Friday, September 12, 2014

Healthy Food - Spinach

Healthy Food - Spinach. Spinach (Spinacia oleracea) is an edible flowering plant in the family of Amaranthaceae. It is native to central and southwestern Asia. It is an annual plant (rarely biennial), which grows to a height of up to 30 cm. Spinach may survive over winter in temperate regions. The leaves are alternate, simple, ovate to triangular-based, very variable in size from about 2–30 cm long and 1–15 cm broad, with larger leaves at the base of the plant and small leaves higher on the flowering stem. The flowers are inconspicuous, yellow-green, 3–4 mm diameter, maturing into a small, hard, dry, lumpy fruit cluster 5–10 mm across containing several seeds.

Common spinach, Spinacia oleracea, was long considered to be in the Chenopodiaceae family, but in 2003, the Chenopodiaceae family was combined with the Amaranthaceae family under the family name 'Amaranthaceae' in the order Caryophyllales. Within the Amaranthaceae family, Amaranthoideae and Chenopodioideae are now subfamilies, for the amaranths and the chenopods, respectively.

  • Bright, vibrant-looking spinach leaves are not only more appealing to the eye but more nourishing as well. Recent research has shown that spinach leaves that look fully alive and vital have greater concentrations of vitamin C than spinach leaves that are pale in color. The study authors suggest that the greater supply of vitamin C helps protect all of the oxygen-sensitive phytonutrients in the spinach leaves and makes them looking vibrant and alive.
  • In a recent study on the relationship between risk of prostate cancer and vegetable intake  including the vegetables spinach, broccoli, cauliflower, cabbage, Brussels sprouts, mustard greens, turnip greens, collards, and kale  only spinach showed evidence of significant protection against the occurrence of aggressive prostate cancer. ("Aggressive prostate cancer" was defined as stage III or IV prostate cancer with a Gleason score of at least 7. Gleason scores are based on lab studies of prostate tissue and common tumor-related patterns.) The study authors did not speculate about specific substances in spinach that may have been involved in decreased prostate cancer risk. However, we know that certain unique anti-cancer carotenoids called epoxyxanthophylls are plentiful in spinach, even though they may not be as effectively absorbed as other carotenoids like beta-carotene and lutein. You can count on seeing future research on neoxanthin and violaxanthin two anti-cancer epoxyxanthophylls that are found in plentiful amounts in the leaves of spinach.

  • Many people are concerned about the nutrient content of delicate vegetables (like baby spinach) when those vegetables are placed in clear plastic containers in grocery store display cases and continuously exposed to artificial lighting. One recent food study has shown that you don't need to worry about the overall status of antioxidants in baby spinach that has been stored and displayed in this way. In this scientific study, the overall nutrient richness of the baby spinach when exposed to constant light was actually higher than the overall nutrient richness of baby spinach leaves kept in total darkness. The period of time in the study was 9 days, and the spinach was kept at 39°F/4°C (a temperature on the lower end of the scale for most home refrigerators). These findings are good news for anyone purchasing baby spinach in "ready-to-eat" containers.
  • One new category of health-supportive nutrients found in spinach is called "glycoglycerolipids." Glycoclycerolipids are the main fat-related molecules in the membranes of light-sensitive organs in most plants. They're indispensable for the process of photosynthesis carried out by plants. However, recent lab research in laboratory animals has shown that glycoglycerolipids from spinach can help protect the lining of the digestive tract from damage  especially damage related to unwanted inflammation. You can expect to see more studies about this exciting new category of molecules in spinach and its potential health benefits.
Healthy Food - Spinach
The English word "spinach" dates to the late 14th century, and is from espinache (Fr. épinard), of uncertain origin. The traditional view derives it from O.Prov. espinarc, which perhaps is via Catalan espinac, from Andalusian Arabic اسبيناخ asbīnākh, from Arabic السبانخ al-sabānikh , from Persian اسپاناخ aspānākh, meaning purportedly 'green hand', but the multiplicity of forms makes the theory doubtful. Healthy Food - Spinach.

Healthy Food - Spinach
Calorie for calorie, leafy green vegetables like spinach with its delicate texture and jade green color provide more nutrients than any other food. Although spinach is available throughout the year, its season runs from March through May and from September through October when it is the freshest, has the best flavor, and is most readily available. Spinach belongs to the same family (Amaranthaceae-Chenopodiaceae) as Swiss chard and beets and has the scientific name, Spinacia oleracea. It shares a similar taste profile with these two other vegetables, having the bitterness of beet greens and the slightly salty flavor of Swiss chard.

Popeye popularized spinach, but it's too bad he ate it out of a can. Fresh spinach retains the delicacy of texture and green color that is lost when spinach is processed. Raw spinach has a mild, slightly sweet taste that can be refreshing in salads, while its flavor becomes more acidic and robust when it is cooked.

There are three different types of spinach generally available. Savoy has crisp, creased curly leaves that have a springy texture. Smooth-leaf has flat, unwrinkled, spade-shaped leaves, while semi-savoy is similar in texture to savoy but is not as crinkled in appearance. Baby spinach is great for use in salads owing to its taste and delicate texture.

Spinach is thought to have originated in ancient Persia (Iran). Spinach made its way to China in the 7th century when the king of Nepal sent it as a gift to this country. Spinach has a much more recent history in Europe than many other vegetables. It was only brought to that continent in the 11th century, when the Moors introduced it into Spain. In fact, for a while, spinach was known as "the Spanish vegetable" in England.

Spinach was the favorite vegetable of Catherine de Medici, a historical figure in the 16th century. When she left her home of Florence, Italy, to marry the king of France, she brought along her own cooks, who could prepare spinach the ways that she especially liked. Since this time, dishes prepared on a bed of spinach are referred to as "a la Florentine."

Spinach grows well in temperate climates. Today, the United States and the Netherlands are among the largest commercial producers of spinach.

Types of spinach
A distinction can be made between older varieties of spinach and more modern ones. Older varieties tend to bolt too early in warm conditions. Newer varieties tend to grow more rapidly, but have less of an inclination to run up to seed. The older varieties have narrower leaves and tend to have a stronger and more bitter taste. Most newer varieties have broader leaves and round seeds. Healthy Food - Spinach.

The three basic types of spinach are:
Healthy Food - Spinach
  • Flat- or smooth-leaf spinach has broad, smooth leaves that are easier to clean than Savoy. This type is often grown for canned and frozen spinach, as well as soups, baby foods, and processed foods. Giant Noble is an example variety.
Healthy Food - Spinach
  • Savoy has dark green, crinkly and curly leaves. It is the type sold in fresh bunches in most supermarkets in the United States. One heirloom variety of savoy is Bloomsdale, which is somewhat resistant to bolting. Other common heirloom varieties are Merlo Nero (a mild variety from Italy) and Viroflay (a very large spinach with great yields).
Healthy Food - Spinach
  • Semi-savoy is a hybrid variety with slightly crinkled leaves. It has the same texture as Savoy, but it is not as difficult to clean. It is grown for both fresh market and processing. Tyee Hybrid is a common semi-savoy.
Health Benefits
We all know that Popeye made himself super strong by eating spinach, but you may be surprised to learn that he may also have been helping to protect himself against inflammatory problems, oxidative stress-related problems, cardiovascular problems, bone problems, and cancers at the same time.

Anti-Inflammatory and Anti-Cancer Benefits from Spinach Phytonutrients
Even though virtually all vegetables contain a wide variety of phytonutrients—including flavonoids and carotenoids—spinach can claim a special place among vegetables in terms of its phytonutrient content. Researchers have identified more than a dozen different flavonoid compounds in spinach that function as anti-inflammatory and anti-cancer agents. (Some of these substances fall into a technical category of flavonoids known as methylenedioxyflavonol glucuronides.) The anticancer properties of these spinach flavonoids have been sufficiently impressive to prompt researchers to create specialized spinach extracts that could be used in controlled laboratory studies. These spinach extracts have been shown to slow down cell division in human stomach cancer cells (gastric adenocarcinomas), and in studies on laboratory animals, to reduce skin cancers (skin papillomas). A study on adult women living in New England in the late 1980s also showed intake of spinach to be inversely related to incidence of breast cancer.

Excessive inflammation, of course, typically emerges as a risk factor for increased cancer risk. (That's why many anti-inflammatory nutrients can also be shown to have anti-cancer properties.) But even when unrelated to cancer, excessive inflammation has been shown to be less likely following consumption of spinach. Particularly in the digestive tract, reduced inflammation has been associated not only with the flavonoids found in spinach, but also with its carotenoids. Neoxanthin and violaxanthin are two anti-inflammatory epoxyxanthophylls that are found in plentiful amounts in the leaves of spinach. While these unique carotenoids may not be as readily absorbed as carotenoids like beta-carotene or lutein, they still play an important role in regulation of inflammation and are present in unusual amounts in spinach.

Decreased risk of aggressive prostate cancer is one health benefit of spinach consumption that should not be overlooked when talking about the anti-cancer properties of spinach. "Aggressive prostate cancer" is defined as stage III or IV prostate cancer which carries with it a Gleason score of at least 7. (Gleason scores are prostate cancer rating measurements that require lab studies of prostate tissue and evaluation of common tumor-related patterns.) Interestingly, in a recent study that evaluated possible prostate cancer-prevention benefits from a variety of vegetables including spinach, broccoli, cauliflower, cabbage, Brussels sprouts, mustard and turnip greens, collards, and kale — only spinach showed evidence of significant protection against the occurrence of aggressive prostate cancer.

Antioxidant Benefits of Spinach
Most of the flavonoid and carotenoid nutrients found in spinach that provide anti-inflammatory benefits provide antioxidant benefits as well. Given the fact that spinach is an excellent source of other antioxidant nutrients — including vitamin C, vitamin E, vitamin A (in the form of carotenoids), and manganese —as well as a very good source of the antioxidant zinc and a good source of the antioxidant selenium—it's no wonder that spinach helps lower risk of numerous health problems related to oxidative stress. Our blood vessels, for example, are especially susceptible to damage from oxidative stress, and intake of spinach has been associated with decreased risk of several blood vessel-related problems, including atherosclerosis and high blood pressure. (Interestingly, the blood pressure benefits of spinach may be related not only to its antioxidants, but also to some of its special peptides. Peptides are small pieces of protein, and researchers have discovered several peptides in spinach that can help lower blood pressure by inhibiting an enzyme called angiotensin I-converting enzyme.)

Two of the carotenoids that are especially plentiful in spinach — lutein and zeaxanthin — are primary antioxidants in several regions of the eye, including the retina and the macula. Although we haven't seen specific studies on spinach intake and prevention of eye-related problems like macular degeneration, we have seen studies showing that human blood levels of lutein can be increased by consumption of spinach in everyday amounts. We've also seen at least one group of researchers suggesting that spinach has a likely role to play in prevention of eye problems, including age-related macular degeneration.

Helping You Bone Up
The wealth of vitamin K provided by spinach is important for maintaining bone health. Vitamin K1 helps prevent excessive activation of osteoclasts, the cells that break down bone. Additionally, friendly bacteria in our intestines convert vitamin K1 into vitamin K2, which activates osteocalcin, the major non-collagen protein in bone. Osteocalcin anchors calcium molecules inside of the bone. All of these vitamin K-related mechanisms point to the importance of vitamin K-rich foods for bone health, and it is difficult to find vegetables that are richer in vitamin K than spinach. (On our World's Healthiest Foods list, only kale provides more micrograms of vitamin K per cup.) Spinach is also an excellent source of other bone-supportive nutrients including calcium and magnesium.

So while spinach probably won't make you super strong the minute you eat it, as it did for Popeye, it will promote your health and vitality in many other ways. It seems like Popeye was pretty smart after all. 

How to Select and Store
Choose spinach that has vibrant deep green leaves and stems with no signs of yellowing. The leaves should look fresh and tender, and not be wilted or bruised. Avoid those that have a slimy coating as this is an indication of decay. Healthy Food - Spinach.

Do not wash spinach before storing as the exposure to water encourages spoilage. Place spinach in a plastic storage bag and wrap the bag tightly around the spinach, squeezing out as much of the air as possible. Place in refrigerator where it will keep fresh for up to 5 days.

Avoid storing cooked spinach as it will not keep very well.

Tips for Preparing and Cooking

Tips for Preparing Spinach
Spinach should be washed very well since the leaves and stems tend to collect sand and soil. Before washing, trim off the roots and separate the leaves. Place the spinach in a large bowl of tepid water and swish the leaves around with your hands as this will allow any dirt to become dislodged. Remove the leaves from the water, empty the bowl, refill with clean water and repeat this process until no dirt remains in the water (usually two to three times will do the trick). Do not leave spinach soaking in the water as water-soluble nutrients will leach into the water.

Spinach sold in bags has been pre-washed and only needs to be rinsed. If you are going to use it in a salad, dry it using a salad spinner or by shaking it in a colander.

The Healthiest Way of Cooking Spinach
Spinach is only one of three vegetables we recommend boiling to free up acids and allow them to leach into the boiling water; this brings out a sweeter taste from the spinach. Discard the boiling water after cooking; do not drink it or use it for stock because of its acid content.

Use a large pot (3 quart) with lots of water and bring to a rapid boil. Add spinach to the boiling water and boil for 1 minute. Begin timing as soon as you place the spinach in the pot if you are using 1 pound or less of spinach. If you are cooking larger quantities of spinach bring the water back to a boil before beginning timing the 1 minute. Do not cover the pot when cooking spinach. Leaving the pot uncovered helps to release more of the acids with the rising steam. Research has shown that the boiling of spinach in large amounts of water helps decrease the oxalic acid content.

Remove spinach from pot, press out liquid with a fork, place in a bowl, toss with our Mediterranean Dressing, and top with your favorite optional ingredients. For details see 1-Minute Spinach.

How to Enjoy

A Few Quick Serving Ideas
Healthy Food - Spinach
  • Add layers of spinach to your next lasagna recipe.
  • Pine nuts are a great addition to cooked spinach.
  • Spinach salads are a classic easy and delicious meal or side dish.
Culinary information

Spinach also has a moderate calcium content. However, the oxalate content in spinach also binds with calcium, decreasing its absorption. The calcium in spinach is the least bioavailable of calcium sources. By way of comparison, the human body can absorb about half of the calcium present in broccoli, yet only around 5% of the calcium in spinach.

Spinach, along with other green leafy vegetables, is considered to be rich in iron. For example, the United States Department of Agriculture states that a 180-g serving of boiled spinach contains 6.43 mg of iron, whereas a 170-g ground hamburger patty contains at most 4.42 mg. However, spinach contains iron absorption-inhibiting substances, including high levels of oxalate, which can bind to the iron to form ferrous oxalate and render much of the iron in spinach unusable by the body. In addition to preventing absorption and use, high levels of oxalates remove iron from the body.

Spinach has a high nutritional value, especially when fresh, frozen, steamed, or quickly boiled. It is a rich source (> 20% of the Daily Value) of vitamin A, vitamin C, vitamin K, magnesium, manganese, folate and iron (table, right). Healthy Food - Spinach.

Individual Concerns

Spinach and E. coli
Several national recalls of spinach-containing products between 2006-2013 have raised consumer concerns about the risk of spinach contamination with E. coli bacteria. Of special concern have been Shiga toxin-producing E. coli (STEC), including E. coli 0157:H7. Thorough washing of contaminated spinach cannot remove E. coli 0157:H7. However, as summarized by the U.S. Food and Drug Administration (FDA), "Cooking fresh spinach at 160°F (71°C) for 15 seconds will kill any E. coli 0157:H7 present." The cooking method we recommend on our website for spinach—a quick boil for approximately 1 minute greatly exceeds this safety standard.

Because many people enjoy spinach in raw form (especially baby spinach), we are often asked about the level of risk involved with consumption of raw spinach. While we have not seen enough data to provide you with an exact risk level here, there is definitely some level of risk involved—although it might be very small with consumption of raw spinach. If your goal is to remove this risk entirely, your best approach is to follow our quick boil cooking method for spinach.

In the case of certified organic raw spinach (and other certified organic raw vegetables), there is one regulation working to help lower contamination risk: raw animal manure cannot be used less than 120 days prior to harvest of a certified organic food if the food (like spinach) has an edible portion that comes into contact with the soil or soil surface. This restriction on the use of raw animal manure can help prevent crops like spinach from being contaminated with bacteria like E. coli 0157:H7. In the case of non-organic raw spinach, there can also be reduction of risk due to irradiation of the spinach a practice allowed by the FDA since 2008. (Since irradiation is a prohibited practice in the production of certified organic foods, however, certified organic raw spinach is not irradiated.)

Spinach and Oxalates
Spinach is 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 spinach. Although early studies on spinach suggested possible interference of oxalates with iron absorption, more recent studies suggest that absorption of non-heme iron (iron from plants) is not significantly impacted by the oxalates contained in spinach. Laboratory studies have shown, however, that oxalates may interfere with absorption of calcium from the body. Exactly how much interference takes place in the case of spinach and calcium absorption is not clear, but at a minimum, you should expect to absorb a minimum of about 10% of the calcium from the spinach that you eat. For example, in one cup of boiled spinach containing about 285 milligrams, you can expect to absorb about 25-30 milligrams. For adults, the Adequate Intake (AI) level for calcium falls between 1,000 and 1,200 milligrams. This recommended amount assumes an absorption rate of about 30%. In other words, about 300-360 milligrams of absorbable calcium are expected each day. While 25-30 milligrams is not an overwhelming amount of calcium from a serving of food, a cup of spinach is extremely low-calorie and can provide you with about 10% of the recommended calcium intake for very few (about 40) calories. Those circumstances make spinach a worthwhile addition to your diet with respect to calcium, even though spinach is not an outstanding source of this nutrient and should not be counted on to boost your calcium intake by large amounts.  

Spinach and Pesticide Residues
Virtually all municipal drinking water in the United States contains pesticide residues, and with the exception of organic foods, so do the majority of foods in the U.S. food supply. Even though pesticides are present in food at very small trace levels, their negative impact on health is well documented. The liver's ability to process other toxins, the cells' ability to produce energy, and the nerves' ability to send messages can all be compromised by pesticide exposure. According to the Environmental Working Group's 2014 report "Shopper's Guide to Pesticides," conventionally grown spinach is among the top 12 fruits and vegetables on which pesticide residues have been most frequently found. Therefore, individuals wanting to avoid pesticide-associated health risks may want to avoid consumption of spinach unless it is grown organically.

Spinach and Purines
Spinach contain naturally occurring substances called purines. Purines are commonly found in plants, animals, and humans. In some individuals who are susceptible to purine-related problems, excessive intake of these substances can cause health problems. Since purines can be broken down to form uric acid, excess accumulation of purines in the body can lead to excess accumulation of uric acid. The health condition called "gout" and the formation of kidney stones from uric acid are two examples of uric acid-related problems that can be related to excessive intake of purine-containing foods. For this reason, individuals with kidney problems or gout may want to limit or avoid intake of purine-containing foods such as spinach. 

Nutritional Profile
Spinach is an excellent source of vitamin K, vitamin A (in the form of carotenoids), manganese, folate, magnesium, iron, copper, vitamin B2, vitamin B6, vitamin E, calcium, potassium, and vitamin C. It is a very good source of dietary fiber, phosphorus, vitamin B1, zinc, protein, and choline. Additionally, spinach is a godo source of omega-3 fatty acids, niacin, pantothenic acid, and selenium. While this mixture of conventional nutrients gives spinach a unique status in the antioxidant and anti-inflammatory department, it is the unusual mixture of phytonutrients in spinach that "seals the deal" in terms of its antioxidant and anti-inflammatory components. In terms of flavonoids, spinach is a unique source of methylenedioxyflavonol glucuronides, and in terms of carotenoids, its difficult to find a more helpful source of lutein and zeaxanthin. The epoxyxanthophyll carotenoids neoxanthin and violaxanthin are also welcomed constituents of spinach leaves.

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