Fermented foods

A healthy gut teems with an ecosystem of thousands of species of microscopic bugs (or “microbes”). This system helps us digest our food and produce vitamins our bodies aren’t capable of making. The balance of the species fluctuates through your life, as you age and as your diet and lifestyle change.

Scientists are discovering these bugs have an influence beyond digestion – microbes have been linked to obesity, autoimmune diseases such as arthritis and diabetes, and mental health conditions including anxiety and depression.

While scientists take their time answering pesky questions – for example, do changes in our gut cause obesity or vice versa? – food manufacturers have few qualms in leaping ahead.

The manufacturer of the Mad Millie brand claims you can “craft your way to good health” with its kefir, sauerkraut, tofu and yoghurt-making kits. “Fermented foods are a great way to improve your gut health and get the best out of your food,” the company says.

Kombucha King had to tone down its marketing after MPI “warned of legal action if we didn’t remove all health claims”.

A bug’s life

Fermented foods contain living microbes at some point in the production process. These microbes may create carbon dioxide and alcohol (yeast in bread and beer) or lactic acid (bacteria in aged cheese, sauerkraut and yoghurt).

Some manufacturers destroy (or pasteurise) the microbes before they sell their product to you, while other products retain the living bugs.

While probiotics may live in your sauerkraut, they may be dead by the time they reach your gut.

Theoretically, eating a food with living “probiotic” bugs influences their counterparts in your gut for the better. The reality is we still don’t know the effect each and every bug may have. There are also other issues to consider.

Our stomachs are deliberately inhospitable to bugs. Stomach acids can’t tell a “good” microbe from a bad one, such as salmonella or giardia. And while probiotics may live in your sauerkraut, they may be dead by the time they reach your gut.

In theory, the more bacteria you ingest, the higher the possibility one will make it through alive. You could also surround the bacteria with a “neutralising” foodstuff, such as milk or yoghurt, to boost their chances of survival (note, these types of foods also trigger your stomach to produce more acid).

Are there any benefits?

Major reviews of scientific studies have found probiotic supplements had no notable, long-term effect on the gut bacteria of healthy adults – even probiotics with billions of bacteria in a milky drink.

While scientists have found food microbes with positive impacts on particular health conditions, the effects are likely specific to the bug tested.

University of Otago senior lecturer Dr Kristin Wickens’ research group found that when pregnant women took a strain of Lactobacillus rhamnosus bacteria, HN001, in early pregnancy their risk of developing gestational diabetes dropped.

This benefit isn’t found in all probiotic species, Dr Wickens says. The effect could also change (for better or worse) if the microbes are ingested with other probiotic species.

Manufacturers' claims

What manufacturers are doing is touting the health benefits of “fermented” or “probiotic” products without naming the species or providing scientific evidence. That’s not much use.

Kombuchas such as Lo Bros and Remedy are promoted as “bubbling with living probiotic goodness” or “promot[ing] gut health”. Yet out of 10 ready-to-drink kombucha brands we looked at, only one, Good Buzz, names its living probiotic microbes on the bottle.

Brand Daily Organics lists the species on its website and says it will add the information on bottle labels. Remedy added the info to its website and says its health claims are also based on other ingredients in its drink, including polyphenols.

Brewers Organic Mechanic and Renes told us their primary probiotic species when we asked.

Nutrition By Nature’s kombucha brewing kit says it contains “lactic acid bacteria (lab tested)” and the company shared its lab analysis with us. The company plans to run further tests and says it will add results to its website.

Another brewer, Batchwell, says it intends to analyse its culture and share this with customers.

Kombucha King says it decided not to list its species following a review of its health claims by the Ministry for Primary Industries (MPI).

Amplify, owned by Frucor Suntory, promotes the “good bacteria” in its product, but refused to tell us the species.

In contrast, The Collective’s range of ready-to-drink kefirs and Mad Millie’s kefir- and yoghurt-making kits list microbial species. Because producers of yoghurt, kefir and kombucha use a culture (also known as a starter or SCOBY) when making the product, they’re able to analyse it for the probiotic species it contains – though this can be expensive.

Kombucha makers may also add specific microbes at the end of the brewing process.

Sauerkraut and kimchi makers don’t always use a culture, because fermenting bacteria naturally lives on cabbage – so the process starts automatically once you’ve sliced and diced. The saltiness of the brine also influences what grows. But if you’re after a certain probiotic species, you’ll need to make sure the product uses a culture.

MPI says, under the Food Standards Code, all foods and beverages describing themselves as probiotic must list their microbial species.

What's the evidence?

The US National Institute of Health has evaluated the evidence behind the health effects of species we saw listed on fermented foods:

Bifidobacterium species:

• Possibly effective for: airway infections (children); constipation; diarrhoea (children or caused by travel); irritable bowel syndrome; ulcerative colitis.

Lactobacillus species:

• Likely effective for: diarrhoea (children).
  
• Possibly effective for: airway infections (children); arthritis; constipation; diarrhoea (caused by antibiotics and travel); eczema (children); hayfever; high cholesterol; ulcerative colitis.

Saccharomyces boulardii:

• Likely effective for: diarrhoea (caused by antibiotics). Possibly effective for: acne; diarrhoea (caused by travel).

Fermented foods aren’t a replacement for medication. If you have a condition and are interested in trying fermented foods or probiotics, talk to your GP or health specialist first. If you’re healthy, follow a balanced diet and stick with the fermented foods you enjoy eating.

The best way to improve gut health

As boring as it sounds, the best advice for boosting the health of your gut is to eat a balanced diet.

Your gut ecosystem is influenced by everything you put in your mouth – from the sugar, fat and salt content of your food to the medications you take.

A diet high in processed foods reduces the diversity of species in your gut, but replace this with foods high in fibre and your microbes will thrive.

This gives plant-based fermented foods such as sauerkraut and kimchi an edge (provided they’re low in sodium). Even if none of the active bacteria survives the journey to the gut, the fibre of the cabbage and other veggies will help keep your resident microbes happy and healthy.

This means keeping an eye on the sweet stuff. Kombucha and kefir products can be high in sugar (see our taste test below).

University of Auckland associate professor Justin O’Sullivan, who is studying microbes and obesity, says variety is likely to be key to a thriving ecosystem of bugs in your gut: “Variety in your food, but also in the way you live.”

Diversity may come from introducing a fermented food to your diet, but it won’t be a miracle cure if you otherwise chow down on poor-quality kai.

What makes things more complicated is the role a person’s genes plays on the gut ecosystem. Dr O’Sullivan says a species that thrives in one person may not in another. “It may work for you, it may not.”

Another factor to consider is the placebo effect. Dr O’Sullivan says a placebo can have a “real effect” on your health.

Taste test

Despite the health hype around kefirs and kombuchas, many of the products we bought had spoonfuls of sugar.

Kombucha Wonder Drink Classique had six teaspoons of sugar in a 414ml bottle, and Good Buzz Raspberry and Lemon’s 330ml bottle two teaspoons. That’s better than the 16 teaspoons of sugar in a 600ml bottle of Coke, but more than you’d get in unsweetened tea and coffee.

Good Buzz says the residual sugar ensures its kombucha isn’t too tart or watered down.

The Collective’s Super Kefir13 Mango Tumeric has two more teaspoons of sugar per serve than its unsweetened variety. The World Health Organization recommends an adult eat no more than 12 teaspoons of added sugar per day – and ideally less than six.

Twelve Consumer NZ staff (three with a sweet tooth) blind-taste-tested three kombuchas and two kefirs with varying levels of sugar. With many panellists describing kombucha as vinegary, we weren’t surprised the Lo Bros brand with raw sugar, naturally fermented glucose and stevia in its ingredient list was the preferred choice.

For sweetened vs unsweetened kefirs, the former was the overwhelming favourite.

If you want to drink your probiotics minus the sweet stuff, Be Nourished’s Raw Sauerkraut Juice offers a dose of Lactobacillus plantarum with just 0.01g of sugar per serve.

The beverage isn’t for the faint-hearted – 10 of our taste panellists said they’d never try it again, describing it as “vile” and even “the devil’s mouthwash”.

Products compared

GUIDE TO THE TABLE PRICES from supermarket and gourmet food store survey in March and April 2018. MICROBES NAMED shows if the microbial species, genus or type of bacteria or yeast is available to customers. ^A indicates the company plans to test for species or type of microbe.

By Olivia Wannan
Investigative Writer