Your Gut and Your Cholesterol
If you've been told your cholesterol is high, the advice you got was probably short: cut down on fatty food, and maybe start a statin. Both have their place in some cases, but there's a part of the story that rarely gets mentioned in a ten-minute appointment, and it's happening in your gut.
The gut microbiome (the bacteria that live inside the digestive system) has an undeniable effect on our cholesterol levels. Some bacteria quietly break cholesterol down before our body can absorb it. Others change the way our liver recycles bile, the digestive juice it makes from cholesterol. And when the lining of the gut gets a little "leaky", fragments of bacteria can slip into the bloodstream and cause the liver to make more cholesterol than it needs.
Your gut is where cholesterol leaves the body
Let's look at the connection between your gut and your cholesterol. Unlike fat, cholesterol can’t be burned for energy. Your body clears it mainly through the gut, and the bacteria living there help decide how much actually leaves.
It starts with bile. Your liver uses cholesterol to make bile acids, which it sends into your gut to help you digest fat. Around 95% of that bile gets soaked back up near the end of the small intestine and sent back to the liver to be used again. Only about 5% actually leaves in your stool.
This is where certain friendly bacteria come in. They carry an enzyme called bile salt hydrolase, or BSH, which snips the bile acids into a form that's harder to reabsorb, so more of them leave the body. Your liver then has to replace them, and to do that it pulls cholesterol out of your blood. Snipped bile acids also make it harder for you to absorb cholesterol from food.
A few gut bacteria go even further and eat cholesterol directly, or turn it into a substance called coprostanol that your body can't absorb, so it simply passes out.
Put simply: The more of these helpful bacteria you have, the more cholesterol your body can clear, rather than recycling it back into your blood.
When the gut leaks: LPS and your liver
Some of the bacteria in your gut wear a protective outer coat made partly of something called LPS (lipopolysaccharide). While it stays inside a healthy gut, LPS does no harm. The trouble starts when the gut lining weakens, a condition that is called "leaky gut". Then small amounts of LPS pass into the bloodstream.
It isn't a dramatic infection. It's more like a low, constant drip, and scientists have a name for it: metabolic endotoxaemia. It tends to go hand in hand with a diet high in fat and low in fibre, with weight gain, with insulin resistance and with a simmering, low-grade inflammation.
Your liver doesn't like this drip, and it reacts in ways that push cholesterol up. In mice, LPS raised blood cholesterol by 41% and made the liver produce more than eight times as much cholesterol as usual. It did this by revving up an enzyme called HMG-CoA reductase, the liver's main cholesterol-making machine (source). This is the enzyme statins are designed to block.
LPS also slows down the liver's ability to turn cholesterol into bile, which, as we've seen, is the body's main exit route. And it gets in the way of HDL, your "good" cholesterol, whose job is to carry cholesterol away from your artery walls and back to the liver for disposal. When researchers gave people and mice small doses of LPS, that clean-up job slowed down (source).
Although most of this comes from animal studies and short experiments in people, the pathway is clear and makes sense. LPS effect on cholesterol is an important piece of the puzzle, sitting alongside your genes, diet, weight, thyroid and blood sugar.
Meet the bacteria on your side
The most exciting discovery so far is a group of bacteria called Oscillibacter. They're surprisingly common, and they eat cholesterol.
In 2024, researchers studied the gut bacteria of 1,429 people taking part in the Framingham Heart Study, one of the longest-running heart studies in the world. People with more Oscillibacter had lower cholesterol, both in their blood and in their stool (source). When the team grew these bacteria in the lab and fed them cholesterol, the bacteria took it in and broke it down into harmless pieces (source). The same people also tended to have lower triglycerides and blood sugar, and higher HDL.
The same study picked out a second helper, Eubacterium coprostanoligenes. It turns cholesterol into coprostanol, which your body can't absorb, and it seems to work as a team with Oscillibacter (source).
Then there are the bile snippers. One particular strain, Lactobacillus reuteri NCIMB 30242, was chosen precisely because it's very good at snipping bile. In a nine-week trial, people taking it saw their LDL drop by 11.6% compared with those on a dummy capsule, and their CRP, a marker of inflammation, came down too (source). Some strains of Lactobacillus plantarum have shown similar promise in smaller studies, though the results are more mixed.
Two more are worth knowing. Akkermansia muciniphila lives in and helps maintain the protective mucus layer of your gut, which may help keep LPS where it belongs, although most of the evidence is from animals so far. And a family called Christensenellaceae turns up more often in lean people with healthier blood fats, but that's a link rather than proof.
One word of caution: it really does come down to the exact strain. Not every Lactobacillus lowers cholesterol, and plenty of general probiotic products have shown little or no effect in trials (source). Oscillibacter and E. coprostanoligenes aren't available as supplements yet, so for now the way to grow them is through what you eat.
So where do statins fit?
Let's talk about statins- the medications that are ususally prescribed to treat high cholesterol levels. Statins work by blocking HMG-CoA reductase, the liver's cholesterol-making enzyme, and they reliably bring LDL down. Large trials show that for every 1,000 people who take one for five years, around 25 heart attacks, strokes and similar events are prevented. For people who've already had one, that figure is about 50 (source).
But here's the thing. A statin turns down the cholesterol factory without asking why the factory was working overtime. It doesn't heal a leaky gut, it doesn't reduce LPS, it doesn't feed your cholesterol-eating bacteria and it doesn't improve the way you clear bile. If your gut is part of the reason your cholesterol is high, that part stays exactly as it was. That's why I see gut work and medical treatment as partners, not rivals.
Statins also have side effects, and you deserve a straight account of them.
The one people talk about most is muscle aches. A large 2022 analysis of around 155,000 people found that statins do cause a small amount of extra muscle pain, mostly mild and mostly in the first year. Stronger doses carried more risk, and for some people it lingered. What surprised many people, though, is that more than 9 out of 10 muscle complaints in people taking statins weren't actually caused by the statin (source). Serious muscle damage is rare, roughly 5 cases for every 10,000 people treated for five years on a standard dose (source).
Over the longer term, statins slightly raise the chance of developing type 2 diabetes, mostly in people who were already heading that way. They also lower your levels of coenzyme Q10, a nutrient your cells use to make energy, because it's made by the same pathway statins block.
Please don't stop a statin on your own, though. If you've had a heart attack or stroke, or you have very high cholesterol that runs in your family. And if you work on your gut alongside your medication, your doctor may, over time, be able to review whether you still need the same dose.
Looking after the bacteria that look after you
The good news is that the most powerful thing you can do is also the simplest: eat plenty of different plant foods, every day. Your cholesterol-friendly bacteria live on fibre, and fibre grabs hold of bile on its own too.
Start with soluble fibre. Oats, barley, beans, lentils, chickpeas, apples, pears, ground flaxseed and psyllium husk all contain the kind of fibre that turns into a soft gel in your gut. That gel traps bile so it leaves your body, and your liver uses up more cholesterol making new bile. Oats and barley are especially well studied: about 3 g a day of their fibre, roughly a bowl of porridge and a slice of oat or barley bread, is officially recognised in the UK as helping to lower cholesterol.
Go for variety. Try to eat around 30 different plants a week. That sounds like a lot, but vegetables, fruit, whole grains, nuts, seeds, herbs and spices all count. Every different plant feeds a slightly different set of bacteria, and a more varied gut is linked to healthier cholesterol.
Feed the gut lining. Onions, garlic, leeks, asparagus, Jerusalem artichokes, chicory and slightly green bananas contain special fibres that bacteria turn into butyrate. Butyrate is the main food for the cells lining your gut, and it helps keep that lining tight, so less LPS gets through.
Add colour. Berries, pomegranate, green tea, dark chocolate (70% or more), olive oil, red onions and fresh herbs are rich in polyphenols. These plant compounds feed protective bacteria like Akkermansia and help calm inflammation in the gut.
Bring in fermented foods. Live yoghurt, kefir, sauerkraut, kimchi and miso add friendly bacteria and have been shown to make the gut more diverse.
Choose probiotics carefully. If you want to try one for cholesterol, look for a product containing the actual strain that was tested, such as L. reuteri NCIMB 30242, rather than a general mix.
Ease off the things that make the gut leak. Lots of saturated fat, sugar, ultra-processed food and alcohol are all linked to more LPS getting into the blood. You don't need to be perfect. Just tip the balance towards the foods above.
And don't forget the basics. Moving every day, sleeping well, finding ways to manage stress and not smoking all help your gut lining and your cholesterol.
Give any changes at least 8 to 12 weeks before you get your cholesterol rechecked. If you'd like a clearer picture of what's going on inside, a functional stool test can show how diverse your gut bacteria are and whether there are signs of inflammation or a leaky gut, so your plan can be built around you.
The bigger picture
Your cholesterol number isn't just about what's on your plate or what you inherited. It's also shaped by the living community in your gut: bacteria that eat cholesterol, bacteria that help you clear bile, and a gut lining that keeps LPS out of your blood.
Statins are a proven tool, and for some people they're the right choice. But they act on the liver, not the gut. Looking after your microbiome is a gentle, low-risk way to work on what may be driving the problem underneath.
This article is for general information and isn't a substitute for personal medical advice. Please don't start, stop or change any prescribed medication without talking to your doctor first.
