Leeks

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 into 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 to enhance their health-promoting qualities. See the Healthiest Way of Cooking Leeks in the How to Enjoy section below.

This chart graphically details the %DV that a serving of Leeks provides for each of the nutrients of which it is a good, very good, or excellent source according to our Food Rating System. Additional information about the amount of these nutrients provided by Leeks can be found in the Food Rating System Chart. A link that takes you to the In-Depth Nutritional Profile for Leeks, featuring information over 80 nutrients, can be found under the Food Rating System Chart.

• Health Benefits
• Description
• History
• How to Select and Store
• Tips for Preparing and Cooking
• How to Enjoy
• Individual Concerns
• Nutritional Profile
• References

Health Benefits

Leeks, like garlic and onions, belong to a vegetable family called the Allium vegetables. Since leeks are related to garlic and onions, they contain many of the same beneficial compounds found in these well-researched, health-promoting vegetables.

Cardiovascular Support

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.

Other Health Benefits

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.

Description

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. Wild leeks, known as ramps, are much smaller in size, but have a stronger, more intense flavor. They are available for a short period of time each year and are often widely sought out at farmers markets when they are in season.

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

History

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.

How to Select and Store

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.

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. 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.

Tips for Preparing and Cooking

Tips for Preparing Leeks

Cut off green tops of leeks and remove outer tough leaves. Cut off root and cut leeks in half lengthwise. Fan out the leeks and rinse well under running water, leaving them intact. Cut leeks into 2-inch lengths. Holding the leek sections cut side up, cut lengthwise so that you end up with thin strips, known as the chiffonade cut, slicing until you reach the green portion. Make sure slices are cut very thin to shorten cooking time. Let leeks sit for at least 5 minutes before cooking.

Healthiest Way of Cooking Leeks

Heat 3 tablespoons of broth in 10-12 inch stainless steel skillet until it begins to steam. Add 1 pound of cut leeks. Cover and Healthy Sauté for 4 minutes. Add 2 more tablespoons of broth, reduce heat to medium low, and Healthy Sauté for 3 more minutes uncovered while stirring frequently. Toss with 2 tablespoons of extra virgin olive oil, 1 teaspoon of lemon juice and salt and pepper to taste.

How to Enjoy

A Few Quick Serving Ideas

• Healthy sauté leeks and fennel. Garnish with fresh lemon juice and thyme.
• Add finely chopped leeks to salads.
• Make vichyssoise, a cold soup made from puréed cooked leeks and potatoes.
• Add leeks to broth and stews for extra flavoring.
• Braised leeks sprinkled with fennel or mustard seeds make a wonderful side dish for fish, poultry or steak.
• Add sliced leeks to your favorite omelet or frittata recipe.

WHFoods Recipes That Feature Leeks

• Poached Eggs Over Sauteed Greens
• Braised Salmon with Leeks
• Sautéed Greens

Individual Concerns

Leeks and Oxalates

Leeks are among a small number of foods that contain measurable amounts 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 leeks. Laboratory studies have shown that oxalates may also interfere with absorption of calcium from the body. Yet, in every peer-reviewed research study we've seen, the ability of oxalates to lower calcium absorption is relatively small and definitely does not outweigh the ability of oxalate-containing foods to contribute calcium to the meal plan. If your digestive tract is healthy, and you do a good job of chewing and relaxing while you enjoy your meals, you will get significant benefits—including absorption of calcium—from calcium-rich foods plant foods that also contain oxalic acid. Ordinarily, a healthcare practitioner would not discourage a person focused on ensuring that they are meeting their calcium requirements from eating these nutrient-rich foods because of their oxalate content. . For more on this subject, please see "Can you tell me what oxalates are and in which foods they can be found?"

Nutritional Profile

Although less well-researched than their fellow allium vegetables (especially garlic and onions), leeks nevertheless contain many sulfur compounds that are either similar to, or identical with, sulfur compounds in these better-researched vegetables. They also contain an impressive amount of polyphenols, including the flavonoid kaempferol. In and of itself, the considerable amount of sulfur found in leeks may play an important role in support of our body's antioxidant and detox systems as well as the formation of our connective tissue. Leeks are an excellent source of vitamin K. They are very good source of manganese, vitamin B6, copper, iron, folate, and vitamin C. Leeks are also a good source of vitamin A (in the form of carotenoids, dietary fiber, magnesium, vitamin E, calcium, and omega-3 fatty acids. The folate found in leeks is partly present in the bioactive form of 5-methyltetrahydrofolate (5-MTHF).

For an in-depth nutritional profile click here: Leeks.

In-Depth Nutritional Profile

In addition to the nutrients highlighted in our ratings chart, an in-depth nutritional profile for Leeks is also available. This profile includes information on a full array of nutrients, including carbohydrates, sugar, soluble and insoluble fiber, sodium, vitamins, minerals, fatty acids, amino acids and more.

Introduction to Food Rating System Chart

In order to better help you identify foods that feature a high concentration of nutrients for the calories they contain, we created a Food Rating System. This system allows us to highlight the foods that are especially rich in particular nutrients. The following chart shows the nutrients for which this food is either an excellent, very good, or good source (below the chart you will find a table that explains these qualifications). If a nutrient is not listed in the chart, it does not necessarily mean that the food doesn't contain it. It simply means that the nutrient is not provided in a sufficient amount or concentration to meet our rating criteria. (To view this food's in-depth nutritional profile that includes values for dozens of nutrients - not just the ones rated as excellent, very good, or good - please use the link below the chart.) To read this chart accurately, you'll need to glance up in the top left corner where you will find the name of the food and the serving size we used to calculate the food's nutrient composition. This serving size will tell you how much of the food you need to eat to obtain the amount of nutrients found in the chart. Now, returning to the chart itself, you can look next to the nutrient name in order to find the nutrient amount it offers, the percent Daily Value (DV%) that this amount represents, the nutrient density that we calculated for this food and nutrient, and the rating we established in our rating system. For most of our nutrient ratings, we adopted the government standards for food labeling that are found in the U.S. Food and Drug Administration's "Reference Values for Nutrition Labeling." Read more background information and details of our rating system.

In-Depth Nutritional Profile for Leeks

References

• Brat P, Georgé S, Bellamy A, et al. Daily polyphenol intake in France from fruit and vegetables. J Nutr. 2006 Sep;136(9):2368-73. 2006.
• Chun OK, Chung SJ, and Song WO. Estimated dietary flavonoid intake and major food sources of U.S. adults. J Nutr. 2007 May;137(5):1244-52. 2007.
• Nimni ME, Han B and Cordoba F. Are we getting enough sulfur in our diet?. Nutr Metab (Lond). 2007 Nov 6;4:24-36. 2007.
• Phillips KM, Rasor AS, Ruggio DM, et al. Folate content of different edible portions of vegetables and fruits. Nutrition & Food Science 2008, 38(2):175-181. 2008.
• Somerset SM and Johannot L. Dietary flavonoid sources in Australian adults. Nutr Cancer. 2008;60(4):442-9. 2008.
• Xiao HB, Jun-Fang, Lu XY et al. Protective effects of kaempferol against endothelial damage by an improvement in nitric oxide production and a decrease in asymmetric dimethylarginine level. European Journal of PharmacologyVolume 616, Issues 1-3, 15 August 2009, Pages 213-222. 2009.