Fermented foods such as yoghurt, kombucha and sauerkraut are widely recognised as being good for our gut health, which, in turn, is linked to better weight control, immunity and mood.
A recent study from Stanford University in the U.S. found that fermented foods also appear to reduce chronic inflammation, thought to lie behind a range of diseases.
It showed that eating up to six helpings a day led to significant increases in the volunteers’ ‘good’ (probiotic) bacteria in the gut after just ten weeks, as well as a reduction in inflammation markers linked to conditions such as type 2 diabetes.
Fermentation involves adding bacteria, yeasts or fungi to foods, which then break down the sugars and starches to create gut-friendly bacteria and lactic acid.
Some fermented foods are also a very good source of prebiotic fibre, which feeds good bacteria in the gut.
Here, Jane Clarke, a dietitian and founder of nourishbyjaneclarke.com, reveals how to make the best choices.
Try: Raw Sauerkraut Classic, 410g, £4.39, ocado.com; Loving Foods Caraway and Juniper Berry Sauerkraut, 500g, £6.95, lovingfoods.co.uk; Pama Classic Farm Style Sauerkraut, 500g, £7.99, pama-raw-food.com
Expert comment: Sauerkraut is made by adding salt to shredded cabbage. The salted cabbage releases water and is left to ferment in its own brine.
As the cabbage ferments, billions of diverse probiotic bacteria grow from the ‘friendly’ lactobacillus bacteria found on the leaves.
Look for raw, unpasteurised products that need to be kept in the fridge as they are likely to have the highest probiotic content. Some sauerkrauts can be pasteurised to give them a longer shelf life, but this destroys most of the good bacteria.
Sauerkraut can be high in salt, so if you have high blood pressure compare labels and choose the lowest-salt option you can find.
The fibre can cause bloating if you’re not used to eating it, so start with just a teaspoon a day and build up to a maximum of two-and-a-half teaspoons a day.
Tip: Add a spoonful of sauerkraut to sandwiches and burgers for a delicious, crunchy health punch.
Pama Classic Farm Style Sauerkraut, 500g, £7.99, pama-raw-food.com
Loving Foods Caraway and Juniper Berry Sauerkraut, 500g, £6.95, lovingfoods.co.uk
Raw Sauerkraut Classic, 410g, £4.39, ocado.com
Try: Asda Extra Special Camembert De Pays, 250g, £2.20, asda.com; Sainsbury’s Taste The Difference Roquefort Cheese, 100g, £2, sainsburys.co.uk; Stichelton Blue Cheese, 250g, £8.95, thecourtyarddairy.co.uk
Expert comment: Fermentation is used to make most types of cheese, but the majority are also pasteurised, which kills most of the beneficial bacteria.
Although not as good a source of probiotics as sauerkraut and kefir, soft, unpasteurised cheeses, which are easy to find in larger supermarkets and delis, are more likely to retain probiotics, which can help with gas and diarrhoea.
Genuine Brie de Meaux, Comte, Camembert and Roquefort are made with unpasteurised milk — just look for the word unpasteurised or ‘raw milk’ on the label.
Cheese is an excellent source of bone-building calcium but can be high in saturated fat and salt, so watch your portion sizes.
Tip: Eat with a source of prebiotic fibre, such as oat cakes, which can help to ‘feed’ good gut bacteria.
Asda Extra Special Camembert De Pays, 250g, £2.20 (left) and Stichelton Blue Cheese, 250g, £8.95 (right)
Sainsbury’s Taste The Difference Roquefort Cheese, 100g, £2, sainsburys.co.uk
Apple cider vinegar
Try: Willy’s Organic Live Apple Cider Vinegar (with live mother), 500ml, £6.95, waitrose.com; Aspall Raw Organic Apple Cyder Vinegar, 500ml, £2.50, tesco.com; Bragg Raw, Unfiltered Apple Cider Vinegar, 473ml, £6.99, boots.com
Expert comment: Fermenting the juice from crushed apples with yeast and bacteria produces acetic acid (vinegar) and ‘the mother’, a stringy-looking culture which can be used to create more vinegar.
Most apple cider vinegars are filtered to remove ‘the mother’, but this can provide more probiotic and prebiotic content, so opt for ‘live’, unpasteurised, unfiltered vinegar.
Several studies have shown that a teaspoon or two of apple cider vinegar after a meal can significantly lower post-meal blood sugar levels — possibly because the acetic acid affects the way starch is digested.
For this reason, people with diabetes and those on potassium-lowering medication should get advice before taking apple cider vinegar.
The acid in neat vinegar may harm tooth enamel over time, so dilute it in water to drink.
Tip: For a salad dressing, blend one part live apple cider vinegar with three parts olive oil, and season.
Willy’s Organic Live Apple Cider Vinegar (with live mother), 500ml, £6.95, waitrose.com
Aspall Raw Organic Apple Cyder Vinegar, 500ml, £2.50, tesco.com
Bragg Raw, Unfiltered Apple Cider Vinegar, 473ml, £6.99, boots.com
Try: The Gutsy Captain Zero Kombucha Passionfruit, 400ml, £2.25, hollandandbarrett.com; Remedy Apple Crisp Kombucha, 24 x 250ml, tesco.com; No1 Living Raspberry Sugar Free Kombucha, 4 x 250ml, £1.99, sainsburys.co.uk
Expert comment: Kombucha is made by adding bacteria and yeast to sugar-sweetened black or green tea and leaving it to ferment for several days. The yeast consumes the sugar, producing probiotic bacteria, ethanol (an alcohol) and ‘fizzy’ carbon dioxide.
The bacteria consume most of the ethanol, turning it into the acetic acid that makes the drink sour, and leaving the drink with a small alcohol content (0.5 per cent, the same as in an overripe banana.)
The fermentation process produces useful amounts of some vitamins, including vitamins B and C, important for building and maintaining healthy cells.
You can buy ready-made bottled kombucha, but the quality of live probiotic bacteria can vary. Look for a low-sugar product, as some kombucha can be quite sugary (3-4 teaspoons per serving).
And choose one made with green tea, which is rich in antioxidants. The combination of caffeine from the green tea and small alcohol content mean children and women who are pregnant or breastfeeding should avoid kombucha.
Tip: Try a glass of kombucha as a refreshing alternative to wine.
The Gutsy Captain Zero Kombucha Passionfruit, 400ml, £2.25, hollandandbarrett.com
Remedy Apple Crisp Kombucha, 24 x 250ml, tesco.com
No1 Living Raspberry Sugar Free Kombucha, 4 x 250ml, £1.99, sainsburys.co.uk
Expert comment: Kefir is a tart, slightly fizzy drink, made by fermenting milk with kefir ‘grains’ that add bacteria, yeasts and enzymes.
It contains a variety of probiotics (three times as many strains as yoghurt), including several types of lactobacillus bacteria that can help the body break down foods, absorb nutrients and fight infection. The yeasts that give it fizz can contribute to a healthy gut, too.
If you have a sensitive gut, kefir can be a good fermented option as it doesn’t contain large amounts of fibre, so won’t cause bloating. Look for unsweetened options.
TIP: Use 100ml kefir with fruit to make a smoothie or pour over cereal instead of standard milk.
Milko Kefir Naturalny Natural Kefir, 1 litre, £1.50, morrisons.com
Arla Organic Kefir Natural, 1 litre, £2.50, waitrose.com
The Collective Natural Kefir, 500ml, £1.75, sainsburys.co.uk
Expert comment: Miso is a protein-rich paste made by fermenting soybeans and a grain (often rice or barley) with aspergillus oryzae, a probiotic fungus. Miso is a good source of essential minerals — including copper, for red blood cell manufacture. It is also rich in energy-boosting B vitamins, vitamin E, for skin health, and vitamin K, for bone and heart health.
Miso is high in salt, however (a teaspoon contains almost a tenth of your daily limit), so I wouldn’t recommend having more than a teaspoon or two a day.
Tip: Look for unpasteurised, ‘live’ miso that needs to be kept in the fridge, as it will contain the highest levels of gut-friendly probiotics (and prebiotics, from the soy beans and grains, to feed them). Stir it into cooked dishes at the last moment to preserve the active bacteria.
Clearspring Organic Japanese Hatcho Miso, 300g, £5.59, clearspring.co.uk
Na’Vi Organics Mi-So Original, 500g, £13.95, naviorganics.uk
Miso Tasty White Miso Paste, 200g, £3.99, waitrose.com
Try: M&S 10% Greek Style Live Yogurt, 500g, £1; Rachel’s Organic Set Greek Style Natural Yogurt, 450g, £1.30, sainsburys.com; Fage Total 5%, 500g, £2.75, asda.com
Expert comment: All yoghurts are made by fermenting milk with live cultures. However, most are then pasteurised, which kills off the original gut-friendly probiotics used to make them.
For really useful probiotic benefits from yoghurt, look for products that claim they have added ‘live cultures’ such as L. Acidophilus and Bifidus on their labelling.
Avoid flavoured and low-fat yoghurts, which can be heavily sweetened and may contain thickeners and flavourings. Opt for full-fat Greek yoghurt, which is both filling and rich in muscle-building protein. A 100g serving provides 9g of protein (the equivalent of two small eggs), as well as 17 per cent of your daily calcium.
TIP: Eat yoghurt with fruit at breakfast, or mix with fresh herbs for a tangy dip.
M&S 10% Greek Style Live Yogurt, 500g, £1
Rachel’s Organic Set Greek Style Natural Yogurt, 450g, £1.30, sainsburys.com
Fage Total 5%, 500g, £2.75, asda.com
Expert comment: An occasional glass of red wine or twice-fermented beer may be good for your microbiota. Despite being fermented, most beers contain very few probiotics. The acids that leach from the hops during the brewing process tend to kill off any live cultures that are formed.
Exceptions include Belgian ‘strong beers’, such as Hoegaarden, Westmalle Tripel and Echt Kriekenbier. These are rich in probiotic microbes, bacteria and yeast, according to a recent study by immunologist Professor Eric Claassen of Amsterdam University. It’s because they’re fermented twice — once in the brewery, and then in the bottle (by adding a different type of yeast).
Red wine — another fermented drink — also seems to have beneficial effects on gut bacteria.
A 2019 study at King’s College London found that one glass a week significantly increases gut bacteria diversity, perhaps due to the fermentation and polyphenols — naturally occurring plant compounds found in red wine.
Tip: Twice-fermented beer or red wine is good for your beneficial gut bacteria.
Marston’s Pedigree Amber Ale, 8 x 500ml, £12.50, marstonsbrewery.co.uk
Hoegaarden Original White Ale, 750ml, £3, ocado.com
Moor Resonance Live Beer 12 x 440ml, £34, moorbeer.co.uk