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Dear Mark: Vegetable Powders, Pro/Prebiotic Timing, RS Questions, and Routine Eating

For today’s edition of Dear Mark [7], we’ve got four questions and four answers. First, I explain the merits and drawbacks of vegetable powders in the event of low produce availability. Next, I discuss whether there’s a perfect time to take your probiotics and prebiotics, or whether it doesn’t matter at all. After that, I answer a quick barrage of resistant starch-related questions, followed by a query regarding a monotonous eating regimen that by all accounts appears to be working very well. Is there a hidden danger in eating similar meals all the time?

Let’s go:

I’ve searched the site, but I didn’t see anything regarding vegetable powders. I work offshore, and the supply of fresh vegetables can be slim. Is there a vegetable powder that you would recommend taking? Are there negative side effects to taking these?


John F.

Vegetable powders are a serviceable hold over for situations where fresh produce is scarce.

There is some nutrient loss during dehydration, usually among the vitamins. Minerals and polyphenols are fairly stable, the latter less so if high heat is used (since they’re often there to protect the plant from oxidative insults, like heat). But even slightly-degraded vegetable-based micronutrition is superior to none of it.

They do help people who need the extra dose of micronutrients, though:

Obese people and heavy smokers [12] tend to be under a lot of oxidative stress [13], so they have a greater need for plant micronutrients, particularly the phytonutrients which often act as antioxidants that counter the stress (or boost our own antioxidant defenses). You’re neither obese nor a heavy smoker (to my knowledge), but you are deprived of plant nutrients [14].

There are dozens of options out there. I don’t know enough about individual products to elevate any single product over the others. Sure, there may be some proprietary methods that “preserve the maximum antioxidant capacity,” but I suspect they’re all pretty good, as most of the ones I’ve seen use relatively low heat to dehydrate the veggies.

I’ve heard good things about the Amazing Grass [15] line of powders. They include herbs, probiotics, and prebiotics along with the fruits and vegetables.

This looks cool, too: vegetable powders that you buy individually [16] and mix yourself. Want a couple ounces of dried beets? You got it! How about leek flakes? They can do that.

I can’t think of any negative side effects, beyond a false sense of security. When a company claims that a single scoop of their product equals 10 servings of vegetables, but a quick review of the nutrition facts fails to show vitamin, fiber, and mineral levels that even approach 10 servings’ worth, the claim is false and you shouldn’t assume that you’ve just eaten an entire head of broccoli (or whatever vegetable is advertised). These powders are a holdover (when you can’t get any real stuff) or a supplement [17] (when you want to add more to your regular diet). They aren’t magic.

Definitely consider vegetable powders if that’s your only option.

Hello Mark,

Looked everywhere and can’t find it. Can you tell me the proper timing to take probiotics and prebiotics supplements?


Certain prebiotics [18], like resistant starch [19], can serve as a vehicle for probiotics. The latter catch a ride on the former [20], pass through your stomach and small intestine without being digested, and make down into the colon – where you want them to go. It’s a neat little probiotic delivery mechanism, so if you do supplement with RS, you’ll want to take probiotics with it.

For anything else, I don’t think it matters what hour of the day you take them. Historically, prebiotics would have come in the form of food, which humans have evolved to eat throughout the day. Historically, probiotics were either consumed in the form of fermented (sometimes unwittingly fermented) foods, food with a few milligrams of soil-based organisms (dirt) along for the ride, dirt under our fingernails, or water with resident microorganisms. In other words, I find it unlikely that we’ve adapted to take pro/prebiotics at any particular time of day.

Thank you for the very informative resistant starch articles. I am very interested in this, as I cannot tolerate prebiotics due to FODMAP issues. However, I have a few questions please. What about konjac as a source of RS? I have seen a product called Slendier Organic Konjac Spaghetti in Ocado in the UK. This is pre-cooked, so how would that affect things with regards to the RS? I understand that parboiled rice has RS, but what about after it has been cooked? Do we have to then cool it? What about cooked & cooled tapioca pearls for RS? Is tapioca flour the same as tapioca starch? Sorry about all the questions & thank you for all your help & information.


Don’t apologize for the questions. It’s what I’m here for!

Konjac is not a source of resistant starch, actually. It’s mostly glucomannan, a prebiotic [18] soluble fiber [21] that can encourage the growth of butyrate-producing gut bacteria [22] in human subjects on a low fiber diet. So in that respect, it’s similar to resistant starch. It can also favorably affect some blood markers [23], like total cholesterol [24], LDL, triglycerides, and fasting blood glucose. Pre-cooking it does not affect the prebiotic fiber content.

Parboiled rice [25] forms resistant starch during the initial parboiling process. By the time it arrives in your pantry, it already contains RS. That doesn’t change during cooking. However, cooling cooked parboiled rice will increase the RS content and repeated cycles of cooking and cooling will further increase the RS content (PDF [26]). Unfortunately, not into perpetuity (although that would be cool if counter to the known laws of physics).

Tapioca pearls contain very little resistant starch. A 100 gram portion contains 44 grams of starch, 40 grams of which are fully digestible (PDF [27]). Not a good source.

Tapioca flour and starch are interchangeable as far as I can tell. Tapioca starch/flour is a good source of RS according to some research, but the reports from users tell a murkier story. Some get the vivid dreams, improved blood glucose [28], and better bathroom visits normally attributed to RS, while others report elevated blood glucose, indicating that they are successfully digesting the starch contained in tapioca starch. If you try tapioca, it would be a good idea to measure your blood glucose before and an hour after to see if you get a big spike (which indicates successful digestion).


First I want to thank you for all of your expertise, well written articles, and delicious supplements. You have been an extremely valuable resource for me as I go on this journey. I recommend you to everyone who asks me about my lifestyle.

On to my question; I have been eating Primally for about 3 years, starting my senior year in college. Back then I ate whatever I could get my hands on that was within the guidelines of primal eating. Now that my life is more regimented I have a very established routine. My supplements are dialed in. Certain dishes “work” for me, meaning that they meet my macro- and micro- nutrient needs. The 2-3 dishes I make are convenient to carry to work and eat on short notice. My workouts are going great. My overall health continues to improve.

Am I exposing myself to any risk by not changing up the meals/supplements I eat regularly? I am always eating the same kind of protein, veggies, roughage, and starches. I take the same supplements week after week. Long-term, could I start seeing diminishing returns from my routine, or even health risks?



I’m of the opinion that short term health is a fair barometer for long term health. Generally, if a way of eating [29] is helping your performance in the gym [30], improving your overall health [31], and providing all the macronutrients and micronutrients you need to live well [32], you’re in good shape for the future. There are exceptions, like ridiculous “cleanses” that make you feel euphoric and high where you lose a ton of weight right away but end up destroying your metabolism, eating away at your lean mass, experiencing massive rebound gains, and ruining your relationship with food [33] in the long run.

There’s also the psychological aspect, which isn’t “just” in your head but can have real world physiological ramifications. Some people do really well on a regimen. They like structure. They thrive on sameness and order. If they were to jump around and switch up their meals on a constant basis, life would be too stressful and their health would suffer. It sounds like you’re one of those people. Others? Others dig chaos. They need something new every day. They thrive on novelty. A steady regimen would be disastrous for them and ruinous for their health.

It sounds like you’ve settled into the right groove. Stick with it. Ride it as long as you can.

There’s certainly evolutionary precedent for monotony. For long stretches of time, early human diets were routine. It was only as the seasons changed and different foods became available and unavailable that diets would shift. Even then, these shifts to new food sources would stay entrenched for weeks and months until the next shift.

The only food that it might make sense to “cycle” are fruits and vegetables, simply because they contain the nutrients that don’t show up in traditional nutrition databases. Vitamins? Minerals? We’ve had those quantified for decades. But we’re still learning about new phytonutrients and the ones we do know seem to have profound effects on a number of health markers, so it’s likely advantageous to eat a variety [34] and hedge our bets. Antioxidant supplements [35] also fall into this category. Treating them as hormetic stressors [36] is probably better than taking them daily, especially if you’re a generally healthy person without any major health issues. That’s actually how I take my own high-antioxidant supplement blend [37] – intermittently, rather than daily. Another way to put it: there’s nothing wrong with eating blueberries every day, but it’s probably better to eat blueberries, raspberries, blackberries, cherries, and strawberries.

If you start to see diminishing returns, it’s okay. You can always change things up. That’s the great thing about diminishing returns; rather than a hard endpoint from which there is no return, they’re simply a helpful signal to alter course. There’s no failure, just feedback, as Art De Vany [38] says.

For what it’s worth, I’m closer to you. I’m an adventurous but opportunistic eater, meaning I enjoy trying new things when they’re in front of me, but at home I rarely feel the need to branch out far from my go-to meals [39]. It seems to be working for me.

That’s it for today, folks. Thanks for reading!