People often tell us that figuring out how to eat a healthful diet has become very confusing. Worldwide, different cultures have evolved a wide variety of different styles of eating that support good health. The one thing that all of these various eating styles have in common is that they all include an adequate variety of different types of foods that, together, meet the body’s needs for all essential nutrients.

Question: Why are we so confused now?

Answer: Nutrition scientists now know more than ever about what is necessary for the human body to function normally and healthfully. This all starts with meeting the body’s needs for more than 40 essential nutrients: minerals, vitamins, water, protein components, fats and carbohydrate. Meeting these needs is "step one." If just one essential nutrient is in short supply, then eating lots of "healthy" foods will not support good health in the long run.

Because a nutrient deficiency can take considerable time before a negative impact on the body is identified, it is difficult for someone to make the connection between a slowly developing health problem and an inadequate diet.

Q: Why don’t current healthy-eating recommendations work for everyone?

A: It is too easy to overlook "step one" (meeting essential nutrient needs). It is human nature to focus on solving the easy dietary problems such as increasing fruits and vegetables in the diet since many people don’t eat enough of these foods. But fruits and vegetables don’t provide all of the essential nutrients in adequate amounts, especially protein. Other types of foods are needed to achieve a healthful diet.

To complicate things more, the mixture of foods that meets the nutrient needs of one person does not work for everyone else. Humans come in very different body sizes and have widely differing amounts and levels of physical activity. These things make a big difference not only in calorie needs, but also in the amounts of protein, carbohydrate and fat that make sense and will support a healthy body.

For example, it is recommended that a lightly active 110-pound person consume about 50 grams of protein per day, 50 grams of fat and about 340 grams of carbohydrate for a total of about 2,000 calories per day. A sedentary 220-pound person who is attempting to lose weight needs about 150 grams of protein per day, about 50 grams of fat and 240 grams of carbohydrate to provide about 2,000 calories. This would provide the 220-pound person with about a 500-calorie deficit to promote the loss of about 1 pound of fat per week along with the protein amount known to minimize muscle loss.

So, overall, the larger person in this example needs about 100 grams more protein and 100 grams less carbohydrate than the smaller person. If the larger person just ate like the smaller person, they would lose lean muscle mass, along with some fat loss, but this would lower their calorie requirements and seriously sabotage their efforts to lose fat in the long run.

The take-home messages are:

» Understand that essential nutrients are absolutely essential.

» Long-term health requires enough, but not too much, of each essential nutrient.

» An eating style that works for one person can be completely wrong for someone else.

Alan Titchenal, Ph.D., C.N.S., and Joannie Dobbs, Ph.D., C.N.S., are nutritionists in the Department of Human Nutrition, Food and Animal Sciences, College of Tropical Agriculture and Human Resources, University of Hawaii-Manoa. Dobbs also works with University Health Services.