Browse evidence-based analysis of health-related claims and assertions
Taking extra leucine — a supplement found in protein — won’t help healthy, fit young adults build more muscle, get stronger, or recover faster from workouts, no matter how much they take or how long they take it, for up to 12 weeks.
Causal
When people with type 2 diabetes take creatine and do strength training, their blood sugar control gets better, shown by lower HbA1c levels.
Taking creatine supplements along with weight training can help older adults build more muscle and get stronger, which might help them stay more active and independent as they age.
Taking creatine supplements might help the brain and spine heal better after serious injuries in animals, by keeping their energy-producing parts working and reducing damage.
Mechanistic
Taking creatine supplements may help your muscles heal faster and get stronger again after a tough workout or injury, especially if you regularly lift weights.
Taking creatine monohydrate every day for up to five years, even at high doses, doesn’t seem to harm your kidneys, liver, or blood in healthy people or those with brain-related diseases like Parkinson’s or ALS.
Correlational
Taking creatine powder every day for a week, then a smaller dose after that, can help your muscles store more energy, making you stronger and better at intense workouts like weightlifting.
Men and women gain muscle at about the same rate when they lift weights the same way, so gender doesn't make a big difference in how much muscle you build.
Quantitative
When you lift weights, your body turns down a protein called myostatin that normally stops your muscles from growing too big, which helps your muscles get larger.
When your muscles get really big—more than 22% larger—they need extra help from special cells to add more nuclei so they can keep growing.
When you lift weights, your muscles grow bigger because your cells first make more protein-making machines (ribosomes) — and the more of these machines you build, the more your muscles grow.
When you lift heavy weights, your muscles grow bigger because your body turns on a special chemical signal (mTORC1) that helps make more muscle proteins and building tools, letting your muscles grow faster.
Taking creatine supplements the right way is probably safe and might help older people and kids stay healthy, without hurting their liver, kidneys, or metabolism, based on studies done so far.
Descriptive
Taking creatine supplements won’t turn you into a steroid user or boost your male hormones in any meaningful way—even though one tiny study saw a short, tiny spike that doesn’t really matter.
Taking creatine supplements won’t make you dehydrated or give you muscle cramps—and might even help prevent them when you’re working out in the heat.
Taking creatine supplements at the normal dose won’t hurt your kidneys if you’re healthy — lots of studies over many years have shown no consistent sign of kidney problems.
Taking 3-5 grams of creatine daily for a few weeks helps you build more muscle and get stronger when you lift weights, but it doesn’t make you gain fat.
If you're a guy who hasn't trained much before, your triceps muscle in the back of your arm grows about the same no matter if you do push-ups, triceps extensions, or a mix of both — the type of exercise doesn't really matter for this part of the muscle.
If you're a guy who's new to lifting and you do both big compound moves and isolated triceps exercises, your triceps will grow more than if you only do one type — not because the exercises add up, but because they hit different parts of the muscle in different ways.
If you're a young guy who's new to lifting, it doesn't matter whether you do bench press first or triceps press first—your strength gains will be the same as long as you lift heavy (80% of your max) and push each set until you can't do another rep.
If you're a young guy who hasn't trained much before, doing exercises like the bench press will make the back part of your triceps grow way more than just doing arm-only exercises like lying triceps extensions.
If you're a young guy who hasn't trained much before, doing exercises that only move your elbow (like lying triceps presses) makes your triceps muscle grow way more than doing exercises like bench presses that use multiple joints at once.
If you're a guy new to lifting and you start your workout with big compound moves like the bench press instead of isolation exercises, your chest muscles grow more—probably because you're not too tired when you do the main exercise.
If you're a guy who's already fairly fit and you do push-ups or bench presses for four weeks, your ability to throw a medicine ball while sitting won't get any better.