HEALTH BENEFITS OF GREEN LEAFY VEGETABLES
GREENS – A NEGLECTED GOLD MINE
Mother was right all along. Grandma also told you they were good for you. So why do Americans eat green leafy vegetables only about once or twice a week? Why are cabbage, broccoli, turnip greens, and spinach rarely seen at the American dinner table? Why is lettuce the only green vegetable that most Americans ever use, when green vegetables are recognized by nutritionists as one of the most inexpensive sources of so many important nutrients?
Leafy vegetables are ideal for weight management as they are typically low in calories. They are useful in reducing the risk of cancer and heart disease since they are low in fat, high in dietary fiber, and rich in folic acid, vitamin C, potassium and magnesium, as well as containing a host of phytochemicals, such as lutein, beta-cryptoxanthin, zeaxanthin, and beta-carotene. One study showed that an increment of one daily serving of green leafy vegetables, lowered the risk of cardiovascular disease by 11 percent. In the Adventist health study, the frequent consumption of green salads by African-Americans was associated with a substantially lower risk of mortality.
Because of their high magnesium content and low glycemic index, green leafy vegetables are also valuable for persons with type 2 diabetes. An increase of 1 serving/day of green leafy vegetables was associated with a 9 percent lower risk of diabetes. The high level of vitamin K in greens makes them important for the production of osteocalcin, a protein essential for bone health. The risk of hip fracture in middle-aged women was decreased 45% for one or more servings/day of green, leafy vegetables compared to fewer servings.
Green vegetables are also a major source of iron and calcium for any diet. Swiss chard and spinach are not considered good sources of calcium, due to their high content of oxalic acid. Green leafy vegetables are rich in beta-carotene, which can also be converted into vitamin A, and also improve immune function. Millions of children around the world have an increased risk of blindness, and other illnesses because of inadequate dietary vitamin A from green leafy vegetables.
Lutein and zeaxanthin, carotenoids found in dark-green leafy vegetables, are concentrated in the eye lens and macular region of the retina, and play a protective role in the eye. They protect against both cataract and age-related macular degeneration, the major cause of blindness in the elderly. Some studies suggest that lutein and zeaxanthin may help reduce the risk of certain types of cancer, such as breast and lung cancer, and may contribute to the prevention of heart disease and stroke.
Green veggies contain a variety of carotenoids, flavonoids and other powerful antioxidants that have cancer-protective properties. In a Swedish study, it was reported that eating 3 or more servings a week of green leafy vegetables significantly reduced the risk of stomach cancer, the fourth most frequent cancer in the world. Cabbage, cauliflower, brussels sprouts, and broccoli are rich in indoles and isothiocyanates, which protect us against colon and other cancers. Broccoli sprouts have been reported to contain 10 or more times as much sulforaphane, a cancer-protective substance, than does mature broccoli. A higher consumption of green leafy vegetables has been shown to significantly decrease the risk of breast cancer and skin cancer.
Studies have identified a gene, connexin 43, whose expression is upregulated by chemopreventive carotenoids and which allows direct intercellular gap junctional communication. In many human tumors gap junctional communication is deficient and its upregulation is associated with decreased proliferation. Hence, the cancer-preventive properties of carotenoids are partly explained by their impact on gene regulation.
Quercetin is a bioflavonoid found in leafy green vegetables. Quercetin has an antioxidant and anti-inflammatory activity and displays unique anticancer properties. Quercetin is a natural compound that blocks substances involved in allergies and acts as an inhibitor of mast cell secretion, and causes a decrease in the release of interleukin-6.
There was considerable concern associated with the E.coli O157:H7 outbreak in the fall of 2006 (26 states were affected) that was associated with contaminated bagged baby spinach. The outbreak resulted in 205 confirmed illnesses and three deaths, with the infection causing bloody diarrhea and dehydration. FDA investigators suggested that the outbreak was possibly caused by the presence of wild pigs on the ranch, or that the irrigation water had been contaminated with cattle feces or grazing deer.
Green, leafy vegetables provide a great variety of colors from the bluish-green of kale to the bright kelly green of spinach. Leafy greens run the whole gamut of flavors, from sweet to bitter, from peppery to earthy. Young plants generally have small, tender leaves and a mild flavor. Many mature plants have tougher leaves and stronger flavors. Collards, Swiss chard, bok choy, and spinach provide a mild flavor while arugula, mizuna and mustard greens provide a peppery flavor. Bok choy is best known for use in stir-fries, since it remains crisp, even when cooked to a tender stage. One should always choose crisp leaves with a fresh vibrant green color. Yellowing is a sign of age and indicates that the greens may have an off flavor. Salad greens provide a whole range of important nutrients and phytochemicals to keep us healthy.
LEAFY GREEN VEGETABLES
“Greens are the No. 1 food you can eat regularly to help improve your health,” says Jill Nussinow, MS, RD, a culinary educator in Northern California and the author of The Veggie Queen. That’s because leafy vegetables are brimming with fiber along with vitamins, minerals, and plant-based substances that may help protect you from heart disease, diabetes, and perhaps even cancer. Even so, Americans are not eating as many vegetables each day as dietary experts recommend.
To encourage you to put more leafy vegetables on your plate, WebMD asked Nussinow to rank the country’s most widely-eaten greens from most nutritious to least. Here’s our top 10 list:
- KALE: This nutrition powerhouse “offers everything you want in a leafy green,” says Nussinow, who gave it her first-place ranking. It’s an excellent source of vitamins A C, and K, has a good amount of calcium for a vegetable, and also supplies folate and potassium. Kale’s ruffle-edged leaves may range in color from cream to purple to black depending on the variety.
Before cooking with kale, collards, turnips, and chard, Nussinow recommends swishing the greens in a water-filled sink, draining the sink, then repeating this rinse until the leaves are dirt-free. Her favorite cooking method for these four greens is to rub the leaves in olive oil or tahini (sesame paste) and cook them for five minutes with garlic, olive oil, and broth.
- COLLARDS: Used in Southern-style cooking, collard greens are similar in nutrition to kale. But they have a heartier and chewier texture and a stronger cabbage-like taste. “Collards are an under-appreciated vegetable and most people don’t know about them,” suggests Nussinow. She says they’re also popular with the raw food movement because the wide leaves are used as a wrapper instead of tortillas or bread. Down South, collards are typically slow cooked with either a ham hock or smoked turkey leg. A half cup has 25 calories.
- TURNIP GREENS: “If you buy turnips with the tops on, you get two vegetables in one,” Nussinow tells WebMD. Turnip leaves are another Southern favorite traditionally made with pork. More tender than other greens and needing less cooking, this sharp-flavored leaf is low in calories yet loaded with vitamins A,C, and K as well as calcium.
- SWISS CHARD: With red stems, stalks, and veins on its leaves, Swiss chard has a beet-like taste and soft texture that’s perfect for sauteeing. Both Swiss chard and spinach contain oxalates, which are slightly reduced by cooking and can bind to calcium, a concern for people prone to kidney stones. Chard contains 15 calories in one-half cup and is a good source of vitamins A and C. Nussinow likes to make a sweet-and-sour chard by adding raisins and vinegar to the cooked greens.
- SPINACH: Popeye’s favorite vegetable has 20 calories per serving, plus it’s packed with vitamins A and C, as well as folate. And because heat reduces the green’s oxalate content, freeing up its dietary calcium, “cooked spinach gives you more nutrition than raw,” says Nussinow. Spinach leaves can be cooked quickly in the water that remains on them after rinsing, or they can be eaten raw in salads. Bags of frozen chopped spinach are more convenient to use than block kinds, and this mild-flavored vegetable can be added to soups, pasta dishes, and casseroles.
- MUSTARD GREENS: Another Southern green with a similar nutrition profile to turnip leaves and collards, mustard greens have scalloped edges and come in red and green varieties. They have a peppery taste and give off a mustardy smell during cooking. Their spiciness can be toned down by adding an acid, such as vinegar or lemon juice, toward the end of cooking, suggests Nussinow. Cooked mustard greens have 10 calories in one-half cup.
- BROCCOLI: With 25 calories a serving, broccoli is rich in vitamin C and is also a good source of vitamin A, potassium, and folate. Americans eat about 6 pounds of it a year. Its stalks and florets add both crunch and color to stir-fries. While some kids may call this veggie “trees,” they often like it best raw or steamed with a yogurt-based dip. Nussinow mixes fresh broccoli into her pasta during the last three minutes of cooking so both are ready at the same time.
- RED AND GREEN LEAF AND ROMAINE LETTUCE: A familiar sight in salad bowls, these lettuces are high in vitamin A and offer some folate. Leaf lettuces have a softer texture than romaine, a crunchy variety used in Caesar salads. Fans of Iceberg lettuce may go for romaine, a crispy green that’s better for you. Nussinow points out “the darker the lettuce leaf, the more nutrition it has,” making red leaf slightly healthier than green. If you don’t drown lettuce in a creamy dressing, one cup contains 10 calories.
- CABBAGE: Although paler in color than other leafy greens, this cruciferous vegetable is a great source of cancer-fighting compounds and vitamin C. Nussinow considers this versatile green “the workhorse of the kitchen.” Available in red and green varieties, cabbage can be cooked, added raw to salads or stir fries, shredded into a slaw, or made into sauerkraut. It’s also a staple of St. Patrick’s Day boiled suppers and can give off a strong smell when cooking. One-half cup cooked has 15 calories.
- ICEBERG LETTUCE: This bland-tasting head lettuce is mostly water. But it’s the country’s most popular leafy green and each of us eats about 17 pounds of iceberg a year. While tops in consumption, it’s last on our list for its health benefits. “It’s not devoid of all nutrition, but it’s pretty close,” Nussinow tells WebMD. Although we’re eating less iceberg than we did two decades ago, it’s still a common ingredient on hamburgers and in taco salads. “It can be a starter green,” says Nussinow, to draw people into a broader array of salad greens.
THE IMPORTANCE OF EATING GREEN LEAFY VEGETABLES (GREENS)
plant-protein-greensDark green leafy vegetables are perhaps the most potent superfood on the planet. They are also the most ignored and avoided foods as well. If you consider the powerful dose of vitamins, minerals, antioxidants and phytonutrients that we get from spinach, kale, chard, collards, dandelion and other greens, it’s a wonder we can live without them.
LEAFY GREEN NUTRITION
Leafy green vegetables have more nutrition per calorie than any other food. Greens make up a significant source vitamins A, C, E and K as well as several B vitamins. They are rich sources of minerals such as calcium, magnesium, iron and potassium. They are rich in fiber, extremely low in fat and carbohydrates and provide an excellent source of protein.
HOW MUCH GREEN SHOULD YOU EAT?
The USDA food pyramid suggests a minimum of 3 servings of leafy greens per week. Most Americans fall short of this recommendation. Most health experts agree that the amount of leafy greens that we should consume is likely much higher than just 3 servings per week!
I eat about 4-6 servings per day (that’s about two small bunches or “heads”), mostly in green smoothies.
DRINK YOUR GREEN SMOOTHIES
Nobody likes to eat a big bowl of leafy greens. I eat a lot of greens each day, but I rarely eat salad. I get my greens from delicious fruit smoothies. I drink my spinach, kale, chard and dandelion greens while savoring the flavors of pineapple, mango, pear and even chocolate!