Kale and spinach are among the most nutritious and inexpensive leafy greens out there. One is a beloved cartoon character’s favorite muscle booster, while the other is a versatile ingredient made popular by an actress-turned-lifestyle guru. Although they are sometimes used interchangeably in salads, smoothies, sandwiches, soups, and other dishes, there are several key differences that set them apart.
Nutritionists often list kale and spinach among the healthiest vegetables, but is one healthier than the other? To answer that question, let’s compare their nutritional value and scientifically proven health benefits.
Kale vs. Spinach: A Little Bit of History
Dating as far back as 200 AD, spinach is the younger of the two. Originally cultivated in central Asia (most likely Persia), this flowering plant was first introduced to Europe in the 9th century but hasn’t made its way to England and France until the 14th century. It hails from the Chenopodiaceae family, which also includes chard, beets, and quinoa.
Although it reached Western Europe at approximately the same time as spinach, kale is at least 20 centuries older. Also known as leaf cabbage, it was first cultivated in the eastern Mediterranean and Asia Minor around the year 2000 BC. It is a member of the Brassica family, with its closest relatives being broccoli, Brussels sprouts, kohlrabi, cauliflower, and cabbage.
Kale vs. Spinach: Nutritional Value
While there’s no reason to count calories when eating leafy greens, it is still worth noting that kale contains twice as many calories as spinach. Their carbohydrate content is the same, but kale contains more fat (0.9g per 100g). However, most of the fat content is in the form of omega-3 fatty acids which are known for their numerous health benefits, so there’s usually no risk of weight gain.
Looking at their nutrient content, spinach packs slightly more dietary fiber and potassium, almost 50% more iron, and more than double the amount of magnesium. On the other hand, not only does kale contain slightly more protein and calcium than spinach but it also packs almost five times as much vitamin C, 60% more vitamin A, and 40% more vitamin K (nine times the recommended daily allowance).
Kale vs. Spinach: Health Benefits
Due to their high nutrient content and low caloric value, both kale and spinach have many proven health benefits. In this section, we’ll take a look at some of them to see if one of these leafy green superfoods is more healthful than the other.
Heart Health
Spinach and kale both contain a number of nutrients that are essential to maintaining optimal heart health. These include copper and iron, both of which are necessary for the synthesis of red blood cells, as well as vitamin K, which your body uses for blood clotting. In addition, there is also vitamin B6, which is known to help reduce the risk of heart disease.
While kale is considerably richer in copper than spinach (10% vs. 2% RDA per serving), they contain approximately the same amount of iron. As already mentioned, kale is also much richer in vitamin K.
Looking beyond just their nutrient content, several studies have found that both kale and spinach can help reduce the risk of heart disease due to their positive effect on several risk factors. For example, a 2008 study found that men who drank kale juice with their meals for three months managed to significantly lower their bad cholesterol and increase their antioxidant markers. Similarly, a 2015 study showed that eating a soup made with spinach for only a week can significantly improve blood pressure.
Brain Health
A study published in 2018 found that older people who ate a single serving of spinach or kale a day managed to significantly slow down cognitive decline compared to those who didn’t eat leafy greens.
Leafy greens are known to contain folate, a naturally occurring form of folic acid which helps prevent brain defects in newborns and is thus especially important for pregnant women. Folate also helps reduce inflammation in the brain as well as the whole body. It also lowers the levels of homocysteine, an amino acid found in the blood that has been linked to brain fog and even brain atrophy in older people.
Both spinach and kale contain a hefty amount of folate. However, spinach fares better in this respect, seeing as you can get 15% of the recommended daily allowance per serving compared to just 5% you get with kale. In addition, both contain similar amounts of vitamin B6, which supports optimal brain function by supporting the production of neurotransmitters in the brain. A deficiency in this vitamin is known to contribute to cognitive decline, which is why it should be an essential part of every healthy diet.
Cancer Prevention
Extensive research shows that dietary fiber found in fruits and vegetables – including leafy greens – can help lower the risk of certain types of cancer, particularly colorectal cancer. As already explained, both spinach and kale contain a decent amount of dietary fiber, although spinach contains slightly more.
In addition to dietary fiber, several studies have shown that certain compounds found in spinach and kale may help halt the spread and growth of cancer cells. For example, a study published in 2016 found that monogalactosyl diacylglycerol, a substance extracted from spinach, can improve the effects of radiation therapy in patients with prostate cancer. Similarly, a 2008 study found that this spinach extract can inhibit the growth of cancer cells in mice even when administered orally.
Kale vs. Spinach: The Final Verdict
Despite some differences in their nutrient content, spinach and kale are both incredibly nutritious and have a range of impressive health benefits. Although kale packs more vitamins and spinach contains more dietary fiber and essential minerals, both are essential to maintaining heart and brain health. There is thus no clear winner of this showdown. Ideally, you should add a few servings of both to your weekly menu.
Some people prefer eating their vegetables raw to preserve their nutritional content. However, that might not be such a good idea with leafy greens, especially kale and spinach. While it’s okay to eat them raw in a salad every once in a while, it is best to cook them before eating to reduce the amount of indigestible fiber and lower the concentration of dietary oxalate, a compound that prevents calcium absorption in the body and may thus also contribute to the formation of kidney stones.
References:
https://lpi.oregonstate.edu/mic/minerals/copper
https://ods.od.nih.gov/factsheets/Iron-HealthProfessional
https://lpi.oregonstate.edu/mic/vitamins/vitamin-K
https://ods.od.nih.gov/factsheets/VitaminB6-HealthProfessional
https://www.ncbi.nlm.nih.gov/pubmed/18548846
https://www.ncbi.nlm.nih.gov/pubmed/26251834
https://n.neurology.org/content/90/3/e214
https://www.mayoclinic.org/health/folate/NS_patient-folate
https://www.ncbi.nlm.nih.gov/pubmed/16102882
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4772032
https://n.neurology.org/content/90/3/e214
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5120455
https://www.ncbi.nlm.nih.gov/pubmed/18594894
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4708574
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