Rich in Health-Promoting Phytonutrients
As members of the Brassica genus of foods, collards stand out as a nutritional superstar. It’s the organosulfur compounds in collards that have been the main subject of phytonutrient research, and these include the glucosinolates and the methyl cysteine sulfoxides. Although there are over 100 different glucosinolates in plants, only 10-15 are present in collards and other Brassicas. Yet these 10-15 glucosinolates appear able to lessen the occurrence of a wide variety of cancers, including breast and ovarian cancers.
Exactly how collards’ sulfur-containing phytonutrients prevent cancer is not yet fully understood, but several researchers point to the ability of the glucosinolates and cysteine sulfoxides to activate detoxifing enzymes in the liver that help neutralize potentially carcinogenic substances. (These detoxifying enzymes include the quinone reductases and glutathione-S-transferases). For example, scientists have discovered that sulforaphane, a potent glucosinolate phytonutrient found in collards and other Brassica vegetables, boosts the body’s detoxification enzymes, potentially by altering gene expression, thus helping to clear potentially carcinogenic substances more quickly.
Sulforaphane, which is formed when cruciferous vegetables such as collards are chopped or chewed, not only triggers the liver to produce enzymes that detoxify cancer-causing chemicals, inhibits chemically-induced breast cancers in animal studies, and induces colon cancer cells to commit suicide, but has been shown in laboratory studies to help stop the proliferation of breast cancer cells, even in the later stages of their growth.
Sulforaphane may also offer special protection to those with colon cancer-susceptible genes, suggests a study conducted at Rutgers University and published online on May 4, 2006, in the journal Carcinogenesis.
In this study, researchers sought to learn whether sulforaphane could inhibit cancers arising from one’s genetic makeup. Rutgers researchers Ernest Mario, Ah-Ng Tony Kong and colleagues used mice bred with a genetic mutation that switches off the tumor suppressor gene known as APC, the same gene that is inactivated in the majority of human colon cancers. Animals with this mutation spontaneously develop intestinal polyps, the precursors to colon cancer. The study found that animals who were fed sulforaphane had tumors that were smaller, grew more slowly and had higher apoptotic (cell suicide) indices. Additionally, those fed a higher dose of sulforaphane had less risk of developing polyps than those fed a lower dose.
According to lead researcher, Dr. Kong, “Our study corroborates the notion that sulforaphane has chemopreventive activity…Our research has substantiated the connection between diet and cancer prevention, and it is now clear that the expression of cancer-related genes can be influenced by chemopreventive compounds in the things we eat.”
Optimize Your Cells’ Detoxification / Cleansing Ability
For about 20 years, we’ve known that many phytonutrients work as antioxidants to disarm free radicals before they can damage DNA, cell membranes and fat-containing molecules such as cholesterol. Now, new research is revealing that phytonutrients in cruciferous vegetables, such as collard greens, work at a much deeper level. These compounds actually signal our genes to increase production of enzymes involved in detoxification, the cleansing process through which our bodies eliminate harmful compounds.
The phytonutrients in cruciferous vegetables initiate an intricate dance inside our cells in which gene response elements direct and balance the steps among dozens of detoxification enzyme partners, each performing its own protective role in perfect balance with the other dancers. The natural synergy that results optimizes our cells’ ability to disarm and clear free radicals and toxins, including potential carcinogens, which may be why crucifers appear to lower our risk of cancer more effectively than any other vegetables or fruits.
Recent studies show that those eating the most cruciferous vegetables have a much lower risk of prostate, colorectal and lung cancer-even whencompared to those who regularly eat other vegetables:
In a study of over 1,200 men conducted at the Fred Hutchinson Cancer Research Center in Seattle, WA, those eating 28 servings of vegetables a week had a 35% lower risk of prostate cancer, but those consuming just 3 or more servings of cruciferous vegetables each week had a 44% lower prostate cancer risk.
In the Netherlands Cohort Study on Diet and Cancer, in which data was collected on over 100,000 people for more than 6 years, those eating the most vegetables benefited with a 25% lower risk of colorectal cancers, but those eating the most cruciferous vegetables did almost twice as well with a 49% drop in their colorectal cancer risk.
A study of Chinese women in Singapore, a city in which air pollution levels are often high putting stress on the detoxification capacity of residents’ lungs, found that in non-smokers, eating cruciferous vegetables lowered risk of lung cancer by 30%. In smokers, regular cruciferous vegetable consumption reduced lung cancer risk an amazing 69%!
How many weekly servings of cruciferous vegetables do you need to lower your risk of cancer? Just 3 to 5 servings-less than one serving a day! (1 serving = 1 cup)
To get the most benefit from your cruciferous vegetable like collard greens, be sure to choose organically grown varieties (their phytonutrient levels are higher than conventionally grown), and steam lightly (this method of cooking has been shown to not only retain the most phytonutrients but to maximize their availability).
Broad Antioxidant Protection
In terms of conventional nutrients, our food ranking system qualified collard greens as an excellent, very good or good source of the three main antioxidants in foods, vitamin C, vitamin E, and vitamin A (through its concentration of pro-vitamin A carotenoids like beta-carotene). While water-soluble vitamin C protects all aqueous environments both inside and outside cells, the fat-soluble antioxidants, vitamin E and beta-carotene (which is converted in the body to vitamin A), cover all fat-containing molecules and structures. Together, these antioxidants seek out and disarm free radicals, which would otherwise cause significant damage to life-sustaining molecules such as enzymes, as well as to cellular membranes, mitochondria and DNA.
Free radical damage has been shown to contribute to the development and progression of virtually all degenerative diseases, including atherosclerosis, colon cancer, osteoarthritis, diabetes, and rheumatoid arthritis. Since they cause inflammation, both directly and by inciting the body’s inflammatory defense systems, free radicals also play a major role in asthma attacks. By ridding the body of these damaging chemicals, the antioxidants found in collard greens may help to prevent or reduce the symptoms of many of these diseases. A cup of cooked collard greens provides 57.6% of the daily value (DV) for vitamin C. 8.3% of the DV for vitamin E, and an amazing 118.9% of the DV for vitamin A.
Another way in which collard greens provide antioxidant support is through their concentration of the trace mineral, manganese. In the human body, manganese functions as an enzyme activator. Just one of the vitally important enzymes manganese activates is the one that helps the body utilize vitamin C. In addition, manganese is an integral component of an internally produced antioxidant enzyme called superoxide dismutase. Superoxide dismutase is found exclusively inside the mitochondria (the energy-production factories within almost all our cells), which it protects from the damaging effects of free radicals. Should a cell’s mitochondria become so damaged that they can no longer produce the energy the cell needs, the cell will literally starve and die, so manganese’s role as a part of superoxide dismutase is extremely important. A cup of cooked collard greens supplies 53.5% of the daily value for manganese.
Calcium-A Mineral for A Lot More than Strong Bones
Collard greens are an excellent good source of calcium. Calcium is widely recognized for its role in maintaining the strength and density of bones. In a process known as bone mineralization, calcium and phosphorus join to form calcium phosphate. Calcium phosphate is a major component of the mineral complex (called hydroxyapatite) that gives structure and strength to bones. A cup of cooked collard greens supplies 22.6% of the DV for calcium along with 4.9% of the DV for phosphorus.
Building bone is, however, far from all that calcium does for us. In recent studies, this important mineral has been shown to:
- Help protect colon cells from cancer-causing chemicals
- Help prevent the bone loss that can occur as a result of menopause or certain conditions such as rheumatoid arthritis
- Help prevent migraine headaches in those who suffer from them
- Reduce PMS symptoms during the luteal phase (the second half) of the menstrual cycle
Calcium also plays a role in many other vital physiological activities, including blood clotting, nerve conduction, muscle contraction, regulation of enzyme activity, and cell membrane function. Because these activities are essential to life, the body utilizes complex regulatory systems to tightly control the amount of calcium in the blood, so that sufficient calcium is always available. As a result, when dietary intake of calcium is too low to maintain adequate blood levels of calcium, calcium stores are drawn out of the bones to maintain normal blood concentrations, which, over many years, can lead to osteoporosis.
Optimizing Immune Function
Collard greens are an excellent source of vitamin A and a good source of zinc, two nutrients that can significantly help immune system function. Vitamin A is critically important for the health of epithelial and mucosal tissues, the body’s first line of defense against invading organisms and toxins. The epithelium is a layer of cells forming the epidermis of the skin and the surface layer of mucous and serous membranes. All epithelial surfaces including the skin, vaginal epithelium, and gastrointestinal tract rely upon vitamin A. When vitamin A status is inadequate, keratin is secreted in epithelial tissues, transforming them from their normally pliable, moist condition into stiff dry tissue that is unable to carry out its normal functions, and leading to breaches in epithelial integrity that significantly increase susceptibility to the development of allergy and infection.
So, when our vitamin A levels are low, we are much more susceptible to infections such as recurrent ear infections or frequent colds, or we may wind up with an immune system that is overactive, leading to autoimmune diseases like rheumatoid arthritis. In fact, low vitamin A levels in Third World countries are blamed for the huge amounts of complications and deaths due to childhood diseases like measles. When children in these areas are given adequate amounts of vitamin A, the number of deaths from these illnesses drops dramatically, just one demonstration of the importance of vitamin A for strong immune function.
Zinc, the most critical mineral for immune function, acts synergistically with vitamin A, promotes the destruction of foreign particles and microorganisms, protects against free-radical damage, is required for proper white cell function, and is necessary for the activation of serum thymic factor, a thymus hormone with profound immune-enhancing actions. Zinc also inhibits replication of several viruses, including those of the common cold.
A cup of cooked collard greens provides 118.9% of the daily value for vitamin A along with 5.3% of the DV for zinc.
Collard greens’ supply of these two nutrients alone is reason enough to rely on this healthful food for immune support, but the same cup of cooked collard greens also contains 57.6% of the daily value for vitamin C.
One of the best-known antioxidant and immune supportive nutrients, vitamin C is vital for the proper function of the immune system. The primary water-soluble antioxidant in the body, vitamin C disarms free radicals, thus preventing damage in the aqueous environment both inside and outside cells. Inside cells, a potential result of free radical damage to DNA is cancer. Especially in areas of the body where cellular turnover is especially rapid, such as the digestive system, preventing DNA mutations translates into preventing cancer. This is why a good intake of vitamin C is associated with a reduced risk of colon cancer.
Free radical damage to other cellular structures and other molecules can result in painful inflammation, as the body tries to clear out the damaged parts. Vitamin C, which prevents the free radical damage that triggers the inflammatory cascade, is thus also associated with reduced severity of inflammatory conditions, such as asthma, osteoarthritis, and rheumatoid arthritis.
Free radicals also oxidize cholesterol. Only after being oxidized does cholesterol stick to the artery walls, building up in plaques that may eventually grow large enough to impede or fully block blood flow, or rupture to cause a heart attack or stroke. Since vitamin C can neutralize free radicals, it also helps prevent the oxidation of cholesterol, lowering the risk of developing atherosclerosis.
Promote Lung Health
If you or someone you love is a smoker, or if you are frequently exposed to secondhand smoke, then making vitamin A-rich foods, such as collard greens, part of your healthy way of eating may save your life, suggests research conducted at Kansas State University.
While studying the relationship between vitamin A, lung inflammation, and emphysema, Richard Baybutt, associate professor of nutrition at Kansas State, made a surprising discovery: a common carcinogen in cigarette smoke, benzo(a)pyrene, induces vitamin A deficiency.
Baybutt’s earlier research had shown that laboratory animals fed a vitamin A-deficient diet developed emphysema. His latest animal studies indicate that not only does the benzo(a)pyrene in cigarette smoke cause vitamin A deficiency, but that a diet rich in vitamin A can help counter this effect, thus greatly reducing emphysema.
Baybutt believes vitamin A’s protective effects may help explain why some smokers do not develop emphysema. “There are a lot of people who live to be 90 years old and are smokers,” he said. “Why? Probably because of their diet…The implications are that those who start smoking at an early age are more likely to become vitamin A deficient and develop complications associated with cancer and emphysema. And if they have a poor diet, forget it.”
If you or someone you love smokes, or if your work necessitates exposure to second hand smoke, protect yourself by making sure that at least one of the World’s Healthiest Foods that are rich in vitamin A, such as collard greens, is a daily part of your healthy way of eating.
Collard greens are an excellent source of folate and a very good source of vitamin B6, both of which are needed to keep levels of homocysteine, a potentially dangerous molecule, low.
Vitamin B6 and folate are both involved in an important cellular process called methylation in which homocysteine is converted into other, benign molecules. Since homocysteine can directly damage blood vessel walls, high homocysteine levels are associated with an increased risk of heart attack and stroke-one risk you can lessen by eating foods rich in folate and B6, such as collard greens. In addition to these B vitamins, collard greens are a very good souce of riboflavin, another important B vitamin for cardiovascular health since it is necessary for the proper functioning of B6. Without riboflavin’s assistance, vitamin B6 cannot change into its active form, the form in which it carries out its many beneficial activities, including the conversion of homocysteine.
But that’s not the only reason riboflavin is of value for cardiovascular health. Riboflavin is also a cofactor in the reaction that regenerates glutathione, one of the body’s most important antioxidants. Among its many beneficial activities, glutathione protects lipids like cholesterol from free radical attack. Only after cholesterol has been damaged by free radicals does this fat-containing molecule pose a threat to blood vessel walls.
Collard greens are also a good source of niacin. Yet another B vitamin with cardiovascular benefits, niacin has been used for years to safely and effectively lower high cholesterol levels, which is also important in atherosclerosis and diabetic heart disease.
In addition to their cardio-protective B vitamins, collard greens are a very good source of potassium and a good source of magnesium, two minerals that have both been shown to reduce high blood pressure, another risk factor for cardiovascular disease. Add to this the fiber that collards supply, which can help lower high cholesterol levels, and you have an exceptionally beneficial food for individuals with atherosclerosis or diabetic heart disease.In a single cup of cooked collard greens is concentrated the cardiovascular benefits provided by 44.2% of the daily value for folate, 21.3% of the DV for dietary fiber, 18.5% of the DV for vitamin B6, 11.8% of the DV for riboflavin, 14.1% of the DV for potassium, 8.1% of the DV for magnesium, and 5.5% of the DV for niacin. All this for a cost of less than 50 calories!
Cholesterol-Lowering Benefits from Indole-3-Carbinol
Researchers from the University of Hawaii have shown that, at the tiny concentration of just 100 micromoles per liter, indole-3-carbinol (a metabolite of the glucosinolate phytonutrients found in collard greens and other ruciferous vegetables) lowers liver cells’ secretion of the cholesterol transporter, apolipoproteinB-100 by 56%! Apolipoprotein B-100 (apoB) is the main carrier of LDL cholesterol to tissues, and high levels have been linked to plaque formation in the blood vessels.
When liver cells were treated with I-3-C, not only was apoB-100 secretion cut by more than half, but significant decreases also occurred in the synthesis of lipids (fats), including triglycerides and cholesterol esters. (Maiyoh GK, Kuh JE, et al., J Nutr.)
A Healthy Transition through Menopause
Collards offer a combination of nutrients especially helpful for women going through menopause. The calcium in collard greens can help prevent the bone loss that frequently occurs at this stage of life. The magnesium may be helpful in reducing stress and can assist in promoting normal sleeping patterns, while the vitamin E, which was mentioned earlier as an antioxidant, has also been shown to decrease the occurrence of hot flashes that many women experience around menopause.
Vitamin E-rich Leafy Greens Slow Loss of Mental Function
Mental performance normally declines with age, but the results of Chicago Health and Aging Project (CHAP) suggest that eating just 3 servings of green leafy, yellow and cruciferous vegetables each day could slow this decline by 40%, suggests a study in the journal Neurology
Compared to people who consumed less than one serving of vegetables a day, people who ate at least 2.8 servings of vegetables a day saw their rate of cognitive decline slow by roughly 40%. This decrease is equivalent to about five years of younger age, said lead author Martha Clare Morris, ScD, with Rush University Medical Center in Chicago. (Morris MC, Evans DA, et al.)
The prospective cohort study, funded by the National Institute of Aging, used dietary data from 3,718 participants (62% female, 60% African American, average age 74). Mental function was assessed with four different tests: the East Boston Tests of immediate memory and delayed recall, the Mini-Mental State Examination, and the Symbol Digit Modalities Test, taken at the start of the study and then again after 3 and 6 years.
After adjusting the results for potential confounders such as age, sex, race, education, and cardiovascular risk factors, the researchers found that consuming an average of 2.8 vegetable servings each day was associated with a 40% decrease in cognitive decline, compared to those who ate an average of less than one (0.9) serving a day.
Of the different types of vegetables, green leafy vegetables had the strongest association, said Dr. Morris.
Surprisingly, no relationship was found between fruit consumption and cognitive decline.
Morris hypothesizes that this may be due to the fact that vegetables, but not fruits, contain high amounts of vitamin E, which helps lower the risk of cognitive decline. Also, vegetables, but not fruits, are typically consumed with a little fat, such as olive oil or salad dressing, which increases the body’s ability to absorb vitamin E.
The Rush University researchers plan further research to understand why fruit appears to have little effect and to explore the effects of citrus fruit, specifically, on cognitive decline.
Practical Tip: If you remember to enjoy at least 3 servings of leafy greens each day, you are much more likely to remember other things as well!
Collards are leafy green vegetables that belong to the same family that includes cabbage, kale and broccoli. While they share the same botanical name as kale, Brassica oleracea, and some resemblance, they have their own distinctive qualities. Like kale, collards are one of the non-head forming members of the Brassica family. Collards’ unique appearance features dark blue green leaves that are smooth in texture and relatively broad. They lack the frilled edges that are so distinctive to their cousin kale. The taste of collards can be described as pleasantly green and bitter.
Like kale, cauliflower and broccoli, collards are descendents of the wild cabbage, a plant thought to have been consumed as food since prehistoric times and to have originated in Asia Minor. From there it spread into Europe, being introduced by groups of Celtic wanderers around 600 B.C. Collards have been cultivated since the times of the ancient Greek and Roman civilizations. While collards may have been introduced into the United States before, the first mention of collard greens dates back to the late 17th century. Collards are an integral food in traditional southern American cuisine.
How to Select and Store
Look for collard greens that have firm, unwilted leaves that are vividly deep green in color with no signs of yellowing or browning. Leaves that are smaller in size will be more tender and have a milder flavor. They should be displayed in a chilled section in the refrigerator case to prevent them from wilting and becoming bitter.
Store unwashed collard greens in a damp paper towel or clean towel in a plastic bag. They should be placed in the refrigerator crisper where they will keep for three to five days, but the sooner they are eaten, the less bitter they will be.
Collard greens are an excellent source of vitamin A, vitamin C, manganese, folate, dietary fiber, and calcium. In addition, collard greens are a very good source of potassium, vitamin B2 and vitamin B6, and a good source of vitamin E, magnesium, omega-3 fatty acids, vitamin B1, vitamin B5, niacin, zinc, phosphorus, and iron, and pantothenic acid, and a good source of protein, naicin, thiamin, phosphorus, zinc, and selenium.
Let collard greens sit for 10 minutes after cutting to increase nutritional value. The latest scientific studies show that cutting collard greens enhances the activation of an enzyme called myrosinase that slowly converts some of the glucosinolate phytonutrients into their active health-promoting forms that have been shown to contain cancer preventive properties. So to get the most health benefits from collard greens, let them sit for 10 minutes after cutting before eating or cooking (heat will inactivate the enzyme.) Additionally, since myrosinase cannot function properly without ascorbic acid (vitamin C), I like to sprinkle collard greens with a little lemon juice (an excellent source of this vitamin) after cutting to further increase the enzyme’s activity.
|Collard greens, boiled
|vitamin B6 (pyridoxine)
|vitamin B2 (riboflavin)
|omega 3 fatty acids
|vitamin B3 (niacin)
|vitamin B1 (thiamin)
|vitamin B5 (pantothenic acid)
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