What Supplements should I be taking is a question I get asked all the time. It's really easy for a teenage athlete to fall into this trap when every time you walk into a GNC or nutrishop you get bombarded by a meathead salesmen that tells you 'You're going to lose your gains, bro" if you don't take this new age powder.
In all honesty, most athletes have no business taking supplements. An athlete should have their diet in check with real quality food, adequate calories, and consistently get 8 hours of sleep per night before they consider taking supplements. That takes discipline to get off Fortnite and go to bed.
In an ideal world there would be no supplements necessary, they’d only be taken for convenience. That being said, the only supplement I’ve ever recommended is creatine. Anything else is eye-wash and a waste of money in my opinion.
To keep it simple, what creatine does is help your fast-twitch system by creating more potential ATP (energy) which can improve performance in short, high-intensity movements such as sprinting, throwing, and hitting. Sounds perfect for a baseball player, But if you’re going to take it you should know what it does and doesn’t do. There are quite a few myths surrounding creatine.
Myth 1 Creatine will make you Bulk
As mentioned before creatine aids in sudden, high-intensity bursts of power. Take all the creatine you want, but if you don’t have a caloric surplus and consistent strength training you’re not going to get bigger. What it does do is allow you to train longer at a higher intensity which in turn can help you build lean muscle mass.
Myth 2 Creatine is all water weight
This is only partially true. Creatine does create some water retention, but it is hardly significant. Certain studies will suggest an initial weight gain of .8 to 2.9 percent of body weight due to water. However, the research also suggests that with continued creatine usage you can expect an increase in lean body mass, and a decrease in fat mass.
The real benefit comes from lifting more weight for more reps and the overall increase in workload you can handle. Yes, there will be an initial small burst of “water weight,” but you’re going to benefit from so much more.
Myth 3 Creatine Causes Dehydration
One of the biggest myths is that creatine will cause muscle cramping and dehydration, but there is currently no data to back up those claims. There are actually studies that suggest creatine enhances performance in hot and humid conditions, and hydration is improved. 
1. Kutz MR, Gunter MJ. Creatine monohydrate supplementation on Body Weight and Percent Body Fat. J Strength Cond Res. 2003;17(4) 817-821
2. Kern, M., Podewils,L. Vukovich, M., Buono, M.(2001) Physiological response to Exercise in the Heat Following Creatine Supplementation. JEP online