10 Supplements That Do Not Work as Advertised

Echinacea is not a new treatment; more than 400 years ago, Native Americans were using it to treat infections and for other medicinal needs. In fact, the flower was officially listed in the U.S. Pharmacopeia and National Formulary (USP-NF) in the first half of the 20th century, but its popularity and usage declined with the introduction of antibiotics.

Today echinacea is having a revival of sorts, and the herbal supplement is commonly taken to prevent the onset of or reduce the symptoms of the common cold and other upper respiratory tract infections. While some swear by the healing power of echinacea, at least if started as the first symptoms appear, scientists can't agree -- but, neither can they disagree. Echinacea may help the body decrease inflammation by perking up your immune system, and if that's the case it may also ease cold symptoms. Although it may not work that way at all. Clear as mud?

A 2007 study found that echinacea supplements did reduce the duration of the common cold by as much as (on average) 1.4 days. If taken before the cold takes hold, echinacea may reduce the risk of catching a cold in the first place by as much as 58 percent [source: Paddock]. However, in 2010 a new study concluded that taking echinacea didn't improve the duration or symptoms of a cold any better than a placebo could; in fact, the most optimistic -- yet statistically insignificant -- outcome suggested it may reduce the length of a cold by about seven hours [source: Paddock]. So the jury's still out.

In addition to treating colds, some people also use echinacea to treat problems including typhoid, malaria, and genital herpes; there's no clinical evidence echinacea would be beneficial treating any such things.

In 1970, scientist Linus Pauling believed the common cold could be controlled with vitamin C, aka L-ascorbic acid. He recommended doses of 3,000 milligrams of the vitamin supplement as the way to prevent catching a cold, and also, over time, to help completely wipe out the offending viruses.

But he was incorrect. Vitamin C is no more effective against an upper respiratory infection than a placebo is, concludes study after study. While one 2007 study found that yes, perhaps high doses of vitamin C -- we're talking vitamin C megadoses of at least 200 mg per day (more than double the average recommended daily allowance for adults) -- may ever-so-slightly reduce the length of your cold, it's only effective for a small number of people (about 8 percent of adults). If you must treat your cold with vitamin C, don't go overboard; more than 2,000 milligrams of vitamin C in a day can irritate your stomach and cause other problems, such as kidney stones. The exception: Marathon runners and other endurance athletes may find vitamin C supplements between 250 milligrams and 1 gram per day may reduce their risk of catching a cold by as much as 50 percent [source: NIH - ODS].

If zinc lozenges and supplements are beneficial in waging war against the common cold, it might be because zinc is an antioxidant. It's also an anti-inflammatory, which may ease your cold symptoms. Or it could be that sucking on zinc lozenges may work because zinc is an anti-viral, literally stopping the cold virus from being able to spread in your mouth and throat. Or it may be that zinc doesn't have any scientific evidence to back up any of the anecdotal evidence. Studies are inconclusive, and only about half of those who've tried zinc report the mineral had any positive impact on the length of their cold or on reducing the severity of their cold symptoms [source: Cleveland Clinic].

Not all zinc supplements are created equal; some research indicates those made with zinc acetate or zinc gluconate, rather than with zinc glycinate or zinc citrate, are more likely to reduce the amount of time you suffer your cold symptoms [source: Prasad]. Timing is important, too. Even if you take the right type of zinc, if you're too late you won't have the benefits; if it's going to work, it'll only do so if you start treating your cold within the first 24 hours of your first symptoms.

Not only are zinc supplements an unreliable cold treatment, neither will they make your hair grow. While technically, yes, zinc can be used against hair loss, that's only in cases where your hair loss is due to a zinc deficiency. Treat the deficiency and your hair loss will stop. But if you don't have a zinc deficiency, increasing your zinc intake won't turn your limp locks luxurious.

Garlic is a boost to any kitchen pantry, and outside your favorite dish it may also have some health benefit; it may help people get their blood pressure under control. Research suggests that garlic may ease hypertension. But if you're taking garlic supplements as a cold remedy, or for any other health benefit, you're probably out of luck.

Garlic contains a sulfur-containing compound called allicin, which may have both antibacterial and antiviral properties, and because of that the vegetable was adopted as potential way to prevent and treat against the hundreds of viruses that cause the common cold. Despite its popularity, though, there's little evidence that eating raw garlic, or taking supplements, can reduce the severity of your cold symptoms or the length of time you suffer your cold, culminating in a 2012 study that concluded more evidence is needed before anyone can claim with certainty garlic's role against rhinoviruses [source: Lissiman et al].

Sun exposure gives the biggest delivery of vitamin D to your body; as much as 80 to 90 percent of all your vitamin D intake happens this way [source: National Institutes of Health]. Supplementing your diet with vitamin D is a good way to prevent bone conditions such as rickets and osteomalacia, as well as to treat the skin condition psoriasis. But if you're taking vitamin D in an effort to reduce your risk of developing heart disease, don't bother. While studies indicate a person with higher levels of vitamin D circulating through his body has a lower risk of developing heart disease or having heart failure than a person with low levels of the vitamin, there's no conclusive evidence that supplementation in an effort to prevent heart failure or boost heart health makes any discernible difference in your health -- and some studies have found vitamin D supplementation had a negative effect on the heart, the very opposite of what you want from your vitamins and minerals [source: National Institutes of Health, Mayo Clinic].

Yohimbe bark is most commonly taken because its active ingredient, yohimbine, is supposed to be an aphrodisiac. Yohimbe has been used in Africa in this way for hundreds of years, but there isn't any conclusive evidence suggesting the supplement works as a sexual stimulant. Yohimbe bark is actually considered unsafe in Germany because of its side effects, and the supplements available in the U.S. contain only small amounts (less than 7 percent) of the active ingredient [source: American Cancer Society].

What's interesting, though, is that some emerging evidence suggests that yohimbine may be effective in treating sexual dysfunction caused as a side effect of certain antidepressants, specifically selective-serotonin reuptake inhibitors (SSRIs) such as the popular brand name antidepressants Prozac, Paxil and Zoloft. Additionally, there is a possibility that yohimbine may also help treat some types of erectile dysfunction (ED) -- mild types caused by psychological rather than physical problems. In this regard, the American Urological Association is unconvinced of its efficacy and recommends further evaluation.

More than 8 percent of Americans have type 2 diabetes -- that's just shy of 26 million people. Many of those people rely on blood sugar (glucose) testing and medications such as insulin, biguanides (including the brand name Metformin) and DPP-4 inhibitors (including brand name Januvia) to keep themselves healthy [source: NDEP]. What if you could improve your blood sugar levels -- whether diagnosed with type 2 diabetes or not -- with a mineral supplement, instead?

Chromium is a mineral your body uses to control its glucose levels. Because of this, it's easy to extrapolate that if you supplement your diet with chromium you'll prevent or control your diabetes. Marketing got something right, right? Well, maybe not right at all. Studies offer conflicting evidence about the effectiveness of chromium supplements to prevent or treat diabetes. For every report finding that chromium supplements do have a measurable positive impact on your glucose levels, another will find no benefit at all to the supplementation.

Dehydroepiandrosterone, known as DHEA, is a hormone your body naturally makes (your adrenal glands produce it). Specifically it's called a prohormone because your body needs it to activate the production of testosterone and estrogen. And because of its connection with our sex hormones, we hope taking supplements will, for example, boost our sex drive. But no study can validate that claim. DHEA supplements are marketed with the fountain of youth in mind; in addition to the improved sex drive claims, DHEA is also touted to slow down the aging process, build muscle and boost your immune system. But there's no evidence these supplements can do anything of the sort, either. Studies overwhelmingly find that taking DHEA supplements is no better than taking a placebo.

Americans spend a lot of money on fish oil purchases -- more than $1 billion per year on over-the-counter fish oil supplements (and that doesn't even count the jar of peanut butter plus omega-3 fatty acids you keep in your pantry) [source: LeWine].

Fish oil will probably not make any discernible impact on your child's intelligence, or protect against Crohn's disease or mental illness including major depression. Many of us take fish oil capsules believing the omega-3 fatty acids will reduce our risk of developing heart disease; while some studies suggest that fish oil supplements may have heart-healthy benefits, conflicting recent research finds its heart benefits may be bunk. Or at the very least, inconclusive or biased. Studies are finding that patients with cardiovascular disease do not have any reduction in their risk of having a(nother) heart attack, nor does fish oil lower their risk of stroke, congestive heart failure or any other cardiovascular condition after taking supplements for a minimum of one year.

While fish oil doesn't live up to the hype that surrounds it, it's also not a snake oil remedy – research shows promise that adding it to your diet helps protect against colorectal cancer. The best way to get your daily intake of fish oil isn't with supplements. Eat fish. (For you non-meat eaters, flax is a good substitute.)

Nearly 40 percent of American adults take a daily multivitamin, and more than 50 percent of American adults take some sort of dietary supplement (the most popular is a daily calcium supplement) [source: Fetters]. While evidence suggests that calcium may actually have a positive impact on your health, there doesn't seem to be any evidence any other ingredient in your multivitamin does anything positive for you. At all. And in addition to that bombshell, some research suggests those of us who take vitamins may die sooner than our friends who skip the supplements. Yes, you read that correctly; in 2011 The Iowa Women's Health Study found multivitamins didn't offer any health benefits to the women taking them -- and also found an association between taking dietary supplements and a shortened lifespan [source: Mursu]. It's entirely possible that this is due to people having a false sense of security about their health; taking a multivitamin may make them less likely to take care of themselves in other ways.

The best thing to do is ditch the daily vitamins and instead make sure you eat a healthy, balanced diet.