Here’s Why Spinach Shrinks So Much When You Cook It

Do you want to see a magic trick right in your kitchen? Grab a handful of spinach and toss it into whatever dish you're cooking. Turn away for a second or two, then turn back. The spinach has magically shrunk to about a tenth of its original volume—amazing, right?

Alright, I know this isn't so much of a magic trick as it is an annoyance. Spinach is notorious for seeming to vanish as soon as it's heated, regardless of how much you add to a recipe. Here's the science behind why that happens.

Why Does Spinach Shrink So Much? 

The main reason spinach shrinks is due to its high water content. In fact, the leafy green is believed to be over 90 percent water. This means that when you cook it, all that water evaporates from the leaves, leaving you with what looks like a lot less vegetable than you started with.

Another contributing factor is the presence of oxalic acid in spinach. This acid responds quickly to heat, encouraging the cell walls in the spinach to break down. This process is accelerated when spinach is cooked in a covered pot or pan: As the oxalic acid leaves the spinach, it collects underneath the lid and then falls back into the spinach, which then causes the spinach to wilt even more. As a rule of thumb, don't cover spinach when cooking it.

How Much Does Spinach Shrink?

Most recipes with cooked spinach will tell you how much raw spinach you need to add. However, it is also helpful to know that 10 to 12 cups of raw spinach will cook down to approximately one cup of cooked spinach. With those numbers in mind, it's always good to remember that when in doubt, add more spinach to your dish than you think you need.

The Benefits of Cooked Spinach 

While it's certainly annoying to see large bunches of spinach shrivel up as soon as it hits the pan, that doesn't mean you should avoid cooking it altogether. Countless recipes rely on cooked spinach. For instance, what would we do if spinach artichoke dip didn’t exist? 

Adding a handful of spinach to soup or casserole can also be an easy way to sneak in extra vegetables to your meal. Given how much spinach shrinks, there's a chance you won’t even be able to notice it in whichever dish you add it to. Plus, cooking spinach can increase its nutrient content. When oxalic acid is cooked out of the leaves, more calcium and iron are released, making cooked spinach an even healthier choice. 

So, if you're intimidated by that big bag of spinach that's been hanging out in the back of your fridge, remember that a handful of spinach—if not more—can elevate a variety of dishes and bring a burst of nutrition to your meals.