Chapter 3
How Much Nutrition Do You Need?
IN THIS CHAPTER
A healthful diet provides sufficient amounts of all the nutrients that your body needs. The question is, how much is enough?
Today, three sets of recommendations provide the answers, and each one comes with its own virtues and deficiencies. The first, and most familiar, is the RDA (short for Recommended Dietary Allowance). The second, originally known as the Estimated Safe and Adequate Daily Dietary Intakes (ESADDI), now shortened to Adequate Intake or simply AI, describes recommended amounts of nutrients for which no RDAs exist. The third is the DRI (Dietary Reference Intake), an umbrella term that includes RDAs plus several innovative categories of nutrient recommendations: EAR (Estimated Average Requirement), AI (Adequate Intake), and UL (Tolerable Upper Intake Level).
Confused? Not to worry. This chapter spells it all out.
RDAs: Guidelines for Good Nutrition
The Recommended Dietary Allowances (RDAs) were created in 1941 by the Food and Nutrition Board, a subsidiary of the National Research Council, which is part of the National Academy of Sciences in Washington, D.C., in order to investigate issues of nutrition that might “affect national defense.” The committee was renamed the Food and Nutrition Board in 1941, after which they began to deliberate on a set of recommendations of a standard daily allowance for each type of nutrient. The standards would be used for nutrition recommendations for the armed forces, for civilians, and for overseas populations who might need food relief.
RDAs originally were designed to make planning several days’ meals in advance easy for you. The D in RDA stands for dietary, not daily, because the RDAs are an average. You may get more of a nutrient one day and less the next, but the idea is to hit an average over several days.
For example, the current RDA for vitamin C is 75 milligrams for a woman and 90 milligrams for a man (age 18 and older). One 8-ounce glass of fresh orange juice has 120 milligrams of vitamin C, so a woman can have an 8-ounce glass of orange juice on Monday and Tuesday, skip Wednesday, and still meet the RDA for the three days. A man may have to toss in something else — maybe a stalk of broccoli — to be able to do the same thing. No big deal.
The amounts recommended by the RDAs provide a margin of safety for healthy people, but they’re not therapeutic. In other words, RDA servings won’t cure a nutrient deficiency, but they can prevent one from occurring.
Proteins, vitamins, and minerals: The essentials
RDAs offer recommendations for protein and 18 essential vitamins and minerals. For the specific amounts, check out Chapter 6 (protein), Chapter 10 (vitamins), and Chapter 11 (minerals).
Recommendations for carbohydrates, fats, dietary fiber, and alcohol
What nutrients are missing from the RDA list of essentials? Carbohydrates, fiber, fat, and alcohol. The reason is simple: If your diet provides enough protein, vitamins, and minerals, it’s almost certain to provide enough carbohydrates and probably more than enough fat. Although no specific RDAs exist for carbohydrates and fat, guidelines definitely exist for them and for dietary fiber and alcohol.
In 1980, the U.S. Public Health Service and the U.S. Department of Agriculture joined forces to produce the first edition of Dietary Guidelines for Americans (see Chapter 16). A new edition of the Dietary Guidelines has been issued every five years since then to set parameters for what you can consider reasonable amounts of calories, carbohydrates, dietary fiber, fats, protein, and alcohol. According to these guidelines, several general rules advise you to
Balance your calorie intake with energy output in the form of regular exercise. Check out Chapter 5 for specifics on how many calories a person of your weight, height, and level of activity (couch potato? marathon runner?) needs to consume each day.
Make foods with complex carbohydrates and dietary fiber (defined in Chapter 8) the base of your total daily calories. These should make up to 900 to 1,300 calories and up to 25 grams dietary fiber on a 2,000 calorie per day diet.
Concentrate on unsaturated fats. For more specific guidelines, check out Chapters 16 and 17 and Chapter 7 for everything you need to know about the individual dietary fats.
Drink alcohol only in moderation. That means one drink a day for a woman and two for a man. As the Guidelines note, neither is a component of the USDA Dietary Patterns.
Different people, different needs
Because different bodies require different amounts of nutrients, RDAs currently address as many as 22 specific categories of human beings: boys and girls, men and women, from infancy through middle age. In 2006, the RDAs were expanded to include recommendations for groups of people age 50 to 70 and 71 and older.
If age is important, so is gender. For example, because women of child-bearing age lose iron when they menstruate, their RDA for iron is higher than the RDA for men. On the other hand, because men who are sexually active lose zinc through their ejaculations, the zinc RDA for men is higher than the zinc RDA for women.
SEVEN RULES FOR LADIES-IN-WAITING
The 2020 edition of the Dietary Guidelines for Americans is the first
