Health Benefits of Collard Greens
Last updated: February 3, 2019
Not only do they make a delicious side dish when sautéed, collard greens are also good for you. Many of the health benefits of collard greens are derived from the their high vitamin K content, but also other nutrients – such as carotenoids and calcium – contribute to the health-boosting properties of this unsung superfood.
Here's a lowdown of the most interesting nutritional benefits of collard greens:
1. Collard Greens Are Rich in Nutrients, Especially Vitamin K
Collard greens are supercharged with vitamin K, though they don't quite beat the superfood kale in terms of vitamin K content. According to nutrition facts data published by the USDA, 1 ounce of cooked (and drained) collard greens provides 96% of the Daily Value for vitamin K, while 1 ounce of cooked kale offers a whopping 193% (1, 2).
Vitamin K, which derives its name from the German word "koagulation", plays a major role in helping your blood clot, protecting you from excessive blood loss when you get injured.
Aside from being loaded with vitamin K, collard greens are an excellent source of vitamin C, carotenoids (including pro-vitamin A) and folate, and a good source of calcium, magnesium, potassium, riboflavin, and vitamin B6 (1).
Eating vegetables that are rich in a wide variety of nutrients can help your body meet its daily nutritional needs and prevent nutrient deficiencies, while keeping your weight in check.
2. Eye Health Protecting Nutrients
Collard greens are packed with the carotenoids lutein and zeaxanthin. These carotenoids are involved in numerous bodily functions, but they are probably best known for their ability to protect eye health.
A case-control study published The Journal of the American Medical Association found that those in the highest quintile of carotenoid intake had a 43% lower risk for age-related macular degeneration, a leading cause of blindness in adults, compared with those in the lowest quintile. This study also found that people who frequently ate collard greens or spinach had a particularly low risk of age-related macular degeneration. (3)
In addition, a growing body of evidence suggests that lutein can help protect the eyes from damage caused by the sun's ultraviolet rays and the harmful blue light emitted by electronic devices such as smartphones. In fact, the evidence is so compelling that ophthalmologist Robert Abel, M.D., has called lutein "nature's sunglasses" in his groundbreaking book, The Eye Care Revolution.
Tip: Drizzle some healthy oil, such as avocado oil, on your collard greens before eating them. Carotenoids are fat-soluble, meaning that they are best absorbed if the meal contains some fat (4).
3. Calcium and Vitamin K for Healthy Bones
Collard greens provide a good amount of calcium which is a key component of bones. Furthermore, the calcium found in collard greens has been shown to be highly bioavailable.
A study published in the Journal of Food Composition and Analysis reported that collard greens – along with kale, celery, Chinese cabbage, pak-chee-lao (Anethum graveolens L.), and soybean sprouts – showed highest calcium bioavailability among the tested plant-based foods (5).
In addition, the high levels of vitamin K in collard greens may add to the benefits collard greens can have for your bones. Indeed, according to a report on vitamin K and bone health written by Dr. Peter Weber, MD, PhD, a compelling body of evidence suggests that vitamin K can increase bone mineral density as well as reduce fracture rates in people with osteoporosis (6).
Tip: Human intervention studies show that vitamins K and D works synergistically on bone density (6). To maximize the bone health boosting benefits of collard greens, eat your collard greens with foods that contain vitamin D, such as fatty fish.
4. Cholesterol-Lowering Properties
Collard greens are right there on top of the list of Brassica vegetables with the highest bile acid binding capacity, which in turn is indicative of strong cholesterol-lowering potential.
An in vitro study published in the June 2008 edition of the journal Nutrition Research found that collard greens and kale, along with mustard greens, had the strongest bile acid binding capacity among the tested Brassica vegetables. Collard greens were found to have even more bile acid binding capacity than broccoli, Brussels sprouts and cabbage. (7)
The cholesterol-lowering properties of Brassica vegetables have also been studies in vivo, with promising results. In one intervention study, people with high cholesterol experienced a significant drop in their total cholesterol and LDL (the bad cholesterol) levels after consuming a Brassica-containing drink twice a day for three weeks. The drink was primarily made of broccoli and cabbage, both of which are members of the same Brassica oleracea species as collards. (8)
In another study, a daily dose of 150 milliliters (2/3 cup) of kale juice resulted in a 10% drop in LDL cholesterol in men with high cholesterol levels. Like broccoli and cabbage, kale is closely related to collard greens (9).
5. A Source of Phytochemicals with Anti-Cancer Properties
Epidemiological studies have associated a high intake of cruciferous vegetables, such as collard greens, with a lower incidence of certain types of cancer (10).
Cruciferous vegetables differ from other vegetables in that they are rich in glucosinolates, phytochemicals than can be converted into a wide range of biologically active compounds (11).
Collard greens are a particularly rich source of a glucosinolate called glucoraphanin, which can be converted into sulforaphane, and glucobrassicin, which is a precursor to indole-3-carbinol (12).
Sulforaphane has been extensively researched for its potential anti-cancer effects, and scientists hypothesize that sulforaphane might help prevent cancer through multiple mechanisms.
For example, sulforaphane has been shown trigger apoptosis (programmed cell death), induce phase II enzymes which are involved in the elimination of mutagens, induce cell cycle arrest, and inhibit NF-κB, a protein complex that is involved in the initiation, development and spread of cancer within the body. (13).
Also indole-3-carbinol, or I3C, has been researched for its potential anti-cancer effects, and I3C and its breakdown products have been found to inhibit the development of cancer in a variety of animal models and tissues when administered before or at the same time as the carcinogen (10).
However, some animal studies have found that I3C can actually promote carcinogenesis in rats under certain circumstances, which has led some experts to caution against the widespread use of I3C supplements for cancer prevention until their potential risks and health benefits are better understood (10).
6. Collard Greens May Aid in Weight Loss
I3C may be best known for its potential anti-cancer properties, but it has also been researched for its potential anti-obesity properties, with promising results.
For example, in an animal study published in the journal Nutrition, I3C resulted in weight loss and reduced fat accumulation in obese mice that were fed a high-fat diet (14). Another animal study, published in The Journal of Nutritional Biochemistry, produced similar results (15).
Researchers believe the I3C may promote weight loss through various mechanisms, including preventing undifferentiated cells from turning into fat cells, fighting chronic inflammation, and stimulating thermogenesis, a metabolic process during which the body burns more calories to produce heat (15).
In addition to providing I3C, collard greens are low in calories and relatively high in fiber, which may further contribute to their potential weight loss benefits.
Book You May Like
Written by Jonny Bowden, PhD, CNS, a board-certified nutritionist and bestselling author, The 150 Healthiest Food on Earth draws on cutting-edge nutrition research to debunk common food myths and to provide evidence-based information about the health benefits of a wide range of foods. You will learn, for example, how full-fat dairy might help protect against diabetes and why artichokes are often used for indigestion.
