Catching the Rainbow

Catching the Rainbow

Leading health organizations like the American Heart Association and the American Institute for Cancer Research recommend “eating the rainbow,” a wide variety of naturally colorful foods. Aside from the fact that 94 percent of Americans don’t even reach the recommended minimum amount of fruits and vegetables (five to thirteen servings, depending on sex, age, and activity), there is a “phytonutrient gap.” Our food isn’t colorful enough. If the average American is supposed to eat about ten servings a day, you can think of that as two servings from each color group—but about eight tenths of Americans eat too little from each color. The worst is violet-blue, our source of anthocyanin pigments, of which about nine tenths of Americans get too little. In the standard American diet, blueberries are the main source, yet on average everyone eats only a single blueberry a day.

The word anthocyanin comes from the Greek anthos, “flower,” and kyanos, “blue.” The color of red, blue, and purple berries comes from the same pigments, whose names still hint at their floral origin—for example, petunidin in blueberries or peonidin in cranberries. Anthocyanins can cross the blood-brain barrier and are presumably responsible for berries improving cognitive performance by enhancing blood flow to the brain, memory, cognitive control, processing speed, attention, and overall cognitive performance. They may also benefit vision.

In the chapter “Preserving Vision,” I talked about the potential of berries to help with macular degeneration, glaucoma, and cataracts, but they’re also good for vision in general. Randomized placebo-controlled double-blind trials showed that anthocyanins from berries can significantly alleviate both the objective and subjective signs and symptoms of eye strain and improve the eyes’ adjustment to brightness and darkness. Anthocyanins appear to be important for regenerating the receptor protein rhodopsin in the retina, which helps convert light rays into electrical signals for the brain, allowing the eyes to adapt more quickly to changing lighting conditions.

As I described in the chapter “Inflammation,” berries act systemically anti-inflammatory throughout the body, but they can also suppress inflammation directly in the gut. 90 percent of all patients with chronic colon inflammation responded to blueberries, with most achieving remission within up to six weeks; however, the disease became active again as soon as the berries were stopped. That is presumably due to the prebiotic effect of anthocyanins on the gut microbiome. Berries increase the number of good bacteria and reduce the bad. For example, if you eat blueberries every day, the amount of lactobacilli and bifidobacteria grows. Black currants and tart cherries had similar effects.

Anthocyanins also improve blood sugar regulation both short- and long-term, in part by increasing insulin sensitivity, so it’s not surprising that there’s an association between higher berry consumption and lower risk of type 2 diabetes. Two well-known Harvard studies that incorporated data from millions of person-years showed that eating at least two servings of berries per week is associated with a 23 percent lower risk of diabetes.

Berries are also thought to acutely improve arterial function, which would explain why higher anthocyanin intake is associated with a significantly lower risk of dying from cardiovascular disease—and therefore lowers overall mortality as well. A bowl of blueberries can even largely offset the impairment in arterial function caused by smoking a cigarette. After just one cigarette, the ability of arteries to relax naturally drops by 25 percent after two hours. But if you eat two cups of blueberries 100 minutes before smoking, the same cigarette causes less than half the damage. (Of course, you prevent the damage entirely if you don’t smoke at all.)

We suspect that this is mainly due to the anthocyanins in berries, since isolated anthocyanins also improve arterial function, though not as well as whole berries. At doses of more than 300 milligrams per day, anthocyanins also lower LDL cholesterol levels. That would be one serving a day, about a half cup of berries with a high anthocyanin content, such as blueberries. Even drinking one cup of blueberry tea daily—ground blueberries in a tea bag, steeped for five minutes—can lower cholesterol levels, but it took three months for the tea to have a significant effect.

Anthocyanins are cleared from the bloodstream in about six hours, so the berries you sprinkled over your oatmeal at breakfast have finished their journey by afternoon. In my opinion, berries are the perfect dessert for any meal. Other fruits also contain anthocyanins, such as plums, pomegranates, and red and black grapes. Thanks to red onions, blue potatoes, red cabbage, or purple barley, anthocyanins can also be part of the main dish. As a snack, I like purple air-popped popcorn; as a side, air-fried purple sweet potato fries. And to drink: What do you think makes hibiscus tea so ruby-red, like Snow White’s lips? Anthocyanins are presumably also responsible for hibiscus’s blood-pressure-lowering effect. In animal models, the anthocyanins in black rice slowed the accelerated aging of mice induced by galactose, and the anthocyanins in purple wheat increased the life span of C. elegans by about 10 percent.

Cherries, Cranberries, Goji Berries, and Grapes

For about 50 years we have known that tart cherries are so anti-inflammatory that they can be successfully used to treat gout, a painful type of arthritis, as I mentioned in the chapter “Inflammation.” In healthy people, too, cherries can alleviate inflammation, as shown by decreasing levels of C-reactive protein. Overall, 11 of 16 intervention studies with cherries, both tart and sweet, found a reduction in inflammation; eight of ten studies measured a reduction in oxidative stress; eight of nine a reduction in exercise-induced muscle soreness and strength loss; in five of seven, blood pressure fell; in five of five, arthritis eased somewhat; and in four of four, participants slept better (presumably due to the melatonin content of cherries, see see.nf/melatoninfoods). Most of these studies lasted less than two weeks, and the test subjects received the equivalent of 45 to 270 cherries per day.

Out of season, you can find tart cherries preserved in water and sweet cherries in the freezer section. (To this day I still like to suck on frozen dark cherries like popsicles—a trick my mom showed me.) In How Not to Die, I recommend using the liquid from canned cherries for hibiscus punch and mixing the cherries with cocoa powder into your morning oatmeal for an explosion of cherry-chocolate flavor.