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Can 'fizzy' milk really keep your gut fighting fit?

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The sharp tang of kefir may not be to everyone’s taste, but the fermented milk drink has a growing legion of fans, as it flies off the shelves. 

Tesco, for example, reported a 400 per cent increase in sales in the 18 months to February this year. Kefir, available in dairy and non-dairy versions, is high in the ‘good’ bacteria thought to contribute to improved gut health, reducing the risk of disease and supporting weight loss. 

It is a source of nutrients such as vitamins A, B, K and calcium. Adding good bacteria to the diet helps rebalance the microbiome — the community of bugs in our guts. Plain yoghurt is also a fermented product that naturally contains the bacteria Lactobacillus bulgaricus and Streptococcus thermophilus. 

Meanwhile, products sold as ‘probiotic’ yoghurt will usually have more beneficial bacteria added, such as Lactobacillus casei and types of Bifidobacteria. But kefir usually has a larger range of potentially health-giving bacteria — with 12 or more varieties rather than the typical one or two added to probiotic yoghurts. 

Another difference — thought to be responsible for kefir’s superior health benefits — is that it often also contains beneficial yeast (which is why it can be fizzy). ‘It’s this micro-organism diversity that can make kefir superior to more simple fermented foods such as yoghurt,’ says Professor Paul Cotter, a microbiologist at Teagasc Food Research Centre in Cork, who studies the health benefits of fermented foods. 

The sharp tang of kefir may not be to everyone's taste, but the fermented milk drink has a growing legion of fans, as it flies off the shelves

The sharp tang of kefir may not be to everyone’s taste, but the fermented milk drink has a growing legion of fans, as it flies off the shelves

A review last year by Professor Cotter, published in the journal Nutrients, suggested that consuming kefir or kefir micro-organisms is linked to reduced inflammation, improved cholesterol levels and healthy blood pressure. 

Meanwhile, a 2015 study in the journal PLoS One suggests peptides (broken down protein) that form during the making of kefir can reduce the clotting that contributes to heart attacks, and improves the absorption of calcium. Kefir is produced when kefir ‘grains’ are added to milk to initiate fermentation. 

They look like gooey mini cauliflower florets and contain different bacteria and yeast. Once the milk is fermented, the grains are removed. 

The liquid left is the kefir. It’s this process that helps distinguish the better products. Many don’t use this technique, as it’s difficult to mass produce, says Professor Cotter. ‘One popular way to scale up involves using a small amount of the kefir produced to start fermenting a new batch. 

Kefir, available in dairy and non-dairy versions, is high in the 'good' bacteria thought to contribute to improved gut health, reducing the risk of disease and supporting weight loss

Kefir, available in dairy and non-dairy versions, is high in the ‘good’ bacteria thought to contribute to improved gut health, reducing the risk of disease and supporting weight loss

‘It’s still quite good, as the consumer is drinking real kefir microbes.’ Other products are made by fermenting milk with a few ‘beneficial’ bacteria extracted from kefir grains. 

‘In this case, they would be very similar to drinking probiotic yoghurt,’ adds Professor Cotter. You can identify a good kefir product as its label will say it’s made with actual kefir grains. It will also list some of the ‘good’ bacteria, but look out for yeasts, in particular Kluyveromyces marxianus or Saccharomyces. It is easy to make kefir (see box), but beware if you buy one. ‘

Some kefirs contain lots of added sugar, flavouring and fruit purees, which as well as impacting calories and oral health, may reduce the wider health benefits of the beneficial bacteria and yeasts,’ says Helen Bond, a dietitian in Derbyshire. 

Here, our experts analyse some kefir products and we rate them. 

ARLA ORGANIC 

1l, £2.50, waitrose.com Per 100ml: Calories, 59; saturated fat, 1.9g; protein, 3.3g; sugar, 3.9g; salt; 0.1g 

CLAIM: Kefir made from organic milk using real kefir grains.

EXPERT VERDICT: ‘It’s notable that real kefir grains are used,’ says Professor Cotter. ‘Only some are named so we won’t know what yeasts and bacteria are in here and the amounts, but those that are identified are useful.’ ‘One of the yeasts it contains is Kluyveromyces marxianus, which has been shown in animal studies to bolster immune function,’ adds Helen Bond. ‘As this is just cultured milk with no added sugar, it’s one of the healthiest options here, and will provide a third of your daily bone-building calcium in a 200ml glass.’ 

8/10 

YEO VALLEY 

Strawberry kefir, 350g, £1.49, most supermarkets. Per 100ml: Calories, 79; saturated fat, 1.3g; protein, 4.2g; sugar, 9.5g; salt, 0.11g 

CLAIM: Has 14 live cultures. With strawberries and sugar. EXPERT VERDICT: ‘It is difficult to judge this as a kefir because it isn’t made the traditional way,’ says Professor Cotter. ‘Instead, it is made by fermenting milk with bacteria — albeit 14 potentially beneficial strains. However, it is missing some of those found in kefir grains.’ Helen Bond adds: ‘There are two teaspoons of added sugar in a half pot serving, which is quite a lot.’ 

4/10 

NOURISH 

Eight 247ml bottles, £15.92, nourishkefir. co.uk Per 100ml: Calories, 59; saturated fat, 1.9g; protein, 3.2g; sugar, 3.8g; salt, trace 

CLAIM: Made with kefir grains, this ‘contains ‘billions of live active cultures’. 

EXPERT VERDICT: ‘The slight fizz this product has is consistent with a genuine kefir that contains beneficial yeasts,’ says Professor Cotter. This was used in a small study by the BBC’s Trust Me, I’m A Doctor, adds Helen Bond, with volunteers who drank 250ml a day showing a rise in beneficial bacteria called Lactobacillales, which are known to help with gut health. 

8/10  

BAKOMA

Kefir yoghurt drink, 390g, 80p, most supermarkets. Per 100ml: Calories, 60; saturated fat, 1.8g; protein, 3.4g; sugar, 4.7g; salt, 0.1g 

CLAIM: Made with milk and starter culture, this is said to help regulate the gastrointestinal tract. 

EXPERT VERDICT: ‘This doesn’t seem very kefir-like,’ says Professor Cotter. ‘It is more like a yoghurt to which two types of bacteria have been added, neither of which is found at high levels in kefirs.’ ‘It’s still a decent source of calcium, and probably has some live beneficial bacteria, but not at the same level as a genuine kefir,’ says Helen Bond. 

3/10 

CHUCKLING GOAT 

Four 900ml bottles, £39.95, chucklinggoat.co.uk Per 100ml: Calories, 50; saturated fat, 2.3g; protein, 2.4g; sugar, 1.1g; salt, trace 

CLAIM: Described as ‘powerful’ kefir with 35 active probiotic strains, the maker says it is ‘proven to actively support your digestion, skin and immune system’. 

EXPERT VERDICT: Professor Cotter says: ‘A list of 35 species is listed, but many are not found in kefir. I’d guess they are microbes from the goat’s gut carried over in small quantities. ‘I wouldn’t recommend this for an immune-suppressed person who already has an unbalanced gut microbiota.’ ‘There aren’t any significant nutritional differences between cow’s and goat’s dairy,’ adds Helen Bond. ‘If you are allergic to one you’re likely to be allergic to the other.’ 

2/10 

KING OF KEFIR 

Cucumber, mint and thyme soft drink, three 330ml bottles, £9.99. amazon.co.uk Per 100ml Calories: 3; saturated fat, 0; protein, 0; sugar, trace; salt, 0 

CLAIM: ‘Teeming with gut-friendly bacteria’ and ‘organic acids, lactobacillus, vitamins, enzymes and antioxidants’. 

EXPERT VERDICT: ‘Water kefirs are made with different grains and contain different bacteria and yeasts,’ says Professor Cotter. ‘There’s less research done on them, so while it is gut-friendly, it’s impossible to talk about specific benefits.’ ‘It’s waistline-friendly and low in sugar,’ adds Helen Bond. 

5/10 

HOW TO MAKE IT YOURSELF  

All you need is milk and kefir grains, which are available online or in health food shops (Live Kefir Company, £11 for 10g, amazon.co.uk). 

Add a tablespoon of the grains to around four cups of milk in a glass jar, cover with a cloth and secure it with an elastic band. Leave it at room temperature until the milk is slightly thickened and still smells pleasant — this will take approximately 24 hours. 

The warmer the room, the faster the kefir will ferment. You can keep it covered and keep tasting it until it’s just as thick and sour as you like it. When it’s ready, sieve out the kefir grains using a plastic sieve (metal can affect the viability of thecultures) and save them in a small container of fresh milk in the fridge, or freeze until you’re ready to make another batch. 

The kefir can be stored, with a lid on the jar, for up to one week in the fridge. Make a dairy-free version with water kefir grains, which you can soak in water or coconut water, plus a little sugar to get the fermentation going.

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