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Should Spinach Be Avoided In People With Thyroid Conditions?

When it comes to avoiding specific foods, I truly believe that if you do enough research you can find a reason to not eat anything.  If you follow a strict Paleo diet then you will be avoiding dairy and grains.  If you’re a vegan then you of course don’t eat meat, fish, dairy, or eggs.  In addition to this, if you have gut problems and are trying to avoid lectins, phytic acid, and other antinutrients, then besides avoiding grains you will want to cut out nuts, seeds, and legumes.  Let’s not forget sugar, and so we might as well cut out the fruit.  And it probably would be a good idea to stop eating nightshade vegetables since they can be inflammatory.  And if you’re hypothyroid then you might want to cut out the goitrogenic foods too.

The focus of this blog post is on spinach, which of course is a very healthy food.  While it might not give you a boost in strength like it does with Popeye, eating spinach is high in nutrients such as vitamin A, magnesium, folate, and vitamin K.  In fact, I frequently add spinach to my smoothies.  Sometimes I will also eat spinach in a salad, along with other greens.  And when I have the forbidden pizza, I enjoy adding spinach and garlic to it.  Even my vegetable-hating children “tolerate” spinach.

If spinach is so wonderful, why did I decide to write a blog post which questions whether people with thyroid conditions should avoid spinach?  Well, there are definitely worse foods you can eat other than spinach.  And as I mentioned before, if you do enough research you can make a case for avoiding just about any food.  But as much as I like spinach, there are risks of eating it with both hypothyroid and hyperthyroid conditions.

Spinach and Hypothyroidism. Spinach supposedly has goitrogenic properties.  However, it’s not as goitrogenic as other foods, such as the cruciferous vegetables.  For more information on goitrogens I would check out my articles entitled “Goitrogens: Thyroid Inhibiting Foods You Should Avoid [1]” and “An Update on Goitrogenic Foods and Their Impact On Thyroid Health [2]“.  If you read these articles you’ll realize that a number of years ago I was opposed to people with hypothyroid conditions eating any goitrogens, but based on the lack of human research studies involving goitrogenic foods I have eased up a bit on this.  Although I’m still cautious about people with hypothyroid conditions eating a lot of goitrogenic foods, in most people, eating a normal amount of these foods shouldn’t cause any problems.

So let’s ask the question “should people with hypothyroid conditions avoid eating spinach?”  As I just mentioned, if someone has a hypothyroid condition then I think it’s fine for them to have one or two servings per day of goitrogenic foods.  However, this also assumes they don’t have an iodine deficiency, as goitrogens interfere with iodine metabolism.  Assuming someone with hypothyroidism or Hashimoto’s Thyroiditis is iodine sufficient then I think it’s fine for them to eat spinach, along with other goitrogenic foods such as broccoli, kale, and cauliflower.

Spinach and Hyperthyroidism. Since spinach is goitrogenic and can therefore inhibit thyroid hormone production if eaten in large quantities, then it might make sense for people with hyperthyroidism and Graves’ Disease to load up on spinach!  From a goitrogenic standpoint I’m not at all concerned about people with hyperthyroidism eating spinach.  So why would there be any problem with people who have hyperthyroid conditions eating this green leafy vegetable?

Well, one of the main concerns with hyperthyroidism is that over a period of time it can lead to a decrease in bone density.  This yet another reason why unmanaged hyperthyroidism can cause problems.  In my articles and blog posts I tend to focus a great deal on the cardiac symptoms, but a decrease in bone density can also be a big concern.  This is even true after the thyroid hormone levels are back within the normal range.  So for example, if someone has elevated thyroid hormone levels for six months which causes a decrease in bone density, then just normalizing the thyroid hormone levels won’t necessarily correct the bone density problem.  So someone can still be more susceptible to suffering from a fracture.

At this point you might be thinking to yourself “what does this have to do with spinach consumption?”  Well, one of the nutrients which is important for strong bones is calcium.  And while other nutrients are also important for proper bone health, such as magnesium, phosphorus, and vitamin D, if someone has a calcium deficiency then this without question can affect bone density.  The good news is that spinach is high in calcium.  The bad news is that it also is high in something called oxalate, which binds to calcium, and therefore reduces its absorption.  As a result, eating a lot of spinach can actually cause a calcium deficiency, and therefore affect bone density.

Spinach Isn’t The Only High-Oxalate Food

Spinach isn’t the only food which has high amounts of oxalates.  Many other foods are high in oxalates, including blueberries, blackberries, raspberries, beets, okra, almonds, cashews, and other whole foods are high in oxalates.  The topic of oxalates probably deserves a separate article or blog post, but just understand that most people are fine eating foods with oxalates.  Although some people have conditions which require a low oxalate diet (no more than 50 milligrams per day), this isn’t a concern for most people.

However, there are risks with eating high amounts of oxalates.  I mentioned how they can potentially affect the absorption of certain nutrients such as calcium.  However, there is also evidence that consuming high levels of oxalates can lead to kidney stones (1) [3] (2) [4].  Once again, this doesn’t mean that eating normal amounts of blueberries, raspberries, spinach, and other high oxalate foods will lead to kidney stones.  One problem is that we’re in a “smoothie era”, and many people load up their smoothies with these foods.  I’m guilty of this myself, as I love smoothies, and in the past I would add 1/2 cup of berries, along with a full cup of spinach on a frequent basis.  I still include the berries, and while I do add some raw spinach every now and then to my smoothies, I don’t do this on a daily basis, as I rotate the vegetables that I add to them.

So let’s ask the question “should people with hyperthyroid conditions avoid eating spinach?”  Well, one thing I should add is that although cooking does seem to reduce the goitrogenic activity of spinach and other goitrogenic foods, cooking doesn’t seem to reduce the oxalate content.  And so from this standpoint it really doesn’t matter if you eat raw or cooked spinach.  I think it’s fine for most people with hyperthyroid conditions to eat spinach, but it probably would be a good idea to not load up on this food.  There are so many different vegetables out there, and while some vegetables other than spinach have a high oxalate content, there are many vegetables with a low oxalate content such as cucumbers, arugula, asparagus, broccoli, cabbage, cauliflower, romaine lettuce, and squash.

In summary, spinach is considered by most people to be a healthy food.  The purpose behind this blog post wasn’t to discourage anyone from eating spinach.  I still eat spinach, and think it’s fine for most people to continue to do so, regardless of whether they have a hypothyroid or hyperthyroid condition.  The main reason I decided to write this post is to demonstrate that there can be risks with eating large amounts of healthy foods.  This doesn’t necessarily mean that eating high amounts of spinach on a frequent basis will inhibit thyroid activity or eventually lead to osteoporosis or kidney stones, but in some people eating a lot of spinach will cause problems.   This is one reason why it’s best to try to eat a wide variety of foods whenever possible, and try your best to avoid eating large amounts of a single food on an everyday basis.