The controversial paleo diet has been dealt another blow by health researchers, who've discovered a link between the so-called 'caveman food lifestyle' and heart disease risk.
Made famous by celebrity chef Pete Evans, a judge on My Kitchen Rules, the strict regimen focuses on meat, chicken, fish, nuts and seeds while avoiding grains, legumes, sugar and dairy.
Researchers from Edith Cowan University have completed the world's first major study of the impact of the paleo diet on gut bacteria and delivered an alarming verdict.
More than double the amount of a key biomarker closely associated with heart disease was found in the blood of paleo-subscribing subjects, lead researcher Dr Angela Genoni said.
"Those who promote the paleo diet often cite it as beneficial for your gut health, but this research suggests there were adverse differences in those who followed the dietary pattern," Dr Genoni said.
High levels of trimethylamine-n-oxide, or TMAO, in the gut is associated with increased risk of cardiovascular disease.
In his promotion of the diet, Evans has espoused its ability to ease and even eliminate health conditions and serious diseases, earning him the ire of many medical professionals.
One of his recipe books was pulped in 2015 just before its release after doctors criticised his suggestion mums replace baby formula with a paleo bone broth.
And nutritionists have warned that excluding whole groups of foods posed potential health risks.
Dr Genoni said the reason for the significantly elevated TMAO in people on the diet appeared to be caused by a intake of red meats, as well as a lack of whole grain intake.
"The paleo diet excludes all grains and we know that whole grains are a fantastic source of resistant starch, and many other fermentable fibres which are vital to the health of your gut microbiome," Dr Genoni said.
"Because TMAO is produced in the gut, a lack of whole grains might change the populations of bacteria enough to enable higher production of this compound. Additionally, the paleo diet includes greater servings per day of red meat, which provides the precursor compounds to produce TMAO."
The paleo diet has attracted numerous health warnings as its popularity has grown, with Melbourne University researchers finding it could increase susceptibility to diabetes.
Expert analysis in 2015 of 35 different diets saw paleo come in dead last in the rankings, with it failing to meet the grade on factors from nutrition and safety to weight loss effectiveness.
Alex Nella, a dietitian at the University of California, warned the typical paleo diet "puts most (people) at risk of deficiencies in calcium and vitamin D".
Evans has regularly attacked those critical of the diet, including prominent dietitians and the Australian Medical Association.