They may know these components are needed for "strong bones" and a "healthy immune system" or that they may "protect against cancer," but that doesn't necessarily help when it's time to select the best bottle from the rows of them available at the neighborhood drug store.
Research and hype about vitamins and herbal remedies has brought more products to the market. Now, in addition to single vitamins, multivitamins and formulas specialized for seniors, women, men and children, there are supplements labeled "active formula" and those laced with herbal remedies such as ginseng, ginkgo and saw palmetto.
Consumers are bombarded with news of the latest studies that tout the benefits of everything from vitamin A to zinc, making it difficult for people to keep the facts straight.
Vitamins are big business. Three out of every five American consumers take dietary supplements regularly, according to the Dietary Supplement Information Bureau. And vitamins, the best- selling of these, account for almost $6 billion in sales annually.
An estimated 59 percent of these consumers take multivitamins. But the products may not deliver what they promise, according to recent testing of multivitamins by ConsumerLabs.com, which provides independent test results to help evaluate health and nutrition products. After a product review is completed, the company posts names of the brands that passes their tests on its Web site, which is accessed through a subscription.
"We found that about 40 percent of multiples weren't up to snuff," said Dr. Tod Cooperman, president of ConsumerLabs.com.
The company tested 27 multivitamins. Only 14 achieved the lab's approved quality status.
There were problems with the supplements that included less than the claimed amount of ingredients, inability to disintegrate (which means they may not be absorbed by the body) and some ingredients exceeding the upper limit, or UL, which is the most that should be taken.
There is no agency responsible for routinely testing dietary supplements for their contents or quality, according to ConsumerLabs.com. So the responsibility for choosing the best vitamin falls to the consumer. But there are some considerations to keep in mind.
"The first step is to determine if you really need it at all, " Dr. Cooperman said.
A person's need for vitamins and minerals varies according to age, gender and conditions such as pregnancy or menopause.
In general, vitamin and mineral supplements are recommended for people age 65 or older, for postmenopausal woman (because it can be difficult to obtain the recommended amounts of calcium and vitamin D) and those who are pregnant or are trying to become so, according to Mayo Clinic Health Information.
You should consider a dietary supplement if you require a special diet or have an illness that affects the way your body absorbs nutrients, such as disease of the liver or intestine, or if you've had surgery on your digestive tract.
Vitamins are recommended if you smoke cigarettes, drink excessively or don't eat well.
Not eating right is probably why most Americans reach for a multivitamin. After all, they've been reminded, repeatedly, that they're not getting the recommended five servings a day of fruits and vegetables those foods most rich with the essential nutrients.
"Absorption from real food is always better," said Dr. Melody Kyzer, nutritionist and assistant professor in health education at the University of North Carolina at Wilmington. "And there are healthy things in real food that they just can't replicate in a vitamin."
But because of unhealthy eating habits, some in the health community began pushing the idea of a daily multivitamin in the 1970s, said Dr. Jose Antonio, who works in sports and nutrition and is co-author of Sports Supplement Encyclopedia.
"Most Americans eat poorly, if they take a multivitamin, at least they can say they're getting the daily recommended amounts," he said.
Dr. Kyzer refers to taking a multivitamin as "dietary insurance" - a way to make up for those days when you don't eat as you should. But, she said, people shouldn't rely only on vitamins to get their nutrients.
Manufacturers want people to choose their particular version of the vitamin. And the labeling information is designed to persuade consumers that the bottle they're holding in their hand is the best choice.
To know if this is really the case, it helps to be familiar with vitamin lingo and understand what Recommended Daily Allowances are and how they are explained on labels.
RDAs are the average amount of each vitamin and mineral needed each day to meet the needs of most people. They're determined by the Food and Nutrition Board of the Institute of Medicine, part of the National Academy of Sciences. There are different allowances, if necessary, to account for differences in sex, age and physical condition.
Generally, labels include the amount of the RDA that one serving supplies for a healthy adult. This amount is listed as the percent of the Daily Value, or percent DV. For example, a label may read that one pill provided 60 percent of the DV, which means another 40 percent is needed through diet to meet the recommended goal.
In 2001, the Institute of Medicine updated the national guidelines on how much of every vitamin and mineral Americans should consume. For the first time, the IOM also compiled a list of the upper limits for some nutrients.
The Food and Drug Administration, which sets the rules for labeling on vitamins, however, has not announced when, or if, it will require vitamin manufacturers to base their labeling on these latest findings. The FDA also does not require labels to list the safe upper doses.
Today's food labels are based on RDAs set in 1968.
The industry is reluctant to change to using RDAs because they'd no longer be able to include the "100 percent" on the label that consumers look for, he said. They also are reluctant because some have too much in them.
The FDA also bases DVs on a 2,000-calorie-a-day diet. Many women and older adults may need only about 1,600 calories a day. And active women and most men need more calories than the average diet. Your DVs for various nutrients generally rise or fall accordingly, according to the Mayo Clinic.
All of this can be a problem when it comes to overdosing on vitamins and minerals.
"There are cases when it's too much of a good thing," Dr. Cooperman said. "They are not benign. Not a lot of people know that there can be side effects."
This is where the UL, or the upper tolerable limit, is a concern. For example, high levels of niacin, one of the B vitamins, can cause flushing of the skin and a tingling or burning sensation, according to ConsumerLabs. These problems aren't life threatening, but some of the multis the lab tested exceeded the UL for the vitamin.
Consumers need to consider not only what is taken into the body through supplements but also through the diet.
Some people also take what's called megadoses of certain vitamins, purposely exceeding the UL, Dr. Antonio said. For example, there's some research that shows that larger doses of vitamin C can help the body recover from exercise.
Some megadoses can cause serious problems. And a person may be getting a megadose without realizing it. For example, the IOM recommends a person consume no more than 3,000 micrograms of vitamin A, an amount routinely included in multivitamins. Higher levels can cause liver disease and, in pregnant women, birth defects. If a person takes that vitamin and consumes a diet high in vitamin A, he or she may be getting too much. The RDA for vitamin A is 900 micrograms for men and 700 micrograms for women.
There always seems to be new information about vitamins and minerals. Experts say it's probably best to look at studies more critically. For example, while many people take vitamin E supplements, there's been some research that shows it may not make a significant difference in well-being.
What to do
So how do you know what's right for you? It's best to consider your individual need and get advice from your doctor if necessary.
Some general guidelines are to be wary of catch phrases and special formulas, especially for multivitamins, according the Nutrition Action Newsletter.
There are more than 40 essential vitamins and minerals; make sure the multi includes a wide variety of these nutrients. Many don't include enough minerals. These trace elements that include magnesium, phosphorus, sodium and potassium can be difficult to get through diet. In fact, the newsletter recommends taking calcium and selenium supplements separately.
It also doesn't hurt to brush up on the way these nutrients work in the body and with each other. Some vitamins are needed together to be effective, such as vitamin D, which is necessary for the absorption of calcium. Others interfere with medication. Vitamin K, for example, shouldn't be taken with some blood thinning prescriptions.
You can access some of this information online at www.mayoclinic.com. You also can subscribe to ConsumerLab.com. Cost is $16 a year for the access to the entire site or $5.25 for a single product review. The company publishes results of its tests online at www.consumerlab.com, including listings of brands that have passed testing. Or try www.usp.org. It's the home page for U.S. Pharmacopeia, a group that has established standards for vitamins, minerals and botanicals.
How to read multivitamin labels
Vitamin labels list how much aof a nutrient is in a serving, usually one pill, and what percentage of the Recom-mended Daily Allowance is in that serving.
Nutrient amounts are in mcg = micrograms, mg = milligrams or IU = international units.
The percentage of the RDA provided is listed as % Daily Value or % DV.
Example: Vitamin A - 450 mcg - DV 50 % means you are getting about half the recommended RDA.
Think that tells you everything you need to know?
Studies are still being done on many nutrients to determine what, if any, upper limits should be recommended.
How many vitamins should I take?
Here are the Institute of Medicine's RDAs for healthy adult men and women, with upper limits noted for those deemed harmful at high doses.
A (Beta Carotene and Acetate) - 900 mcg men, 700 mcg women (not tro exceed 3,000 mcg)
B-1 (Thiamin) - 1.2 mg men, 1.1 mg women
B-2 (Riboflavin) - 1.3 mg men, 1.1 mg women
B-6 1.3 mg (not to exceed 100mg)
B-9 (Folic Acid) - 400 mcg (not to exceed 1,000 mcg)
B-12 (Cobalamin) - 2.4 mcg
BIOTIN - 30 mcg
C - 90 mg men, 75 mg women, 35 more mcg smokers (not to exceed 2,000)
D - 5 mcg (not to exceed 50 mcg)
E - 15 mg (not to exceed 1,000)
K - 120 mcg men, 90 mcg women
NIACIN - 16 mg men, 14 mg women (not to exceed35 mg)
PANTOTHENIC ACID - 5 mg
CHOLINE - 500 mg men, 425 mg women (not to exceed 3,500 mg)
CALCIUM - 1,000 mg (not to exceed 2,500 mg)
PHOSPHORUS - 700 mg (not to exceed 4,000 mg)
MAGNESIUM - 400 mg men, 320 mg women (not to exceed 350 mg from supplements)
CHROMIUM - 35 mcg men, 25 mcg women
COPPER - 900 mcg (not to exceed 10,000 mcg),
FLUORIDE - 4 mg men, 3 mg women (not to exceed 10 mg)
IODINE - 150 mcg (not exceed 1,100 mcg)
IRON - 8 mg men, 18 mg women (not to exceed 45 mg),
MANGANESE - 2.3 mg men, 1.8 mg women (not to exceed 11 mg)
MOLYBDENUM - 45 mcg (not to exceed 2,000 mcg)
SELENIUM - 55 mcg (not to exceed 400 mcg)
ZINC - 11 mg men; 8mg women (not to exceed 40 mg),
* Source: RDAs are based on the latest reports, including new upper limits, released in 2001 from the Institute of Medicine, a private science organization that sets the nation's RDAs for nutrients. Some of these RDAs are not yet reflected in U.S. Food and Drug Administration labeling standards.Get the latest wellness, nutrition and fitness information in our Health Club section
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