Cooked vs Uncooked Greens by the Numbers

When I conjure an image in my mind of “healthy food”, fresh green vegetables inevitably appear, but perhaps this is not the only healthy way to eat greens…

In a recent article I discussed my preference for eating cooked kale as opposed to kale salad or some other uncooked form of kale. In that piece, I made the claim that even though cooking can remove some nutrients from greens, it doesn’t remove all of them, and because cooking has the effect of “shrinking” the greens, the end result is that you will eat more and it will all work out in the end.

Given the choice, I think most people would choose fresh spinach over frozen because it just looks so incredibly healthy! (Source: pixabay)

That statement was based on an analysis of cooked vs uncooked kale using USDA nutrition data. For today’s article I’ve decided to share that data, do a deeper dive on that question, and do a thorough comparison of nutritional data comparing cooked and raw greens. For the purposes of this comparison I will use two very popular salad greens that are also popular as cooked greens: kale and spinach.

Kale nutrition by the numbers

The two tables above display nutritional data for kale. The table on the left is for cooked kale (boiled and drain with no salt added), and the table on the right is for raw kale. I’ve chosen boiled and drained kale for this comparison because it is arguable that this is the most extreme way to cook a green, with many things being extracted and dumped out with the water. Suffice it to say, it bears to reason that the cooked numbers would be different with steamed or sautéed kale (and arguably higher in terms of mineral content). Each table shows the nutrition data for one cup of kale in terms of the the actual amount by weight in the 1st column, the percent daily value (%DV) in the second column, and the amount per 100 grams in the third.

The first distinction is simply how much more a cup of cooked kale weighs (118g) in comparison to raw kale (21g). This is important because we tend to eat according to volume; that is to say, we eat until we feel full, and we feel full when our stomach is full of food. Since cooked kale has a greater weight by volume than raw kale, we can simply eat more of it per sitting. This has important nutritional ramifications because at the most basic level, more food means more nutrition. For this reason, it can be seen that for every single nutritional component on the tables, there is more in a cup of cooked kale than there is in a cup of raw kale, both in terms of weight and %DV.

Of course, this begs the question: what if we hold the weights constant? This is why I added the third column which simply shows the nutritional component weight per 100 grams. For many of these items we can see that the weights are close, with some slightly higher or lower, but the larger difference show up with the vitamins & minerals. The big difference is with vitamin C, where the raw kale has about 5 times as much vitamin C as the cooked. There is about twice as much iron, calcium and potassium, in raw kale as there is in cooked kale, and there is about 20% more phosphorus in the raw kale. Interestingly there is also more sodium in raw kale (53mg/100g vs 16mg/100g), but this makes sense because sodium is water soluble, and the cooked kale was boiled and drained. This might also explain the lower numbers for for some of the other minerals in cooked kale.

So in general we can say that by weight, raw kale has more vitamins & minerals than cooked kale… by this really doesn’t matter, because you would have to eat a bucket of raw kale to come close to the nutritional benefit of simply eating a cup cooked kale.

Spinach nutrition by the numbers

For spinach we see a very similar comparison to that of the kale. Per 100g we see that the fat, carbs, fiber, sugar and protein are close, and there’s more vitamins and minerals in the raw than than with the cooked, with a considerable difference in terms of vitamin C.

Again, none of this matters because all of those vitamins and minerals are present in the cooked spinach, and since a cup of cooked spinach weighs about six times as much as a cup of raw spinach, it is much easier to get a good dose of those vitamins and minerals by eating cooked spinach.

What about enzymes

One popular argument against cooking vegetables is that the process of cooking kills enzymes that are present in the vegetables, thereby rendering the vegetables less healthy for us since it is argued that the enzymes can help with digestion and are good for us in other ways. From what I have read, this is simply not the case. The plant enzymes are are needed by the plants. We have our own enzymes. To us, the plant enzymes are just another source of food. Our stomach acids break plant enzymes down, and then they are broken down further by our own digestive enzymes.

To suggest that we need a steady supply of fresh, raw greens to be healthy simply contradicts reason. How on earth did people live long, healthy lives in northern climates prior to the advent of the supermarket and global supply chains? My grandmother lived to be 93. My great-grandmother lived to be 98. My great-great grandmother lived to be 96. None of these women had a steady diet of salads and kale-smoothies year-round. Fresh greens were expensive out of season, if they were available at all. They had some fresh greens in summer and fall, but most of the greens in their diet were cooked… and they were fine.

Final Thoughts

The purpose of this article was not to try to convince anyone to stop eating salad, or smoothies, or any other form of raw greens. I love salads and gorge on them every chance I get. Rather, the point was to show people that fresh greens are not absolutely necessary for a healthy diet. This is important when it comes to making affordable choices in the grocery store. As the winter months roll on, the price of fresh greens will continue to rise, but the price of frozen greens will be far more stable. That one dollar brick of spinach in the frozen food aisle is much better value than the six dollar bag of spinach in the produce section. Sure, the dish made from the “brick” might not “look” as healthy as a salad - but it all looks the same once it’s in your stomach, and your body will thank you for eating all of that spinach, regardless of how it is prepared.

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Here’s a video on how I freeze kale: