Fermented Foods Ranked: From Superfoods to Foods to Avoid

Gut Instincts with Dr. Steven Gundry

Fermented foods have been part of human diets for thousands of years. Long before refrigeration, traditional cultures relied on fermentation to preserve food and transform ingredients. Today, fermented foods are often promoted as gut-friendly staples—but according to Dr. Steven Gundry, not all fermented foods deserve the same reputation.

In this episode of Gut Instincts, Dr. Gundry ranks a wide range of fermented foods from S-tier (superfoods) to F-tier (foods best avoided), explaining how ingredients, fermentation methods, added sugars, and modern production practices influence their place on the list.

Understanding Fermentation and Modern Labels

Fermentation occurs when bacteria or yeast consume sugars in food, producing acids, gases, or alcohol. While this process is ancient, many modern products marketed as “fermented” differ significantly from their traditional counterparts.

Dr. Gundry repeatedly emphasizes one rule: always read the label. Added sugars, grain fillers, and modern processing can drastically change the final product.

Kefir: A Potential Superfood with Caveats

Kefir is traditionally made by fermenting a sugar-containing liquid with kefir grains. Today, kefir comes in many forms:

Milk kefir
Water kefir
Coconut kefir

Key Considerations

Many commercial kefirs contain added sugars or fruit juices
High sugar content often appears in total carbohydrates
Some products resemble candy more than fermented food

Ranking:

Low-sugar versions: S-tier potential
Most grocery-store versions: A to B tier, sometimes lower

Kombucha: From Superfood to Sugar Bomb

Kombucha is fermented tea made with sugar and a SCOBY (symbiotic culture of bacteria and yeast).

What to Watch For

Some brands contain as much sugar as soda
Low-sugar versions exist but require careful label checking

Ranking:

Low-sugar kombucha: S-tier
High-sugar kombucha: F-tier

Yogurt: A Classic Fermented Food with Modern Problems

Yogurt is often considered the archetypal fermented food, but Dr. Gundry urges caution.

Common Issues

Most U.S. yogurts contain added fruit sugars
Vanilla yogurt is often just as sugary as fruit varieties
Most are made from A1 cow milk, which may be problematic

Better Options

Goat yogurt
Sheep yogurt
Unsweetened varieties only

Ranking:

Most U.S. yogurts: C to F tier

Labneh: A Rare Standout

Labneh is a strained yogurt similar to Greek yogurt but thicker and spreadable.

Often made with safer milk sources outside the U.S.
Rare in American grocery stores
Common in Europe

Ranking:

Traditionally made labneh: S-tier

Sauerkraut: A Reliable Superfood

Sauerkraut is fermented cabbage. While many people seek “live” versions, Dr. Gundry explains that:

Stomach acid kills most bacteria anyway
Dead bacteria still provide beneficial signals
Shelf-stable sauerkraut offers similar benefits

Ranking:

All properly fermented sauerkraut: S-tier

Pickles: Fermented vs. Brined

Not all pickles are fermented.

Brined pickles are preserved with salt only
Fermented pickles allow bacteria to consume sugars

Label Tip

Look specifically for the word “fermented”

Ranking:

Fermented pickles: High tier
Brined pickles: Lower tier

Kimchi: Fermented and Flavorful

Kimchi is fermented cabbage, usually with hot peppers.

Fermentation breaks down compounds in peppers
Traditionally fermented hot sauces work the same way

Ranking:

Kimchi: S-tier, alongside sauerkraut

Sourdough Bread: Not What It Used to Be

Although traditional bread was always fermented, modern sourdough in the U.S. presents issues:

Most U.S. wheat is treated with glyphosate
Fermentation does not sufficiently neutralize modern wheat

Ranking:

U.S. sourdough bread: F-tier

Cottage Cheese: Sometimes Fermented, Often Not

Cottage cheese is not automatically fermented.

Most U.S. versions use A1 cow milk
Some brands are labeled “fermented”
Casein A2 versions exist but are rare

Ranking:

Properly fermented A2 versions: Good
Most U.S. cottage cheese: Low tier

Mozzarella: A Common Misconception

Most mozzarella sold in the U.S.:

Is not fermented
Uses A1 cow milk
Is often wrapped in plastic

Exception

Buffalo mozzarella (from water buffalo)

Ranking:

Standard mozzarella sticks: F-tier
Traditional buffalo mozzarella: Better option

Beer: A Fermented Food That Falls Short

Beer is fermented from grains like wheat or corn.

Fermentation does not eliminate gluten
Many people report poor tolerance

Ranking:

Beer: F-tier

Tempeh: Fermented Soy Done Right

Tempeh is fermented soybeans, unlike tofu.

Buyer Beware

Many U.S. tempeh products include grains like wheat or rice
Gluten is not broken down during fermentation

Ranking:

Grain-free tempeh: High tier
Grain-containing tempeh: Lower tier

Soy Sauce vs. Fish Sauce

Soy Sauce

Most U.S. soy sauce contains gluten
Labels can be inconsistent

Ranking:

U.S. soy sauce: F-tier

Fish Sauce

Naturally fermented
Gluten-free
Made from fermented fish

Ranking:

Fish sauce: S-tier

Miso: Fermented Soy with Conditions

Miso is fermented soy and differs from tofu.

Can be used as seasoning or soup base
Avoid adding tofu to miso soup

Ranking:

Miso alone: S-tier

Apple Cider Vinegar: Look for the Mother

Apple cider vinegar contains fermentation byproducts.

The “mother” consists of settled yeast
This is where beneficial compounds remain

Ranking:

Apple cider vinegar with the mother: S-tier

Natto: An Acquired Taste

Natto is fermented soybeans with a strong flavor.

Contains notable compounds
Taste can be challenging unless familiar

Ranking:

If tolerated: S-tier

Olives: Not Fermented, Still Valuable

Olives are usually brined, not fermented.

Contain a natural microbiome
Support gut diversity through different mechanisms

Ranking:

Olives: High tier

Fermented Beets: A Traditional Win

Beets contain natural sugars that ferment easily.

Fermentation removes sugar
Produces beneficial byproducts

Ranking:

Fermented beets: High tier

Wine and Champagne: Fermentation Matters

Wine is fermented by yeast.

Fermentation improves polyphenol availability
Red wine contains more polyphenols than white
Champagne retains yeast sediment (“lees”) for years

Ranking:

Red wine (moderation): S-tier
Champagne: S-tier

Final Ranking Recap

Superfoods (S-Tier)

Sauerkraut
Kimchi
Labneh (traditional)
Miso
Apple cider vinegar (with the mother)
Natto (if tolerated)
Fish sauce
Fermented beets
Red wine & champagne (moderation)

Conditional Choices

Kefir
Kombucha
Tempeh (grain-free only)
Pickles (must say fermented)

Foods to Avoid (F-Tier)

Most U.S. yogurts
U.S. sourdough bread
Standard cottage cheese
Mozzarella sticks
Beer
U.S. soy sauce

Closing Thoughts

Fermented foods can still play a role in modern diets—but how they’re made matters. According to Dr. Gundry, just a few carefully chosen fermented foods per week can make a meaningful difference.

That’s his gut instinct.