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.
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.
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. Best if cut very thinly.
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.
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
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.
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..
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 immune-supportive vitamin A and anti-inflammatory vitamin K. They are very good source of bone-building manganese as well as heart-healthy vitamin C, folate and vitamin B6. Leeks are also a good source of digestion-supporting dietary fiber; bone-healthy magnesium, calcium, and copper; enzyme-generating molybdenum; and heart-healthy potassium. The folate found in leeks is partly present in the bioactive form of 5-methyltetrahydrofolate (5-MTHF).