Supplements sold at big-box department store retailers have been found to have fillers in place of what their labels claim to have.
What does this mean for you?
That if you're filling your supplement needs from the same place you get your laundry detergent, you're probably just making a charitable donation.
Unfortunately, the FDA doesn't really regulate supplements.
Does this explain why there's much conflicting research about whether preventative health and performance products like supplements work?
In part, yes. Most of the studies on supplements do not factor in sourcing, quality, bioavailability, correct application, nor do they even bother to check for label truthing to ensure that what is being tested is actually in the product.
Does this mean you should stop taking supplements? No. I believe in supplementation and use them strategically as a piece of the puzzle when working with clients. But you need to seriously re-conceptualize where and how you buy them, and possibly your value on your own health.
If something is important to your health, fitness, and performance, why are you buying it in a dollar store fashion? Are you truly seeking a solution or are you looking for a discount and taking something to feel better about taking it? These are the questions I would ask to identify something larger, being the role of your health/fitness in your own life.
When buying supplements, always be sure that it's regulated by an independent, third-party body, and has been lab-validated. These things are listed on the label and/or company website. You wouldn't eat at a restaurant that failed its health inspection...
Remember that supplements are meant to fill nutritional gaps that are ever-present in modern society, given the reality of the degradation of the American food supply. Once foundations are covered, conditionally-essential items and accessories can be plugged in.
However, the foundation of your nutrition needs to be and will always be-nutrient-dense food. "Eat food. Not too much. Mostly plants." -Michael Pollan