I’ve been using a cyclical keto diet for the past few years. I noticed that my fiber seems to be consistently low. Do you have any recommendations for supplements or foods that would be acceptable in a ketogenic diet?

It was really interesting when he sent me the advance copy, the PDF, and I read it because we had kind of independently arrived at a similar approach to ketogenic diet, intermittent fasting, and fasting. We talk occasionally. We’re in touch via email, but we hadn’t talked a lot about this. And so, it’s interesting for both of us to realize that we had kind of arrived at the same place in terms of what we believe works for most people based on our own exploration individually with ourselves and then also based on my experience treating a lot of patients.

One of the things that I’ve come to believe is that doing a ketogenic diet all the time is not a good idea for most people, and I know you said cyclical, Justin, so I know you’re not doing that, but I just wanted to clarify for others. Some people can thrive that way. Certainly, we all probably know one or two people that that seem to, but in most cases, there are some pretty significant downsides. I think one of them is the effect that it can have on the microbiome, but how often you cycle, I think, is the question because if you’re doing keto most of the time and then you only really cycle out of it occasionally, that might not be enough to increase the fiber intake.

Mercola in this book is kind of interesting. It’s basically time-restricted eating every day, so maybe a six- or eight-hour window of food intake, so intermittent fasting is kind of the backdrop. And then, maybe on three or four of those days or five, depending on your goals, you’re eating a keto-type of diet, one day you do what he calls a keto fast. It’s not a complete fast of zero calories. It’s 300 to 600 calories of certain macronutrient ratios. It sounds like the fasting-mimicking diet but it’s not, so you might do one fast day and then a big refeed day where you’re eating a lot more carbohydrates, including fibrous carbohydrates. You could have sweet potatoes, potatoes, cooked and cooled potatoes, which are really high resistant starch. You could have cooked and cooled white rice, which is really high in resistant starch. You could do two refeed days in a in a week, where you’re having more like 100 to 150 grams of carbohydrate with a lot of resistant starch; that could really help the gut flora. You can also take a completely noncaloric, prebiotic, fiber-type of supplement, even on the days where you’re doing ketogenic diet, without interfering with ketosis. I think ​Biotagen​ is a good option, I think, and I have it on my website. It’s called ​Prebiogen​. There’s the one from Microbiome Labs, which makes MegaSporeBiotic, I think it’s called ​MegaPreBiotic​. It’s got nondigestible oligosaccharides that have been shown to increase A​kkermansia​ and ​Faecalibacterium prausnitzii.​ I can never pronounce that one, which is a very protective species, and then of course Bifidobacteria. This is a relatively new prebiotic. It’s got galactooligosaccharides, GOS, FOS, and xylooligosaccharides. These are pretty evidence-based strains that can make a really big difference.