Fermented foods for better gut health

Naturally fermented foods are getting a lot of attention from health experts these days because they may help strengthen your gut microbiome—the 100 trillion or so bacteria and microorganisms that live in your digestive tract. Researchers are beginning to link these tiny creatures to all sorts of health conditions from obesity to neurodegenerative diseases.

Fermented foods are preserved using an age-old process that not only boosts the food’s shelf life and nutritional value, but can give your body a dose of healthy probiotics, which are live microorganisms crucial to healthy digestion, says Dr. David S. Ludwig, a professor of nutrition at the Harvard School of Public Health.

Not all fermented foods are created equal

The foods that give your body beneficial probiotics are those fermented using natural processes and containing probiotics. Live cultures are found in not only yogurt and a yogurt-like drink called kefir, but also in Korean pickled vegetables called kimchi, sauerkraut, and in some pickles. The jars of pickles you can buy off the shelf at the supermarket are sometimes pickled using vinegar and not the natural fermentation process using live organisms, which means they don’t contain probiotics. To ensure the fermented foods you choose do contain probiotics, look for the words “naturally fermented” on the label, and when you open the jar look for telltale bubbles in the liquid, which signal that live organisms are inside the jar, says Dr. Ludwig.

Try making your own naturally fermented foods

Below is a recipe from the book Always Delicious by Dr. Ludwig and Dawn Ludwig that can help get you started.

Spicy pickled vegetables (escabeche)

These spicy pickles are reminiscent of the Mediterranean and Latin American culinary technique known as escabeche. This recipe leaves out the sugar. Traditionally, the larger vegetables would be lightly cooked before pickling, but we prefer to use a quick fermentation method and leave the vegetables a bit crisp instead.

  • 2 cups filtered water
  • 1 to 1-1/4 tablespoons sea salt
  • 2 tablespoons apple cider vinegar
  • 1 jalapeño or a few small hot chiles (or to taste), sliced
  • 1 large carrot cut into 1/4-inch-thick rounds or diagonal slices
  • 1 to 2 cups chopped cauliflower or small cauliflower florets
  • 3 small stalks celery (use only small inner stalks from the heart), cut into 1-inch-long sticks
  • 1 bay leaf
  • 1 cabbage leaf, rinsed

Warm the water (no need to boil). Stir in the sea salt until it dissolves completely. Set aside to cool (use this time to cut the vegetables). Add the vinegar just before using. The brine can be made ahead of time and stored in a sealed glass jar on the counter to use when ready to pickle.

Set a quart-size canning jar in the sink and fill it with boiling water to sterilize. Empty the jar and tightly pack the vegetables and bay leaf inside to within 1 to 2 inches from the top of the jar. Pour the brine over the vegetables to fill the jar to within 1 inch from the top. Wedge the cabbage leaf over the top of the vegetables and tuck it around the edges to hold the vegetables beneath the liquid.

Set jar on the counter and cover with a fermentation lid. (Alternatively, use a standard lid and loosen it a bit each day for the first few days, then every other day, to allow gasses to escape.) Let pickle for three to five days, depending on the indoor temperature. Check the taste after a couple of days, using clean utensils. Vegetables will pickle faster in warmer climates. Make sure the vegetables stay packed beneath the level of the liquid and add salted water (2 teaspoons sea salt dissolved in 1 cup warm filtered water) as needed.

When the vegetables are pickled to your liking, seal the jar with a regular lid and refrigerate. Vegetables will continue to slowly pickle in the refrigerator. They will keep for about one month. Taste for saltiness before serving and, if desired, rinse gently to remove excess salt.

Calories: 1 (per 1 tablespoon)

Carbohydrate: 0 g

Protein: 0 g

Fat: 0 g

Excerpted from the book Always Delicious by David S. Ludwig, MD, PhD, and Dawn Ludwig. Copyright © 2018 by David S. Ludwig, MD, PhD, and Dawn Ludwig. Recipe reprinted with permission of Grand Central Life & Style. All rights reserved. 

Related Information: The Sensitive Gut


  1. Alex

    Assuming that the vinegar is added to introduce some starter cultures: if you use filtered (i.e. commercially available) vinegar it probably won’t work as intended. There are simply no bacteria in it. It probably will, however, prevent fermenting bacteria and fungi from growing (but also potentially harmful ones).

  2. Claudia

    Remove the vinegar please. The lacto fermentation has nothing with vinegar but at the end can produce the vinegar.
    I am born in north Europe where fermentation (lacto fermentation, without vinegar, please, forgive the vinegar, replace sugar with an apple or any fruit, there is simple ways!!) was the source of vegetable for 6 months of year and a daily component all the year.
    There are several possibilities to increase the lacto bacillus and acidofilus and bulgaricus in your gut, for free, some without salt. Sourdough is a type of fermentation, beer and wine again (all these are with yeast and some lacto-bacillus, wild yeast for home made products) , lacto fermentation is in yougurt home made and needs 5 minutes of effort, sour milk or sour heavy cream (and fermented and NOT pasteurized cheeses) again are thanks to lacto fermentation and bacteria around us. East europe has kambucha (here sugar needed) or borch or kwass or elder-flowers juice or to not forget the kefir etc. Fermentation with salt solutions is great for vegetables and jars can resist all the winter.

    Happy to have an immersion to simple and traditional food in France. Hope to spend a wonderful summer again, eating only in local markets from villages.

    And not forget: all these bacteria live around us happily. Just to not destroy the ecosystem and keep the balance. The dirt is not so bad how it is promoted.

  3. Rose

    …The jars of pickles you can buy off the shelf at the supermarket are sometimes pickled using vinegar and not the natural fermentation process …
    This piece of the text is contradicting to the recipe which recommends “2 tablespoons apple cider vinegar”. Is that ok?

  4. Agatha

    In Cameroun West Africa we grew up eating a fermented breakfast porridge made from corn called pap, there is also fermented cassava for fufu etc These gut friendly foods has really helped in keeping us healthy.

  5. Obus

    You don’t need to add salt or vinegar. But a small amount of sugar might be helpful. I ferment cabbage regularly by cutting it up and putting in jar with enough water to cover. The first time I did this, I added some drops of the clear liquid i found on the top of some yogurt in a jar in my refrigerator. Now I add some liquid from the previous batch. This supplies the necessary micro-organisms to start the process.

    I recently found a jar of fermented cabbage which had been sitting in my fridge for two years. It was still in perfect order.

  6. Randy

    This comment is in reply to J’s comment – migraines are principly due to lack of magnesium in your diet – consider reviewing this post http://howtonutrition.info/how-to-stop-headaches-with-these-natural-remedies/

  7. J

    Except those with migraine, who find that avoiding foods with tyramine (all fermented and aged foods), to be beneficial in reducing frequency or severity of migraine symptoms and auras.
    So no cheeses (except fresh like farmers, Havarti, cream cheese are OK), no red wine, no stout ales, no aged foods like sauerkraut or kimchi, no aged sauces (no Franks Red Hot, no Sriracha, etc.), no refrigerated leftovers (freeze portions instead).
    There are some foods with naturally occurring tyramine but, except for fava beans, which have a very high amount, most can still be eaten in moderation. Avocado is good for you. But, maybe not a lot of it in one day for migraine suffers. Go easy on the guacamole dip at parties!
    Cut out all tyramine foods and then add each in, starting with natural ones like avocado. When you see which bother you, edit them out of your diet. But most of us can live without most of these things just fine!
    The fermented food craze, like all food crazes in the U.S., is overly promoted, overly hyped, and potentially ruinous to those with migraine.


    All interesting comments. Like many cures, it’s a carefull rebalancing act. As the traditional saying goes: a little bit of bad is good, too. Sounds good!

  9. N. Schultz

    This is sad, if true. I just read your article and was writing down the ingredients when I looked at the posts below. If true, Harvard, you should retract, correct or stand by your article. Are the responses/posts correct?

  10. Richard

    I agree with Travis & Shane s replies. Well said & more completely explained.

  11. Rich

    Harvard Medical are amatuers in the ” Natural healing ” arena. They are trying to show a different image/reputation in order to attract more readers & subscribers.

    They post some useable/ pertinent info, but are playing “catch up” with other countries in terms of alternative methods of wellness & healthcare.

  12. P Worden

    Way too much salt for my cardiac diet.

  13. Mark

    Maor Roffe:
    You have no clue to what fermented foods are and what they do. Use some critical thinking and do som research.

  14. Maor Roffe

    This is ridiculous info, how can Harvard post something promoting items found to cause cancer? Last I read, there has been much evidence showing that cultures the frequently eat salty pickled food items have higher incidence of associated cancers.
    Google “gastric cancer and pickled foods”, “stomach cancer and pickled foods” and you’ll find tons of data and research on the subject.
    Im shocked. I’d expect Harvard to be so much more careful with the information the push out and promote.

  15. Shane

    You don’t need to add vinegar and if you do, you’ll thwart the natural succession of microbes that acidify and preserve. Instead of acetic acid, you want lactic acid created from lactobacillus for a traditional ferment.

    Also, traditional ferments last almost forever under refrigeration, not a month.

    Bubbles as a sign of being “natural fermented” is incorrect. At most, that will only tell you it’s a young ferment.

    C’mon Harvard!

  16. Travis

    I’ve made my own kombucha before, and sugar is essential to the fermentation process in transforming tea -> kombucha.

    I feel it would have been a similar situation for the recipe you shared – so I’m wondering why you decided to leave out the sugar?

    I thought that the bacteria needed the sugar for the fermentation process.

Commenting has been closed for this post.