Welcome to our crash course on supplements, where we answer your top questions about popular health boosters. 

Q: Just what is a dietary supplement?

The Dietary Supplement Health and Education Act (DSHEA) of 1995 created the definition of supplements, cementing this unique class of foods. Dietary supplements must be ingested through the mouth—whether as a pill, tablet, capsule, softgel, chewy gummy, chewable tablet, melt-away, powder, drink, or bar. And the kinds of ingredients included can be wide ranging, indeed. Here's a look at the main types of ingredients in supplement products, all of which are regulated by the law.

Q: How long do supplements stay in my system?

Nutraceuticals (a food or supp that contains health-giving additives) differ significantly in the amount of time the active ingredient(s) remain in your body. Water-soluble nutrients, such as vitamin C, generally will be metabolized and leave the body the same day of use or even within a few hours after consumption. Fat-soluble nutrients, such as vitamin A, can be stored in the liver for weeks and distributed to body tissues as needed.

Q: How long should I take a supplement before deciding if it works or not?

The answer to this question depends on two things: the supplement and the expected outcome. For example, joint-health ingredients glucosamine and chondroitin usually take six to eight weeks before they start to work. Melatonin, on the other hand, generally starts to work within the first week or even the first day.

Q: Is it OK to take a supplement one day but not the next?

That depends, says Michael Holick, PhD, MD, author of The Vitamin D Solution (Penguin, 2010). For example, vitamin D is stored in fat cells so you don't have to take it every day. Maintenance supplements however, such as multivitamins, calcium, or ginseng, should be taken daily—as should any supp taken for long-term therapeutic effects. "There are some supplements that may be used acutely for specific effects, and those don't have to be taken on a daily basis," says Gene Bruno, provost at Huntington College of Health Sciences. "For example, valerian taken for better sleep or L-theanine taken for stress relief generally do not need to be taken daily."

Q: What are the different forms of supplements?

From capsules and tablets to gummies and powders, supplements come in many forms. Learn the unique benefits of each.

Q: Who takes supplements, and why?

Get the facts in this handy infographic, featuring data from the Council for Responsible Nutrition (CRN)'s 2014 Consumer Survey on Dietary Supplements, conducted by Ipsos Public Affairs.

Q: What's the difference between the RDA, DRI, and DV for a vitamin or mineral?

Nothing. The old-school Recommended Daily Allowance (RDA) and its updated equivalents, the Dietary Reference Intake (DRI) and Daily Value (DV), all mean the same thing: the minimum amount of a nutrient the general population needs to stave off a deficiency disease. For example, most healthy people need 90mg per day of vitamin C in order to not get scurvy.

Q: Which supplements are the most popular?

According to SPINS, a consumer insights agency for the natural, organic, and specialty products industry, these were the top 10 most popular supplements of 2014.

Q: How much should I be getting?

We asked Michael Murray, ND, author of The Encyclopedia of Natural Medicine (Atria, 2012) for recommended intake levels of important nutrients. Murray advises reading labels to find a multivitamin formula that contains vitamins and minerals in these ranges. "Be aware that you will not find a formula that provides all of these nutrients at these levels in one pill—it would simply be too big. You would need to take at least three to six tablets per day to meet all these levels," Murray says. "While many one-a-day supplements provide good levels of vitamins, they tend to be insufficient in minerals. Your body needs the minerals just as much as it needs the vitamins—the two work hand-in-hand."

Here are optimum intake ranges to guide you in selecting a high-quality multivitamin:

Q: Can I be healthy without taking supplements?

America's mainstream health model recognizes only two states of being: diseased and healthy. But there is a vast difference between the minimum amount of a nutrient required so you don't get sick, and the maximum amount you might want to get in order to function optimally—because there's more to living in a state of vitality than just not being sick.

"It is the goal of optimal health that drives people to take nutritional supplements," says Murray, ND. "If someone believes optimum nutrition simply means a level that provides no obvious signs of nutrient deficiency, their answer to whether supplementation is necessary is going to be different from someone who thinks of optimum nutrition as the level of nutrition that will allow a person to function at the highest degree possible with vitality, energy, and enthusiasm for living."

Q: Are probiotics something I should take long-term or only immediately after taking an antibiotic?

Probiotics typically move through the gut and must be replenished regularly, so everyone (except for those with severely compromised immune systems) can and should consume them every day. More probiotics are being recommended simply as part of a healthful diet. "Whether consumed through a supplement or fortified foods, consumers should be making probiotics a part of their daily life," says Mike Bush, vice president of the International Probiotics Association.

Q: Can supplements interact with prescribed medications?

Yes, some of them can. St. John's wort is the most common example. This popular herb is often taken for mild depression, but it can also increase the metabolism of or reduce the blood concentrations fo many prescribed drugs.

For example, St. John's wort may increase the metabolism of oral contraceptive estrogens, prolong narcotic-induced sleep time, change the effects of some antihypertensive drugs, and decrease the effects of Xanax, says Bruno. As you can see, it is vital that you discuss your use of St. John's wort with your physician if he/she is prescribing you pharmaceuticals of any kind. Most other medicinal herbs—including echinacea, garlic, gingko, ginseng, goldenseal, and milk thistle—don't regularly interfere with prescribed medications; in 2012 German researchers concluded that these six botanicals produce no adverse effects when interacting with pharmaceuticals.

Foods can interact with prescribed medications, too. The most notorious example is grapefruit juice, which inhibits the liver detoxification of certain drugs in the intenstines—and to a lesser extent in the liver—making them more powerful.

Another problem, however, is that some prescribed drugs can interfere with or deplete the body of some essential nutrients. A common example is statins, which are taken to lower cholesterol levels. Some research suggests that statins deplete the body of coenzyme Q10.

Q: Can I trust the health claims made on a supplement box?

Supplements are officially regulated as foods, not as pharmaceutical drugs. This is why you'll often hear people say that supplements are unregulated. That's not true—it's just different. According to the FDA, only drugs can treat diseases; therefore a supplement can't legally claim to treat a disease, such as diabetes or heart disease. Supplements have their own class of claims, which are called "structure and function" claims.

What this means is that the supplement makers are allowed to communicate a possible health effect on the structure of an organ or the function of a part of the body's physiology. So you won't see words on a bottle of glucosamine and chondroitin saying, "This joint-health formula cures arthritic pain," but you might see something like, "This formula supports joint health." In some cases, research shows a joint-health formula can, indeed, cure joint pain—but according to the law, the manufacturer can't say that, specifically.

At Delicious Living, we have a Standards Department that reviews all advertisers, including supplement companies, to verify their claims are valid and true.

Q: What supplements should I consider?

Talk to your healthcare provider to determine which types of supplements you'd most benefit from using on a regular basis. This nifty flowchart can help you hone in on beneficial options to consider.