This post initially appeared on Science Blogs

A while back, ERV had a post about the tenuous link between Vitamin D and all sorts of effects on health (and I shamelessly co-opted her title). Then, PalMD dissected the spurious link between Broccoli and cancer. Now it's my turn:

A new study has revealed that naturally occurring chemicals found in the skin of the nut boost the immune system's response to such infections.

Researchers found almond skins improved the ability of the white blood cells to detect viruses while also increasing the body's ability to prevent viruses from replicating and so spreading inside the body.

Oh Guardian, I thought you were better than this[Telegraph - my bad]. Let's see what the actual paper showed.

The setup

They took human peripheral blood mononuclear cells (PBMC's) - that's basically all lymphocytes (T-cells and B-cells) plus monocytes, any circulating macrophages, and a few others - and incubated them with different components of almonds. Natural skins (NS), boiled skins (BS) and these same skins that have been treated with various types of in vitro digestion using gastric or intestinal enzymes. Then they infected these cells with a virus for 24 hours, and looked how much virus came out.

The results

On the x-axis, you have the various almond parts, and the y-axis shows "plaque-forming units" (PFU's) of virus, which is just a measure of infectious virus extracted after infection. The difference between the first bar (the PBMC's treated with almond skins) and the last bar (untreated cells) doesn't look that impressive, but it's plotted on a log scale, which means there's almost 10 times less virus with the almond skins - so far so good. But... (there's always a but)

The Problems

There are so many. First off, the digested almonds didn't do anything. This is all in vitro (in a tissue culture dish), so you'd have to take any result with a tablesoon of salt, but even the most relevant in vitro condition was completely ineffective. So unless you're planning on grinding up almond skins and injecting them directly into your blood-stream (DON'T DO THIS!), this study doesn't acutally show anything.

Second, the mechanism of action seems pretty straightforward - the undigested skins induced inflammation. They measured cytokine production from their PBMC's, and a bunch of cytokines, especially IFNγ, TNF, and especially type-1 interferons were produced. Lots of things cause inflammation, and those would all restrict viral replication in this assay. But systemic inflammation is generally bad. So if you actually did grind up almond skins and inject them into your blood-stream (again, DON'T DO THIS), presuming you don't die because of almond particles clogging up your capillaries, the best you can expect is a fever, and some tissue damage all over your body. You might decrease your chance of getting a cold, but it's probably not worth it.

Finally, this study was funded by the Almond Board of California. I suppose it's no wonder that the conclusions were wildly over-blown. Arena, A., Bisignano, C., Stassi, G., Mandalari, G., Wickham, M., & Bisignano, G. (2010). Immunomodulatory and antiviral activity of almond skins Immunology Letters, 132 (1-2), 18-23 DOI: 10.1016/j.imlet.2010.04.010

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