Does creatine make you smarter?

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Is creatine a weird steroid-like hormone or drug?

No. Creatine is a nutrient. Most omnivores eat a gram or two per day from meat. Your body also synthesizes a gram or two per day. You need creatine to deliver energy inside of cells. It is normal and non-weird.

Does creatine increase testosterone?

Unlikely. This concern comes from one study in 2009 on 16 male rugby players.1 But that study is considered extremely suspect. There have been at least twelve other studies that all found no change or physiologically irrelevant changes. Beyond that, it’s implausible that creatine would increase testosterone, because we know what creatine does and it has nothing to do with hormones.

Does creatine make you go bald?

No. Or, rather:

No study ever reported that. One study reported the opposite. There is no mechanistic reason to think that would happen. There are good mechanistic reasons to think that would not happen.

These rumors all trace back to speculation built on top of that same single 2009 study. But that study is contradicted by later research, and anyway didn’t measure hair. Anything is possible, but as far as I can tell, it’s equally plausible that creatine would increase hair growth. And if you’re really worried about this: Are you going to stop eating meat?

Is creatine safe?

Probably. The International Society of Sports Nutrition says:

Available short and long-term studies in healthy and diseased populations, from infants to the elderly, at dosages ranging from 0.3 to 0.8 g/kg/day for up to 5 years have consistently shown that creatine supplementation poses no adverse health risks and may provide a number of health and performance benefits.

It’s been studied extensively, and no risks have been found. The way it works doesn’t suggest any risks. And supplementing a few grams per day doesn’t put you far outside the range that people get from normal food.

Does creatine make you stronger?

Yes.

It’s very rare for a supplement to have such strong and consistent evidence. A widely-cited review says that short-term supplementation increases maximal power/strength by 5-15%. This in turn may increase the long-term gainz from strength-training exercise. Creatine also increases sprint performance by 1-5%. Though, there seems to be little if any benefit for endurance exercise like long-distance running.

But how does creatine make you stronger?

Before answering that, can I go on a rant about how muscles work?

…OK?

Great! Here’s how muscles work:

All cells have a molecule called ATP floating around inside, which they use for energy. Muscle cells have proteins in them called myosin. When ATP bumps into myosin, the myosin breaks the ATP down into ADP. This releases energy which is physically captured by the myosin as elastic strain. When triggered by neurons, myosin releases that mechanical energy. When you decide to move your arm, your brain triggers many muscle cells, carefully orchestrating the myosin twitches into large-scale movement.

Now, here’s something that’s crucial for our story: Very little energy is stored as ATP. Your body contains ~100 grams of ATP, representing ~10,000 joules of energy.2 But your body at rest burns ~100 watts. So you only store enough ATP to keep yourself alive for ~100 seconds. If you sprint, you could easily burn ~3000 watts, which would use all your stored ATP in ~3 seconds.

Through the magic of eating, you’re always making more ATP. Typically, your mitochondria recycle ~1 gram of ADP back into ATP per second, the same amount you need to stay alive.3 If you start running, your body can ramp that up to ~10 grams per second, though tricks like breathing faster and speeding up your heart.4 But it takes a minute or two for your mitochondria to really get cranking.5

So then why am I able to sprint for longer than three seconds?

Because creatine acts as an additional energy reservoir, coupled to the ATP reservoir. After you eat or synthesize creatine, 60% is converted into phosphocreatine. This is done by an enzyme that grabs a creatine molecule and an ATP molecule and moves a phosphate group between them.

This “charges” the creatine into phosphocreatine and “discharges” the ATP into ADP.6

But if your ATP levels drop—e.g. because you’re running away from a tiger—those enzymes will run in reverse, meaning they “discharge” phosphocreatine into creatine and “charge” ADP back into ATP. This happens almost instantly, so that ATP and phosphocreatine deplete at the same rate.7

At rest, your muscles contain around 3-4 times as much phosphocreatine as ATP. So the “extra” energy storage in phosphocreatine is much larger than the “base” storage in ATP itself. That’s why you can sprint for ten seconds rather than just three seconds.

Does supplementing creatine increase creatine levels in muscle cells?

Yes. Typical levels are:

Vegetarian: 100 mmol / kg Omnivore: 120 mmol / kg Someone who supplements creatine: 140 mmol / kg

So, everything seems to add up. If you supplement creatine, you increase your levels by ~16.67%, implying ~12.5% more total short-term energy storage.8 That’s in line with the 5-15% increase in strength seen in creatine trials.9 It also seems to make sense that creatine trials find little benefit for endurance exercise. If you don’t have sudden bursts of activity, a larger short-term energy reservoir won’t really help you.

But isn’t this all very strange?

Well, I find it strange. All else equal, more strength is good. The body already knows how to make creatine. If you can just raise creatine levels and get more strength with no downsides, then shouldn’t evolution have done this already? Some variant of the Algernon argument would suggest that the fact that creatine works so well should be impossible.

You might think that higher creatine levels are bad somehow, and that’s why evolution didn’t make them higher. But that seems wrong. Creatine levels vary naturally based on what you eat. If higher levels were bad, evolution could have brought them down. But it doesn’t. It just lets them vary.

Often, evolution makes us “worse” to reduce our energy expenditures, because evolution hates it when we starve to death.10 But the body only spends 1-2 calories per day synthesizing creatine, and more creatine in muscle cells doesn’t have any significant metabolic cost.

I think the boring explanation is that for our evolutionary ancestors, modest increases in short-term strength just weren’t a big deal. We were exhaustion hunters, not 1-rep max deadlift hunters.11 Also, more creatine causes your muscle cells to draw in some extra water, which slightly increases energy usage for long-distance running.12 So, if you happened to get extra creatine from meat, great. If not, whatever. In the range where creatine fluctuates based on diet, I suspect creatine levels just didn’t have much impact on reproductive success.

Still, we must acknowledge that creatine is unusual. I wish we could tell our bodies, “Hey, we have access to unlimited amounts of food. Stop worrying about conserving energy and concentrate on being awesome.” But we have very few ways to do that. As far as I can tell, the list of normal nutrients that have been proven to increase strength is: protein, creatine, beta-alanine, the end.

So creatine is special. And creatine makes you a little stronger. Does it make you a little smarter, too?

Is creatine used by the brain?

Yes. Most parts of the body don’t contain significant creatine. But the brain does, along with muscles, the heart, and testes. Neurons use it to play the same game muscles do with ATP and phosphate groups and so on.

How much creatine is in the brain?

Maybe half as much as in muscle. The number of interest here is the ratio of phosphocreatine to ATP, indicating how much phosphocreatine increases local energy storage. We saw above that in muscle, that ratio is 3 to 4. In the brain, the numbers are a little sketchy, but the ratio seems to be more like 1.5 to 2.13

But why? Why would the brain use creatine?

Good question! The brain doesn’t have bursts of energy usage like muscles do. Yes, the brain uses ~20% of all calories despite only making up ~2% of body mass.

But the brain is unusual in that it needs all that energy just for basic housekeeping, and doesn’t ramp up with usage. Contrary to the common myth, thinking hard does not burn significantly more calories. (Demonstration: Start thinking hard, and watch as your heart rate does not increase.)

So muscles use creatine for sprints. But the brain doesn’t have sprints. So what the hell is the brain using creatine for?

The most common theory seems to go like this: Actually, muscles don’t just use creatine as an extra energy reservoir. They also use it to deliver energy inside of cells. You see, creatine diffuses faster than ATP inside of cells. So even with endurance exercise, creatine is still being used: Enzymes near the mitochondria use ATP to “charge” creatine into phosphocreatine and enzymes near myosin use that phosphocreatine to “recharge” ADP back into ATP. Even though the net change in creatine is zero, it helps “shuttle” energy from the mitochondria to the myosin.

Under this theory, what neurons and muscle cells share is that parts of the cell locally use a lot of energy, when they get triggered. So even though your brain doesn’t “sprint”, it still uses creatine to avoid local energy deficits.

There’s also experimental evidence that creatine is important for the brain. We’ve created genetically altered mice with brains that lack the enzymes needed to convert creatine to and from phosphocreatine. They display severely limited spatial learning and somewhat smaller brains.

Some humans also naturally have creatine deficiency. In some variants, people have trouble synthesizing creatine. This leads to lower levels throughout the body, including skeletal muscle where 95% of creatine lives. Nevertheless, the primary symptom is related to the brain, namely intellectual disability. Muscle weakness and seizures are also common. Other people have creatine transporter deficiency, meaning creatine can’t cross the blood-brain barrier. This leads to lower levels in the brain only. This leads again to intellectual disability and also often muscle weakness or seizures. (That muscle weakness is despite the fact that the muscle cells themselves have normal creatine levels.)14

So somehow, creatine is very important for the brain.

Does supplementing creatine increase creatine levels in the brain?

Probably, though likely less than in muscle.

Creatine can definitely cross the blood-brain barrier.