Green vegetables are literally a gold mine of nutrients and phytochemicals. So why does the average American eat green leafy vegetables only once or twice a week? Why are cabbage, broccoli, Brussels sprouts, turnip greens, arugula, and collards rarely seen at the American dinner table? Green is the future, and green vegetables must be a part of that future. Green vegetables are an inexpensive source of so many important nutrients, but in addition, their production does not harm the environment as animal production does.
Reduced Risk of Chronic Diseases
Leafy vegetables are ideal for weight management since they are typically low in calories, unless they get overloaded with rich or excessive dressings. Greens are also 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; they also contain a host of protective phytochemicals, such as lutein, beta-cryptoxanthin, zeaxanthin, and beta-carotene.
One study showed that adding an increment of 1 daily serving of green leafy vegetables lowered the risk of cardiovascular disease by 11 percent. There is strong evidence that nitrate in greens and beet root increases the production of nitric oxide. Moderate amounts of this molecule improve dilation of blood vessels and inhibits platelet aggregation.1 These two factors improve blood flow.
Glucosinolates are found almost exclusively in cruciferous vegetables such as cabbage, broccoli, kale, and Brussels sprouts. As cruciferous veggies are digested and metabolized, they release anti-inflammatory compounds called isothiocyanates. Because inflammation plays a pivotal role in most chronic disease, eating a daily serving of cruciferous greens may help to curtail inflammation from chronic diseases. Green cruciferous vegetables also improve the liver’s ability to detoxify toxins.2 Quercetin, a major bioflavonoid found in green leafy vegetables, exerts a strong antioxidant and anti-inflammatory activity. It can block substances involved with allergies, and displays unique anticancer properties.
In the Adventist Health Study, the frequent consumption of green salads by African Americans was associated with a 40 percent reduced 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 one serving per day of green leafy vegetables was associated with a nine percent lower risk of diabetes.3
Bone Protection and More
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 percent for 1 or more servings per day of green leafy vegetables, compared to fewer servings. In addition, green leafy vegetables are rich in betacarotene, which can be converted into vitamin A. Millions of children around the world have an increased risk of blindness because of inadequate dietary vitamin A obtained from green leafy and other vegetables.
Source of Calcium and Iron
Green vegetables are also a major source of iron and calcium. Swiss chard and spinach are not considered good sources of calcium, due to their high content of oxalic acid which chelates or binds the calcium. The availability of calcium from other greens like kale, however, can run as high as 50 to 60 percent—which is considerably better than the 30 to 35 percent provided by milk.
Pigments Fight for Us
Lutein and zeaxanthin are major carotenoids found in dark-green leafy vegetables. These plant pigments are concentrated in the eye lens and macular region of the retina where they play an important protective role in the eye. In particular, they protect against age-related macular degeneration, the major cause of blindness in the elderly.4,5
Some studies suggest that lutein and zeaxanthin may also 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.
Cancer Fighting Activities
Green veggies contain a variety of many carotenoids, flavonoids, and other powerful antioxidants with cancer protective properties. In a Swedish study, it was reported that eating three or more servings a week of green leafy vegetables significantly reduced the risk of stomach cancer, the fourth most frequent cancer in the world.6 Cabbage, cauliflower, Brussels sprouts, and broccoli are all rich in indoles and isothiocyanates, biological compounds that protect us against colon cancer 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 as well.
The carotenoid pigments in vegetables contain cancer preventive properties that are partly explained by their impact on gene regulation. Studies have identified a gene, connexin 43, the expression of which is upregulated by the carotenoids. This upregulation is significant, since it is associated with a decreased proliferation of tumor cells.
Green leafy vegetables provide an attractive spectrum of shades, from the bluish-green of kale to the bright kelly green of spinach. These greens also run the whole gamut of flavors, from sweet to bitter, and from peppery to earthy. Young plants generally exhibit 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 lend a peppery flavor. Bok choy is best known for its use in stir-fry dishes, since it remains crisp, even when cooked to a tender stage.
Salad greens provide a whole range of important nutrients and phytochemicals to keep us healthy. Those parts of the vegetable that are exposed to the sun while growing tend to contain higher levels of phytochemicals. 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. The flavor of a vegetable dish can often be enhanced by the appropriate use of a fresh herb such as basil, parsley, or dill. Garlic, onion, lemon juice, olive oil, sesame seeds, or other healthful toppings can nicely complement a serving of green vegetables.
Commercial green packaging tells the consumer that a food is considered healthful. In the produce section, nature’s own dark green packaging also represents good health. So when you shop for groceries, think green!
Danger in a Bag
Recently, there have been outbreaks of food poisoning associated with the use of some vegetables. For example, a widespread outbreak of E.coli O157:H7 poisoning was associated with contaminated bagged baby spinach. The outbreak resulted in over 200 confirmed illnesses and 3 deaths. FDA investigators suggested that wild pigs or deer grazing nearby, or maybe contaminated irrigation water possibly caused the outbreak. Better regulations and thorough washing before serving will help reduce any risk to the consumer. Sprouts, as well, should be thoroughly washed since their potential contamination may also pose a health risk. By carefully handling fresh produce, the collage of health benefits from eating vegetables can be fully enjoyed. Since food poisoning occurs much more frequently from the consumption of animal products than from vegetables, plant foods are still the optimal choice. Growing your own produce is another good choice that can further reduce the risk of contamination.
Preparation is Key
While steaming, stir-frying, and microwaving vegetables produces a limited detrimental effect upon both the nutrient and phytochemical level of vegetables, boiling them in a surplus of water tends to cause significant losses of these valuable substances. We should keep in mind, however, that certain phytochemicals may be more bioavailable when exposed to heat. Thus the adequate cooking of some vegetables may actually facilitate greater absorption of these phytonutrients. For example, the cancer protective phytochemicals in broccoli and tomatoes are best available from the cooked vegetable, rather than in its raw state. Vegetables that are frozen or canned are normally picked at the peak of their ripeness and prepared to retain as much as possible of their nutritional value. Conclusion: Green vegetables are powerfully loaded with a variety of vitamins and minerals such as magnesium, calcium, and iron. While they contain very little fat, what fat they do contain is very high in crucial omega-3 fatty acids. Green vegetables are also well-endowed with carotenoids, flavonoids, indoles, and isothiocyanates.
All of these health-promoting phytochemicals provide protection against various chronic diseases. Because these phytochemicals may cause the vegetable to take on a slightly bitter flavor, people may be less inclined to eat them. However, in view of the multiple benefits of green vegetables, it is advisable to enjoy at least one serving a day for good health. So think green and power-up for the future!
- Blekkenhorst Lauren. Cardiovascular Health Benefits of Specific Vegetable Types: A Narrative Review. Nutrients. 2018 May; 10(5): 595. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5986475/↩
- Sturm C., Wagner A.E. Brassica-derived plant bioactives as modulators of chemopreventive and inflammatory signaling pathways. Int. J. Mol. Sci. 2017; 18:1890. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5618539/↩
- Fraser Gary. Association among Health Habits, Risk Factors, and All-Cause Mortality in a Black California Population. Epidemiology. Vol. 8, No. 2 (Mar., 1997), pp. 168-174 (7 pages) https://www.jstor.org/stable/3702503↩
- Silvio Buscemi. The Effect of Lutein on Eye and Extra-Eye Health. Nutrients. 2018 Sep; 10(9): 1321.↩
- Delcourt C. Plasma Lutein and Zeaxanthin and Other Carotenoids as Modifiable Risk Factors for Age-Related Maculopathy and Cataract: The POLA Study. Clinical and Epidemiologic Research | June 2006.↩
- Lawson. Cancer Epidemiology Biomarkers & Prevention. Vol.15. pages 1998-2001. ↩