Erica Sonnenburg Ph.D.

The Good Gut

Is Your Microbiome on a Paleo Diet?

…not unless you’re gorging yourself on plants

Posted Jul 06, 2015

Ferdinand Reus, Creative Commons
Baobab tree (Adansonia digitata) in Tanzania
Source: Ferdinand Reus, Creative Commons

Based on a couple of the comments I received on my last post “You May Be on a Paleo Diet, but Is Your Microbiome?”, I feel that I need to clarify some of my points. Some people took that post as an attack on the paleo diet, which was not what I intended. In many ways, I feel that I also follow a “paleo” diet, but in my case I try to replicate as much as possible the nutritional aspects of what our ancestors ate with a specific focus on my gut microbiota.  90% of our associated cells and 99% of our associated genes are bacterial, and this microbial community plays a vital role in our health, so our diet needs to reflect that reality.

Here is an example of a day of paleo eating as described in “The Paleo Solution” by Robb Wolf:

Breakfast – 2 to 4 eggs, almonds, small fruit or berries

Lunch – Chicken fajita salad

Snack – chicken, apple, avocado slices

Dinner – Salmon, green beans, side salad

I calculated the amount of dietary fiber present in these foods. I had to make some assumption since in some cases quantities weren’t specified, but I was fairly generous in the amount of plants and adjusted the quantities so that the total calories was about 2,000. The amount of dietary fiber we consume is critical since these complex carbohydrates are what feed out gut bacteria.

This menu contains approximately 28 grams of dietary fiber, not bad considering the average American is consuming about half that. In fact 28 grams of fiber for a 2,000 calorie diet is the recommended daily allowance of fiber. It is not surprising that going from a standard American diet to one similar to this would be a huge improvement.

If you look at the consumption of dietary fiber by modern-day hunter-gatherers, which is likely a good approximation our diet in the Paleolithic era, it’s more like 100 to 150 grams of fiber per day. So while the western version of the paleo diet is an improvement over the standard American diet, as far as the microbiota is concerned, it is not Paleolithic. In fact, it is probably a closer approximation to the amount of fiber our early agrarian ancestors ate. It is for this reason that I brought up the question of whether a paleo diet is truly Paleolithic from a gut bacteria standpoint.

One of the issues affecting the amount of dietary fiber we consume is the domestication of plants. One hundred grams of wild blueberries has 4.2 grams of dietary fiber compared to 2.4 grams for the plump juicy product of selective breeding. This is just one example where a wild variety is still available. The baobab fruit the Hadza eat has about 40 grams of fiber per 100 grams. Unfortunately we have bred out much of the dietary fiber that was once present in our Paleolithic foods.

Outside of foraging for wild plants in our backyards or moving to Tanzania, one way around this issue is to add legumes to the diet. One cup of sliced jicama has 6 grams of dietary fiber. But if you dip it in a ¼ cup of hummus, the fiber content is boosted to almost 10 grams. While chickpeas aren’t considered “paleo”, as far as our microbiota is concerned, the amount of fiber they provide gets us closer to what our ancestors’ consumed. Eating legumes is not a requirement to get enough fiber. The paleo diet menu I mentioned above contains no grains or legumes and still has the recommended daily allowance of fiber (assuming you don’t skimp on the plant portions of the meal). But if you want your microbiota to eat “paleo” you likely have to triple the amount of fruits and vegetables you eat (which might be easier if you eat less meat) or include fiber-rich legumes in your diet.

In science when someone makes a questionable claim, the response is “show me the data”. In other words, provide evidence to prove that what you are saying is accurate. If you are on a paleo diet, spend a day or two or even a whole week charting exactly how much dietary fiber you are eating. If you are getting the 28 grams per day for a woman or 37 grams per day for a man the US Dietary Guidelines recommends, you are probably doing a good job feeding your microbes. If you’re getting less than that, you need to re-evaluate the proportions of foods you have on your plate or try replacing some of the meat with high fiber sources of protein.


De Filippo, C., et al. “Impact of Diet in Shaping Gut Microbiota Revealed by a Comparative Study in Children from Europe and Rural Africa.” Proc Natl Acad Sci U S A 107.33 (2010): 14691–6. Print.

Schnorr, S. L., et al. “Gut Microbiome of the Hadza Hunter-Gatherers.” Nat Commun 5 (2014): 3654. Print.