Does one size fit all?

"If you've ever suspected that not everyone should eat the same thing or do the same exercise, you're right," says the cover of Peter D'Adamo's Eat Right 4 Your Type.

D'Adamo claims that your blood type determines what foods you should eat to avoid obesity, cancer, heart disease, ear infections, learning disabilities, strep throat, infertility, and more. (Example: Type Os should go for ground beef and broccoli but avoid cantaloupe and whole wheat bread).

The book hasn't a shred of evidence to back up its promises. But it's cashing in on an extremely appealing idea: No one wants to be lumped with the masses. Why not tailor diets to the individual?

The dairy, egg, meat, salt, and sugar industries love the one-size-doesn't-fit-all concept. It's being held aloft not just by food industry PR departments, but by three myths about diet and health.

"Eat less fat, especially saturated fat. Eat less cholesterol, sodium, and sugar. Eat more fruits, vegetables, beans, and whole grains."

It doesn't matter if you listen to the American Heart Association, the American Cancer Society, the National Heart, Lung & Blood Institute, the National Cancer Institute, the Surgeon General, or the National Academy of Sciences. For two decades, every health authority has sung virtually the same song.

But recently, a few voices have begun to hum a different tune.

Some are authors of new diet books: "The popular belief that this one diet (low-fat, high-fiber, high-complex-carbohydrate) is the solution to all of our health concerns has turned out to be a myth," writes Louise Gittleman in Your Body Knows Best. "It sells magazines, that's for sure."

Clearly, it no longer sells diet books. That's part of the problem. Publishers can't make a profit on the 63rd book with the same eat-less-fat message. But individualized diets open up a whole new market.

And they're the latest strategy for food industries whose sales are hurt by diet advice to the general public.

When the government revised its Dietary Guidelines for Americans in 1995, the egg, salt, and sugar industries argued (unsuccessfully) that only some people had to put a limit on those foods.

Now the National Dairy Council is leading the charge. "Support is building for the concept that dietary guidelines to decrease chronic disease risk have to consider genetic variability," wrote the Council's Gregory Miller and Susan Groziak in the August issue of the Journal of the American College of Nutrition.

"As with any population-wide guideline, the Dietary Guidelines assume that everyone is at equal disease risk," they added. "However, scientific evidence does not support this 'one size fits all' approach...."

The question is: Why should the Dairy Council care about genetic differences? Could it have anything to do with the fact that fat, saturated fat, and cholesterol are fatal flaws of most cheeses, ice creams, and other fatty dairy foods?

"We've always tried to have sound scientific support for our educational messages about the role of dairy foods in a healthy diet," was Miller's answer.

In September, the American Medical Association held a media briefing called "Nutrition: An Individualized Approach Based on Family History." Who footed the bill? The National Dairy Council.

The food industry doesn't have good science to support its attack on population-wide diet advice. What it has are three widely held. Myths that make its arguments sound good.

Myth #1: It's all in my genes.

"People think that everything is genetic," says David Hunter, an epidemiologist at the Harvard School of Public Health.

"They think that some people are time bombs and others have nothing to worry about, so you shouldn't burden them with lifestyle changes.

"In fact, a relatively small component of cancers is due to powerful genes." The same goes for heart disease. And the impact of less-powerful genes can be influenced by lifestyle. For example:

* Breast cancer. Mutations in two genes called BRCA-1 and BRCA-2 appear to cause breast cancer in women from families where the disease is rampant. Yet "only five to ten percent of breast cancer cases are due to those or other potent mutated genes," says Hunter.

A woman with a mutation in the powerful BRCA-1 gene, for example, has up to an 85 percent chance of getting breast cancer over her lifetime.

Other, less-powerful, genes raise the risk, but not nearly as much.

"In our Nurses' Health Study, a 30-year-old woman with neither a mother nor sister with breast cancer has a seven percent chance of getting the disease by age 70," says Hunter. "A 30-year-old with both a mother and sister with breast cancer has a 17 percent risk."

In other words, for most women, family history isn't as important as many people think. "Roughly 85 percent of the nurses who were diagnosed with breast cancer had neither a mother nor sister with breast cancer," says Hunter.

* Colon cancer. Last August, scientists at Johns Hopkins Medical School in Baltimore found a mutation in a gene that increases the risk of colon cancer in an estimated six percent of Jews of European origin (see "Dodging Colo-Rectal Cancer").

But "of the 130,000 cases of colon cancer diagnosed each year, the majority--50 to 85 percent--have no major genetic component," says Johns Hopkins researcher Steven Laken.

* Heart disease. So far, scientists haven't found genes that explain much of the risk for heart disease.

"We've identified certain genes that indicate that people are both at high-risk and responsive to dietary changes, but their effects are small," says Ron Krauss, who chairs the American Heart Association's Nutrition Committee. Krauss conducts research at the Lawrence Berkeley National Laboratory at the University of California, some of it funded by the National Dairy Council.

So knowing whether you had those genes wouldn't tell you much about your risk of heart disease. What's more, most genes make people susceptible to disease. They rarely cause it.

"Most of us have genes that make us susceptible to adverse effects of saturated fat, cholesterol, sodium, and weight gain," says Jeremiah Stamler, a cardiovascular disease expert and professor emeritus at Northwestern University Medical School in Chicago.

"But those genes do not write our fate," he adds. Whether they raise the risk of disease depends on how much saturated fat, cholesterol, sodium, and weight gain we're exposed to.

What's more, says Krauss, "people have gotten the notion that if you have a family history of heart disease, you won't respond to dietary changes as well as others. The surprise is that you're likely to do better on a cholesterol-lowering diet than people with no family history."

Myth #2:1 don't need to change my diet if I'm healthy.

Why not save diet advice for people who have high cholesterol or high blood pressure or other risk factors for heart attack or stroke?

Because most of us are at risk...and many of us don't know it.

"From age 35 on, most people have blood pressure and blood cholesterol levels that are above-optimal and that increase risk," says Stamler.

"Optimal" is lower than "normal." For blood pressure, optimal means systolic pressure (the higher number) less than 120 and diastolic pressure (the lower number) less than 80. For blood cholesterol, optimal is less than 180, he adds. Only 20 to 25 percent of the population has such low numbers.

What's more, many people who start out with optimal levels move on to "normal," "high-normal," and then "high" as they get older.

"Unless you give dietary recommendations to everyone, you end up with a large number of people drifting into the high-risk group," explains Stephen Havas, an epidemiologist at the University of Maryland Medical School who served on the Expert Panel on Population Strategies for Blood Cholesterol Reduction of the National Heart, Lung and Blood Institute (NHLBI).[1]

"With heart disease, for example, the percentage of people with high cholesterol goes up dramatically as the population ages," he adds. "So does the percentage of people with high blood pressure. But if people follow general dietary guidelines, much of that is preventable and you can reduce the pool of people that go into the high-risk group."

So why not wait until you enter that group and then treat your blood pressure or cholesterol with diet or drugs?

"Treatment is effective in lowering the risk, but a treated patient has twice the risk of heart attack or stroke

of someone who never had high blood pressure," says Paul Whelton of Tulane University in New Orleans, who chaired the NHLBI's Working Group Report on the Primary Prevention of Hypertension.[2]

And only about half the people who take drugs to lower their blood pressure--which are expensive and have side effects--lower it below 140 over 90. That's the border between "high-normal" and "high."

But even those who never approach the high-risk range can benefit.

"The risk is lower for every milligram of cholesterol or every millimeter of blood pressure you get down, even for people in the so-called normal range," says Havas. "So the lower you can get, the better off you are."

The same rules apply to other illnesses. "The higher your weight, the higher your risk of diabetes," he explains. "There is no sudden point above which the risk rises."

Myth #3: If I follow advice for everyone, I'll neglect my needs.

No one would argue that a 60-year-old woman and a 20-year-old man should eat the same number of calories.

Premenopausal women need more iron than men or postmenopausal women. Vitamin D requirements go up with age. Calcium needs go down at age 19 and up again after age 50.

And of course, doctors or dietitians routinely prescribe diets to treat kidney disease, gout, gallbladder disease, and many other illnesses.

But health experts would be in a pickle if they let those or other differences keep them from advising the general public.

"If you argue that every person is different, you'd have no public health recommendations on smoking, vaccinations, or anything else," says Stamler.

"Tens of millions of people are exposed to the polio virus, but only a few get paralytic polio. Does that mean we shouldn't vaccinate the general public?"

The answer, say most experts, is general diet advice to reduce the risk of heart disease, cancer, and other big killers in everyone, and, if possible, a second set of guidelines for people at high risk (See "Diet by the Numbers").

"The American Heart Association promotes population guidelines that apply to everyone," says Krauss. "Then we recommend more-restrictive diets for people at high risk."

For example, the NHLBI recommends that everyone aged two or older get less than ten percent of their calories from saturated fat and less than 300 mg of cholesterol per day to prevent heart disease and stroke.

But if that doesn't lower LDL cholesterol sufficiently, it recommends cutting saturated fat to less than seven percent of calories. Likewise, if limiting cholesterol to 300 mg a day doesn't lower LDL enough, people should drop down to 200 mg a day.[3]

When it comes to cancer, it's much tougher to tailor diets to the individual. Still, knowing one's family history or other risk factors might make a difference (see "Risky Business").

Says Harvard's Hunter: "People with a bad family history may want to take the overall recommendations more seriously."

[1] Circulation 83: 2154, 1991.

[2] Arch. Intern. Med. 153: 186, 1993.

[3] J. Amer. Med. Assoc. 269: 3015, 1993.

RELATED ARTICLE: FOOD & FITNESS

No matter what your risk of disease, you'll be healthier if you:

* Eat Jess saturated fat (red meat, cheese, whole milk, ice cream, butter, pies, etc.).

* Eat less trans fat (stick margarine, shortening, fried chicken and fish, french fries, cakes, pies, doughnuts, and biscuits).

* Eat less cholesterol (limit egg yolks to no more than four per week and meat, fish, and poultry to no more than six ounces a day).

* Eat less sodium (canned & dried soups, fast food, frozen dinners, pizza, processed meats and cheeses).

* Eat eight to ten servings of fruit, vegetables, and beans a day.

* Eat more whole-grain breads and cereals.

* Eat more low-fat or fat-free milk, yogurt, and cheese (two or three servings a day).

* Limit high-sugar foods (soft drinks, fruit drinks, cakes, cookies, candy, sweetened cereals, etc.).

* If you drink, limit alcohol to two drinks a day (for men) and one drink a day (for women).

* Exercise at least 30 minutes on most days (brisk walking, running, aerobics, etc.).

RELATED ARTICLE: DIET BY THE NUMBERS

When it comes to heart disease, many people know their numbers-their total cholesterol, LDL ("bad") cholesterol, HDL ("good") cholesterol, triglycerides (which are bad), and blood pressure. And some of those people prefer their diet advice in numbers (rather than foods). So here are our numbers for the general public and for those at high risk. Some go beyond the advice of the National Heart, Lung and Blood Institute and the American Heart Association.

Fat. Eat a lower-fat diet (20 to 25 percent of calories from fat). If you have low HDL and high triglycerides, don't go on a very-low-fat diet (15 percent of calories or less from fat). If you're overweight, losing weight--even as little as ten pounds--is the most effective way to raise HDL and lower triglycerides. If you're a smoker, quit. If you don't exercise, start.

Saturated Fat. Eat a low-saturated-fat diet (seven or eight percent of calories). If you have high LDL, cut sat fat further (to five or six percent of calories).

Cholesterol. Get less than 300 mg a day. If you have high LDL, drop to 200 mg a day.

Sodium. Get less than 2,400 mg a day...even less if you have high blood pressure.

RELATED ARTICLE: DODGING COLO-RECTAL CANCER

Cancer of the colon or rectum kills more Americans than any cancer but lung. Some researchers believe it doesn't have to.

Eating less saturated fat and red meat and more fruits, vegetables, whole grains, and beans may prevent some of those deaths.

And if people at high risk got colonoscopies more often, they might catch the precursors before they turn into cancer.

Who's at high risk? Researchers don't have definite numbers. But the risk is about double for people with a parent, child, or sibling who has colon cancer or adenomatous polyps, which can become cancerous.

And, according to Johns Hopkins's Steven Laken, people of Eastern European Jewish ancestry also have a higher risk.

One out of six has a mutation in the APC gene, which makes the DNA in their colons more susceptible to damage by carcinogens.(1) (The mutation is rare in non-Jews.) But, adds Laken, if people get colonoscopies and other tests, "the risk is practically zero." (See "Risky Business".)

A colonoscopy is an examination of the entire colon using a flexible probe. "With colonoscopies, we can remove any precancerous polyps," says Laken. Experts estimate that it takes an average of ten years for a polyp to become malignant.

Johns Hopkins recommends a baseline colonoscopy at age 50 and one every ten years after that for most people. If you test positive for the gene, it recommends a baseline at age 35 and one every two years after.

Anyone can get a blood test for the gene, but Johns Hopkins recommends it only for Jews with a family history of colon cancer. Any physician can draw the blood and send it to Johns Hopkins, but you need to consult with a physician or genetic counselor before and after getting the test. Call [phone] for more information.

(1) Nature Genetics 17: 79, 1997.

RELATED ARTICLE: Risky Business

Here are seven of the top killers in the U.S. and advice on how to avoid them ("What Everyone Should Do"). That advice applies to most people, but knowing that you have one of the major risk factors for a disease ("What Raises Your Risk") may motivate you to follow the advice more rigorously. Obviously, your doctor may tailor these general guidelines to you.

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