New to ferments

It depends on the ferment, but the nature of ferments means that, generally, they last very well when microbial activity is slowed right down in the cold of the fridge. Be guided by the best before dates on the ones you buy, and use your sense of sight, smell and taste on the ones you make yourself. The acidity of the ferment acts as a natural preservative. Fermentation does continue in the fridge, but much more slowly, so your ferments will become increasingly sour as time passes. Watch out for carbon dioxide build up in the ferment container. For more active ferments, like water kefir and sodas, you may need to “burp” the bottle or container to release the gas on a regular basis.

This can be the most common practical issue in vegetable fermentation. Vegetables must remain submerged beneath the brine, as any exposure to air creates conditions where surface mould can develop (because of the presence of oxygen in the air). Push them back down firmly and use a weight to keep them submerged, a clean stone works well.

Start small one tablespoon of fermented vegetables with a meal, or a small glass of kefir or kombucha once a day. Some people experience bloating or digestive changes when they first introduce ferments as your gut adjusts, which is normal and usually settles. Once you are comfortable, gradually increase the amount and variety. Regular daily consumption of small amounts is far more beneficial than occasional large servings.

No. Fizzing and bubbling is a sign of active, healthy fermentation. Carbon dioxide is a natural by-product of the process. If you are using sealed jars, open them briefly once or twice a day during active fermentation to release the gas, known as “burping” the jar, to avoid excessive pressure building up. This is particularly important in the first few days when fermentation is most vigorous. If you are using a purpose-made jars that have a rubber seal or an airlock, the gas escapes automatically. Please note that water kefir tends to produce the most carbon dioxide while fermenting, so if you make this at home, it is wise to store it in plastic bottles. Then, as the gas builds up, you will notice the bottle becoming very hard and that will prompt you to release the gas that has built up by opening the lid and then closing it again.

For the vast majority of people, ferments are not only safe, but actively beneficial, and increasing their consumption is a positive step for health. However, there are specific groups and circumstances where caution is warranted, and a small number of situations where ferments should be avoided or introduced only under professional guidance.

People who are immunocompromised
People who have never eaten ferments before and who are taking certain immunosuppressant medications, or are severely immunocompromised should seek advice from their doctor or a nutritionist before introducing live fermented foods. However, if you are already in the habit of consuming ferments and then need to take immunosuppressant medications or become immunocompromised, it is generally safe to continue to consume ferments to the same extent you were previously. If you make your own, you will need to continue to ensure you are being conscientious about basic food hygiene; washing containers in hot soapy water, ensuring your hands are clean and that the surfaces are clean when you are making. Also ensure that you never “double dip” – that is tasting a ferment with a spoon and then putting the spoon back into the ferment after it has been in your mouth. If you have any specific concerns, check with your GP or a nutritionist. While generally supportive to health, the live bacteria and yeasts present in unpasteurised ferments could theoretically pose a risk when immune defences are very severely compromised. This does not necessarily mean ferments must be avoided, but how and what and how much to consume should be guided by a clinician.  

People taking monoamine oxidase inhibitors (MAOIs)
MAOIs are a class of antidepressant medication that interact with tyramine, a compound that forms naturally during fermentation, particularly in aged and fermented foods such as miso, soy sauce and aged cheeses. Consuming tyramine-rich foods while taking MAOIs can cause a potentially serious rise in blood pressure. Anyone taking MAOIs should discuss dietary restrictions carefully with their prescribing doctor, pharmacist or with a nutritionist, as the list of foods to avoid is broad and specific.

People with histamine intolerance
Fermented foods are among the highest dietary sources of histamine, which is produced as a natural by-product of microbial activity by some microbes during fermentation. Most people process dietary histamine without difficulty, but those with histamine intolerance may experience symptoms including headaches, skin flushing, nasal congestion, digestive discomfort, heart palpitations or hives after consuming ferments. Aged ferments such as mature sauerkraut, kimchi, miso and mature milk kefir tend to be higher in histamine than younger ferments. If histamine intolerance is suspected, a low-histamine diet trial under the guidance of a nutritionist can help clarify whether ferments are a trigger. And if you make your own, you can eat them young when histamine levels tend to be low.

People with small intestinal bacterial overgrowth (SIBO) also known as small intestinal microbial dysbiosis (SIMD)
Some practitioners advise caution with ferments during active SIBO/ SIMD treatment, as introducing additional live bacteria and fermentable substrates into an already dysbiotic small intestine can worsen bloating, gas and discomfort in some individuals. Others find ferments helpful even during treatment. The picture varies considerably from person to person. If you have been diagnosed with SIBO/.SIMD or suspect you have it, it is worth introducing ferments gradually and under guidance.

People with certain gut conditions during flares
Those with inflammatory bowel disease; Crohn's disease or ulcerative colitis, generally tolerate and benefit from ferments. There is growing evidence supporting their role in gut health in these conditions. However, during an active flare, when the gut lining is inflamed and compromised, large amounts of live fermented foods may not be well tolerated. Starting with small amounts and building gradually is advisable.

Infants under 12 months
Unpasteurised ferments can be introduced when babies are weaned after 6 months, but cautiously and in small amounts. Ferments containing honey (such as Jun kombucha) should be avoided until your baby is a year old.  

Pregnant women
Risk from bacterial contamination (for example from Listeria) in commercially made ferments is very low. The same is true of your home-made ferments, provided you follow sensible food safety rules (clean hands, utensils and jars) and the basic rules of safe fermentation.  While the risk from a well-made home ferment is very low, some pregnant women who do not already consume ferments may prefer to err on the side of caution and wait to introduce these foods and drinks until after the first trimester.

A note on starting symptoms
Many people experience some bloating, changes in bowel habit or increased gas in the first few weeks of introducing ferments. This is common, usually temporary, and reflects your resident gut microbes adjusting to new microbial input. Starting with small amounts and building gradually almost always resolves this.