Taking supplements while on a crash diet may give you vitamins and minerals, but not the proteins, fats and carbohydrates that muscles need to keep working, warns the California Dietetic Assn.
According to a recent study at the University of Toronto, after just two weeks of severely restricted calorie levels--400 calories a day, supplemented with vitamins and minerals--microscopic signs of atrophy set in as muscles prepared themselves for famine.
"We can consume all the vitamin and mineral supplements in the world, but without adequate calorie intake a person could starve to death," said registered dietitian Cheryl Loggins, CDA president.
In fact, Loggins said, a 400-calorie diet is not safe by any standards.
According to CDA, a body needs protein, dietary fat and carbohydrates as well as the 13 major vitamins and minerals plus trace elements to function properly. If an adequate balance of these nutrients is not consumed, even with a daily calorie level of at least 1,200 calories the result will be weak muscles and fatigue.
"Eating low-calorie foods from the nutrient-based food groups--milk, meat, vegetables and fruits, breads and cereals--provides all the nutrients necessary to a healthy, active life style without the need for vitamin or mineral supplements," Loggins said.
The average healthy adult needs two daily servings each from the milk and meat groups and four daily servings from the vegetables/fruits and breads/cereals groups for optimum nutrition.
A sample day's menu, providing about 1,380 calories, might start off with sliced strawberries mixed in a cup of low-fat yogurt with a whole-wheat English muffin and 2 teaspoons of butter, totaling 400 calories.
Lunch might consist of a whole-wheat roll with 2 ounces of lean roast beef and 1 1/2 ounces of Swiss cheese with a teaspoon of mayonnaise and a sliced apple--560 calories.
Dinner could be a stir-fry chicken dish with celery, broccoli and carrots and 1/2 cup steamed rice--about 420 calories.
"This menu provides all recommended servings from the nutrient-based groups while keeping calorie levels low," she said.