Low-starch diets have become increasingly popular in recent years and are said to lower blood sugar levels and weight, as well as reduce the risk of diabetes.

But a new study found that this diet can raise cholesterol levels too high in some people, increasing the risk of heart disease, heart attack and stroke.

It is estimated that around half of UK adults have high cholesterol. Cholesterol can cause dangerous fatty deposits to build up in the arteries, causing about one in five deaths each year. Low-carbohydrate foods such as potatoes and bread contain about 75 percent fat, 20 percent protein, and 10 percent carbohydrates.

This diet plan has previously been touted to increase good cholesterol levels. HDL helps remove fatty deposits from the arteries.

However, new research suggests that low-starch diets may increase bad cholesterol levels in high-risk individuals, particularly because they may include foods high in fat.

“While some people may benefit from a low-carb diet, it’s not equally beneficial for everyone,” said Alexa Bard, an author on the research team. “Dietary advice is sometimes presented as if it’s the same for everyone,” he said. Among individuals who were genetically at risk for cholesterol, the greatest increase in bad cholesterol was seen with the highest intake of saturated fat.

The research team hopes that in the future, their method will help doctors and dieticians identify people who are more likely to develop harmful changes in cholesterol from certain foods. Saturated fats are found in many foods, but most of them are found in animal meat and dairy products. Palm oil is also a source of saturated fat.

In contrast, unsaturated fats are found mostly in plants and fish. Current guidelines in the UK suggest that saturated fat should not exceed around 10% of calories consumed per day. For men this means a maximum of about 30 grams of saturated fat per day, while women are advised to consume no more than 20 grams of saturated fat per day.

British Department of Health (NHS) guidelines recommend reducing saturated fat and replacing it with unsaturated fats, including omega-3 fats, where possible to reduce the risk of heart disease. For people on a low-carb diet, this means choosing foods like nuts, seeds and olive oil instead of butter, fatty meats and processed meats.