Spinach

Spinach, originally from the Middle East, has become one of the world's most popular vegetables. It is appreciated both for its taste and its many health benefits. 

Quick Facts
General Information
  • Scientific nameSpinacia oleracea
  • Plant typeVegetable
  • Native regionNorth Africa/Middle East
  • Main producer(s)China, United States of America
  • Main Economic UseCulinary, Agricultural industry
Spinach

Spinach is one of the most nutrient-rich foods in existence, and its reputation reflects its nutritional value. Although it experienced a boost in popularity during the thirties with the creation of the cartoon character Popeye, who used spinach to fuel his super strength, it was first cultivated at least 2,000 years ago in Persia (modern-day Iran). Today, spinach enjoys worldwide popularity, and is ranked 11th out of the 50 most popular vegetables in the United States.

Medicinal and Nutritional Information

Quick Facts (Medicinal and Nutritional Information)
  • Medicinal actionDigestive, Osteoprotective
  • Key constituentsVitamin K, glycoglycerolipids, CoQ10 (coenzyme Q10)
  • Ways to useCapsules, Liquid extracts, Food, Powder
  • Medicinal rating(4) Very useful plant
  • Safety rankingSafe

Health Benefits of Spinach

While spinach is largely valued for its nutritional content, providing many of the vitamins required by the human body, it is also well-known as a superfood due to some of the medicinal properties that it has been found to possess. Consumption of spinach has been shown to bring the following benefits:

  • Strengthening bones. Eating spinach helps to reinforce bones and make them less susceptible to breaking.

  • Protecting the digestive tract. Along with promoting regular digestion, spinach helps prevent inflammation of the intestines.

How It Works

Spinach has one of the highest concentrations of vitamin K, which is responsible for promoting the proper absorption of calcium (also found in spinach) in the body. Vitamin K directs the calcium to be absorbed by the bones, where it promotes bone strength, rather than the heart, where it can cause calcification and other health problems. 

Spinach's glycoglycerolipids, essential for the process of photosynthesis in plants and some bacteria, promote digestion and reduce inflammation in the digestive tract. This leafy green vegetable additionally contains CoQ10 (coenzyme Q10), also known as ubiquinol, a naturally-occurring metabolic enzyme that allows tissue regeneration and is necessary for the synthesis and proper functioning of cell membranes and lipoproteins.

Spinach also contains very high levels of minerals, mainly iron, manganese, and magnesium, as well as vitamins, including A (retinol), B2 (riboflavin), B6 (pyridoxine), B9 (folic acid), C (ascorbic acid), and E (tocopherol), the last two being powerful antioxidants that protect the immune system and help prevent diseases.

Spinach is also a great source of beta-carotene, a precursor of vitamin A, necessary for cellular regeneration and good eye health.

Digestive properties are also present in cinnamon and sage , whereas prune and soy can provide similar osteoprotective benefits.

Spinach Side Effects

Did you know?

Boiling spinach greatly reduces soluble oxalate content and is more effective than steaming and baking.

The consumption of spinach should be limited, because it contains fairly high levels of oxalic acid, an organic compound that may cause calcium deficiency or kidney stones in large doses. Symptoms of calcium deficiency include muscle spasms, brittle nails, and weak bones. 

That being said, as part of a well-balanced diet spinach has no adverse side effects. Various studies indicate that the oxalic acid content of spinach doesn't significantly reduce calcium uptake from other foods. Only high amounts of spinach can create a nutritional problem.

Spinach Cautions

Spinach may interact with warfarin, an anticoagulant drug, so those taking this medication should avoid high doses of spinach. Recently, spinach has also been the subject of several recalls due to contamination by E. coli. To avoid falling ill, consumers should thoroughly clean or cook spinach before eating it.

How to Consume Spinach

Quick Facts (How to Consume)
  • Edible partsLeaves
  • TasteMildly bitter

Spinach has very few forms of consumption outside of culinary preparations. Eating spinach is the easiest way to absorb its nutrients and benefit from its medicinal properties, so it is commonly used as an ingredient in the kitchen.

Food

Main preparations: Raw, cooked, frozen, canned, juiced

For preparing culinary dishes, the spinach leaf is the favored part of the plant to be used. Stems are rarely used in any food.

  • Raw. Fresh, raw spinach leaves - often added to salads - provide the most health benefits.

  • Cooked. While spinach leaves lose some of their nutritional value when cooked, the process of cooking spinach can reduce the amount of oxalic acid present. Being water-soluble, some nutrients, such as vitamin C and folate, get dissolved by the heat. However, because it greatly reduces its volume, a cup of cooked spinach represents more of other important nutrients, such as iron, that also become easier to be absorbed by the body.

  • Frozen. Although not as nutritional as fresh spinach, frozen spinach retains its nutrients better when frozen than when kept at room temperature. 

  • Canned. Canned spinach is the least nutritious form of spinach.

  • Juiced. Spinach can be made into juice or blended into a smoothie for a nutritional drink.

Remedies

Main preparations: Liquid extract, powder, capsules

  • Liquid extract. This preparation concentrates the chlorophyll content of the dark green, leafy spinach, as well as CoQ10, which is responsible for cellular regeneration and energy production. Just add 20 - 30 drops to a glass of juice or water four times a day to reap the benefits of this concentrated form of spinach. 

  • Powder. Dried and finely ground, spinach powder preserves the antioxidant properties of this herb, and it is often consumed as a sport supplement. However, it ranks behind most of the culinary preparations in nutritional value. 

  • Capsules. Both spinach extract and powder can be found in capsule form, which allows for easier ingestion and better dosage control. 

Buying

Quick Facts (Buying)
  • Where to buySupermarkets, Big online retailers, Farmers' markets, Online herb stores, Local herbal store, Organic markets

Fresh and Canned Spinach

Fresh, raw spinach is easily found globally in grocery stores and local markets. Canned and frozen products are also sold in the same locations, although they may not be quite as commonly available as the raw leaves. Spinach in juice form is difficult to find outside of juice bars or raw food restaurants, but spinach smoothies are simple to make at home with the raw leaves and a few other ingredients. Recipes for these smoothies are widely available, either online or in health-focused cookbooks.

Spinach Supplements

Spinach leaf extract, powder, and capsules are not as ubiquitous or easy to find as fresh and frozen spinach leaves. They are most likely to be found through online retailers, but are also available in certain herbal shops and health stores.

Growing

Quick Facts (Growing)
  • Life cycleAnnual
  • Harvested partsLeaves
  • Light requirementsFull sun, Partial shade
  • SoilMedium (loam), Well-drained
  • Soil pH6.6 – 7.3 (Neutral)
  • Growing habitatTemperate climates
  • Planting timeEarly spring, Late summer, Fall
  • Plant spacing average0.1 m (0.30 ft)
  • Potential insect pestsAphids, Slugs, Leafminers
  • Potential diseasesLeaf spot, Rust, Anthracnose, Damping-off, Downy mildew

Because of its specific temperature and moisture requirements, spinach can be a moderately difficult plant to grow. However, its leaves provide so much nutritional value that it is worth the effort for those who can create a garden environment in which spinach will thrive.

Growing Guidelines

  • Spinach seeds should be sown in well-drained soils that are also rich in organic matter. An ideal pH of 6.5 - 7.5 will generate the optimal growth.

  • It is advised to plant spinach four weeks before the average latest frost date and keep it at a temperature range of 50 - 60°F (10 - 15°C).

  • Spinach requires partial shade, so it should not be planted in an area that receives full, direct sunlight.

  • Leaves may be harvested periodically once a plant has at least six true leaves, or the entire plant may be harvested once it reaches maturity.

  • Spinach is a weak competitor and is very susceptible to weeds, so care should be taken to prevent weed growth around the plant.

  • Some pests may damage the spinach plant, including aphids, spinach leafminer, and slugs. Diseases can affect the plant as well, but several varieties with resistance to common diseases have been developed and are widely available.

Detailed information about growing spinach can be found in the herb garden section.

Additional Information

Quick Facts (Additional Information)
  • Other usesCosmetics

Plant Biology

Spinach is a leafy, flowering annual plant that can grow up to one foot (30 cm) tall. Its leaves vary in size from 1 - 12 inches (2 - 30 cm) and grow alternately on a round, reddish stem. Spinach leaves are oval to triangular shaped, and can be either smooth or curly. The plant's flowers are typically small and can range from green to yellow-green. 

  • Classification

    Spinacia oleracea is a member of the Amaranthaceae family, as well as the Chenopodioideae subfamily. This family is known for its leafy greens, and it also contains plants such as beetroot (Beta vulgaris), amaranth (Amaranthus spp.), and quinoa (Chenopodium quinoa).

  • Related Species and Varieties of Spinach

    Many other species of leafy greens are colloquially called spinach, but none belong to the same genus as S. oleracea, nor do they possess all of the same benefits. These species include New Zealand spinach (Tetragonia tetragonioides), Malabar spinach (Basella alba), water spinach (Ipomoea aquatica), and Chinese or African spinach (Amaranthus gangeticus), all of which tolerate warm weather better than S. oleracea and are often used as culinary substitutes in warmer climates.

    However, S. oleracea does have several different varieties or cultivars, many with resistances to different diseases. Each of these cultivars can be categorized into one of the following three types:

    'Savoy'. This type of spinach has a wrinkly, curly leaf. It is often grown for local markets because of its appealing look and longer shelf life, but the leaf texture makes it harder to clean.

    'Flat' or 'smooth leaf'. As its name implies, this type of spinach grows flat, smooth leaves. This variety is harvestable earlier than the savoy and its leaves are easier to clean, so it is often used for canning.

    'Semi-savoy'. The semi-savoy variety is a hybrid between the savoy and the flat or smooth leaf variety. Its leaves are flatter than the savoy, but not as flat as the flat or smooth leaf.

Historical Information

Spinach has always enjoyed relative popularity, and its reputation has only grown over the years. It was first cultivated in the Middle East, most likely somewhere in Persia. It was introduced to China in the sixth century, and brought to Europe by way of Spain by the 15th century. In the United States, spinach has been a common crop since it was first cultivated on American soil in 1807

Economic Data

Spinach is today considered a superfood, meaning that it is packed with vitamins and nutrients essential for one's health, so it enjoys a position of economic importance. The largest producer of the vegetable is China, but the United States is in second place. In 2014, the United States produced 772.6 million pounds (350.4 million kg) of spinach. 

Popular Beliefs

Spinach is undoubtedly an excellent source of iron, but for many years, it was thought to be much more iron-rich than it truly is. Thanks to the miscalculations of scientist Dr. Emil von Wolf in 1870, spinach was believed to have an iron content 10 times higher than its actual level. Dr. von Wolf misplaced a decimal point when measuring the iron levels, and his mistake was only noticed 67 years later. In fact, many people today still mistakenly consider spinach to be richer in iron than it is.

In 1929, the cartoon Popeye the Sailor first ran in a newspaper's comics section. Popeye famously used spinach to give himself the super strength he used to beat the comic's villains. The cartoon gained so much popularity that the spinach industry credited it with boosting spinach sales 33% over the course of the thirties. 

Other Uses

The most common non-culinary uses for spinach are cosmetic. The plant is rich in phytonutrients, vitamins, and minerals that are beneficial to hair and skin, so many facial masks and nourishing hair products contain crushed or blended spinach leaves. 

Spinach is a healthy addition to any kitchen, as it is a food densely packed with several important nutrients. It can be found worldwide and is highly valued for its heart-healthy and bone-strengthening properties.

Bibliography

  • Journal of Agricultural and Food Chemistry, Effect of different cooking methods on vegetable oxalate content, 2005
  • The Encyclopedia of Nutrition and Good Health, p. 592
  • Better Nutrition
  • The World's Healthiest Foods, Spinach
  • Michigan State University, Greening your health with spinach
  • Agricultural Marketing Resource Center, Spinach
  • AYU - An International Quarterly Journal of Research in Ayurveda, Spinacia oleracea linn: A Pharmacognostic and Pharmacological Overview, 2010
  • United States Department of Agriculture, Economic Research Service, Commodity Highlights
  • Colorado State University, Extension, Colorado Spinach
  • University of Wisconsin, Master Gardener Program, Spinacia oleracea
  • University of Arizona, College of Agricultural Sciences, Spinach Seed
  • Advances in Food and Nutrition Research, p. 142
  • Oregon State University, Linus Pauling Institute, Micronutrient Information Center, Coenzyme Q10
  • Cornell University, Growing Guide, Spinach
  • University of Florida, Extension, Eating Defensively: The Nutrition and Food Safety Benefits of Cooked Produce