Co-authored with Jill Parnell
Despite being around since Neolithic times, fermented foods are a relative new guy to the nutrition trend party, at least in North America. With ringing endorsements cropping up all over the place promising everything from improved digestion to an enhanced immune system and longevity, it's no wonder they are popular!
The first evidence of controlled fermentation comes from Asia around 6,000 BC with, you guessed it, wine as the first product. But beyond alcohol production, fermentation with bacteria, fungus and/or yeast is a common method for preserving grains, fruits and vegetables, dairy and even meats. Although popular throughout the world, most fermented foods aside from sourdough bread and yogurt have not been as popular in North America as they are elsewhere.
Most proponents attribute the beneficial effects of eating fermented foods to the presence of natural probiotics (1), those friendly little gut bacteria and yeast inhabiting our gut.... BUT not all fermented foods are a source of probiotics. A good rule of thumb? If it's shelf stable, cooked or has been pasteurized, there are no friendly little microorganisms in there. Only certain kinds of bacteria and yeast that are known to confer health benefits are considered probiotics (2), namely bacteria classified as Bifidobacterium and Lactobacillus, as well as Saccharomyces boulardii yeast (2,3,4,5,6).
The Real Bacterial Deal
These foods are produced using fermentation, most often lacto-fermentation, and provide a source of live probiotics.
- KEFIR. Originating in central Asia, kefir is made with a yeast and bacterial starter. The result is like a thick, tangy and slightly carbonated milk. Traditionally, it has a low alcohol concentration too! An acquired taste for some, mix with fruit like yogurt rather than drinking as a beverage if you're new to kefir.
- YOGURT. The most well-know fermented food in North America, yogurt contains several bacterial strains -- lactobacilli, streptococcus thermophilus, and sometimes bifidobacteria. Opt for high-protein Greek yogurt and watch the added sugar content.
- KIMCHI. Spicy and sour! This Korean staple is made by fermenting cabbage and other vegetables with the aptly-named Lactobacillus kimchi bacteria, then allowing it to ferment in a jar buried in the ground. There are seasonal and regional versions of kimchi -- 187 varieties!
- NATTO. Made from soybeans fermented with Bacillus subtilis, natto is a great source of probiotics. Popular for breakfast in Japan, it's often described as slimy, ropey and pungent -- not for the uninitiated... and we speak from experience!
- KOMBUCHA. Sweetened black tea that is fermented with bacteria and yeast, kombucha is a tart and slightly fizzy beverage booming in popularity... but with limited evidence of health benefits. Watch the sugar content -- sugar is necessary for the fermentation, so calories can be high. Don't overdo it!
The Microorganism Maybes
Probiotic content depends entirely on method of preparation for these foods, so be saavy and read the label.
- MISO. Made from soybeans and rice/barley fermented with the fungus Aspergillus oryzae, some claim miso paste is a source of Lactobacillus strains but there's not much data to support this. Many brands are also pasteurized, which kills bacteria -- as does boiling in miso soup!
- PICKLES. Most commercial brands don't use traditional lacto-fermentation but rather vinegar as a preservative agent. Many also contain yellow food colouring, so read the ingredients! For probiotic pickles, look to the refrigerated section for fermented options... but they're still high in salt!
- SAUERKRAUT. Ditto for sauerkraut. This "sour cabbage" is traditionally produced when lactic acid bacteria ferment sugars found in the sliced cabbage. But modern day, grocery store varieties are pasteurized, effectively killing any beneficial probiotics. Look to reputable commercial brands if you go the unpasteurized route.
- DRY SAUSAGES. While some dry sausage varieties like salami MAY use lactic acid fermentation prior to drying, the high salt content and low moisture are not ideal for probiotic viability. Dry sausages are also high in salt and fat, and may contain nitrates.
The Probiotic Impostors
These foods, while often fermented with yeast or bacteria, DO NOT provide a source probiotics due to processing, pasteurizing and/or cooking.
- SOY SAUCE. While soy sauce is made from soybeans and grains fermented with mold and/or bacteria, it is pasteurized and filtered to remove any microorganism, including any probiotics in the original "mash." Extremely high in salt, one tablespoon contains close to the upper limit for sodium.
- ALCOHOL. While beverages such as wine and beer are fermented with yeast, too bad the yeast effectively die of alcohol poisoning during the fermentation process! No probiotics here! Any health benefits are likely attributable to the antioxidant content of polyphenols.
- TEMPEH. Common in Indonesia, tempeh is a soybean cake that is fermented with fungus, not probiotics. Although it's an excellent source of vegan protein and fibre, tempeh does not contain probiotics.
- SOURDOUGH BREAD. Certainly delicious, but no probiotics here! Although Lactobacillus bacteria in the starter increases shelf life and perhaps reduces glycemic load of sourdough bread (7), the lactic acid bacteria don't survive an oven hotter than 150°F.
Our advice? Know your fermented food frauds! Despite information floating out there in the ether (read: dodgy websites), many fermented foods touted as probiotic sources are not. Consuming natural sources of probiotics may be fantastic for your health, but you cannot possibly benefit from friendly microorganisms not actually found in your food!
In addition to our shelf-stable rule of thumb, start reading foods labels and ingredients lists to wade through the hoopla. Look for "live cultures" for evidence of actual probiotics. Aside from probiotics, fermented foods may deliver other nutritional benefits like increased vitamin availability and digestibility (2,4,6) BUT we chose to focus on probiotic content here because they get the most health buzz!
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