With their unique combination of flavonoids and sulfur-containing nutrients, the allium vegetables belong in your diet on a regular basis. There's research evidence for including at least one serving of an allium vegetable in your meal plan every day. If you're choosing leeks, make your individual portion 1/2 cup or greater, and try to include at least one cup of chopped leeks in your recipes.
Many people are unfamiliar with how to cook leeks or how to include them in a Healthiest Way of Eating. We recommend cutting them very thinly and preparing them by using our Healthy Sauté method of cooking. Like their allium cousins, onions and garlic, let leeks sit for at least 5 minutes after cutting and before cooking. Our Tips for Preparing and Cooking and How to Enjoy sections below will give you more details on the best ways to bring leeks into your meal plan.
Leeks contain important amounts of the flavonoid kaempferol, which has repeatedly been shown to help protect our blood vessel linings from damage, including damage by overly reactive oxygen molecules. Interestingly, one of the mechanisms involved in this blood vessel protection may involve increased production of nitric oxide (NO), a naturally occurring gas that helps to dilate and relax the blood vessels, as well as decreased production of that asymmetric dimethylarginine (ADMA), a substance that blocks production of NO.
Often overlooked in leeks is their important concentration of the B vitamin folate. Folate is present in leeks in one of its bioactive forms (5-methyltetrahydrofolate, or 5MTHF) and it is present throughout the plant (including the full leaf portion, not only the lower leaf and bulb). While it's true that we still get about 50% more 5MTHF from the bulb than the leaves, this distribution of folate throughout the plant makes leeks a cardioprotective food from top to bottom. (Folate is a key B complex vitamin for supporting our cardiovascular system, because it helps keep our levels of homocysteine in proper balance. Excessively high levels of homocysteine are a risk factor for many cardiovascular diseases.)
Also present in leeks are impressive concentrations of antioxidant polyphenols. These polyphenols play a direct role in protecting our blood vessels and blood cells from oxidative damage. The total polyphenol content (TPC) of leeks averages about 33 milligrams of gallic acid equivalents (GAE) per 100 grams of fresh edible portion (FEP). By contrast, the TPC of red bell peppers averages 27 milligrams; cherry tomatoes, 24 milligrams; and carrots, 10 milligrams. So even though leeks are less concentrated than some of their fellow allium vegetables in terms of total polyphenols (garlic provides about 59 milligrams GAE/100g FEP, and onions provide about 76 milligrams), they are still a highly valuable food in terms of these phytonutrient antioxidants and provide us with important cardiovascular benefits for this reason.
Unfortunately, leeks have received less research attention than their fellow allium vegetables (especially garlic and onions), and for this reason, there is less documentation of their likely health benefits. Given their substantial polyphenol content, including their notable amounts of kaempferol, we would expect to see overlap with garlic and onions in terms of support for many health problems related to oxidative stress and chronic low-level inflammation. These health problems would include atherosclerosis, type 2 diabetes, obesity, rheumatoid arthritis, and allergic airway inflammation. We would also expect to see leeks providing measurable amounts of protection against several different types of cancer, mostly likely including colorectal cancer. It's important to remember that even in the absence of research studies to confirm health benefits, leeks still belong to the same allium vegetable family as onions and garlic and contain many health-supportive substances that are similar to (or identical with) the substances in their fellow allium vegetables.
Leeks, known scientifically as Allium porrum, are related to garlic, onions, shallots, and scallions. Leeks look like large scallions, having a very small bulb and a long white cylindrical stalk of superimposed layers that flows into green, tightly wrapped, flat leaves. Cultivated leeks are usually about 12 inches in length and one to two inches in diameter and feature a fragrant flavor that is reminiscent of shallots but sweeter and more subtle.
With a more delicate and sweeter flavor than onions, leeks add a subtle touch to recipes without overpowering the other flavors that are present. Although leeks are available throughout the year they are in season from the fall through the early part of spring when they are at their best.
The flavonoids in leeks are most concentrated in their lower leaf and bulb portion. The flavonol kaempferol is one of leeks' premiere flavonoids, and it's also most concentrated in the lower leaf and bulb. Leeks rank ahead of white onions in terms of their kaempferol content, but they still provide slightly less kaempferol than red onions. For other types of flavonoids, including quercetin, leeks appear to provide lower concentrations than most types of onions.
Leeks enjoy a long and rich history, one that can trace its heritage back through antiquity. Thought to be native to Central Asia, they have been cultivated in this region and in Europe for thousands of years.
Leeks were prized by the ancient Greeks and Romans and were especially revered for their beneficial effect upon the throat. The Greek philosopher Aristotle credited the clear voice of the partridge to a diet of leeks, while the Roman emperor Nero supposedly ate leeks everyday to make his voice stronger.
The Romans are thought to have introduced leeks to the United Kingdom, where they were able to flourish because they could withstand cold weather. Leeks have attained an esteemed status in Wales, where they serve as this country's national emblem. The Welsh regard for leeks can be traced back to a battle that they successfully won against that Saxons in 1620, during which the Welsh soldiers placed leeks in their caps to differentiate themselves from their opponents. Today, leeks are an important vegetable in many northern European cuisines and are grown in many European countries.
Leeks should be firm and straight with dark green leaves and white necks. Good quality leeks will not be yellowed or wilted, nor have bulbs that have cracks or bruises. Since overly large leeks are generally more fibrous in texture, only purchase those that have a diameter of one and one-half inches or less. Try to purchase leeks that are of similar size so as to ensure more consistent cooking if you are planning on cooking the leeks whole. Leeks are available throughout the year, although they are in greater supply from the fall through the early part of spring.
At WHFoods, we encourage the purchase of certified organically grown foods, and leeks are no exception. Repeated research studies on organic foods as a group show that your likelihood of exposure to contaminants such as pesticides and heavy metals can be greatly reduced through the purchased of certified organic foods, including leeks. In many cases, you may be able to find a local organic grower who sells leeks but has not applied for formal organic certification either through the U.S. Department of Agriculture (USDA) or through a state agency. (Examples of states offering state-certified organic foods include California, New York, Oregon, Vermont, and Washington.) However, if you are shopping in a large supermarket, your most reliable source of organically grown collard leeks is very likely to be leeks that display the USDA organic logo.
Fresh leeks should be stored unwashed and untrimmed in the refrigerator, where they will keep fresh for between one and two weeks. Wrapping them loosely in a plastic bag will help them to retain moisture.
Here is some background on why we recommend refrigerating leeks. Whenever food is stored, four basic factors affect its nutrient composition: exposure to air, exposure to light, exposure to heat, and length of time in storage. Vitamin C, vitamin B6, and carotenoids are good examples of nutrients highly susceptible to heat, and for this reason, their loss from food is very likely to be slowed down through refrigeration.
Cooked leeks are highly perishable, and even when kept in the refrigerator, will only stay fresh for about two days. Leeks may be frozen after being blanched for two to three minutes, although they will lose some of their desirable taste and texture qualities. Leeks will keep in the freezer for about three months.
If you'd like even more recipes and ways to prepare leeks the Nutrient-Rich Way, you may want to explore The World's Healthiest Foods book.
|vitamin K||26.42 mcg||29||16.4||excellent|
|manganese||0.26 mg||11||6.3||very good|
|vitamin B6||0.12 mg||7||3.9||very good|
|copper||0.06 mg||7||3.7||very good|
|iron||1.14 mg||6||3.5||very good|
|folate||24.96 mcg||6||3.5||very good|
|vitamin C||4.37 mg||6||3.3||good|
|vitamin A||42.22 mcg RAE||5||2.6||good|
|vitamin E||0.52 mg (ATE)||3||1.9||good|
|omega-3 fats||0.07 g||3||1.6||good|
Density>=7.6 AND DRI/DV>=10%
Density>=3.4 AND DRI/DV>=5%
Density>=1.5 AND DRI/DV>=2.5%