Today I round out my Wahls-inspired series on the health benefits of eating various classes of plant matter. If you’re just now joining us, be sure to watch the video in which Terry Wahls explains how eating a Paleo diet rich in leafy greens, cruciferous vegetables, and brightly colored produce (plus meat and seaweed and fish and offal) coincided with a regression in her rapidly-progressing MS. Then, read the previous two installments on leafy greens and crucifers to get completely caught up.
All ready? Good.
You know how those deep red beets sliced in half to show off the insides, those taut blueberries, those purple and violet mottled, oddly-shaped heirloom tomatoes lightly dusted with soil, and those glistening blackberries sitting in your periphery pop out and draw your gaze as you make your way through the farmers’ market? That’s not just clever product placement. It’s actually because of the pretty colors. It’s innate. It’s by “design.” Mother nature, you see, is a masterful visual merchandiser who comes up with all these lovely colors so that plants can reproduce. But wait – how does color help plants reproduce?
Simple. Plants tend to be stationary. Except for the ents, they are, quite literally, rooted in place. A tomato plant can’t walk, can’t kneel and lovingly place its firstborn into a shallow womb dug into the soft, fertile earth. That would be awesome to see, but it’s not gonna happen. What does happen is that colorful plants catch the eye of hungry organisms who eat the fruit, swallow the seed, and poop it out someplace else, thus giving it a chance to take hold, germinate, and develop into a full-blown adult plant. In order to disseminate their progeny across the land, many plants must therefore manufacture pigments – colorful compounds that draw the eye and signal “food source” to mobile, hungry organisms. Being mobile, hungry organisms ourselves, we are also attracted to colorful fruits and vegetables.
And for good reason. See, mother nature is also thrifty. It’s rare that she manufactures a compound with only one use – she likes her creations to multitask – and plant pigments are no different. They serve multiple roles in plants in addition to attracting animals, such as protecting it from UV damage, dampening the effects of excess light, enabling photosynthesis, and even acting as endogenous antioxidants (plants can’t really sip red wine and pop supplements, after all). Luckily, it appears that we can leverage many of these pigments for our own gain by eating brightly colored fruits and vegetables.
Which is why both Terry Wahls and I recommend eating a wide variety of them. There are hundreds of different bioactive plant pigments, each with unique effects. Rather than isolate just one or two, by eating a variety of colorful plants we ensure consumption of a wide range of potentially health-promoting plant pigments.
I could end this post now with the basic advice to “eat colorful foods and lots of them.” This would cut down on reading time, ingratiate myself to vegan and vegetarian readers, and still manage to convey an effective, actionable message. But alas, I know you guys like the gritty details. It’s not enough (for most of you) to read someone tell you that eating blueberries and purple sweet potatoes is healthy. Sometimes you want to vividly imagine those anthocyanins sliding down your gullet, preventing the oxidation of omega-3 fatty acids in your gut, and interacting with your body at the cellular level to produce beneficial antioxidant and/or hormetic effects. Sometimes you want to know what you’re putting inside your body on a deeper level. If that’s you, keep on reading. If it’s not, just go out, eat some colorful produce, and you’ll be fine.
When I put this post together, I struggled with formatting. Should I cover each individual pigment? With dozens of them out there, that would be a large undertaking. Should I cover each plant? Plants contain multiple pigments, so it could get confusing rather quickly. Should I cover each color? That’s confusing, because there’s a lot of overlapping and combinations of different pigments into different colors. I decided to break them up into pigment categories.
Anthocyanins and Other Flavonoids
Since I already mentioned anthocyanins, let’s start there. Anthocyanins are flavonoids, the most common type of polyphenol. Pretty much any fruit, vegetable, or flower with a significant amount of purple or blue gets that color from anthocyanins. Even some reds can be anthocyanin-based. The deeper the color, the more anthocyanins. We’re talking:
Blueberries – Anthocyanin-rich blueberry juice improved cognitive function and memory in aging adult humans.
Raspberries (black and red) – Raspberry juice shows anti-atherosclerotic effects in hyperlipidemic rodents, and although human studies are lacking, there is a strong basis for considering them a healthful food.
Blackberries – Perhaps my favorite berry, blackberries are rich in flavonoid pigments with in vivo evidence of protection against neurological degeneration and bone loss.
Purple sweet potatoes – Tons of references in my sweet potato post (that’s my post about sweet potatoes, not my sweet post about potatoes). Same goes for regular purple potatoes.
Purple tomatoes – In addition to carotenoids (more on those below), purple tomatoes also contain significant levels of anthocyanins.
Purple carrots – Same goes for purple carrots.
There are even vegetables that have feet (roots?) both in the colorful camp and the sulfur-rich or leafy-green camps. Like:
Red leaf lettuce – Leafy green and colorful.
Radicchio – Leafy green and colorful.
Red cabbage – Sulfur-rich and colorful (with 36 different anthocyanins).
Purple cauliflower – Sulfur-rich and colorful.
Purple kale – Leafy green, sulfur-rich, and colorful.
I could go on, but I won’t. The point is that any plant with these colors is going to contain these compounds, because these compounds literally are the colors. That means I’ve missed the vast majority of anthocyanin sources, but it also means that you’ll have an easy time finding them out there in the world. Eat up (but rinse your mouth out after; they stain) and go for blues, reds, and purples.
Oh, yeah. There are a couple other relevant flavonoids. Anthocyanins get the most press, but there are other foods with potentially beneficial health effects due to flavonoid content.
Turmeric – Contains curcumin, which gives the spice its distinctive, persistent yellow color. I’ve written an entire piece on the health benefits of turmeric, and curcumin is responsible for the lion’s share of them.
Apples and onions – A light yellow pigment, quercetin is found in apples and onions (except for white onions). Red and yellow onions are high in quercetin (PDF), while most of the quercetin in apples resides in the skin.
Carotenoids are pigments that provide the orange, yellow, and red colors found in foods like carrots (get it?), sweet potatoes, cantaloupes, bell peppers, squash, watermelon and tomatoes. You’ve got beta-carotene, alpha-carotene, beta-cryptoxanthin, gamma-carotene, and beta-zeacarotene, which can be partially converted to retinol, the active (animal) form of vitamin A. You’ve also got lutein, lycopene, and zeaxanthin, which cannot be converted to vitamin A.
Don’t rely on carotenoids to fulfill your vitamin A requirements. Liver and egg yolks are much better, more reliable sources. Besides, beta-carotene supplementation doesn’t seem to work very well. In several studies, it has appeared to increase the risk of lung and prostate cancer, and a 2007 Cochrane review found that beta-carotene supplements were associated with an increase in general mortality. “Supplementation” of alpha-carotene, via carotenoid-rich fruits and vegetables, however, appears to have the opposite relationship. Huh, food’s good for you… who knew?
Get carotenes through orange vegetables and fruits, like squash, carrots, sweet potatoes, cantaloupes, and bell peppers.
The other carotenoids – the ones that don’t convert to vitamin A, like lutein, lycopene, and zeaxanthin – appear to be helpful. Both lutein and zeaxanthin accumulate in the retinas of our eyes, where they seem to play major roles. The more lutein and zeaxanthin you eat, the more it accumulates in your retina (although this is most pronounced in patients with low baseline pigment levels). Low dietary intake of lutein and zeaxanthin are associated with elevated incidences of age-related macular degeneration, and a similar relationship was found for cataracts.
Get lutein and zeaxanthin through spinach, kale (what doesn’t kale have?), dandelion greens, chard, collards, romaine lettuce, paprika, and turnip greens.
Lycopene does some cool stuff, too. It reduces lipid peroxidation in people with heart disease, as well as protects the skin against UV-related damage from the sun. There’s also a lot of research into the effect of lycopene intake on cancer.
The best sources of lycopene are cooked tomato products, like tomato paste or sauce, especially cooked with fat (but not sunflower oil!), but lower levels can be attained through raw tomatoes, pink grapefruit, pink guava, and watermelon. The absolute best source, however, is gac, a Vietnamese fruit that beats tomatoes by 70-fold. It also contains high levels of other carotenoids, all of which are bound by long chain fats, making them even more bioavailable. Anyone every try gac?
Although betalain pigments are described as “deep red” and “purple” and sound similar to the anthocyanin family, they are not the same. They look different (just compare a beet to a strawberry – not quite the same). In fact, betalains and anthocyanins have never been found in the same plant; they appear to be mutually exclusive. Besides the beet (where “betalain” gets its name), rhubarb, and the stems of chard, there aren’t very many sources of readily edible betalains. I suppose you could throw together a floral salad of bougainvillea, amaranth, and purple cacti, but for the most part, you’re going to get your betalains from beets.
All beets contain all betalains, just in different ratios. In purple or red beets, betacyanins predominate. In yellow beets, betaxanthins predominate.
Possible benefits of betalains include:
A beet extract rich in betacyanins showed cytotoxic effects on human prostate and breast cancer lines.
Well, I hope that’s enough to convince you to include more color in your diet. As you can see, not all of the benefits of plant pigments are “proven,” but they’re probably all quite safe in the amounts you’ll find in foods. So go ahead and eat up a wide variety. If they do turn out to be helpful, you’ll have hedged your bet quite nicely.
With all that said, what are your favorite brightly colored edible plants? How do you like to get your anthocyanins, carotenoids, and betalains (well, I bet I can guess how you get that last one)?
Let me know in the comment section!