Clarifying Common Nutrition Terms

June 16, 2006 01:00 PM

By Charles Stuart Platkin

We see and hear these nutrition catchphrases all the time, yet we rarely know exactly what they mean. Here are the definitions of a few common terms that can guide you on the highway to health.

Daily Values (DVs): You can find the DVs on the Nutrition Facts panel of a food label. They are intended to be a quick reference for the consumer to determine how much of a particular nutrient is included relative to what the Food and Drug Administration has determined to be the average needs of the "typical" consumer -- although this can vary depending on an individual's weight and gender.

"The term [daily values] is used by the FDA to help calculate the amount of a particular nutrient contained in a single serving size as compared with the recommended daily intake of that nutrient," explains Teresa Moore, Ph.D., R.D., L.D.N., a professor of exercise science at the University of South Carolina. "A food that has a Daily Value of 10 percent for fat per serving provides 10 percent of the daily requirement of fat for that day." So, for example, if the recommended daily intake of sodium is 2,400 milligrams, and a serving of cereal provides 240 milligrams of sodium, the cereal's DV for sodium would be 10 percent.

There are 10 food components whose daily values must appear on food labels. In addition to those, 22 other food components are optional.

Essential Nutrients: These are substances that must be obtained in the diet because the body either cannot make them or cannot make adequate amounts of them. "It refers to both vitamins and minerals, along with amino acids and certain fats that must be consumed in the diet to support normal metabolism and maintain health. These nutrients are 'essential' because unless they are regularly provided from foods, the body is vulnerable to a deficiency syndrome," says David L. Katz, M.D. associate professor of public health and director of the Prevention Research Center at Yale University School of Medicine and author of The Flavor Point Diet (Rodale, 2005).

If you've heard this term before, it was probably in regard to omega-3 fatty acids, the compounds found in certain fish and nuts that provide necessary nutrients. There is some ambiguity about the best way to introduce these essential nutrients into the body. In the case of omega-3s, eating fish provides you with the compound in the form your body needs, whereas omega-3s in walnuts require your body to convert them into a usable form. Nutrients work synergistically, so it is still unclear whether taking supplements -- a pared down, basic form of a given substance -- is as effective as consuming essential nutrients through a diet of naturally nutrient-rich foods.

Essential Minerals: Minerals are "inorganic" substances. That doesn't mean they aren't natural, just that they have been mined from the earth and do not come from any plant or animal. In fact, there are 92 naturally occurring elements, of which about 15 or so have proved to be essential to human health. Those include: calcium, chromium, chlorine, copper, fluorine, iodine, iron, magnesium, manganese, molybdenum, phosphorus, potassium, selenium, sodium and zinc. They help in the production and maintenance of bones, teeth, hair, blood, nerves, skin, enzymes and hormones. They are critical in maintaining the healthy functioning of the nervous system, blood circulation and energy production. The body doesn't produce these minerals, but they are found in most of the foods we normally eat, such as fruits, vegetables, meats, nuts, beans and dairy products.

Bioavailability: The bioavailability of a nutrient in a certain food is the amount of that nutrient our bodies are capable of absorbing. In other words, it's how much of a nutrient you actually receive. "Nutrients can be bound by proteins or can interfere with each other, so the level ingested and the level available can be quite different," says Katz. For example, if you take a calcium supplement such as calcium carbonate, you will only absorb 40 percent, explains Fran Grossman, M.S., R.D., a nutritionist at Mount Sinai Medical Center in New York City.

Oftentimes the amount available is much less than the amount of nutrient in the food itself, which means learning about the bioavailability of foods in your diet is necessary for calculating not only how many vitamins you're putting into your body but also how much of those vitamins and minerals your body is taking out of the food.

To illustrate the importance of bioavailability, consider the calcium in a half-cup of cooked spinach (120 mg) and a half-cup of milk (150 mg). It seems as though eating spinach should provide you with just slightly less calcium than milk. But it doesn't even come close. While our bodies absorb 32 percent of the calcium in milk (or 48 mg), only 5 percent of the calcium in spinach is absorbed (6 mg). Bioavailability also varies by individuals. For instance, someone who is iron-deficient will absorb more iron from food than someone who has adequate iron stores.

Metabolic Syndrome (a.k.a. Syndrome X): This syndrome describes a combination of risk factors for heart disease, stroke and type 2 diabetes, including abdominal obesity, blood fat disorders that cause plaque buildup in the artery walls, high blood pressure and insulin resistance, which refers to the body's inability to properly process sugar. Other conditions associated with the syndrome include physical inactivity, aging, hormonal imbalance and genetic predisposition. "Generally, these risk factors can be reversed by adopting healthy eating and exercise habits," says Joanne R. Lupton, Ph.D., a professor of nutrition at Texas A&M University.

Having at least three of the following measurements means that an individual has metabolic syndrome and is at increased risk for developing type 2 diabetes, coronary heart disease, heart attack or stroke.

* Abdominal or waist circumference:

* Men: greater than 40 inches
* Women: greater than 35 inches

* Triglycerides ( type of fat in blood stream) greater than 150 mg/dl

* HDL cholesterol (high-density lipoprotein or "good" cholesterol):

* Men: less than 40 mg/dl
* Women: less than 50 mg/dl

* High blood pressure (hypertension) over 130/85

* Hyperglycemia (fasting blood sugar ) over 110 mg/dl

According to the National Heart, Lung, and Blood Institute (NHLBI) and the American Heart Association, metabolic syndrome affects more than 26 percent of adults, or more than 50 million Americans.

CHARLES STUART PLATKIN is a nutrition and public health advocate, author of the best seller Breaking the Pattern (Plume, 2005), Lighten Up (Penguin USA/Razorbill, 2006) and Count Down (Simon and Schuster, January 2007) and founder of Integrated Wellness Solutions.