As promised, in this second part of “Get Your Leafy Greens On!” we’re going to take a closer look at the nutrition and health benefits of the top four green superfoods according to plant-based pioneer Dr. Joel Fuhrman’s Aggregate Nutrient Density Index (ANDI).
Kale, collard greens, mustard greens and watercress, all cruciferous vegetables, are tied for first place in Dr. Fuhrman’s system, each with maxed out ANDI scores of 1,000. With this kind of variety to choose from, there’s no need to get “kaled out.” Kale has surged in popularity in recent years but it’s good to know you can shake it up with these other leafy green nutritional superstars. (Nothing against kale, of course! I love kale chips as much as anyone else.)
Cook ‘Em Up
Let’s give a shout out for cooking those greens. While raw foods offer enzymes and fresh-grown vitality, when it comes to collard greens, mustard greens, kale, broccoli, green bell pepper and cabbage, cooking apparently offers some unique and critically important health benefits.
A 2008 study found that steam cooking these veggies increases their bile acid binding capacity. Bile is a complex alkaline fluid secreted by the liver and stored in the gall bladder which aids the digestion and absorption of fats and fat-soluble vitamins in the small intestine. Increased bile acid binding capacity is associated with reduced absorption of fat, the lowering of cholesterol levels and a reduced risk of both heart disease and cancer.
Now that’s something worth steaming for!
The Master Antioxidant: Glutathione
Glutathione is a very important antioxidant comprised of the amino acids glutamine, glycine and cysteine and which is found in every single cell in the body. One great way to boost glutathione levels is to eat foods high in sulfur.
Cruciferous vegetables such as kale, collard greens, mustard greens and watercress (along with broccoli, cabbage, kohlrabi, horseradish and many other fine veggies) are rich sources of sulfur-containing compounds called glucosinolates. Get your greens on!
Some studies have shown links between low levels of glutathione and the development of various diseases. That would make sense, given the wide range of bodily processes that glutathione is involved with, including immune function, sperm development, enzyme function, DNA formation, fat processing, and the removal of mercury from the brain.
Research indicates that glutathione may help prevent cancer, reduce the symptoms of Parkinson’s disease, reduce the intensity of autism spectrum disorders, and improve insulin sensitivity, among many other potential benefits.
Antioxidants are substances typically found in plants such as vitamins C and E, beta-carotene, manganese, lycopene (found in tomatoes and other red fruits and vegetables) and flavonoids (found in tea, citrus fruits and berries, for instance), among many others, which fight off the free radicals which cause oxidation.
Free radicals are highly reactive, unstable molecules that can damage cells and DNA, accelerate aging, and may be implicated in the development of cancer and other conditions. Unlike most other antioxidants, the liver can actually manufacture glutathione, but levels can decrease with age and for other reasons.
Leafy greens are a great source of antioxidants.
Indole-3-carbinol is a type of glucosinolate found in cruciferous vegetables which has detoxifying effects on the body, removing hormones, pharmaceuticals, toxins and other bad stuff. It is believed to prevent certain types of cancer and to boost immune function, including particular effectiveness against HPV (human papillomavirus, which is associated with cervical cancer.)
But it doesn’t stop there. Mustard greens, collard greens, kale and purslane are especially high in a group of phytonutrients (plant-based nutrients) called phenols, according to a 2007 study of greens consumed by African-Americans in the southern United States.
According to the George Mateljan Foundation’s The World’s Healthiest Foods website, “… only these four vegetables were found to contain significant amounts of the flavonoids kaempferol, isorhamnetin, and quercetin, as well as the phenolic antioxidant ferulic acid.
With respect to isorhamnetin—a flavonoid that has been of special interest in several cancer-related studies—mustard greens were shown to have the second highest concentration of this flavonoid (placing right behind kale).”
With that favorable introduction to mustard greens, there’s no better place to start our journey!
Mustard greens are the leafy green tops of a species of the mustard plant. Consumption of mustard greens goes back 5,000 years to the Himalayan region. India, Nepal, China and Japan are the current top producers of mustard greens but they’re also grown in the United States.
They can be eaten raw in smoothies and salads or cooked by sautéing, steaming or boiling, for instance, which tends to mellow out their distinctly peppery flavor.
Make no mistake, these under-appreciated greens offer some serious nutrition. One cup of boiled mustard greens provides a whopping 524% of the recommended daily allowance (RDA) of vitamin K and 177% of the RDA for vitamin A. Can you spell n-u-t-r-i-e-n-t d-e-n-s-i-t-y?
Mustard greens are also a good source of vitamin C (59% of the RDA) and folic acid (26%). These off-the-radar greens are also surprisingly good sources of protein, with one cup yielding nearly 8 grams. When it comes to minerals, mustard greens are high in manganese (18% RDA), calcium (10%) and potassium (8%).
And all this nutrition for just 21 calories! Can you beat that?
Mustard greens are also a star when it comes to isothiocyanates. Isothiocyanates, you ask? Not exactly a household word, but one worth familiarizing yourself with if you’re concerned about health. Like indole-3-carbinol, isothiocyanates are a type of the sulfur-containing glucosinolates found in cruciferous vegetables and they pack a punch when it comes to the prevention of cancer.
In a study of eight cruciferous vegetables, including broccoli, Brussels sprouts, cabbage, cauliflower, collard greens, kale, mustard greens and turnip greens, mustard greens came out on top in terms of isothiocyanate content!
According to the National Cancer Institute, isothiocyanates have been found to inhibit the development of bladder, breast, colon, liver, lung and stomach cancer in animal studies.
Other health-promoting attributes of isothiocyanates include protecting cells from DNA damage and anti-inflammatory, antiviral and antibacterial effects. (Studies in humans so far have yielded mixed results.)
Collard greens have been growing in popularity recently, with some people calling this staple southern leafy green “the next kale.” Collard greens are an amazing source of vitamin K, with one cup of boiled greens providing an unbelievable 1045% of the RDA!
Collard greens are also an excellent source of vitamin A (308%), vitamin C (58%), folic acid (44%), manganese (41%), calcium (27%), iron (12%) and magnesium (10%).
On the other hand, collard greens have less than half the protein content of mustard greens, with one cup providing a mere 4 grams.
Collard greens also offer an ample supply of essential fatty acids, providing 177 mg of omega-3s and 133 mg omega-6s per cup, the highest level of essential fatty acids of the winners.
These slightly bitter greens grow in the southern United States as well as in Brazil, Portugal, Montenegro, northern Spain, northern India, southeastern Europe and parts of Africa.
Like mustard greens, watercress, grown in watery beds (hence the name!), has a peppery flavor and is likewise underappreciated and little-known. Formerly perceived as a weed, watercress was not formally cultivated until the early 1800s in the United Kingdom.
It’s now grown globally and is best eaten raw in salads or smoothies or lightly steamed. Watercress pales a bit in comparison to its three other winning leafy green cousins. One cup of raw watercress supplies 106% of the RDA of vitamin K, 24% of vitamin C and 22% of vitamin A.
In terms of minerals, one cup provides no more than 4% of the RDA of any particular mineral and only 2 grams of protein.
Its micronutrient profile is considerably less rich than that of mustard greens, collard greens and kale. In terms of essential fatty acids, it provides a rather negligible amount, 8 mg of omega-3s and 4 mg of omega-6s.
So, what makes watercress so special and worthy of a first-place ANDI score?
To be honest, we’re not entirely sure!
And last, but not least, what would any discussion of leafy green superfoods be without kale?
Kale is a well-known, well-established vitamin and mineral plant superstar, with one boiled cup providing 1328% of the U.S. RDA of vitamin K. That’s more than twice as much vitamin K as any of the other three leafy green winners.
It provides 354% of the RDA of vitamin A, just slightly more than collard greens, and 89% of the RDA of vitamin C, more than any of the others. In terms of minerals, kale doesn’t shine quite as brightly, offering 27% of the RDA for manganese, 10% of copper and 9% of calcium.
Kale provides 134 mg of omega-3s per cup and 103 mg of omega-6s, less than collard greens but more than mustard greens at 31 mg of omega-3s and 34 mg of omega-6s.
Go Deep Leafy Green!
So, there you have it. While kale is nothing to shake a fork at, there are also lots of other superfood greens out there for you to try. When it comes to nutrition, variety is key.
Who knows what healthful compounds they have yet to discover? Broaden your green spectrum and your body and your taste buds will thank you.