Leeks and garlic

By now most of us have some level of awareness with respect to the role that probiotics and fermented foods can play in reducing our risk for certain diseases or in supporting better digestive health overall.  The addition of healthy bacteria to the gut, however, is only a small part of the bigger picture: creating an intestinal environment that fosters sustainable beneficial bacteria populations.

This requires eliminating ingredients (such as emulsifiers) and chemicals (such as glyphosate-see webinar offered on 01/25/17 on this topic) known to reduce the numbers of important families and the regular consumption (several times per day) of fermentable fibers and prebiotic-rich foods.  This list of foods is predominantly made up of vegetables, both starchy and non-starchy, with some other unique sources that may or may not work for you.

One recent investigation found that women who ate significant amounts of garlic and leeks (two of the best prebiotic foods I could name) had markedly lower risk of developing breast cancer.  Yet, when these foods were extensively cooked there was a loss of that protective effect.  This could largely be explained by the fact that most prebiotics are somewhat degraded or pre-digested by extensive cooking.


Pourzand A, Tajaddini A, Pirouzpanah S, et al. Associations between Dietary Allium Vegetables and Risk of Breast Cancer: A Hospital-Based Matched Case-Control Study. Journal of Breast Cancer. 2016;19(3):292-300. doi:10.4048/jbc.2016.19.3.292.

It is not to say that we can’t cook these vegetables to obtain at least some prebiotic value, it just reaffirms what previous research has shown with respect to the loss of this beneficial attribute after say, browning onions in a sauté pan or frying vegetables to the point where they are almost completely broken down.

With this important aspect of nourishing critical families of bacteria, here are some other incredible sources of prebiotics.

  1. Jerusalem Artichokes: if you cook them, you have to leave them al dente!
  2. Unsweetened coconut.  One study showed that when dried coconut was fed to dogs, their bifidobacter levels took off.  This is a very good thing. However, this must be an unsweetened variety.
  3. Raw scallions. Just as with garlic and leeks, adding these liberally to your guacamole or sour cream dip can feed the microbiome in a way few other plants can.
  4. Dandelion greens and/or roots.  As a member of the chicory family, this extremely nutritious weed offers us 7 different types of fermentable fiber.  It could be a top 5 medicinal plant all around!
  5. Daikon radishes.  Use these to combine with something like goat cheese or avocado to make an incredibly healthy appetizer. Radishes of all types offer great benefits with their prebiotic effect being towards the top of the list.

 For more on how to look at fiber closely, see the blog from August 4, 2016.


John Bagnulo MPH, PhD. - Director of Nutrition