Is spinach truly a reliable source of iron?

While Scooby loves his snacks, Garfield adores his lasagna, and Cartman can't get enough of cheesy poofs, none of these rivals the iconic relationship Popeye has with spinach. When Popeye consumes spinach, his forearms grow exponentially, he gains immense strength, and perhaps most curiously, he helps propagate one of pop culture's most enduring myths.

Popeye took his first bite of spinach in a cartoon strip on July 3, 1932. Despite his mumbled speech, his actions spoke volumes: Spinach is both beneficial and necessary. Decades later, parents continue to tell their children, 'Eat your spinach,' believing its iron will help them grow big and strong, just like Popeye.

But the actual story isn't quite like that. Popeye's line was: 'Spinach is full of vitamin 'A' an' tha's what makes hoomans strong an' helty' [source: Cronin]. It turns out Popeye didn't eat spinach for iron; instead, he gobbled it for vitamin A, specifically beta-carotene, which his body converted into vitamin A.

Spinach, or Spinacia oleracea, is an annual plant consumed for its elliptical leaves, ranging from 2 to 30 centimeters (0.78 to 22 inches) in length. While it's unclear which variety of spinach Popeye favored, it's likely he preferred flat leaf spinach, the smooth-leaved kind that is typically canned or frozen [source: Leafy Greens Council]. On the other hand, curly leaf spinach, or savoy spinach, has crinkled leaves and is commonly sold pre-washed in supermarkets or salad bars. It has a slightly sweet taste and is called baby spinach when harvested early. There's also a hybrid of the curly and flat leaf types, known as semi-savoy [source: University of Georgia].

Popeye's spinach habit isn't the only misconception about this leafy green. Another myth is that spinach isn't really a great source of iron, a belief that stemmed from a simple math error. Let's uncover the myths and truths about this veggie.

Spinach's History and Nutrition

Spinach has been cultivated in Asia for so many centuries that its origins stretch back further than recorded history. Although scholars and spinach experts can't pinpoint its exact birthplace, one thing is clear: Spinach would surely be in the running for a lifetime achievement award. By the 1400s, it had spread throughout Asia and become a staple in European kitchens. Today, it’s a versatile green enjoyed around the globe in everything from casseroles and pasta dishes to soups and salads [source: Colorado State University].

At present, China dominates the global spinach supply, accounting for approximately 85 percent of the world's production. The United States follows as the second largest producer, with 280,000 metric tons (618,000 pounds) harvested in 2011 alone [source: Borris]. California is by far the leading U.S. producer, followed by Arizona, New Jersey, and Texas [source: USDA].

The debate over spinach's iron content stems from a 1972 report by nutritionist Professor Arnold Bender. He claimed that 19th-century German researchers had made an error by placing the decimal point in the wrong place, which inflated spinach's iron content by a factor of 10. This misunderstanding was widely accepted as truth for over three decades, even though criminologist Mike Sutton later disproved the story. Sutton demonstrated that these German researchers never existed [source: Kruszelnicki, Sutton].

So, what’s the real deal with spinach’s iron content? According to the USDA, the numbers are as follows:

A cup of cooked fresh spinach contains roughly one milligram more iron than 3 ounces (85 grams) of beef liver, traditionally known for its high iron content. It's also much richer in iron than lettuce. In fact, you'd need to consume the whole head of lettuce to gain only 2.02 milligrams of iron—just a fraction of what’s found in spinach [source: USDA].

Spinach contains oxalic acid, which can inhibit the absorption of iron. To enhance iron absorption, it is beneficial to pair spinach with foods such as meat, fish, poultry, citrus fruits, and certain vegetables like broccoli, sweet peppers, tomatoes, and potatoes [source: Tsang].

The Truth About Spinach

Spinach is a nutrient-dense food. Besides being rich in iron, it is packed with vitamins B and C, along with antioxidants such as beta-carotene (which the body converts into vitamin A) and lutein. Spinach is also a valuable source of minerals like magnesium and zinc [source: Seay].

When choosing canned or frozen spinach, the process is simple: check the expiration date, compare prices, and make your choice. Fresh spinach, however, requires more attention. It should be consumed when it is vibrant in color, with crisp, upright leaves that display a deep, rich green, reminiscent of rainforests and lush canopies. Make sure to inspect the leaves for any bruising, damage, or yellowing areas.

Spinach is commonly cultivated in sandy soil, so unless you're buying pre-washed spinach, it's essential to rinse the leaves by soaking them briefly in cold water. Swirl them around and then discard the water to remove any dirt or debris. After a few cycles, you’ll have perfectly clean spinach [source: Beck]. Keep in mind that fresh spinach loses its nutrients daily when stored in the refrigerator, so it’s a good idea to only buy what you’ll consume quickly [source: Science Daily].

When cooking with spinach, it’s important to note whether the recipe calls for fresh, canned, or frozen spinach. Fresh spinach is 92% water, meaning you’ll need much more of it to match the amount of canned spinach [source: University of Kentucky]. This explains the variations in iron content on the previous page. Regardless of how you consume it, one thing is certain: spinach is beneficial to your health.