Like HowStuffWorks on Facebook!

How Nutrition Works


The Basics of Supplements
©2006 Publications International, Ltd. Supplements are meant to augment good nutrition -- not replace it.

Nutritionists like to insist on "food first," but that isn't necessarily the end of the story. Sometimes supplements -- nutrients in pill or liquid form -- are needed to round out a balanced diet. With smart supplementation, you may be able to make a good diet better or at least provide a measure of insurance against a deficit. But getting nutrients from food is always the best way to balance eating.

Supplements, by definition, are there to supplement a diet, not substitute for it. Pills can't provide you with the disease-fighting phytochemicals that are in plant foods. Moreover, they certainly can't make a high-calorie, low-fiber diet a healthy one. Downing single nutrients in large amounts can be risky because of the interactions among nutrients. That's why a multivitamin-mineral supplement may be best for most people, with exceptions for certain key nutrients.

Who might benefit from supplements? You'll notice that unless they fall into one of the special categories listed, men as a group are noticeably absent from this roster. However, men who do not eat a balanced diet and are worried about their nutritional status certainly might also benefit from a multivitamin-mineral supplement. They're best off seeking out a supplement especially formulated for men, as it won't contain iron.

  • Breast-fed infants need a source of iron when they reach four to six months of age. Breast milk provides very little iron, and by this time, their body stores are depleted. Fortified cereal or formula fills the bill. For bottle-fed babies, a formula with supplemental iron is recommended. A fluoride supplement is also recommended, to prevent dental decay, if there is an insufficient amount in the local water supply.
  • Children usually get what they need from the foods they eat. If their eating habits tend toward long jags or if they are vegetarians, a multivitamin-mineral supplement can provide insurance.
  • Pregnant women and women planning to conceive are good candidates for a multivitamin-mineral supplement. It's wise to be sure nutrient levels are optimal before becoming pregnant. This is particularly important in the case of folate, as low levels are linked to birth defects that occur in the first few weeks after conception -- often before a woman even knows she is pregnant. It is important that women of child-bearing age get 400 micrograms of folate a day, either from a multivitamin or from a folic acid supplement.  Pregnant women should get 600 micrograms of folate and also have an increased need for water, the vitamins B6, C, and D and the minerals calcium, copper, iron, and zinc.
  • Breast-feeding women are also candidates. Although their increased nutrient requirements can largely be met by the extra food needed to meet their increased calorie needs, a supplement can help insure against depletion of the vitamins B6, C, and D, and the minerals calcium, magnesium, and zinc. Calcium needs may dictate a separate supplement.
  • Vegans and children who are vegetarians may not get all the nutrients their bodies need. Most vegetarians are no more likely to need a supplement than anyone else, but the exceptions may be growing children and adult vegans (who also shun dairy and eggs in addition to meat, fish, and poultry). They may need other sources of vitamin B12, vitamin D, calcium, iron, and zinc.
  • Seniors over 50 need more of some nutrients and less of others, so they shouldn't pop pills indiscriminately. They need more folate and vitamins B6, B12, and D, though the body may have its own mechanisms for filling the B12 and folate gaps.  Postmenopausal women almost certainly need a calcium supplement. The DRI for women in this group is 1,200 milligrams per day.

Guidelines For Savvy SupplementingOnce you've decided whether or not you want to supplement, you have to choose from the rows upon rows of vitamins, minerals, and scads of other more questionable substances thrown in-between. It can be daunting, but don't be swayed by clever advertising or scare tactics.Strict rules govern what's allowed on supplement labels, but not what's printed in promotional literature displayed nearby. Wild claims made in places other than the label are suspect. Here are some helpful tips to guide you through the maze of supplements:

  • Check the supplement for which nutrients are present. Key nutrients to look for include vitamin B6, folic acid, magnesium, and zinc. Consider it a plus if the supplement contains some of the less popular, but no less important, minerals like boron, chromium, copper, and manganese.
  • Choose a supplement with close to 100 percent of the DRI for most nutrients listed. Up to 250 percent for water-soluble vitamins (C and the B complex) is OK. Avoid those that contain unbalanced amounts of key nutrients, since many of them work together.
  • Don't fall victim to tunnel vision -- looking to single supplements for each individual nutrient. A multivitamin-mineral supplement embraces more nutrients than you could swallow with single supplements, and you're less likely to have an imbalance of nutrients that creates the opportunity for large doses of one nutrient to interfere with the absorption of another nutrient.
  • Don't look to a multivitamin-mineral supplement to provide you with any significant calcium or magnesium. If much of either is added, it simply makes too large a pill to swallow. Instead, calcium is one case when a single supplement makes sense. Choose calcium alone, or a calcium-vitamin D combo (if you aren't also taking a multivitamin with vitamin D). Look to food sources such as tuna and wheat germ to boost your magnesium intake.
  • Try to choose a calcium supplement with smaller doses (500 or 600 milligrams) that you can take two or three times during the day; spreading out the doses improves absorption and lessens the likelihood of constipation.
  • Don't choose a calcium supplement made of bone meal or dolomite. Though some tests show them to be safe, others reveal the presence of lead and other toxic metals. Choose calcium carbonate or calcium citrate supplements over calcium gluconate ones. There is more available calcium in them.
  • Look for a multivitamin-mineral supplement without iron if you're a man or a postmenopausal woman. You probably do not need the extra iron, and there is a small chance it could be harmful if you've inherited the gene for iron-overload disease.
  • Look for a multivitamin-mineral supplement with beta-carotene as its vitamin A source; it's safer than vitamin A as retinol. Be aware, however, that supplements that boast "with beta-carotene" often lump it together with vitamin A on the label, making it impossible to tell how much beta-carotene you're actually getting.
  • Check the supplement's expiration date. Vitamins and minerals can deteriorate over time, losing their effectiveness. Vitamin A is notorious for this. Deterioration happens sooner if you keep them in the humidity of the bathroom. Find a drier place.
  • Don't waste money on supplements that contain numerous unrecognized nutrients, such as lecithin, pangamic acid (sometimes misrepresented as "vitamin B15"), choline, orotic acid, rutin, and other made-up vitamins ("vitamin B17" or "vitamin U"). Some of these are required by other animals but not humans, some are made in the body, and some are simply nonessential nontoxic substances. They aren't harmful, but too many of them can add unnecessary bulk, making a supplement harder to swallow.
  • Don't pay extra for inconsequential attributes, such as "natural," "chelated," or "time-release." Vitamins E and C may be more potent in their natural forms, but the difference is not significant. Some, like folic acid, are actually better absorbed in their synthetic form. Time-release is primarily a gimmick. In the case of calcium, time your own release by spacing out your doses. As for niacin, the time-release form of nicotinic acid is dangerous, as it can be toxic to the liver. Even claims of "no sugar or starch" are meaningless; starch in a supplement can actually improve nutrient absorption.
  • Don't assume a brand name and higher price are any indication of quality. Although some generic and no-name brands may not dissolve as well as name brands, generally what you see on the label is what you get. Some private-label brands are identical to name brands but are less than half the price.
  • Check with your doctor before taking antioxidant supplements.
  • Don't use supplements as an excuse to eat a poor diet. Don't let yourself develop a false sense of security that you're "covered."

Whole Foods And PhytochemicalsJust when we thought we knew it all, along come phytochemicals to prove that we don't. Our parents and grandparents witnessed vitamin discoveries in the first half of this century. The next generation came of age when more and more minerals were being recognized for their importance.Now, our children and grandchildren will explore the myriad of mysterious phytochemicals in foods. The word phytochemicals refers to protective compounds found in plants. They are neither vitamins nor minerals, for they are not essential to life, but they may hold the key to optimal health. Genistein in soy foods, lycopene in tomatoes and watermelon, polyphenols in tea, psoralens in celery, sulforaphane in broccoli, allylic sulfides in garlic, and ellagic acid in strawberries -- these are just a few of the exciting discoveries of the past decades.Scientists continue trying to identify the role of these and other phytochemicals and find out just what they do. The task is daunting. In an orange alone, it's been estimated there are 150 phytochemicals that provide various benefits, such as cancer prevention, cholesterol-lowering properties, and heart disease protection. Some researchers have futuristic notions of isolating some of these chemicals and then concentrating them into a single super-duper protective cocktail. However, it's premature to be so optimistic.To benefit from phytochemicals, you need only to start eating more fruits and vegetables. You've probably heard the call to eat at least four servings per day. That's just the beginning. The real goal, say experts, is to eat five to nine servings of different-colored fruits and vegetables a day.

Until now, researchers have focused on the beta-carotene and fiber in fruits and vegetables as the reason for their protective effect, but maybe that's not all there is to it. Maybe there's something else they have in common. Enter phytochemicals.

A lot of the same foods rich in beta-carotene are rich in other carotenoids that appear to have anticancer effects as well. Lycopene is one of them. Studies suggest that people who eat a lot of tomatoes and other sources of lycopene may have less risk of cancers of the gastrointestinal tract and prostate.  

Eating more fruits and vegetables helps you reap the benefits from all the phytochemicals -- known and unknown.

Now that you know what kind of foods and components your body needs, it's time to learn how to find them. In the next section, you will learn how to read a food nutrition label.

This information is solely for informational purposes. IT IS NOT INTENDED TO PROVIDE MEDICAL ADVICE. Neither the Editors of Consumer Guide (R), Publications International, Ltd., the author nor publisher take responsibility for any possible consequences from any treatment, procedure, exercise, dietary modification, action or application of medication which results from reading or following the information contained in this information. The publication of this information does not constitute the practice of medicine, and this information does not replace the advice of your physician or other health care provider. Before undertaking any course of treatment, the reader must seek the advice of their physician or other health care provider.