When I got going with green smoothies, in late April 2010, I was guided by friends to opt for kale and collards as the greens of choice over tender greens to add to fruit. A short while into my green smoothie days, I read Victoria Boutenko‘s Green for Life and, later, Green Smoothie Revolution. The former, especially, got me energized to keep moving forward with my dietary transition.
There’s a critical piece of information these books and lots of articles in the mainstream news media and health websites leave out, however, and it’s about distinguishing between tender greens and other greens, which are classified as cruciferous vegetables. I disagree with Boutenko’s claim that “greens can be combined with any other foods,” based on her lumping all leafy greens into one category, and would further argue that human beings aren’t designed to eat kale, collards, Swiss chard and the like.

I’ve enjoyed plenty of experience eating all kinds of greens with fruits, almost always blended as green smoothies. In fact, from late April 2010 through September 2013 (1,250 consecutive days), I had one, two, three, four or even five meals of green smoothie every single day, and these green smoothies featured kale, collards, Swiss chard and dandelion, for the most part, in the first two-and-a-half years of this time period. It wasn’t until September 1, 2012, when Arnold Kauffman, owner of the Lansdale, Pennsylvania, raw food café Arnold’s Way, suggested I ditch these harsher greens in favor of using romaine lettuce in my green smoothies. This is the best piece of dietary advice I’ve ever received from Arnold, who’s been a mentor in my life the past seven years.
In the words of Arnold, wowie kazowie—what a difference I felt in digestion! Arnold also suggested I embrace red leaf lettuce for my salads, switching from romaine, based on my wanting variety in greens choices. If I had my choice, I’d actually use red leaf lettuce in green smoothies most days because the leaves are much more tender compared with romaine leaves. What drives my decision to use romaine, however, is mostly economical: Heads of romaine run much larger compared with red leaf heads, and their prices usually are about the same.
I’ve interviewed and talked to hundreds on the raw food path in the past several years, and I like to bring up the subject of tender greens at times. Some such as Paul and Yulia Tarbath are in agreement with me that our bodies’ design doesn’t favor harsher greens, and others tell me they’ve never considered eliminating kale from their diets. I’ve recommended to some folks to drop kale and the like, and some have gotten back to me, touting tremendous improvement in digestion.

Of course! Cruciferous vegetables do not combine well with fruits! I take food combining seriously because I have experienced optimal digestion when adhering to these simple guidelines. As long as I’m eating ripe fruits, not moving around too much when eating or experiencing stress, my digestion tends to purr like a happy, content kitten.
If you’re blending bananas and kale or collards, for example, I challenge you to swap romaine or red leaf lettuce in place of these cruciferous vegetables and experience the difference in digestion yourself.
Now, I’ve found that green leaf lettuce is more fibrous and doesn’t make for smooth smoothies! I’m also not a fan of using celery, which is considered a tender green, in green smoothies. I do enjoy eating about a pound of these salty sticks with my lunch smoothies, almost always made from bananas, romaine lettuce and Daily Green Boost barley grass juice powder. Cucumbers, which are nonsweet fruits but, like the tender greens lettuce, celery and baby spinach, are considered neutral foods, also don’t work well in green smoothies.
I’ll leave you with a clincher: Six months after ceasing use of all cruciferous vegetables in green smoothies, I tried kale once again with bananas. I was in such extreme pain, doubled over for quite a while, that I had to call it a half-day of work at my old day job. About six hours after the onset of pain, my body bounced back, and I knew definitively never to blend cruciferous vegetables with fruits again.
PS, let me emphasize: I use only baby green kale, chard, spinach and lettuce leaves. The full grown leaves slow my digestion, even the lighter lettuce. KP
Kim, thank you for sharing about how you feel with greens!