A couple years ago, Dr. Rita P.-Y. Chen published in Scientific Reports. Although her paper was called “Polyhydroxycurcuminoids but not curcumin upregulate neprilysin and can be applied to the prevention of Alzheimer’s disease,” her results started showing up in the popular press as, “Eat Indian food to prevent Alzheimer’s disease!” Her experience became a good lesson for my students as we practiced limiting jargon and providing interesting information.
A recent paper in Nature reminded me of the curry mania, as Dr. Gregory J. Hannon’s paper “Asparagine bioavailability governs metastasis in a model of breast cancer” was summarized in the Mirror as, “Asparagus causes breast cancer, but don’t worry, because they only tested this in mice.” I won’t even link to the Mirror, because the lack of detail and citation is alarming. For a good summary and some insightful commentary, check out “Spread of breast cancer linked to compound in asparagus and other foods” in The Guardian:
Asparagine is an amino acid that is made naturally in the body as a building block for proteins. But it is also found in the diet, and in high levels in certain meats, vegetables and dairy products.
The international team of cancer specialists from Britain, the US, and Canada studied mice with an aggressive form of breast cancer. The mice develop secondary tumours in a matter of weeks and tend to die from the disease within months.
Writing in the journal Nature, the researchers describe how they reduced the ability of breast cancer to spread in the animals by blocking asparagine with a drug called L-asparaginase. To a lesser extent, by putting the animals on a low-asparagine diet worked too. Inspired by the results, the scientists examined records from human cancers and found that breast tumours that churned out the most asparagine were most likely to spread, leading patients to die sooner. The same was seen in cancers of the head, neck and kidney.
I highly recommend the article from The Guardian (and supporting quality journalism) and won’t recapitulate the main points here. Instead, let’s talk a bit about metastasis, or “How did they find breast cancer in my mother-in-law’s femur?”
Metastasis means movement–cancer cells that originated in breast tissue moved into the bloodstream, traveled to a different organ (like the lungs or brain), and were able to generate more cancer cells in the new location. Most cells stay in one place, so scientists looked into the differences between cells that stay and cells that move. (In fact, most cells don’t become cancerous, so scientists also look into the differences between normal and cancerous cells.) In this study, one of the ways the “stay” cells differed from the “move” cells was how much asparagine they could produce. “Move” cells produced a lot more asparagine than the “stay” cells.
That’s only half the evidence.
The other half comes from what happens when the scientists reduced how much asparagine was in the cells–the “move” cells weren’t able to move.
So, WHY doesn’t this study mean that we should all stop eating asparagus? Hey, I’m not a huge fan of asparagus, so don’t let me stop your boycott, but don’t do it because you think you’ll prevent breast cancer. For one thing, asparagine is an amino acid that is in a lot of food, not just asparagus. For another, this study is talking about cancer cells that stay versus cancer cells that move. Their conclusions don’t necessarily mean that eliminating asparagine can prevent cancer altogether.
There are some cool findings in this paper, but simply claiming (AHEM, MIRROR) that asparagus causes breast cancer does NOT pass the smell test.