Spinach: Health benefits, nutrition facts (& Popeye)

Since the days of Popeye, spinach has been famous for its ability to make you "strong to the finish." While this leafy green won’t cause your biceps to inflate like balloons, it is dense in vitamins and minerals, low in calories and versatile in cooking. 

Spinach may also help with several health conditions, according to Megan Ware, a registered dietitian nutritionist based in Orlando, Florida. "Eating spinach is beneficial for maintaining healthy skin, hair and strong bones, as well as helping with digestion, lowering the risk for heart disease and improving blood glucose control in diabetics," she told Live Science.

Spinach is believed to come from Persia, according to Arizona State University. It had arrived in China by the seventh century and reached Europe in the mid-13th century, according to The Agricultural Marketing Research Center. For some time, the English referred to it as the "Spanish vegetable" because it came through Spain via the Moors. According to BBC Good Food, use of the word "Florentine" to describe a dish with spinach can likely be traced to Catherine de Medici, the Italian wife of France’s Henry II. It is believed that Catherine, who loved spinach, brought her own cooks from Florence to cook spinach in her preferred style.

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Spinach is a member of the Chenopodiaceae family, which also contains nutritionally powerful foods like beets and Swiss chard. There are three types of spinach:  

• Savoy spinach, which has curly or heavily wrinkled, dark green leaves
• Semi-savoy spinach, which is somewhat less wrinkly and good to use in cooking
• Flat-leaf spinach, the popular, smooth-textured variety that works well in salads and is best eaten raw. Baby spinach is a type of flat-leaf spinach. 

Nutritional profile

"Spinach is one of the best sources of dietary potassium and magnesium, two very important electrolytes necessary for maintaining human health," Ware said. "It provides a whopping 839 milligrams of potassium per cup (cooked). As a comparison, one cup of sliced banana has about 539mg of potassium." 

Ware noted that there are several health benefits to potassium, among them “protection against loss of muscle mass, preservation of bone mineral density and reduction in the formation of kidney stones," she added. "Only 2 percent of U.S. adults meet the daily 4,700 mg recommendation for potassium."

The George Mateljan Foundation’s analysis of spinach’s nutritional properties placed it at the top of their nutrient-rich food list. "Spinach is an excellent source of vitamin K, vitamin A (in the form of carotenoids), manganese, folate… copper, vitamin B2, vitamin B6, vitamin E, calcium … and vitamin C." Spinach’s calcium, however, cannot be as easily absorbed as calcium from dairy, and you should only expect to absorb about ten percent of it. 

Spinach is also a very good source of zinc, dietary fiber, phosphorus, vitamin B1 and choline. It contains a unique and beneficial mixture of phytonutrients, as well as anti-oxidants, flavonoids and carotenoids. 

"Spinach is also one of the best non-heme (plant-based) sources of iron," Ware added. The same is true of spinach’s protein content; most of the calories in spinach come from protein. This makes it a popular food for vegetarians. At only 7 calories per cup of raw spinach and 41 per cup of cooked spinach, it’s also a great choice for dieters. 

Here are the nutrition facts for spinach, according to the U.S. Food and Drug Administration, which regulates food labeling through the Nutritional Labeling and Education Act:

Health benefits

Bones

The National Osteoporosis Foundation recommends eating spinach for its vitamin K and magnesium content. Just one cup of cooked spinach contains an incredible 987 percent of your daily vitamin K needs and 39 percent of your magnesium ones.

According to the US National Library of Medicine, in the past few decades it has become clear that vitamin K is important to bone health. A review also published in Nutrition noted that vitamin K intake might reduce fracture rates, work with vitamin D to increase bone density and positively affect calcium balance. Your body uses vitamin K when building bones, and the effects seem to be especially important for women: low vitamin K levels were associated with low bone density in women, but not in men. 

An earlier study published in the American Journal of Clinical Nutrition found that low intakes of vitamin K were associated with an increased risk of hip fractures in middle-aged women. This is especially interesting because the women saw results from eating lettuce, showing that dietary consumption of vitamin K via eating vegetables (not supplements) is beneficial. 

When it comes to men, the affects of vitamin K and bone health may become more apparent as they age, with reduced risk of hip fracture among both elderly women and elderly men who consumed more vitamin K.

The high level of potassium in spinach is also helpful in protecting against bone mineral density loss, said Ware. Additionally, spinach contains calcium, well known to be important for bones. The calcium in spinach is, however, difficult to absorb so the Physicians Committee for Responsible Medicine recommends getting calcium from other vegetable sources, such as broccoli and kale, or dairy. 

Blood

This is the most common type of anemia, and women are its largest risk group. Without sufficient iron, your blood can’t produce enough hemoglobin, a blood protein that gives blood cells their red color and transports oxygen to organs. Eating iron-rich foods is important for those suffering from or at risk of anemia, and with 36 percent of your daily iron needs per cooked cup, spinach is a good option. The National Organization of Women’s Health, as well as the National Heart, Lung and Blood Institute recommends eating spinach as part of an anemia prevention or treatment program. 

Skin and hair

"Want healthier-looking hair? Eat more spinach!" said Ware. "Spinach is high in vitamin A, a nutrient required for sebum production to keep hair moisturized. Vitamin A is also necessary for the growth of all bodily tissues, including skin and hair." 

According to the Linus Pauling Institute at Oregon State University, vitamin A is a compound in retinoids, which are popular in anti-aging skin treatments. Furthermore, vitamin C can help keep skin looking youthful and aids in wound healing. "Adequate intake of vitamin C, which spinach can help to provide, is needed for the building and maintenance of collagen, which provides structure to skin and hair," said Ware. 

Cancer-fighting

Spinach is a standout in terms of its mix of phytonutrient components. According to World’s Healthiest Foods, unlike most other fruits and vegetables, spinach contains cancer-fighting agents called methylenedioxyflavonol glucuronides. It is also an excellent source of antioxidants lutein, zeaxanthin, neoxanthin and violaxanthin. All of these are anti-inflammatories, which can be helpful in cancer prevention. 

Spinach’s high levels of chlorophyll may have anti-cancer and anti-carcinogen effects. A review of anti-cancer diet research published in Nutrition Journal explained that this is because chorophyll helps bind together hydrocarbons, aflatoxins and other hydrophobic molecules that may be associated with cancer and expels them.

Some studies have noted possible anti-cancer effects among prostate, breast and prostate cancers. One study published in the Journal of Nutrition looked at 15 kinds of carotenoids to see if they combatted cancer cells and found only neoxanthin from spinach and fucoxanthin from brown algae to be significantly effective. 

A three-year study from the early 1990s found that women who ate raw spinach or carrots more than twice a week had a lower risk of breast cancer, while a more 2010 study looked at the relationship between flavonoid intake and ovarian cancer. Among its many findings, this large-scale study saw a lower risk of ovarian cancer among women who ate the most spinach than those who ate the least. 

Asthma

"The risks for developing asthma are lower in people who consume a high amount of certain nutrients, one of these being beta-carotene," said Ware. Beta-carotene may also help asthma sufferers reduce their symptoms. A study from the Annals of Asthma, Allergy & Immunology found that people with exercise-induced asthma did not develop symptoms during a seven-minute intense exercise session after consuming 64 mg of beta-carotene for one week. "Many people automatically think of orange fruits and vegetables when thinking of beta-carotene, but spinach is also an excellent source," said Ware. 

Spinach’s magnesium content may also be good for asthma sufferers. Magnesium can be an effective emergency treatment for asthma attacks. But a literature review of studies involving magnesium and asthma found that only intravenous magnesium is conclusively helpful; oral or vaporized magnesium’s effectiveness is unclear. 

Diabetes

"Spinach contains a powerful antioxidant known as alpha-lipoic acid, which has been shown to lower blood sugar levels and increase insulin sensitivity and decrease peripheral neuropathy [weakness or numbness in the hands or feet] in patients with diabetes," said Ware. 

The University of Maryland Medical Center notes that much of the research has been done with intravaneous alpha-lipoic acid, however, so it’s less clear that consuming the antioxidant by mouth has the same results. A study published in Diabetes Care found that consuming 600 mg of alpha-lipoic acid by mouth every day for five weeks improved neuropathic symptoms, such as stabbing and burning pain, numbness in feet and paresthesia (a tingling or itching sensation), more than a placebo. 

Heart

Ware noted that spinach’s potassium levels are heart-healthy. “High potassium intakes are associated with a reduced risk of stroke, lower blood pressure, lower risk of death from heart disease.” 

Potassium is an essential part of heart health. Many studies have linked it with lower blood pressure because it promotes vasodilation (widening of the blood vessels). One study of 12,000 adults, published in Today's Dietician, showed that those who consumed 4,069 mg of potassium each day lowered their risk of cardiovascular disease and ischemic heart disease (characterized by reduced blood flow to the heart) by 37 percent and 49 percent, respectively, compared to those who took 1,793 mg per day. 

Spinach’s astronomical levels of vitamin K are also associated with heart health and blood clotting. According to the Linus Pauling Institute, vitamin K is an essential factor in blood clotting, and lack of it can cause hemorrhages. There are also suggestions that vitamin K might reduce the risk of heart disease because without it, mechanisms that stop the formation of blood vessel calcification may become inactive. Studies are still inconclusive, however, and one review of them, published in Advances in Nutrition, suggested that future research should focus specifically on vitamin-K deficient patients. 

Pregnancy

The essentiality of folic acid (also known as folate) during pregnancy is well-documented. Folic acid can help prevent neural tube defects — specifically spina bifida and anencephaly — that occur early in pregnancy. 

Since it’s hard for women to get enough folic acid from food alone, the Centers for Disease Control recommends taking 400 mcg if you are pregnant or might become pregnant. But spinach can also help increase your folic acid intake, with 66 percent of your daily (pre-pregnancy) folate needs per cooked cup. 

Eyes

Spinach is a good source of carotenoids lutein and zeaxanthin, which are associated with helping to prevent age-related macular degeneration and cataracts. According to The Scripps Research Institute, studies have shown that those who ate spinach three times per week had a 43 percent lower risk of developing macular degeneration. 

Risks of eating spinach

"Suddenly increasing your consumption of spinach could be harmful if you are taking blood thinners such as Coumadin (warfarin)," said Ware. "It is important that you maintain a consistent intake of foods containing vitamin K (like spinach), which play a large role in blood clotting."

Spinach ranks number two on the Environmental Working Group’s 2021 Dirty Dozen list. That means it may be exposed to high levels of pesticides. If possible, you should buy organic spinach, but be sure to wash it thoroughly regardless of what type it is. 

"If your kidneys are not fully functional, consuming too much potassium could cause an excess amount of potassium in the blood and even be fatal," said Ware. Spinach also contains oxalates, which can be harmful to those with kidney or gallbladder problems. Excessive accumulation of oxalates can crystalize and cause problems, according to World’s Healthiest Foods.

Eat more spinach!

Ware provided some tips on how to incorporate more spinach into your diet:

• Incorporate spinach into recipes you already make at home. Throw a few handfuls into your favorite pasta, soup or casserole.
• Sautee spinach in a small amount of extra virgin olive oil and season with ground black pepper and freshly grated Parmesan cheese. Serve as a base for grilled chicken or salmon.
• Add spinach to your wrap, sandwich or flatbread instead of regular lettuce, or use it as a base for your salad.
• Add spinach to any egg dish, like an omelet, scramble or quiche.
• Throw a handful of spinach into a smoothie or juice — it will change the color but not the taste!

About that sailor man...

Popeye the Sailor Man made his debut in 1929 in a comic strip called "Thimble Theatre" and jumped to animated cartoons in 1933. According to Comics Kingdom, he was a "good guy underdog with bulging forearms, a mean uppercut and a penchant for canned spinach."

Popeye's love for spinach became a common plot device — popping open a can often gave him super-strength. Spinach growers credited Popeye with a 33 percent increase in U.S. spinach consumption and saving the spinach industry in the 1930s, according to Comics Kingdom.

In 1937, Crystal City, Texas, a spinach-growing town, erected a statue to honor Popeye and his creator, E.C. Segar, for their positive influence on America’s eating habits, making Popeye the first cartoon character ever immortalized in public sculpture.

Some sources claim that the reason Segar chose spinach as the source of Popeye's strength was due to an error in an 1870 study that measured the vegetable's iron content. The scientist who conducted the research is said to have misplaced a decimal point, giving spinach ten times the amount of iron it actually has. However, author Mike Sutton says this story is a myth, and that spinach was chosen for its vitamin A content.

Additional resources

Take a look at this handy booklet from the University of the District of Columbia, What's So Great About Spinach?, plus find yourself a tasty recipe for cooking with spinach at BBC Good Food.

Bibliography

• Zhu Gelin (朱格麟 Chu Ge-ling), Sergei L. Mosyakin2, Steven E. Clemants, Chenopodiaceae
• Elena Jovanovski, Laura Bosco, Kashif Khan, Fei Au-Yeung, Hoang Ho, Andreea Zurbau, Alexandra L. Jenkins, and Vladimir Vuksan, Effect of Spinach, a High Dietary Nitrate Source, on Arterial Stiffness and Related Hemodynamic Measures
• Natalie Olsen, R.D., L.D., ACSM EP-C, 
• Megan Ware, RDN, L.D., 
• Health Benefits and nutritional benefits of spinach, https://www.medicalnewstoday.com/articles/270609