First and foremost, a supplement is, by its very definition, meant to be something added to an already balanced diet. If your diet sucks, no amount of supplementation will help you. Begin by getting your diet right; then, and only then, should you consider taking supplements.
Secondly, it is important to note that supplements are not drugs. If they were drugs, they would only be available by prescription, yet GNC and bodybuilding.com do not require a physician's referral. The definition of a drug is a "chemical substance used in the treatment, cure, prevention, or diagnosis of disease or used to otherwise enhance physical or mental well-being." Yes, drugs can enhance your mental and physical wellbeing, but they can also get you disqualified from any major sporting even in the world (steroids, HGH etc.).
Supplements, on the other hand act more through supplying your body with the vitamins, nutrients and minerals that it needs. Yes, any dietitian will tell you that you can get all the vitamins and nutrients you need from a diet, but when you are training twice a day and working a 40 hour/week job you have neither the time nor the resources to eat 4800 kcals, or to get your 180 grams of protein from whole food sources. This is where supplements come into the picture.
It is also important to note that supplements are not regulated by the FDA, or any other governing body for that matter. There is no guarantee that what the label says is actually what is in the bottle. The best and most recent example of this is what happened to CrossFit Games Competitior, Richard Bohlken. Bohlken tested positive for an illegal substance, which was present in the protein powder that he was taking. A supplement company can put whatever they want on the label, yet fill your bottle with flour, for all you know.
One way to decrease the likelihood of this happening to you, is to buy supplements that have a GMP or USP seal on them, which stands for Good Manufacturing Practices and US Pharmacopeia. These seals better guarantee a) that what they say is in the bottle actually is in the bottle (USP) and b) that they clean out the machines between runs so there is no cross contamination (GMP). Ultimately, you are still taking the risk that what you buy is most definitely what they say is in the bottle.
So, you are a competitive athlete and need a little extra vitamins and nutrients in your body. You don't have to go and buy everything you can get your hands on that you've read helps to improve performance. In fact, most supplements are a waste of your money. You are paying for marketing and fancy labels rather than for supplements that work. For example, the label on the bottle states "this formula increases strength by 15%". What they don't tell you is that the placebo increased it by 12% as well, so in reality, it is only a 3% increase in strength.The funny thing about this 3% is that strength values vary anywhere between 7-12% on a daily basis, so 3% is really just a good day in the gym. Most supplements don’t have a huge effect on strength or other performance variables like VO2 because performance adaptations are more heavily dependent on the training stimulus then the supplements.
Most research is done with two groups: a placebo group who get a fake supplement (most often sugar) and an experimental group that gets the supplement. A baseline is measured for both groups that then participate in an intervention/training period before a retest. Both groups commonly show improvements after the training period, and if the supplement improves significantly more than the placebo they deem it a great and effective supplement. However, as the example above highlights, the improvement over a placebo may be less than 3% which is statistically significant but really not meaningful.
Now, onto talking about the about the "good" behind supplements. Supplements are beneficial especially when heavy (high intensity and/or volume) training is being performed, as supplements do supply the body with valuable nutrients that it needs to recover from a workout. The most common and effective supplements are protein powders, Creatine, Fish oil and a Multi Vitamin. These have been proven to have positive effects on recovery, energy, and antioxidant capabilities. I will dive further into how and why these work, as well as some other common supplements used by athletes in follow up posts, but the first take home message is:
You must first eat healthy by having a good diet that comes from whole foods
Be very cautious when buying supplements, as they are not regulated and very often over-hyped.
Supplements do not compensate for poor training.
Only take what you need, not what "might work."