hundreds of different kinds of carotenoids, and some appear to be better antioxidants than beta-carotene. We shouldn't ignore these other constituents.

Q: Is high blood pressure linked to salty diet in China?

A: We'll know more when we finish a new survey, but it appears that regions where salt intake was high have greater rates of stroke, high blood pressure, and coronary heart disease. Those regions averaged 30 grams of salt a day, and that's the average for a group of 30 people, so it could be quite a bit higher for individuals within that group.

Q: Is fiber linked to cancer in China?

A: We haven't fully analyzed this question. We do know that in China, average fiber intakes for certain counties go as high as 70 grams per day.

This is very exciting, because Americans have been advised to increase their fiber intake from 10 to between 20 and 30 grams a day. But some people worry that fiber may bind minerals, and that if we get much higher than 30 grams, we will compromise our mineral status.

We haven't analyzed the data on all minerals, but we have looked at iron status in adults. If that's any indication, high fiber intakes don't appear to affect mineral status at all.

Q: How do the Chinese get enough iron without eating meat?

A: We hear in the West all the time that heme-iron--which occurs in meat, fish, poultry, and eggs--is important to have because it's better absorbed. Some people use heme-iron to justify the consumption of those animal products.

Iron from plants has always had second-class status. But in China, 90 percent of iron intake is from plant products and we don't see any compromise in iron status in adults.

That's not to say that there aren't some problems in youngsters or pregnant women. We don't have those data yet. But if there are problems in some areas, I would want to rule out the effects of parasites before attributing low iron status to a diet low in heme-iron.

Q: What else do we incorrectly think we must get from animal foods?

A: Some populations in the world are considered low in riboflavin because they don't have enough meat and milk. It's almost a public relations tool for the milk and meat industries.

It turns out that meat is a rather poor source of riboflavin, so that's a bit of a myth. Dairy products are a good source, but if you look at their riboflavin content per calorie, they have only a third of what's in leafy plants.

Q: Are the Chinese low in riboflavin?

A: Researchers have always thought so. There were even a couple of intervention trials in China to see if this B-vitamin could reverse the precursor lesions for esophageal cancer.

Using the Recommended Dietary Allowance of our country, we had to conclude from our survey that about 90 percent of the Chinese were moderately to severely deficient in riboflavin. I just couldn't believe a whole nation was that deficient in riboflavin.

So I took another look at the scientific literature on riboflavin and came to the conclusion that the RDA is too high, probably reflecting our dietary lifestyle more than anything else.

Q: Are our RDAs reliable?

A: The advantage of having the China data is that it will make us go back and re-examine our own data. I'm becoming a cynic about all the detailed information in the Western literature that's used to justify the RDAs and our other nutrition concepts.

Those concepts have all been obtained on Western subjects by Western investigators who bring to the study their own biases and ways of eating.

We often begin with the assumption that what we do is best. Then we hunt for evidence to justify doing things the way we've always done them.

Q: Will children grow as well on a plant-based diet?

A: In this country we want our children to grow as fast as they possibly can. So we give them rich, high-protein, high-calcium diets that build bones and muscle. And they grow fast.

But one of the products of fast growth is earlier sexual maturity, and an earlier age of menarche in girls is a risk factor for breast cancer later in life. So the most rapid rate of growth isn't necessarily the best rate of growth.

Q: Would we end up shorter?

A: Our children would grow more slowly, but I think their ultimate height would be near their genetic potential, because they'd get another growth spurt around 18 to 20 years of age. I've seen that with my five children.

We may not get the professional football players like the Washington Redskins without pushing protein. But their ultimate body size won't be much different...and they'll be healthier for the rest of their lives.

Q: What does your family eat?

A: We have a varied diet, with different casseroles made of vegetables and grains or pasta and occasionally a little meat for flavor. At least one, and usually two, meals each day include a generous fruit or vegetable salad. We drink mostly fruit juices or water, and our desserts have only half or a third of the sugar and fat called for in the recipes.

Q: Are there lessons the Chinese can learn from us?

A: The Chinese do have higher rates of liver, esophageal, cervical, and stomach cancer. But if you take away infant mortality, which is a lot higher in China, their lifespan does not appear to be different than ours.

I would urge them to continue eating mostly plant foods, but to improve the quality and variety of foods. Whereas in our country we ought to eat fewer animal foods. This study offers the Chinese an opportunity to learn from our mistakes.