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Creatine Myths Exploded

There’s an old saying that when you’re at the top, someone’s always trying to bring you down. The adage certainly applies to creatine.

There’s an old saying that when you’re at the top, someone’s always trying to bring you down. The adage certainly applies to creatine. Since its commercial introduction in 1993, creatine has become one of the most popular bodybuilding supplements, and for good reason. Countless studies prove its effectiveness, the scientific consensus being that it works for 80 percent of its users. The other 20 percent usually eat red meat habitually. Red meat contains high levels of natural creatine, and those who eat it regularly tend to have more creatine stored in their muscles. That’s why they don’t respond as dramatically to the supplement as vegetarians or those who eschew eating meat.

Along with its commercial success, however, creatine has also been subject to much unfounded criticism. The misinformation is fueled by poorly researched popular media reports about its effects. Indeed, some newspaper and television news features have identified creatine as a steroid. In fact, it’s an amino acid by-product synthesized in the liver, kidney and pancreas from three amino acid precursors: methionine, glycine and arginine. The body produces about one gram of creatine a day, and if you eat meat, you get another gram or two as well. Labeling creatine a drug of any kind is an example of shoddy research.

Popular media, though, aren’t the sole purveyors of creatine misinformation. Science journals regularly publish alarming reports suggesting a dark future for creatine users. A closer perusal of them usually shows how irrelevant they are for those in good health. It’s like those reports that eating lots of protein is risky for those with kidney failure.

There’s zero evidence that either creatine or a high-protein intake is hazardous for people who have normal kidney function.

Among the side effects attributed to creatine are excess kidney stress, muscular cramps and dehydration. Two recently published studies, however, definitively prove that the claims are false. 

The theory is that creatine use promotes a shift of water from extracellular and into intracellular compartments. Critics say that that makes it hard to maintain cooler body temperature and alters electrolyte, or mineral, balance, leading to muscle cramps. Studies that have found muscle cramps and overheating with creatine use have by and large involved athletes training in hot weather, when they may not have been drinking enough water to balance sweating and other fluid loss from the heat and exertion. Other studies show the opposite: Creatine appears to offer significant protection against heat illness, dehydration and muscle cramps.

That makes sense because creatine increases total body water, which would protect against dehydration while lowering core body temperature.

Then there’s the fear that creatine affects kidney function. The primary waste product of creatine metabolism, creatinine, is excreted through the kidneys, and with compromised kidney function, excess creatinine could produce kidney stress. In fact, a primary test of kidney function is called the creatinine-clearance test; in it excess creatinine points to problems with the filtering mechanism in the kidneys. Just because a clinical test uses a particular substance as a marker of bad kidney function, however, doesn’t prove the substance caused the problem.

One study, which reviewed the literature about the effects of creatine in relation to muscle cramps and dehydration, cited a 1998 case study published in the Lancet describing a 25-year-old man who experienced a decline in kidney function after taking 20 grams of creatine a day. Complicating the report was the fact that the man had kidney disease. When he stopped using the creatine, his symptoms abated, leading the authors to suggest that creatine was toxic to kidney function. A French newspaper reported that three days after the review was published, but it totally overlooked the fact that the man already had serious kidney disease. In any case, taking 20 grams of creatine after you’ve done a typical creatine-loading phase of five days is just plain foolish, as nearly all of the creatine is rapidly excreted once the muscles are loaded.

Besides questionable human studies pointing to creatine-induced renal stress, a number of animal studies have been used to bolster that criticism, but those, too, are red herrings, since creatine isn’t a normal nutrient for many animal species and may not even be absorbed. For example, creatine intake causes chronic hepatitis in mice but not in rats. In contrast, humans easily and rapidly absorb it, even though many ads attempt to deny that so they can sell “superior” creatine supplements.

Complicating the picture is the fact that the creatinine test, the primary test for kidney function, isn’t accurate for those who use creatine, particularly during a loading phase. A recent study compared men, ages 18 to 35, who got either 10 grams of creatine or a placebo daily for three months. The researchers used a newer test of kidney function that measured a serum protein called cystatin C. Cystatin C is regularly filtered in the kidneys and easily reabsorbed, since it has a low molecular weight. A loss of cystatin C is a good indicator of a defect in the glomerular filtration system of the kidneys and isn’t affected by creatine metabolism.

The study found that, based on monitoring cystatin C excretion, taking in 10 grams of creatine daily for three months had no adverse effects on kidney function.

The subjects also participated in aerobic exercise for 40 minutes three times a week. Tests on those in the placebo group showed that the exercise alone improved kidney function. That was attributed to the health-promoting effects of exercise, such as more efficient glucose control, lower blood pressure and a reduction in oxidative stress and bodyfat levels. Significantly, those are the same factors that offer lifelong kidney protection, suggesting that regular exercise is one of the best things you can do to preserve kidney function. IM


Dalbo, V.J., et al. (2008). Putting the myth of creatine supplementation leading to muscle cramps and dehydration to rest. Brit J Sports Med. In press.

Gualano, B., et al. (2008). Effects of creatine supplementation on renal function: a randomized, double-blind, placebo-controlled clinical trial. Eur J Appl Physiol. In press.

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