WHOLE TRUTH ABOUT A GREEN POWERHOUSE
Spinach packs a bigger nutritional punch than most other vegetables, and with fewer calories, but there are some side issues to chew over
Stories about spinach often reference Popeye, the sailor who ate it to gain immense strength. But if you need to bring a cartoon character into a conversation about healthy eating, consider the Hulk from the Marvel comic books.
In addition to their shared colour, spinach packs a nutritional punch that looms large even among its peers.
“I think spinach is unique,” says Dr Joseph Roberts, an assistant professor of nutrition at Arizona State University in the US.
Dark, leafy greens are recommended as part of a healthy eating pattern. “They are largely considered nutritional powerhouses,” Roberts says, because they are nutrient-dense. In other words, “you can get a lot of nutrition without a lot of calories”.
The goodness within
Roberts, who was the lead author of an academic review about spinach that was published in the journal Food & Function in 2016, says spinach is a good source of vitamins A, C and B9, or folate.
According to the US Department of Agriculture, one cup of raw spinach has only seven calories. But it provides 121 per cent of the vitamin K that a man should consume each day and 161 per cent of the amount recommended for women. The amount of vitamin K in spinach is about four times more than lettuce, about five times more than broccoli and eight times more than cabbage.
Cooked spinach, per cup, provides 129 per cent of the recommended daily vitamin A for women and 105 per cent of the suggested amount for men. Spinach also provides more of the minerals magnesium, potassium and iron than cabbage, lettuce or broccoli.
The veggie is also rich in phytochemicals – compounds found mostly in plants that have a range of health-boosting properties. They have long been known to function as antioxidants, which help fight inflammation and ageing, Roberts says.
Spinach is also one of the best plant sources for lutein, a type of plant-based pigment known as a carotenoid that has been linked to better eye and brain health.
Some studies have looked at spinach thylakoids, which are parts of a plant cell that turn sunlight into energy. Extracts made from spinach thylakoids have been shown to increase satiety, the feeling of being full after eating, although Roberts says such an effect has not been studied extensively in whole spinach.
However, he says, spinach is high in fibre, “something that most Americans need to increase their consumption of”.
Fibre has been shown to help protect against heart disease, diabetes and more. Raw spinach has a little more than half a gram of fibre per cup. In boiled spinach, you will get more than four grams per cup. Spinach is 91 per cent water, and cooked spinach has more leaves than the same volume of raw.
Some caveats
So, what is not to like? Well, there are a few possibly serious issues to consider. Spinach is high in oxalates, which can interfere with the body’s ability to absorb minerals, Roberts says. Spinach has a lot of calcium, but oxalates bind to that in the intestines.
“This can lead to the formation of kidney stones in certain people,” he says. People prone to kidney stones are sometimes put on a low-oxalate diet.
Boiling spinach can decrease the amount of oxalates you consume, Roberts says.
Vitamin K, which plays an important role in blood clotting, can interfere with the blood thinner warfarin. That is less of an issue with newer blood thinners, Roberts says, but people on warfarin should “be consistent in their consumption of vitamin K”, which will help stabilise warfarin levels.
And when you do decide to serve spinach, perhaps do not use Popeye as a role model.
Aside from the health risks associated with smoking a pipe, he might be getting sodium he does not need. One cup of the canned stuff can have from 440mg to nearly 750mg; the American Heart Association recommends limiting sodium to no more than 2,300mg a day, with an ideal limit of 1,500mg for most adults.
Fresh is best
The important thing is to find a form of spinach that you enjoy DR JOSEPH ROBERTS, ARIZONA STATE UNIVERSITY
Roberts says for all fruits and vegetables, “the fresher, the better”. So, at the grocery store, he would go for a fresh bundle of spinach over a bag or plastic container, on the assumption that the fresh bundle was probably picked more recently. If you do buy fresh, he said, consume it soon. “You don’t want to let it sit in your refrigerator for a long period of time because the nutrient content does decrease.”
Frozen foods are typically processed close to the harvest site and can actually have higher nutrient levels, he says.
How to cook it for greatest benefit
How you prepare your spinach matters. Boiling can decrease the content of vitamins B and C, as well as some phytochemicals. Those compounds end up in the cooking water, Roberts says, so “one way to salvage that is to use that cooking water as a base for a soup”.
Popeye would be pleased to know spinach pairs well with olive oil (the cartoon character’s love interest is Olive Oyl). Vitamins K and A as well as lutein need a little fat to be absorbed by the body, so Roberts recommends sautéing spinach in a little oil, or eating it raw with a little oil drizzled on top.
And then there are smoothies. “This is how I eat my spinach every day,” says Roberts, who has about a cup of spinach each morning. Chopping up the spinach can increase the bioavailability of lutein and other compounds, he says.
“The important thing, of course, is to find a form of spinach that you enjoy,” he says.