“Eat the rainbow” is one of those morsels of dietary wisdom that sounds suspiciously like an ad for Lucky Charms. But once you get past the whole cereal thing, it’s actually brilliant advice.


The “rainbow” refers to colorful plant compounds  – reds, yellows, blues, greens, purples, and oranges – that confer health benefits to the hairy animals that eat them. These compounds are broadly known as polyphenolic compounds, or polyphenols for short. Resveratrol is a polyphenol. Oleuropein from olive oil is a polyphenol. Tannins from coffee and tea are polyphenols.


Polyphenols are our friends because they lower inflammation. And like I wrote about last time, inflammation is probably the most important marker for healthy aging.


Within the class of polyphenols are a subset of phytochemicals called flavonoids. All that good stuff in dark chocolate? Yeah, flavonoids. The much studied catechins in tea? Also flavonoids. We still haven’t identified most of these compounds, but the ones we have identified have potent antiinflammatory, anticancer and neuroprotective effects.


Anthocyanins are purple


Within the world of flavonoids are purplish, bluish, reddish compounds known as anthocyanins. Anthocyanins come in six categories: cyanidin, delphinidin, malvidin, pelargonidin, peonidin, and petunidin. These will make perfect names for my kids.


The most studied, and perhaps most potent, of the anthocyanins is a purple pigment known as cyanidin. I only learned about cyanidin recently, and the amount of research on just one pigment is staggering.


Just one pigment. In the class of anthocyanins. In the class of flavonoids. In the class of polyphenols. In the class of stuff you put in your body.


At least, stuff you should be putting in your body. Let’s get to why.


Purple combats cancer


Before we dive in, a note on anthocyanin research. Many studies showing benefits – killing cancer cells, for instance – were in vitro studies. In other words, the cancer was exposed to anthocyanins in a test tube, not a warm body. Do the benefits translate to warm bodies? Hard to say. Because of this, I’ll focus on in vivo studies – studies that use mice or humans as subjects.


Even in vivo, anthocyanins show promise against cancer. For instance, mice with tumors lived longer when they were given anthocyanin extract from red beans. And mice given anthocyanins from black rice showed improvements in breast cancer. Their cancer cells literally exploded through increased expression of a mechanism called apoptosis. 


Purple lowers blood sugar


Anthocyanins also have formidable effects on blood sugar. In one clinical study, researchers showed that anthocyanin extract reduced blood sugar just as well as Metformin, the preferred diabetes drug. And since Metformin seems to cause liver problems and B12 deficiency, natural alternatives are much needed.  


But if you’re non-diabetic, what’s so great about lowering blood sugar? In a nutshell: high blood sugar leads to problems with insulin (the hormone that transports glucose to cells), which in turn increases your risk for cancer, dementia, and heart disease. Yeah, the big three.


Purple, ROS, and the brain


In the brain too, anthocyanins have benefits. To understand those benefits though, a little explanation is needed.


One reason we age (in the brain and elsewhere) is due to damage caused by reactive oxygen species (ROS). ROS are byproducts of normal metabolism. ROS are generated when we breathe. They can’t be stopped entirely. They will cause damage.


ROS accumulation can be slowed though, and your body accomplishes this task using enzymes like glutathione peroxidase and superoxide dismutase. Even if you haven’t done a dissertation on these enzymes, rattling them off in mixed company will make you sound smart. Take it from me.


What’s this got to do with brain health? Well, inhibit ROS, so the theory goes, and you preserve cognitive function. It’s essentially damage control for your gray matter. And a sweet way to control this damage is by eating flavonoids like anthocyanins.  


One study on mice, in fact, showed that anthocyanins reduced amyloid plaques in a model of Alzheimer’s disease. The berry-fed mice even behaved better than the control mice.


Research-wise, that’s just the tip of the cyano-berg. (Yeah, I made that up). If you really want your brain to explode, spend a quiet evening with this comprehensive review.


Anthocyanin content of foods


By now you’re probably wondering what foods have the highest anthocyanin content. For answers, check out this chart from the Linus Pauling Institute (scroll down a bit until you hit Table 2. Anthocynanidin Content).


According to the chart, blueberries have the broadest spectrum of anthocyanins. Others, however, have much higher concentrations of cyanidin. It’s not always clear from the literature what anthocyanin does what, so eating a wide range is probably prudent.


Me? I eat blueberries and red cabbage almost every day. Here’s why: even if anthocyanins aren’t hugely bioavailable, the positive effects on human cells are too profound to ignore. Plus there’s considerable evidence in vivo for warm blooded mammals like you and me.


Let’s face it: of all the colors of the rainbow, who knew that purple was so healthy?


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