It's the " wonder spice your body needs, "according to Bon Appétit. Celebrity physician Dr. Josh Ax claims that it combats infections, cancer, heart disease, neurodegenerative diseases, and stomach ulcers. WebMD touts that it "contains magical nutrients-the kind that practically cast spells to keep you strong and healthy."

I'm talking about turmeric, the root that has been used for centuries in Indian cooking. Its popularity has recently traveled West-it's become so trendy, in fact, that Starbucks has recently started selling a turmeric latté and Juice Press sells three types of turmeric smoothies.

I'm pro-turmeric myself, but more for its flavor (it's a relative of ginger) than its healing powers. That's because the research is suggesting that turmeric is a magical cure is woefully unconvincing. What's more, the key ingredient in turmeric that's supposedly responsible for its health benefits-curcumin-is so chemically unstable that it breaks down in the body before it has the chance to do anything much at all.

Let's start with some numbers.

People typically use turmeric in powder form (you'll find it in the spice section of the supermarket). But its key ingredient, curcumin, only makes up 3 percent of pure turmeric powder by weight. So if you heed the Food Babe's advice and add a pinch or two of turmeric powder to your smoothie, you'll only consume about 15 milligrams of curcumin. By comparison, in clinical studies, that you can see how curcumin affects health, at least 500 milligrams of curcumin a day. You'd have to consume more than 8 teaspoons' worth of turmeric powder daily to get this much.

And even if you did not eat dozens of teaspoons of turmeric a day, your body would absorb only a small fraction of its curcumin. In most clinical studies, researchers give their subjects special curcumin concoctions that are more readily absorbed than the natural curcumin found in turmeric. That's because, according to a 2017 review paper published in the Journal of Medical Chemistry by researchers at the University of Minnesota, the University of Illinois at Chicago , and Brigham and Women's Hospital in Boston, natural curcumin breaks down so quickly in the body. It may even degrade while it's on the shelf. The review paper concludes that curcumin's stability "is abysmal compared with commercial drugs." (Some curcumin advocates suggest that turmeric should be consumed with black pepper, because a component of pepper is called piperine boosts curcumin absorption . That's true, but researchers warn that piperine can also interfere with drug metabolism and increase the risk of drug toxicity.

In another talk study, researchers at the University of Michigan and other institutions gave six people each 10 grams of curcumin and gave another six people each 12 grams of curcumin-the latter is equivalent to 192 teaspoons of turmeric powder-and then analyzed their blood. They were only able to find intact curcumin molecules in one of the subjects 30 minutes later. (They did find partially broken-down curcumin molecules in the other subjects at different time points, but it's unclear what kind of biological effects they have.)

But what about all the studies?

It's true: Thousands of studies have been conducted on turmeric and curcumin-on average, about 50 new papers come out every week . Some do not have the same interesting biological effects. The problem is, most of the studies have been called, 79 in vitro studies, which means that researchers looked at what curcumin does to isolated cells and other biochemical extracts in lab experiments. Yet scientists shouldn’t extrapolate from these types of studies to make conclusions about how curcumin affects the human body after it’s eaten. Thousands of compounds kill cancer cells in the lab, yet we still don’t have a pill that cures cancer. And although some animal studies have shown that curcumin has promising effects, some also suggest that curcumin could pose risks; one study found that it damaged rats' genetic material in certain situations, while a study in mice reported that the curcumin of the body's stores of iron, which could trigger iron deficiency.

A few clinical trials have directly investigated the effects of curcumin on people with various ailments, but they have not been conclusive. For instance, despite articles with headlines like "Move Over, Prozac: How is Turmeric Helps with Depression," controlled clinical trials have generally not found that curcumin helps with deviation symptoms. (In the article the above mentioned above, psychiatrist Kelly Brogan describes a recent trial that had non-statistically significant results, no, curcumin did not work any better than the comparison treatments.) A 2014 review of the evidence published in the 94 Journal of Clinical Psychiatry concludes that based on the available evidence, "curcumin has questionable or no antidepressant benefits."

And though I tried, I could not find a single clinical trial showing that curcumin works as a treatment for cancer, infections, heart disease or Alzheimer's. One trial that has been cited as an exciting evidence that curcumin has been published in 2012 and investigated the effects of curcumin on rheumatoid arthritis symptoms-but this one is difficult to interpret, too. In it, the researchers gave 500 milligrams of a highly absorbable form of curcumin to 15 people with rheumatoid arthritis every day for eight weeks. They gave 15 other patients diclofenac, a pain drug similar to ibuprofen, and then a third group of 15 subjects took a combination of diclofenac and curcumin. They found that all of the subjects experienced improvements in joint pain and swelling. Yet it's hard to draw clear conclusions because the study was small and because the researchers knew exactly which treatments the subjects were getting. (If the researchers hope the curcumin has benefits, they might as well have changed their clinical behavior in a biased manner.)

According to the 2017 review paper published in the 101 Journal of Medicinal Chemistry, curcumin "Has never been shown to be conclusively effective in a randomized, placebo-controlled clinical trial for any indication."

This does not mean turmeric is useless. But temper your expectations.

Just because studies have not yet shown that curcumin and turmeric could not be treated in the right quantities. We just need a lot more research-clinical research, in humans, that is. In vitro studies are valuable for establishing new research questions and areas to investigate, but they do not give us relevant medical information, and it's irresponsible for doctors and nutritionists to claim that they do. I mean, sure: If you like sprinkling turmeric in your latté, go for it. But do not expect that it will do anything other than add a splash of color and a hint of peppery flavor.

Melinda Wenner Moyer is a science and health writer based in New York. She regularly contributes to Slate and Scientific American. You can find her on Twitter and Facebook.

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