Low-carb diets can trigger a dangerous increase in cholesterol for genetically predisposed adults, a study by Stanford University School of Medicine has found.
The research showed that participants on carbohydrate-restricted eating plans who carried a higher genetic risk of elevated blood fats experienced the sharpest spikes in low-density lipoprotein, known as bad LDL cholesterol.
While low-carbohydrate eating plans are widely promoted for weight management and keeping blood sugar levels down to slash the risk of diabetes, scientists warned that high-fat foods can elevate cardiovascular dangers for vulnerable individuals.
Alexa Barad, the lead author of the study, emphasized that dietary advice should account for individual genetic differences rather than applying broad assumptions.
"Diet advice can sometimes be presented as one-size fits all," Barad said. "While some people find a low-carb diet raises their cholesterol, others see no effect."
Genetic risk and low-carbohydrate diets
Researchers at the Stanford University School of Medicine set out to investigate whether genetic profiles could help identify individuals who benefit from eating fewer carbohydrates, as well as those who face a potentially deadly surge in blood cholesterol.
To test the theory, scientists examined data from a clinical trial involving more than 600 adults who followed either a healthy low-carbohydrate diet or a healthy low-fat diet over the course of one year.
Initial findings from the broader trial demonstrated no clear advantage for either eating plan when it came to overall weight loss.
The research team then focused on a subset of 431 participants for whom genetic data was available. They tracked each individual's genetic makeup, saturated fat consumption, and changes in bad LDL cholesterol over a six-month period.
Among participants following a low-carbohydrate plan, those genetically predisposed to higher bad cholesterol were significantly more likely to experience dangerous increases. Scientists attributed the rise to dietary habits, as people on low-carb diets often replace carbohydrate-heavy foods with items high in fat, such as red meat and cheese.
Saturated fats and artery health
The study revealed that participants with the highest genetic risk experienced the largest increases in bad LDL cholesterol when they consumed higher levels of saturated fat.
Typical low-carbohydrate eating plans derive approximately 75 percent of their total daily intake from fat, 20 percent from protein, and just 10 percent from carbohydrates such as potatoes and bread.
While low-carbohydrate diets have previously been credited with boosting high-density lipoprotein, or good HDL cholesterol, which helps clear fatty deposits from blood vessels, the high fat content poses serious risks for genetically susceptible individuals.
High cholesterol causes fatty plaque deposits to accumulate along artery walls. Over time, these deposits narrow the blood vessels and restrict blood flow, significantly increasing the likelihood of a heart attack or stroke.
The Stanford team hopes that their genetic screening method will eventually allow doctors and nutritionists to identify patients who are likely to experience harmful cholesterol changes before prescribing specific dietary regimens.
Dietary guidelines and health risks
Saturated fats are found in many common foods, with the majority coming from animal sources including meat and dairy products, as well as plant sources such as palm oil. Unsaturated fats, by contrast, are primarily found in plants and fish.
In the United Kingdom, current official guidelines recommend that saturated fat should account for no more than 10 percent of a person's daily calorie intake. This translates to a maximum daily limit of 30 grams of saturated fat for men and 20 grams for women.
Guidance from the NHS recommends cutting down on saturated fat and substituting it with unsaturated alternatives, including omega-3 fatty acids, to protect cardiovascular health.
For individuals following a low-carbohydrate eating plan, health experts recommend choosing healthy fats such as nuts, seeds, and olive oil instead of butter, fatty cuts of meat, and processed meats.
Cardiovascular disease in the UK
Around half of all UK adults are estimated to have high cholesterol, a condition where deadly fatty plaque builds up in the arteries and contributes to the deaths of about one in five people every year.
Cardiovascular disease remains the biggest killer in the UK, with an estimated eight million people currently living with heart and circulatory conditions.
Every year, around 200,000 people in the UK suffer a heart attack or stroke. Stroke alone strikes approximately 100,000 Britons annually when blood supply to part of the brain is cut off, claiming around 34,000 lives each year as one of the nation's leading causes of death.
