Weight Loss

Hundreds of scientists are looking to gene therapy to help cure intractable diseases, including the following:

•   Cystic fibrosis. The most common deadly inherited disease among Americans, cystic fibrosis affects those who lack a gene to make the chemical that causes salt to move beneficially in and out of the cells. As a result, phlegm clogs the lungs of victims, drowning them. They often die in their teens.

At the National Institutes of Health in Bethesda, Dr. Ronald Crystal gave gene therapy to four cystic fibrosis patients in their 20s. To solve the salt problem, he used a common cold virus to carry the missing gene into their lung cells. Their condition is stable, but it’s too early to tell, said Dr. Crystal, who now heads the Division of Pulmonary and Critical Care Medicine at New York Hospital. Still, he says, “This has the potential to cure cystic fibrosis.”

•   Familial hypercholesterolemia. This rare disease affects people who lack a gene enabling the liver to regulate and store cholesterol. As a result, cholesterol piles up, sticking to the walls of blood vessels, clogging or narrowing them, and impeding blood flow. Patients often die of heart attacks before their teens. Dr. James Wilson, director of the Institute for Gene Therapy at the University of Pennsylvania in Philadelphia, grew the liver cells of three such patients in lab dishes and sprinkled the cells with a virus spliced with the missing gene. He then injected the patients with their altered liver cells. His first subject was a woman of 26 who’d had her first heart attack at age 16. “She has had no problems since the procedure,” says Dr. Wilson. “She is not totally cured but is significantly improved.”

Questions have been raised. For example, if scientists found genes for intelligence and used gene therapy on early embryos to produce more intelligent children, would it be moral? “The ‘designer child’ is way down the road,” said Arthur Caplan, director of the Center for Biomedical Ethics at the University of Minnesota. “But, in 50 years, I’d be shocked if we weren’t in debate about designing our descendants.”

There may be more questions than answers now, but scientists know gene therapy is giving them a handle on something earthshaking. They are not about to let it go.

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Need for calculated diet

A number of conditions require control of the quantities of one or more constituents of the diet; for example, obesity, diabetes mellitus, hyperlipidemias, and others. A daily calculation for the specific foods of the menu would be extremely time consuming and impractical. As a matter of fact, even the detailed calculation would give only an approximate value for the actual intake because no two samples of the same kind of food are completely identical in their composition. Furthermore, people vary considerably in their metabolism from day to day.

Exchange lists

There is a practical, rapid method for planning diets by using average values for groups of foods. The Exchange Lists for Meal Planning, revised 1976 were prepared by a joint committee of The American Dietetic Association, The American Diabetes Association, and the National Institutes of Health.

An exchange list is a grouping of foods in which the carbohydrate, protein, and fat values are about equal for the items listed. The six exchange lists include:

List 1. Nonfat milk is the basis for the milk exchanges. If low-fat or whole milk is used, the adjustment is made by (1) using the fat value stated in the table for the calculation of the diet, or (2) subtracting the designated fat exchanges from the day’s total for fat.

List 2. All vegetables except starchy vegetables are included here. Starchy vegetables appear on List 4, Bread Exchanges.

List 3. Fruit exchanges are based on the amounts of fruits or fruit juice that will supply 10 gm carbohydrate. Thus, one may choose for an exchange 1 small apple, or 1/2 small banana, or 1/2 cup orange juice, or 2 prunes, etc.

List 4. Bread exchanges include breads, rolls; dry and cooked cereals; starchy vegetables; and some prepared foods. When prepared foods are used, fat exchanges as specified must be subtracted from the day’s total. For example, if 2 pancakes are used for 2 bread exchanges, the day’s fat allowance would be reduced by 2 exchanges.

List 5. Lean meat is the basis for the meat exchanges. When medium-fat or high-fat meats are used the adjustment is made by (1) calculating for the values of these meats in the development of the diet plan, or (2) subtracting the designated fat exchanges from the day’s total for fat. The meat list also includes dried peas and beans and peanut butter.

List 6. Fats high in polyunsaturated fat are listed separately from those high in saturated fat.

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