A century ago, our forebears were happy to eat eggs and bacon for breakfast and a big meal of steak or fried chicken for dinner. They worked hard, they liked the taste, and they didn't worry about high-fat food.
Then, in the middle of the 20th century, the cholesterol theory of heart disease was developed. Scientists found they could force rabbits to develop plaque in their arteries by feeding them butter and cheese. Fat was vilified, and most physicians forbade eggs.
Eating eggs, in fact, became tantamount to a sin. Needless to say, eating butter or steak was even worse.
The late Robert Atkins was ostracized when he challenged the low-fat orthodoxy. Cardiologists condemned his high-protein weight-loss diet, which included bacon and steak. Studies that showed the Atkins approach did not raise cholesterol were ignored.
Nutrition experts were convinced that if people stuck to a low-fat, high-vegetable diet, they would be much healthier. But that theory has taken a beating lately.
Most of what we know about diet and health has come from observational studies: ask people what they eat and see what happens to them. This is the way we learned that eating fish can reduce the risk of fatal heart attacks and that a diet rich in vegetables and fruit seems to lower the risk of many kinds of cancer.
At the end of the 20th century, scientists decided to test these ideas in a giant experiment. More than 48,000 women over 50 years old were recruited into a dietary intervention trial.
Some (40 percent) of the women were instructed to reduce the amount of fat in their diet, replacing it with extra vegetables, fruits and grains. The training took place in groups and one-on-one, and the women made dietary changes. The other 60 percent of the women were not asked to change the way they ate.
After approximately eight years of follow-up and massive number crunching, the news is in, and it's disappointing. The researchers had expected that women who adopted the more virtuous low-fat, high-veggie diet would be protected from heart attacks, strokes, breast cancer and colorectal cancer. But despite the large number of women participating, the results were not significant.
For cardiovascular disease, the investigators found a trend favoring survival in women who ate the least saturated fat and trans fatty acids (and the most vegetables). But a trend is hardly the kind of solid evidence policymakers need before they recommend major changes in a country's diet.
For breast cancer, too, there were not significant differences between the women following a low-fat diet and those continuing on their regular regimen. A trend favored the low-fat lifestyle, but the scientists were left scratching their heads about why the results were not more definitive.
No one is suggesting that a high-calorie, high-fat diet of eggs and bacon, burgers and shakes, steak and fries is good for health. But the dietary changes that seemed so obviously beneficial in the early 1990s can no longer be treated as gospel.
Dietary recommendations have too often been based on dogma rather than on data. If the facts don't fit our preconceived notions, perhaps we need to re-examine our faith in the low-fat approach.
Joe Graedon is a pharmacologist. Teresa Graedon holds a doctorate in medical anthropology and is a nutrition expert. Their syndicated radio show can be heard on public radio. In their column, Joe and Teresa Graedon answer letters from readers. Write to them in care of this newspaper or e-mail them via their Web site: www.PeoplesPharmacy.com.