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Thursday, 25 July 2013

Green Leafy Vegetables - Nutritional Powerhouses

Eat Your Greens!

By Laura Dolson

A nutrition professor once told me that it was common for our ancient ancestors to eat up to six pounds of leaves per day. He imagined them walking along from one place to another, just picking and eating leaves as they went. Can you imagine eating a grocery bag full of greens each and every day? Few of us even eat the minimum USDA recommendations of 3 cups of dark green vegetables per week. And yet, these veggies deliver a bonanza of vitamins, minerals, and phytonutrients.

Health Benefits

Dark green leafy vegetables are, calorie for calorie, probably the most concentrated source of nutrition of any food. They are a rich source of minerals (including iron, calcium, potassium, and magnesium) and vitamins, including vitamins K, C, E, and many of the B vitamins. They also provide a variety of phytonutrients including beta-carotene, lutein, and zeaxanthin, which protect our cells from damage and our eyes from age-related problems, among many other effects. Dark green leaves even contain small amounts of Omega-3 fats.
Perhaps the star of these nutrients is Vitamin K. A cup of most cooked greens provides at least nine times the minimum recommended intake of Vitamin K, and even a couple of cups of dark salad greens usually provide the minimum all on their own. Recent research has provided evidence that this vitamin may be even more important than we once thought (the current minimum may not be optimal), and many people do not get enough of it.
Vitamin K:
  • Regulates blood clotting
  • Helps protect bones from osteoporosis
  • May help prevent and possibly even reduce atherosclerosis by reducing calcium in arterial plaques
  • May be a key regulator of inflammation, and may help protect us from inflammatory diseases including arthitis
  • May help prevent diabetes
Vitamin K is a fat-soluble vitamin, so make sure to put dressing on your salad, or cook your greens with oil.

Almost Carb-Free

Greens have very little carbohydrate in them, and the carbs that are there are packed in layers of fiber, which make them very slow to digest. That is why, in general, greens have very little impact on blood glucose. In some systems greens are even treated as a "freebie" carb-wise (meaning the carbohydrate doesn't have to be counted at all).
Note on oxalates: Some greens contain substances called oxalates which may bind some percentage of the calcium in the greens. 

Types of Greens

I think of greens as divided into three groups, depending on how much cooking they require.

Salad Greens

Obviously, salad greens are usually eaten raw. In general, the darker the color, the more nutritious. Iceberg lettuce, for example, is extremely low in nutrients compared with its more colorful relatives - romaine lettuce has 8 times the vitamin A and 6 times the vitamin C as iceberg lettuce. When you have a choice, a variety of greens is always best, as each has its own constellation of nutrients.
The best salad dressings have healthful oils such as olive oil. Soy and corn oil have a lot of omega-6 oil, and it is to steer away from them for the most part, as many nutrition experts feel we consume too much omega-6 fat. Mayonnaise is made mainly from oil, so check the type of oil before you buy, as most are soy oil based. For most cooking uses, try to buy oils which are mostly monounsaturated fat rather than polyunsaturated (check the labels).
It's easy to make your own dressing right in the bowl. Start with vinegar, lemon juice, or lime juice - add salt, pepper and seasonings as desired, and whisk in some oil (about three times the oil as vinegar). 

Quick-cooking Greens

These greens can either be eaten raw or lightly cooked. Spinach is the most obvious example of this category. It takes only seconds to cook a spinach leaf. A benefit to cooked greens is that they shrink so much that you can more easily get lots of nutrition from them. Six cups of raw greens become approximately one cup of cooked greens.
Most quick-cooking greens take just a few minutes to cook. Chard (Swiss chard) is a quick-cooking green, and also can be eaten raw, though it isn't usually. Chard is now available in many colors, which are often milder-tasting than the more traditional chard. I recently saw a suggestion to chop up the stems and put them in tuna salad instead of celery. If you haven't tried chard, you really should - you may be surprised! Chard and the more familiar spinach are good places to start with cooked greens, as they are so easy, and not as bitter as some others.
Beet greens are also quick-cooking (and delicious), and are actually related to chard and spinach. Escarole, dandelion greens, and sorrel are also relatively quick-cooking greens.
Cabbage isn't very leafy, but I think of it in this category as well, even though it is related to the heartier greens kale and collards.

Hearty Greens

Many people seem to have a deep-seated fear of kale and collard greens (at least outside the U.S. South), but I encourage you to give them a try, as they have the most nutritional benefits of all. Over time, they may even become favorites.
Kale and collard greens are the most common examples of hearty greens. They do require cooking, although not as much as many people think. Yes, you can cook collards for an hour, but if you cut the greens from the fibrous stems they can be tender in 10-15 minutes. I also like kale cooked about that amount of time.

How to Wash Greens

The easiest way to wash greens is to put them into a lot of water and swish them around. The dirt sinks to the bottom that way. I use a large pot with an insert to drain pasta. I swish the greens, remove the insert and shake, and then let dry for a few minutes before storing.

How to Store Greens

Ideally, the greens should be dry or almost dry, and stored in a bag with as much of the air pushed out as you easily can. I like to put a barely damp paper towel in for just the right amount of moisture. Then, put them in the vegetable drawer of your fridge.

How to Cook Greens

Greens can be braised (cooked fairly slowly in a small amount of liquid, usually a flavorful stock), sautéed (cooked quickly in a small amount of oil), or a combination of the two. They can also be steamed or boiled, but most people like to add some other flavors which go well with greens (see below), and this is easier with braising or sautéing.
Another way to make greens is to bake them with cheese gratin-style or with eggs and cheese. (recipe coming soon)
Greens can also be thrown into almost any soup or skillet dish, especially the milder-tasting greens such as chard.

Flavors Which Go Well With Greens

When you read recipes for greens, certain ingredients emerge again and again, becuase they go so well with greens. Any combination of these will usually be a winner:
  • Smoked meats, including bacon, sausage, procuitto, and smoked turkey (smoked paprika or chipotle can also provide the smokey flavors)
  • Garlic
  • Lemon or vinegar
  • Hot chiles in some form (dried pepper flakes, hot sauce, etc.)
  • Anchovies (I'm not kidding, you can't taste fish, but they really make a difference)
  • Worcestershire Sauce
  • Dairy - Cream and/or cheese

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