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An apple contains 100MILLION bacteria, scientists say

Apples contain 100MILLION bacteria including healthy probiotics – but 90% of them are found in the core

  • Researchers in Austria compared organically grown apples to shop-bought ones
  • They suggest 10million bacteria are in the apple’s flesh, with most in the core 
  • Organic apples have a wider variety of bacteria than intensely farmed ones

A single apple may contain as many as 100million bacteria, scientists say.

The crunchy fruits are a popular staple and have health benefits which can keep you out of the doctor’s office – or so the saying goes.

And the reason for their healthiness may lie in the diversity of bacteria they bring into the gut.

Bacteria in the stomach and intestines, known as the microbiome, vary between people and have been closely linked to overall health and various illnesses.

Having a wide range of bacteria is considered to be a sign of good health and the 10million in the flesh of an apple could be a useful boost, with the possibility of 10 times as many as that for people who eat the core and seeds, too.

Apples may contain up to 100million bacteria in a single fruit, scientists suggest, with about 90 per cent of them in the seeds and the core (stock image)

Researchers from the Graz University of Technology in Austria examined the bacteria in shop-bought apples and fresh organic ones.

They separated the flesh, stem, peel, seeds and the crusty bit at the bottom (the calyx) and analysed the bacteria they found on them.

‘Putting together the averages for each apple component, we estimate a typical 240g apple contains roughly 100million bacteria,’ said Professor Gabriele Berg.

Around 90m of these bacteria are thought to be in the seeds, so people who throw away the core may be eating more like 10m.


Scientists this year said looking at the levels of bacteria someone has in their gut may be able to predict their risk of developing inflammatory bowl disease, diabetes or having a premature labour if they’re pregnant. 

Inflammatory bowel disease  

For a year, Harvard scientists tracked 132 people with conditions such as Crohn’s disease and some healthy people for comparison. They took stool samples every two weeks, and checked how microbes affected the immune system or metabolism.

As the diseases wax and wane, so does microbial activity, researchers reported in the journal Nature. Surprisingly, many times a patient’s gut microbiome changed radically in just a few weeks before a flare-up.

Some of the microbes produce molecules that keep the intestinal lining healthy, likely one reason the disease worsened when those bugs disappeared, Proctor said.

Premature birth

Researchers from Virginia Commonwealth University found a warning sign of premature birth in the vaginal microbiome, which changes over the course of pregnancy.

Tracking nearly 600 pregnancies, the team found that women who delivered preterm, especially African Americans, tended to have lower than normal levels of a type of Lactobacillus bacteria as early as the first trimester. 

Type 2 diabetes

A Stanford University-led research team tracked 106 people for four years, some healthy and some pre-diabetic. Up to 10 per cent of pre-diabetics will develop diabetes each year, but there’s little way to predict who.

The researchers found a list of microbial and inflammatory early warning signs of brewing diabetes.

People who are insulin-resistant showed delayed immune responses to respiratory infections, correlating with tamped-down microbial reactions. 

The study found the variety of different types of bacteria was larger in organic apples, suggesting they’re healthier.

And the organic ones contained higher amounts of specific groups of bacteria known to be healthy for humans, such as the probiotic Lactobacilli.

Professor Berg said: ‘Freshly harvested, organically managed apples harbor a significantly more diverse, more even and distinct bacterial community, compared to conventional ones.

‘This variety and balance would be expected to limit overgrowth of any one species.

‘And previous studies have reported a negative correlation between human pathogen abundance and microbiome diversity of fresh produce.’

The microbiome of gut bacteria has been found in the past to be linked to the health of the vital organs, including the heart and brain.

Some nutrients from red meat, for example, can be converted in the gut to a chemical called trimethylamine N-oxide which, in large amounts, may contribute to heart disease or stroke by encouraging blockages in the arteries.

And serotonin, a chemical known for controlling mood and sleep, is almost all produced in the gut and a lack of resources to make it could affect the brain.

Low levels of serotonin are believed to be linked to a lower mood or anxiety, difficulty sleeping and memory problems.

Eating a wide range of foods including a lot of fruit and vegetables is the best way to increase the diversity of bacteria, fungi and other microbes in the gut.

Professer Berg said her team’s work added to past findings that there are many more fungi in organically grown apples than in intensely farmed ones.

One of her colleagues, Birgit Wasserman, added: ‘The microbiome and antioxidant profiles of fresh produce may one day become standard nutritional information, displayed alongside macronutrients, vitamins and minerals to guide consumers.

‘Here, a key step will be to confirm to what extent diversity in the food microbiome translates to gut microbial diversity and improved health outcomes.’

Their research was published in the journal Frontiers in Microbiology.


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