- A two-day, calorie-reduced oat-based diet produced a marked reduction in LDL cholesterol in people with metabolic syndrome
- Benefits appeared linked to changes in the gut microbiome and microbial metabolites formed from oats
- Effects on cholesterol were still seen weeks later, although smaller daily oat intake without calorie restriction had weaker results
Oats have long been linked with metabolic health, but a trial from the University of Bonn suggests that an intensive, short-term oat-based approach may have a stronger effect than many people would expect.
The study focused on people with metabolic syndrome – a cluster of risk factors that often travel together, including excess body weight, raised blood pressure, elevated blood glucose and abnormal blood lipids.
Even without a diagnosis of diabetes, metabolic syndrome increases the likelihood of developing type 2 diabetes and cardiovascular disease.
Participants followed a calorie-reduced diet for two days that consisted almost entirely of oatmeal.
They ate three oat-based meals per day, using oats boiled in water, with only small additions of fruit or vegetables.
The target amount was 300 grams of oats per day and total calorie intake was roughly half their usual level.
A control group also followed a calorie-reduced diet, but without oats.
Both groups improved – reducing calories tends to do that.
However, the oat-based group saw a more pronounced change, particularly in LDL cholesterol, often described as harmful cholesterol because higher levels are linked with plaque build-up in blood vessels.
In the oat group, LDL fell by around 10 per cent. Participants also lost weight on average and saw a small reduction in blood pressure.
The team then looked for an explanation beyond simple calorie reduction.
Their findings point towards the gut microbiome.
Oat intake increased the abundance of certain gut bacteria, and these microbes produced phenolic compounds when breaking down components of oats.
One of these compounds, linked in other research to cholesterol metabolism, rose in the body.
The researchers also observed microbial processing of the amino acid histidine, which can otherwise be converted into molecules suspected of promoting insulin resistance.
Importantly, the cholesterol benefits from the two-day intensive intervention appeared to persist weeks later.
That raises the possibility that short, periodic oat-based phases could be a practical strategy for some people.
The study also compared this approach with a separate six-week intervention where people ate a more modest amount of oats each day – 80 grams – without major dietary restriction.
The effects there were smaller, suggesting dose and context matter.
In this trial, oats had the strongest impact when used in high amounts alongside calorie reduction.
The next question is the one that matters most for real life: whether repeating a short intensive oat phase at regular intervals can produce sustained, preventative benefits over the long term.