Individuals following a ketogenic low-carbohydrate diet are more likely to have higher cholesterol levels than those on other meal plans, academics have said.
Researchers from the University of Bath have found that a ketogenic (keto) diet can also reduce good gut bacteria, such as Bifidobacterium.
More than 50 healthy individuals took part in the 12-week trial, where they either followed a moderate sugar diet (control), a low-sugar diet (less than 5% of calories from sugar), or a keto low-carbohydrate diet (less than 8% of calories from carbohydrates).
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The results have shown that the participants in the keto diet had higher cholesterol levels, while those in the low-sugar diet saw a significant reduction in their cholesterol.
In addition, the composition of the gut microbiome was altered by the keto diet and reduced Bifidobacteria – beneficial bacteria often found in probiotics which produces B vitamins, inhibits pathogens and harmful bacteria and lowers cholesterol.
Participants on the keto diet also had a lower glucose tolerance than those in the other groups, the study has reported.
Senior author Dr Aaron Hengist said: “Despite reducing fat mass, the ketogenic diet increased the levels of unfavourable fats in the blood of our participants, which, if sustained over years, could have long-term health implications such as increased risk of heart disease and stroke.”
Fellow author Dr Russell Davies said: “Dietary fibre is essential for the survival of beneficial gut bacteria like Bifidobacteria.
“The ketogenic diet reduced fibre intake to around 15 grams per day, half the NHS recommended intake.”
He added: “This reduction in Bifidobacteria might contribute to significant long-term health consequences such as an increased risk of digestive disorders like irritable bowel disease, increased risk of intestinal infection and a weakened immune function.”
Professor Javier Gonzalez, who oversaw the research, said: “The ketogenic diet reduced fasting glucose levels but also reduced the body’s ability to handle carbs from a meal.
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“By measuring proteins in muscle samples taken from participants’ legs, we think this is probably an adaptive response to eating less carbohydrates day-to-day and reflects insulin resistance to storing carbs in muscle.”
Professor Gonzalez continued: “This insulin resistance is not necessarily a bad thing if people are following a ketogenic diet, but if these changes persist when people switch back to a higher carbohydrate diet it could increase the risk of developing type 2 diabetes in the long-term.”
Professor Dylan Thompson, who also oversaw the work, concluded: “The ketogenic diet is effective for fat loss, but it comes with varied metabolic and microbiome effects that may not suit everyone.
“In contrast, sugar restriction supports government guidelines for reducing free sugar intake, promoting fat loss without apparent negative health impacts.”
Read the study in the journal Cell Reports Medicine.
