The Pros and Cons of Kale [Can You Eat Too Much?]

Looking for the pros and cons of eating kale? With so much media-hype around this leafy green, you might have asked yourself: “Is this really good for me? What are the actual benefits?


But fear not…We put together the ultimate, no nonsense guide to kale. It’s everything you wanted to know – and more – backed by peer-reviewed scientific research with no fluff!

Let's get started!

Kale Pros and Cons Quick Summary

In a hurry? Here's a quick list of our findings on the pros and cons of kale.

Kale Pros

  • Provides a huge amount of nutrients for a low amount of calories
  • Improves Immune System Function
  • Improves Cholesterol Levels
  • Provides a huge boost of antioxidants
  • Reduces risk of glaucoma
  • Assists in eliminating bile acids (which can reduce cancer risk)

Kale Cons

  • May cause thyroid problems if too much is ingested in its raw form.

In summary, kale is an awesome vegetable and you should strive to eat it on the daily. If you're consuming tons of it, or have a history of thyroid issues it's best to lightly steam or blanch it first.

So the next time you're at the grocery store, be sure to add kale to your shopping list.

History of Kale

Even though for most people, kale seemed to just pop up recently out of no where as the latest new “superfood”, it has actually been around for a long time!

Conservative estimates state  the cultivation of kale dates back over 2,000 years ago. It was widely popular in Europe up until around the time of the middle ages. Over time, kale cultivation was phased out to grow what become modern-day cabbage.

Kale and cabbage are actually part of the same family of species known as Brassica oleracea. The reason why they are so drastically different in our eyes today is due to countless generations of selective breeding.

How This Article Was Made

Before we get into the nutrients kale provides and the specific research has been done on the leafy vegetable, one should be aware how this information may differ from other sources.

We've compiled only information that has been backed by peer-reviewed scientific studies, which should be the gold standard when it comes to understanding nutrition. We've removed all anecdotal claims and speculation from this review. Anecdotal and speculative  claims are often used to promote products such as diet books and supplements. While not inherently malevolent, these claims can often be misleading and are not scientific.

The Nutrition Facts (Micro & Macronutrients)

Kale Nutrition Facts from Wikipedia (1)

By taking a look at the macro and micronutrient profile, we can see a 100 gram serving of both raw and cooked kale are high in Vitamin K, C, and A. While raw kale may have more vitamins and minerals overall than cooked, cooked kale does have higher vitamin K availability.

While these nutrition facts indicate that raw kale may pack a more nutritious punch than cooked gram for gram, cooking kale may make the leafy green more palatable and allow one to to consume more volume. This would result in more nutrient consumption overall.

Now that we know the nutrient content of kale, let us take a deeper look at the actual effects it has when consumed and in vitro (studied inside a test tube or petri dish).

A special thank you to Dr. Greger from who made these awesome, easy to understand, and informative videos using only peer-reviewed scientific literature. We will be referencing some of his work as well as individual peer reviewed studies during this article.

Kale and the Immune System

A very simple laboratory study done with kale and white blood cells revealed that kale can have an extremely positive impact in our white blood cell’s ability to produce antibodies.

It also made no difference if the kale was cooked or raw. In fact, in terms of antibody production, the cooked kale outperformed its raw counterpart! (4)

Kale and the Immune System (3)

We couldn’t find an actual human trial on this (probably because they are extremely time consuming and expensive to fund), but that’s not to say that this study isn’t extremely indicative of the positive impact kale can have on the human immune system. 

Good/Bad Cholesterol (Serum Lipid Profile)

Another study done in Japan (on actual humans this time), showed the amazingly beneficial impact that kale shots had on cholesterol levels. In this case, the (34) study participants drank 3-4 shots of kale juice over a 12 week period.

This nutrition intervention had a tremendous impact on their Serum Lipid Profiles (good and bad cholesterol).

It also had massive impact on the levels of antioxidants on their blood (more on that in the next section). (6)

Check out this short video below from Dr. Greger for the full study breakdown:

Smoking vs. Kale Juice (5)

What About Antioxidants?

As noted in the previous section, the participants in the kale shot study had a huge increase in the antioxidant levels in their blood (aside from the participants who smoked).

We hear about antioxidants all the time, but why are they actually important and how do they work?

Delicious Looking Free Radical Neutralizing Foods

Free radicals (the stuff that antioxidants neutralize) are produced as a part of digestion.

When we have too many of these free radicals floating around it can cause a whole host of problems including (but not limited to):

  • Heart Disease
  • Cancer
  • Depression
  • Sexual Disfunction
  • Rapid Aging

That's why it is important to neutralize these free radicals with anti-oxidant rich foods, including kale, that have a drastic impact on the antioxidant levels in the blood (see previous section).

Other foods such as berries are crucially important in this equation as well. 

Kale and Glaucoma Risk Reduction

Consuming kale (and collard greens) will give you an abundant amount of zeaxanthin, a phytonutrient with eye-protecting properties.

A study done on African-American women showed that a mere 2 to 3 servings per 3 month of kale/collard greens reduced the risk of glaucoma by half!

Check out the video below for more details on the study:

The Relationship of Greens and Glaucoma (7)

Kale and Cancer (bile acids)

It's a common claim among "snake oil salesmen" that a certain food or supplement  can prevent or treat cancer. Because cancer is a complex thing, it's important to take everything in it's proper context.

Bile acid is an integral part of our digestive system, one of its main functions is to help us get rid of excess cholesterol. This is why our liver puts bile acids into our intestines for this very function.

However, these bile acids have the potential to be absorbed back into the body and promote cancer growth. This is especially true within the breast tissue where these carcinogenic bile acids seem become concentrated.

One way to combat this is having a diet rich in whole plant food based fiber which can speed up the process of food moving through the body.

But what does this have to do with kale?

It turns out that another way to effectively get rid of bile acids is to consume foods that absorb the acids themselves. Kale is one of the most effective plant foods in absorbing bile acids topped only by Okra and Beets (see details in the video below).

Bile Binding and Vegetables (8)

Can You Eat too Much Kale?

While many people on the internet falsely use clickbait and scare tactics to say that there are health downsides to kale, it does not mean that it is completely false. Just like anything in life, you can indeed get too much of a good thing. But how much is too much?

Much like all cruciferous vegetables, there are compounds (called goitrogens) that can actually interfere with thyroid function if you consume them raw. They do this by blocking the thyroid's ability to uptake iodine. However, you can mitigate this somewhat by increasing your intake of iodine rich foods such as sea vegetables. While there's no exact amount that can be cited to cause damage, you're most likely better off cooking your kale anyway.

Cooking the kale (as we'll get into below) deactivates the culprit enzymes and will make it more delicious as well! That is unless you're making a kale salad multiple times a day. If this is the case (even though we don't recommend it), be sure to keep an eye on your iodine intake and either supplement or regularly intake iodine rich foods such as seaweed. (9)

How to Prepare Kale to Eat

Okay, so you want to eat more kale, but how? Here are some of my favorite ways...

  • Lightly steam chopped kale and toss it with lemon, pepper and nutritional yeast. Combine with rice and beans for a hearty yet refreshing treat.
  • Blanch some kale and keep it handy in your freezer in a bag. Then, throw it with some frozen bananas, raspberries, cherries cocoa powder and ground flaxseeds into a smoothie blender. The final result is a chocolate flavored green smoothie that's to die for!
  • Throw it on a baking sheet sprinkled with garlic powder, onion powder, nutritional yeast, salt and pepper. The end result is cheesy kale chips to die for!

Final Word on Kale

Unlike most "fads" in the health world, it's safe to say that the popularity of kale shouldn't be dismissed as just another meaningless craze.

As our featured recipes have shown, it's also really versatile and can be eaten in so many delicious ways.

So what's our conclusion?

Eat more kale (just not a boatload of raw kale!)



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