Kale vs Spinach: Let’s not fight about it

Kale vs Spinach nutrition

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Quiz time: What’s healthier, kale or spinach? In this post, I’ll cover a topic that has led to much debate: when it comes to kale vs spinach, which one is healthier? Does one have a nutritional advantage over the other? In this post, we’ll be exploring the differences and health benefits of these two nutritional powerhouses, examining the nutrients in kale vs spinach, and explaining why either one is just as “good for you”. Keep on reading if you want to see an end to this food fight.

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Kale vs Spinach Nutrition

OK, so in order to evaluate the differences between these two green leafy vegetables, let’s see what the specific nutritional profile is for each, as well as some of the health benefits they provide. Remember that although they may seem alike, kale and spinach come from different plant families. Therefore, there are differences when it comes to flavor, color, and texture.

On the other hand, since both vegetables provide very similar nutrient profiles, I’m going to focus on the select nutrients they’re particularly high in. (I won’t bore you with 0.1 mcg amounts of any nutrients, even though the links are provided if you want a more complete nutrient profile).

Kale nutrition facts and health benefits

Fresh Curly Kale
Tip: Rub raw kale leaves with a little olive oil to soften them up before eating

Kale (scientific name Brassica oleracea) is an edible leaf from the cabbage family. Its leaves vary in color from green to violet, and can it can be a bit tough in terms of texture. 

The Dietary Guidelines for Americans 2020-2025 state that for leafy vegetables, 1 portion is equivalent to 2 cups when they’re consumed fresh. Therefore, I’ll present kale’s nutritional profile based on what would be 1 leafy green vegetable serving (or 2 cups of kale).

Kale contains the following nutrients per 2 cups, raw, according to the USDA’s Food Data Central:

NutrientsAmounts% Daily Value (DV) based on a 2000 calorie diet
Calories 14 0%
Protein1.2 g2%
Total Fat0.6 g0%
Polyunsaturated Fat0.28 g
Monounsaturated Fat0.044 g
Total Omega-3 fatty acids75.8 mg
Total Omega-6 fatty acids57.9 mg
Total Carbohydrates1.8 g0%
Dietary Fiber1.8 g6%
Vitamin A6457 IU129%
Vitamin C39.2mg44%
Vitamin D
Vitamin E (Alpha Tocopherol)0.282%
Vitamin K163.6 mcg136%
Folate26 mcg7%
Calcium106.6 mg8%
Iron0.68 mg4%
Potassium146 mg4%

As we can see, kale is very high in vitamin A and Vitamin C, which are very powerful antioxidants

Antioxidants benefit us by reducing oxidative stress, and therefore lowering the risk of developing chronic health conditions such as:

  • Cardiovascular disease
  • Diabetes
  • Cancer

Kale is extremely high in vitamin K, which is necessary for blood clotting and for keeping bone demineralization under control. It’s also a pretty decent source of potassium, iron, calcium, and folate. 

This green veggie is also high in carotenoid antioxidants, namely lutein and zeaxanthin, which are associated with protection against age-related macular degeneration. In layman’s terms, it helps protect your eye health. Being a cruciferous vegetable (like cabbage and broccoli), kale also contains sulfur,  which is necessary for the synthesis of glutathione, another potent antioxidant that protects your cells from damage.

Finally, kale has a good ratio of omega-3 and omega-6 fatty acids. For the record, omega-3 fatty acids tend to reduce inflammation, while omega-6 fatty acids tend to increase it. It seems that including more omega-3s than omega-6s in your diet can have a beneficial, anti-inflammatory effect throughout your body. 

Spinach nutritional facts and health benefits

Fresh spinach
Spinach has a smoother, more tender texture than kale, which makes it great for smoothies and salads

Like kale, spinach (scientific name Spinacia oleracea) is also an edible leaf, but it comes from the beet family. Spinach leaves are much smoother and tender in texture than kale, and their taste is much more subtle.

As we did for kale, we will evaluate spinach’s nutritional content based on 1 portion of leafy green vegetables, in other words, 2 cups, raw:

NutrientsAmounts% Daily Value (DV) based on a 2000 calorie diet
Calories 13.8 0%
Protein1.8 g4%
Total Fat0.2 g0%
Polyunsaturated Fat0 g0%
Monounsaturated Fat0g0%
Total Omega-3 fatty acids58 mg
Total Omega-6 fatty acids10.9 mg
Total Carbohydrates2.2 g1%
Dietary Fiber1.4 g6%
Sugars0.2 g
Vitamin A5626 IU112%
Vitamin C16.8 mg28%
Vitamin D
Vitamin E (Alpha Tocopherol)1.2 mg6%
Vitamin K290 mcg362%
Folate116.4 mcg30%
Calcium59.4 mg6%
Iron1.6 mg9%
Potassium334 mg10%

Spinach is high in vitamins A, C, and K, just like kale. However, it has a much higher vitamin K content. It also has more folate compared to kale. Folate is crucial for preventing neural tube defects during pregnancy.  It’s also necessary for red and white blood cell formation, as well as for producing  DNA and RNA.

Spinach also has more vitamin E and potassium than kale does. When it comes to iron in kale vs spinach, spinach has the upper hand.

In terms of  omega-3 and omega-6 fatty acids, spinach has less than kale, but it still has a good ratio of omegas-3 to 6.

And although it has lower amounts than kale, spinach is also high in lutein and zeaxanthin, the two powerful antioxidants we discussed above. The polyphenols found in spinach also contribute to this leafy green’s potent antioxidant properties. 

So, is kale healthier than spinach?

So, what’s the final verdict? As you can see, the nutrients in kale vs spinach are very similar. So it all boils (or better, steams ) down to what your particular nutritional needs are.

For example, for blood-related nutritional deficiencies, spinach is the best option since it’s higher in iron, folate, and vitamin K. On the other hand, kale has more vitamin C and vitamin A, which are antioxidants that can help boost the immune system’s health. Kale has more calcium, but spinach has more potassium. 

Therefore, this dietitian decrees that neither of these greens is better than the other: they’re BOTH winners and nutritional superstars!

The infographic below gives you a summary of how both of these veggies compare, and how both can provide you with many health benefits.

Infographic comparing the nutrient profiles of kale and spinach
The results are in and…it’s a tie!

Can you substitute kale for spinach or vice versa?

Yes, but there are some things to consider. Since kale has a tougher texture than spinach, sometimes it needs a longer cooking time than the latter. For example, in a soup, kale should be added at the beginning of the cooking process, not at the end like spinach. It can also be helpful to cut it up into strips in order for it to cook completely. Due to its texture, kale can also be baked in the oven with some olive oil, herbs, and spices, for some crispy and healthy kale chips.

Chopping up kale into smaller pieces is also helpful when consuming raw kale. It can also be mixed with other softer, leafy greens in order to have a variety of textures. It’s also recommended to massage the leaves with some olive oil, which helps soften them up (plus you get the added bonus of the fats from olive oil, which helps to better absorb kale’s vitamin A and lutein content ). 

When substituting spinach for kale, remember that spinach cooks much more quickly and has a very delicate texture (TL;DR: it can get slimy and mushy if cooked for too long). Therefore, cooking times may decrease in order to avoid overcooked spinach. When adding spinach to a hot dish, it’s better to incorporate it during the last few minutes of cooking.

And although kale smoothies are very popular, spinach is much easier to blend into a lump-free consistency than kale. Spinach’s tender leaves are also better suited for salads and sandwich fillings. 

Kale vs Spinach: Raw or cooked?

Here’s another debate, and this one also has some important points to consider. Here, I’ll break down whether each of these vegetables retains their nutrients better in their raw state, or if it’s healthier to cook them.

Is Kale healthier raw or cooked?

According to this paper that evaluated different cooking techniques and nutrient retention in kale, raw kale had the highest levels of carotenoids. The cooking methods that resulted in the highest levels of antioxidant activity were steaming and stir-frying. Steaming, the preferred cooking method, “resulted in significant increases in antioxidant activity levels in all of the evaluation methods”. This method also led to increased polyphenol levels in kale.  

On the other hand, boiling led to decreases in anthocyanin and polyphenol levels. As it is true for most vegetables, it’s always important to avoid boiling, steaming, or stir-frying for too long or with too much liquid in order to prevent nutrient losses. 

Raw kale tends to have a bitter taste that some people may find off-putting, but this can be reduced by cooking. If you prefer cooked kale, make sure to do so by steaming it for a short time, with very little liquid. 

The main concern that many people have with regards to eating raw kale is that it’s very high in goitrogens. These are naturally occurring substances that can block iodine from entering the thyroid gland. For a healthy person who gets enough iodine, this isn’t a problem. But, for those who have an underactive thyroid (hypothyroidism), an excess of goitrogens may further suppress thyroid activity and increase the risk of goiter. However, research has shown that a moderate intake of goitrin from vegetables, such as kale, is not likely to pose any health problems, even for those with thyroid issues. 

Final Verdict: Kale retains its nutrients better in its raw state, but if you prefer it cooked, steaming for a short amount of time is the best way to retain its nutrients.

Is Spinach healthier raw or cooked?

It seems spinach also retains its nutrients better when it’s eaten raw. In fact, this very recent research paper compared lutein bioavailability with different methods of preparing spinach. The authors found that liquefying spinach (as in smoothies) increased the liberation of lutein and that adding dairy (such as milk or yogurt due to its fat content) helped increase it further. Chopping spinach up, or blending it in a high-speed blender, also improved the amount of lutein released from its leaves. 

Since lutein is degraded by heat, this study also found that boiling, steaming, and pan-frying reduced lutein liberation. Curiously, the authors found that reheating the food in a microwave compensated for the loss of lutein in cooked food-but only to some extent. They found that lutein is released from the spinach as the plant structure is degraded by the microwave. Still, the results of this study recommend avoiding heating spinach as much as possible. 

Vitamin C is also very sensitive to heat, so subjecting spinach to heat could significantly reduce the content of this powerful antioxidant. 

Final verdict: Try to eat your spinach raw, such as in smoothies, sandwich fillings, and salads in order to get the most amount of nutrients. 

How to incorporate more leafy greens into your diet

Eating more leafy green vegetables can definitely help support your overall health. But many people don’t like how they taste or simply don’t know how to prepare them. Here are some ideas to help you incorporate more of these nutritional superheroes into your diet:

  • Blended into smoothies or green juices
  • In soups and stews
  • In frittatas
  • As sandwich fillings
  • In salads
  • With scrambled eggs
  • In pasta dishes
  • Blended into dips, pesto and hummus
  • As a wrap instead of flour tortillas

These are just a few examples, but feel free to get creative with these veggies, and experiment until you find the ways that are most appealing to you. 

So, do you think we can finally wave the white flag in the war between kale vs spinach? Is there one you prefer in terms of taste, texture, or availability? How do you like to include these greens? Is there a new way you’d like to try them?

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