True Cellular Formulas Team - September 19, 2023

Why Raw Kale May Be Bad for Health

Unveiling the Other Side of the Superfood

Why Raw Kale May Be Bad for Health

Kale has earned its place in the spotlight as one of the most nutritious leafy greens available. Often heralded as a "superfood," it's packed with essential vitamins, minerals, and antioxidants that can offer a wide range of health benefits. Yet, like many things in life, too much of a good thing can turn into a bad thing. This article aims to explore the lesser-known side of this green powerhouse—why consuming raw kale in large amounts can actually be detrimental to your health.

Nutritional Benefits of Kale

Vitamins and Minerals

Kale is often lauded for its rich nutritional profile, making it a go-to choice for health-conscious individuals.[1] It is abundant in crucial vitamins like Vitamin K, which aids in blood clotting; Vitamin A, which is essential for vision and immune function; and Vitamin C, which supports skin health and boosts the immune system.[2-4]


Beyond its vitamin content, kale is also a treasure trove of antioxidants like quercetin and kaempferol. These antioxidants neutralize free radicals in the body, reducing oxidative stress and lowering the risk of chronic diseases like cancer and heart disease.

High Fiber Content and Benefits of Fiber

One of the less-celebrated but equally important components of kale is its high fiber content. Dietary fiber is crucial for a well-functioning digestive system and offers benefits like improved bowel movements, lower cholesterol levels, and better regulation of blood sugar. A diet rich in fiber can also contribute to weight management by promoting a sense of fullness and reducing overall calorie intake.[1]

By looking solely at these benefits, it's easy to see why kale has become such a popular choice for salads, smoothies, and other health-focused recipes. However, it's important to take a closer look at some of the potential drawbacks that can come from consuming raw kale in excess.

Why Raw Kale Can Be Harmful

Oxalates and Kidney Stones

Kale contains oxalates, naturally occurring substances found in plants, animals, and humans. While oxalates are generally harmless in moderate amounts, high levels can contribute to the formation of kidney stones—hard mineral deposits that can cause significant discomfort and require medical treatment.[5] If you're prone to kidney stones or have a history of them, it may be wise to limit your intake of raw kale.

Goitrogens and Thyroid Function

Another concern with raw kale is its content of goitrogens, compounds that can interfere with thyroid function.[6] Consuming large amounts of raw kale can lead to an enlarged thyroid gland and disrupt the production of thyroid hormones, which play a crucial role in metabolism, energy levels, and overall hormonal balance.[7] This is particularly concerning for individuals with pre-existing thyroid conditions.

Digestive Issues

While the high fiber content in kale can be beneficial for digestion, consuming it raw and in large amounts can have the opposite effect for some people.[8] Raw kale is tough to digest and may lead to gas, bloating, and abdominal discomfort. Cooking kale can make it easier to digest, but those with sensitive digestive systems should approach with caution.

At this point, it's clear that while kale has many health benefits, there are also valid concerns associated with excessive consumption of it in its raw form. Next, let's explore how to safely incorporate this leafy green into your diet without compromising your health.

How to Safely Include Kale in Your Diet

Cooking Methods

One way to mitigate some of the potential risks associated with raw kale is to cook it. Cooking can lower the levels of oxalates and goitrogens, making it a safer option for those concerned about kidney stones or thyroid issues.[9] Various methods such as steaming, sautéing, or even roasting can make kale easier to digest and may even increase the bioavailability of some nutrients.

Moderation is Key

As with many foods, the key to enjoying kale's health benefits without the associated risks lies in moderation. Eating kale less often, rather than every day, can help you avoid accumulating too much of the harmful compounds. Moreover, it's essential to have a varied diet rich in different fruits, vegetables, and other food groups to ensure you are getting a well-rounded set of nutrients. 

It’s vital to re-frame kale, and understand the potential health risks of overconsuming it. Many people consume it purely because it’s a healthy food, so if you take one thing away from this article, it can be to question what you do blindly in the name of “health.” 

Consult Your Healthcare Practitioner

If you have existing health conditions like kidney stones or thyroid issues, or if you are taking medications that might interact with kale (like blood thinners), it's a good idea to consult a healthcare professional for personalized advice. They can provide guidelines on how much kale can be safely included in your diet and whether you should opt for cooked over raw.

By taking these precautions, you can continue to enjoy kale as part of a balanced, healthy diet while minimizing the risks that come with excessive consumption of it in its raw form.


Kale has rightfully earned its reputation as a superfood, offering a plethora of essential vitamins, antioxidants, and dietary fiber. However, like many things in life, it comes with its own set of caveats. Consuming raw kale in excess can lead to potential health risks like kidney stones, thyroid issues, and digestive discomfort. But this doesn't mean you should eliminate kale from your diet altogether. By cooking it, eating it in moderation, and consulting healthcare professionals for personalized advice, you can enjoy the benefits of kale while minimizing its drawbacks. Knowledge is power, and being informed about both the pros and cons of this leafy green can help you make better dietary choices for a healthier life.

  1. Caitlin Terpstra, R.D. “Kale: Discover Superfood Secrets.” Mayo Clinic Health System, 17 Mar. 2023, 
  2. “Vitamin K.” The Nutrition Source, 7 Mar. 2023,
  3.  “Office of Dietary Supplements - Vitamin A and Carotenoids.” NIH Office of Dietary Supplements, U.S. Department of Health and Human Services, 
  4. Carr, Anitra C, and Silvia Maggini. “Vitamin C and Immune Function.” Nutrients vol. 9,11 1211. 3 Nov. 2017, doi:10.3390/nu9111211
  5. Mitchell, Tanecia et al. “Dietary oxalate and kidney stone formation.” American journal of physiology. Renal physiology vol. 316,3 (2019): F409-F413. doi:10.1152/ajprenal.00373.2018
  6. Babiker, Amir et al. “The role of micronutrients in thyroid dysfunction.” Sudanese journal of paediatrics vol. 20,1 (2020): 13-19. doi:10.24911/SJP.106-1587138942
  7. Felker, Peter et al. “Concentrations of thiocyanate and goitrin in human plasma, their precursor concentrations in brassica vegetables, and associated potential risk for hypothyroidism.” Nutrition reviews vol. 74,4 (2016): 248-58. doi:10.1093/nutrit/nuv110
  8. Ho, Kok-Sun et al. “Stopping or reducing dietary fiber intake reduces constipation and its associated symptoms.” World journal of gastroenterology vol. 18,33 (2012): 4593-6. doi:10.3748/wjg.v18.i33.4593
  9. López-Moreno, M., et al. “Antinutrients: Lectins, Goitrogens, Phytates and Oxalates, Friends or Foe?” Journal of Functional Foods, vol. 89, 2022, p. 104938, doi:10.1016/j.jff.2022.104938.

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