Eating a diet rich in live bacteria and fermented foods could slash ‘bad’ cholesterol, study finds

Eating fermented foods containing live microbes – from kombucha to kefir – could help slash ‘bad’ cholesterol and support heart health, new research suggests. 

Fermented foods high in probiotics have long been linked to improved gut diversity which over time can relieve digestive issues, support brain health and even ward off cancer. 

But now Australian researchers say they could help boost levels of ‘good’, or HDL cholesterol, aid weight loss and support blood sugar control, lowering the risk of chronic disease. 

Experts at The University of Newcastle found that people who more frequently ate foods containing live microbes saw their levels of beneficial HDL cholesterol increase, whilst blood sugar levels decreased, reducing the risk of type 2 diabetes.

Cholesterol is a type of fat, or lipid, found in all cells in the body.

Good cholesterol, or high-density lipoproteins (HDL), carry excess fat in the bloodstream back to the liver where it can be filtered out of the body.

When HDL levels fall too low, levels of so-called bad cholesterol can build up unchecked. Over time, this restricts blood flow, increasing the risk of heart attack, stroke and even dementia.

Probiotics are foods that have had living microorganisms added to them, such as kimchi, yoghurt and sourdough, which restore the natural balance of bacteria in the gut when it has been disrupted. 

A lot of foods containing probiotics, like kimchi, are also high in fibre, which has been shown to slash levels of bad cholesterol by as much as 35 per cent in a month. 

This is because soluble fibre turns into a gel-like substance in the gut, which binds to cholesterol and stops it being absorbed into the bloodstream 

But the new findings suggests eating more live cultures could increase levels of good cholesterol – independent of LDL cholesterol levels, whilst also lowering blood glucose levels. 

For the study, researchers developed a database of 200 common Australian food and drinks – and estimated how many live microbes each food contained. 

Most foods including vegetables, cereals and meat fell into the low category, 21 food items were classified as moderately high in live microbes and just two foods fell into the high category: yoghurt and sour cream. 

A total of 58 healthy adults who were not trying to conceive, pregnant, on weight loss medication, were included in the final study and tracked for three to six months.

The researchers estimated how much of each food group participants ate each day, in grams, and how many calories those foods provided. 

Self-report questionnaires featured options ranging from ‘never’ up to ‘7 times a day.’ Standard portion sizes for each foot item were derived from the most recent National Nutrition Survey data. 

Overall, participants predominately ate foods in the low live-microbe group, averaging around 1.9kg a day and contributing the most calories. 

Men were found to eat significantly more low live-microbe foods than women, whilst non-smokers are more fermented foods.  

People who reported eating more foods containing live microbes tended to have lower body weight and BMI, smaller waist circumference, better blood sugar control and higher levels of ‘good’ cholesterol. 

The researchers hypothesised this could be because the fermentation process triggers the production of short chain fatty acids in the colon, which have been shown to help regulate metabolism, cardiovascular and inflammatory biomarkers. 

Publishing their findings in the journal Nutrition Research, the team said: ‘These markers are well established as cardiometabolic risk factors because of their relationship with obesity.’

Low HDL cholesterol has long been shown to increase the risk of a major heart event by two to three per cent.  

‘Therefore, the consumption of foods with estimated medium and high live microbe content may have a protective role in cardiovascular disease risk management,’ they added.

However, they added further studies are needed to determine causality. 

The researchers also did not take into account potential confounding variables such as physical activity and alcohol intake. 

 They concluded: ‘Evaluating both gut microbiota composition and the production of beneficial metabolites, such as shirt chain fatty acids, could provide valuable insights into the underlying mechanisms.’ 

Experts have previously highlighted evidence behind the link between fermented foods and increased levels of good cholesterol, with a 2024 study findings that supplementing probiotics in people with type 12 diabetes significantly increased HDL levels. 

It comes as a separate study published last month found that eating nothing but porridge for just two days could help slash bad cholesterol and protect the heart. 

Experts at the University of Bonn found that people at high risk of heart disease saw their levels of harmful LDL cholesterol, linked to higher risk of heart attack and stroke, drop by 10 per cent after following a calorie-restricted diet made up almost entirely of porridge for two days. 

The effects remained stable six weeks after the dietary intervention.

Cardiovascular disease remains the world’s biggest killer, responsible for around 30 per cent of deaths and long-term disability worldwide. 

More than half of UK adults are now believed to be living with high levels of harmful cholesterol, which can increase the risk of heart disease, heart attack an stroke.