Sunday, November 27, 2011

from Mark's Daily Apple

Dear Mark,

There are several “Green Drink” formulas on the market now – usually comprised of powdered dehydrated dark greens like spinach, kale, broccoli, etc. Do these confer the same benefits as eating the vegetables, and are they readily absorbable by our bodies?

Normally, humans have trouble extracting massive amounts of nutrition from raw greens like spinach, kale, and broccoli. We might enjoy the crunch they provide, the texture, and even the taste, but the simple fact is that we are not equipped with the necessary cellulase – a digestive enzyme – to fully breakdown the cellulose that makes up around a third of said raw leafy vegetables’ cellular structure. Without breaking down cellulose, we can’t access all the vitamins and nutrients located therein. The impressive stomachs of certain animals, like cows and sheep and gorillas, contain billions of symbiotic microorganisms that make cellulase so the animal can derive the bulk of their nutrition from fibrous plants, but ours do not.

That’s why we cook, chew, blend, liquefy, ferment, sprout, and process our food. So that we can bypass our physiological limitations and access the nutrients. What about green drinks?

As you point out, green drinks consist of powdered, dehydrated vegetable matter. Dehydrating and then turning into powder leafy greens should, in theory, break down enough cellulose to make the nutrients bioavailable to humans, similar to the idea behind consuming vegetable smoothies. There’s some evidence that blending fruit and vegetables into smoothies makes them more bioavailable, though the quality of research varies:

In one, apple smoothies resulted in greater absorption of apple polyphenols, but the controls were poor – two others groups who either consumed cloudy apple juice or apple cider. I would have liked to have seen a group that simply ate whole apples.
Another review paper (PDF) found that, by and large, increasing the surface area of a food (by juicing, chopping, blending, or pureeing) increases the bioavailability of the nutrients in that food. In other words, the more pieces and the smaller those pieces, the greater the nutrient accessibility.

Since powdered vegetation has far more exposed surface area than even well-chewed whole vegetation, I think the nutrients should be plenty bioavailable – assuming dehydration preserves nutrients. Does it?

Dehydration of leafy greens reduced carotene availability compared to fresh greens, but both groups of children – those who ate dehydrated greens and those who ate fresh – improved their vitamin A status. Both were effective; fresh was moreso.
Freeze-drying seems to be better at preserving carotene content than sun- or heat-drying.

I’m definitely a fan of just eating the whole fruit or vegetable over a powder, but it seems like green drinks can be a helpful tool. If you’re interested, I’d suggest you try one out for a few weeks and see how you feel. Oh, and since we also know that fat improves absorption of many nutrients (it’s why I always cook my spinach in butter), be sure to mix it with coconut milk or add a couple egg yolks. I’d also seek out products that use gentle dehydration techniques, preferably freeze drying. A lot of the “raw vegan” green drink mixes should be gently dehydrated

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