Even if you don’t grow your own vegetables, you see their vivid colors come alive in farmers’ markets and supermarket bins—from deep orange winter squash to dark green spinach leaves.
Longtime vegetable gardeners can’t help but have noticed that seed catalogs have exploded with colorful new vegetable varieties over the past few years. Coral, burgundy and deep-purple carrots. Lettuce in shades of fuschia, bronze and burgundy. Purple-, magenta-, black,- pink-, and deep yellow-fleshed potatoes. Orange, purple and near-black tomatoes. Orange, purple and chartreuse cauliflower. Bright yellow, orange, brown, and purple bell peppers.
Even if you don’t grow vegetables, you’ve probably seen or read half a dozen articles in the past year or two touting the health benefits of a “rainbow diet” of deeply-colored fruits and vegetables.
Fruit and Vegetables Protect From Disease
It turns out the marketplace has begun to reflect scientific findings of the past few decades. “Since the 1970’s, an abundance of evidence has demonstrated that people who eat a lot of fruit and vegetables are healthier and seem to be protected from chronic disease,” says Beverly Clevidence, a nutritionist with the U.S. Agricultural Research Service’s Food Components and Health Laboratory since 1984.
Indeed, study after study has confirmed that people who eat more fruits and vegetables, particularly more deeply colored varieties, have less heart disease, cancer, diabetes, osteoporosis, and age-related neurological decline.
“Something must be responsible, so scientists set out to find out what,” says Clevidence.
There’s a lot at stake. Chronic diseases, responsible for 70 percent of American deaths, currently afflict 40 percent of Americans and 80 percent of older Americans. Half the nation’s elders suffer from two or more chronic health conditions. With the population of elders rising dramatically and the incidence of chronic diseases increasing among children, it’s no wonder researchers are eager to learn why eating fruits and vegetables confers so many health-protecting benefits.
The Power of Pigments
Increasingly, researchers around the world have begun to focus on pigments, the compounds plants make that create the beautiful colors we appreciate in flowers, fruits, and foliage.
Scientists define pigments as light-harvesting molecules. Each pigment selectively absorbs certain bandwidths of visible light and reflects the others. The reflected wavelengths are the colors we see.
The first plant pigment–chlorophyll—arguably the most important molecule on Earth—appeared at least 2.5 billion years ago. The photosynthetic reactions it initiates produce all the food and the all the oxygen that sustains the animal life on the planet.
Some pigments work with chloropyhlls as photosynthetic accessory pigments. Pigments serve higher plants as signaling agents, attracting pollinators to their flowers and seed-dispersing animals to their ripe fruits.
But pigments also protect plants from excessive, tissue-damaging solar radiation and assault from free radicals, protect them from environmental stress, defend against attacks by microbes, insects and animal predators, heal damaged tissues, serve as growth regulators, and probably act in many other ways still undiscovered.
Plants: Master Chemists
“Plants are the master chemists,” says Mary Ann Lila, who directs the Plants for Human Health Institute at North Carolina State University. “Because plants can’t move around, they have to manufacture what they need, not merely to grow, but to defend, protect, and heal themselves. It makes sense that the compounds plants produce in response to stress would help a human under similar circumstances.”
Increasingly, scientists have begun to focus on the health-promoting benefits of pigments, the light-harvesting molecules plants manufacture that selectively absorb certain bandwidths of visible light and reflect the others.
Pigments serve and protect plants
Since plant science has confirmed that many pigments protect plants from damage, and medical researchers believe that this type of damage plays a role in the development of most chronic diseases, a lot of research has focused on trying to understand the value of pigments.
Photo by Sveta Zarzamora/Getty Images.
Why not simply extract the pigments and put them into pills?
“Well, there’s a lot of research heading in that direction,” says James Joseph, a neuroscientist and senior researcher at the Tufts University Human Nutrition Research Center on Aging in Boston. “But when you start taking these things apart, the compounds don’t act like they do in the whole food. In fact extracts can even produce the opposite effect, especially in high doses.”
“If you take something out of a plant and put into a pill, it’s more expensive, probably less effective, and possibly dangerous,” says retired USDA ethnobotanist James A. Duke, author of 30 books and a huge phytochemical (chemicals plants have manufactured naturally) database, and an authority on medicinal plants. “Plus it’s not occurring with its natural synergists. Most phytocompounds work together, with synergistic or additive effects.
“But you can’t overdose on vegetables,” Duke says. “Variety is the key. Get the most variety of colorful fruits and vegetables you can the most cheaply.”
He also encourages consumers to “graze in the field,” learning to identify and eat weeds and other plants from the wild. “Wild plants have to produce more [protective compounds] to protect themselves, and they pass that protection along to you and me.”
The more we clearly connect the health benefits of pigments, the more acceptable nutritional approaches to human health will become to the medical community.
Clevidence adds, “Meanwhile, we just do the science and report what we learn, building our knowledge base brick by brick.”
“For now, we should apply what we know, and the message is not sexy: ‘Eat more fruits and vegetables. Eat a little fat, from any source, with green and yellow vegetables. Steam, microwave, or add red and purple vegetables to soup so you don’t pour those water-soluble anthocyanins (pigments) down the drain.”
There’s a lot at stake
Just over a quarter of Americans eat the current USDA recommendation of three servings of vegetables a day, and most experts call for nine servings to get the maximum benefits.
Children ages two to 18 eat even less: dark green or orange vegetables make up only eight percent of the veggies children eat and fried potatoes account for nearly half.
So remember: Eat your (colorful) veggies!