The World's Healthiest Foods
Collard greens

Long a staple of the Southern United States, collard greens, unlike their cousins kale and mustard greens, have a very mild, almost smoky flavor. Although they are available year-round they are at their best from January through April.

While collard greens share the same botanical name as kale they have their own distinctive qualities. Like kale, collards are one of the non-head forming members of the Brassica family along with broccoli and cauliflower. The dark blue-green leaves that are smooth in texture and relatively broad distinguish them from the frilly edged leaves of kale.

 


Health Benefits

Rich in Anti-Cancer Phytonutrients

As members of the Brassica genus of foods, collards stand out as an anti-cancer food. 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 clear, 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).

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 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 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 phosphorous 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 daily value 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.

Protection against Emphysema

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 rats 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.

In his initial research, Baybutt took just weaned male rats and divided them into two groups, one of which was exposed to cigarette smoke, and the other to air. In the rats exposed to cigarette smoke, levels of vitamin A dropped significantly in direct correlation with their development of emphysema. In the second study, both groups of rats were exposed to cigarette smoke, but one group was given a diet rich in vitamin A. Among those rats receiving the vitamin A-rich foods, emphysema was effectively reduced.

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. (October, 21, 2004)

More Cardiovascular Protection

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.

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 homosyteine.

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 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!

A Healthy Transition through Menopause

Collards offer a combination of nutrients espeically 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.

Give Yourself the Gift of Health

Much more could be said about the potential benefits of collard greens, which are also a good source of protein (1 cup provides 4 grams or 8% of the daily value for protein), thiamin, iron and omega-3 fatty acids. In all, this truly exceptional vegetable is an excellent, very good or good source of 20 vital nutrients, and is therefore helpful in the prevention or healing of a wide variety of different conditions. So, if you don't already eat collard greens, do something nice for yourself and give them a try.

Description

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.

History

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

How to Enjoy

For some of our favorite recipes, click Recipes.

Tips for Preparing Collard Greens

Collard greens should be washed very well since the leaves and stems tend to collect sand and soil. Before washing, trim off the roots and separate the leaves. Place the collard greens in a large bowl of tepid water and swish them around with your hands, as this will allow the sand to become dislodged. Remove the leaves from the water, empty the bowl, refill with clean water, and repeat this process until no dirt remains in the water (usually two to three times will do the trick).

If your recipe calls for leaves only or if the stems are overly thick, they can be easily removed. Just take each leaf in hand, fold it in half lengthwise, hold the folded leaves near the base where they meet the stalk, and with the other hand, gently pull on the stem. You can also use a knife to separate the leaves from the stems.

A Few Quick Serving Ideas:

Drizzle cooked collard greens with olive oil and lemon juice.

Serve steamed collard greens with black-eyed peas and brown rice for a Southern inspired meal.

Use lightly steamed, cooled and chopped collard greens as a filling in your sushi vegetable rolls.

Healthy sauté collard greens with tofu, garlic and crushed chili peppers for a meal that will definitely add spice to your life.

Safety

Collard Greens and Oxalates

Collard greens are among a small number of foods that contain any measurable amount of oxalates, naturally-occurring substances found in plants, animals, and human beings. When oxalates become too concentrated in body fluids, they can crystallize and cause health problems. For this reason, individuals with already existing and untreated kidney or gallbladder problems may want to avoid eating collard greens. Oxalates may also interfere with absorption of calcium from the body. For this reason, individuals trying to increase their calcium stores may want to avoid collard greens, or if taking calcium supplements, may want to eat collard greens 2-3 hours before or after taking their supplements.

Nutritional Profile

Introduction to Food Rating System Chart

The following chart shows the nutrients for which this food is either an excellent, very good or good source. Next to the nutrient name you will find the following information: the amount of the nutrient that is included in the noted serving of this food; the %Daily Value (DV) that that amount represents (similar to other information presented in the website, this DV is calculated for 25-50 year old healthy woman); the nutrient density rating; and, the food's World's Healthiest Foods Rating. Underneath the chart is a table that summarizes how the ratings were devised. For more detailed information on our Food and Recipe Rating System, please click here.

 

Collard Greens, Boiled, Drained
1.00 cup
49.40 calories
Nutrient Amount DV
(%)
Nutrient
Density
World's Healthiest
Foods Rating
vitamin A 5945.10 IU 118.9 43.3 excellent
vitamin C 34.58 mg 57.6 21.0 excellent
manganese 1.07 mg 53.5 19.5 excellent
folate 176.70 mcg 44.2 16.1 excellent
calcium 226.10 mg 22.6 8.2 excellent
dietary fiber 5.32 g 21.3 7.8 excellent
tryptophan 0.05 g 15.6 5.7 very good
potassium 494.00 mg 14.1 5.1 very good
vitamin B6 (pyridoxine) 0.24 mg 12.0 4.4 very good
vitamin B2 (riboflavin) 0.20 mg 11.8 4.3 very good
vitamin E 1.67 mg 8.3 3.0 good
magnesium 32.30 mg 8.1 2.9 good
protein 4.01 g 8.0 2.9 good
omega 3 fatty acids 0.18 g 7.2 2.6 good
vitamin B3 (niacin) 1.09 mg 5.5 2.0 good
vitamin B1 (thiamin) 0.08 mg 5.3 1.9 good
zinc 0.80 mg 5.3 1.9 good
phosphorus 49.40 mg 4.9 1.8 good
iron 0.87 mg 4.8 1.8 good
vitamin B5 (pantothenic acid) 0.41 mg 4.1 1.5 good
World's Healthiest
Foods Rating
Rule
excellent DV>=75% OR Density>=7.6 AND DV>=10%
very good DV>=50% OR Density>=3.4 AND DV>=5%
good DV>=25% OR Density>=1.5 AND DV>=2.5%

References

  • Baybutt RC, Hu L, Molteni A. Vitamin A deficiency injures lung and liver parenchyma and impairs function of rat type II pneumocytes. J Nutr. 2000 May;130(5):1159-65.
  • Ensminger AH, Ensminger, ME, Kondale JE, Robson JRK. Foods & Nutriton Encyclopedia. Pegus Press, Clovis, California.
  • Ensminger AH, Esminger M. K. J. e. al. Food for Health: A Nutrition Encyclopedia. Clovis, California: Pegus Press; 1986.
  • Fortin, Francois, Editorial Director. The Visual Foods Encyclopedia. Macmillan, New York.
  • Li T, Molteni A, Latkovich P, Castellani W, Baybutt RC. Vitamin A depletion induced by cigarette smoke is associated with the development of emphysema in rats. J Nutr. 2003 Aug;133(8):2629-34.
  • Thimmulappa RK, Mai KH, Srisuma S et al. Identification of Nrf2-regulated genes induced by the chemopreventive agent sulforaphane by oligonucleotide microarray. Cancer Res 2002 Sep 15;62(18):5196-5203.
  • Wood, Rebecca. The Whole Foods Encyclopedia. New York, NY: Prentice-Hall Press; 1988.

This page was updated on: 2005-05-06 20:29:41
© 2002 The George Mateljan Foundation