Niki Bezzant: What is the keto diet and is it actually harmful?
Sometimes there is quite a difference between the way nutrition research is reported and what the research actually shows.
Coverage of a recent study about high- versus low-carb diets included headlines like "Why the keto diet might be ruining your gut" and "High-fat diets hurt the helpful bugs within". Just reading these headlines does not tell the whole story.
This was a trial comparing three different diets in healthy people in China. One group was given a high-fat diet consisting of 40 per cent fat and 46 per cent carbohydrate; one group had a moderate-fat diet of 30 per cent fat and 56 per cent carbs; and another a low-fat diet made up of 20 per cent fat and 66 per cent carbs.
All three diets were 14 per cent protein. The participants had their food provided, and because they are the most-consumed carbohydrate foods and oils in China, the carb sources were white rice and wheat flour and the fat came from soybean oil.
In the higher-fat eaters, there were changes in the gut bacteria - fewer beneficial bacteria and more of the types associated with high cholesterol and inflammation.
This suggests that in countries where people are in transition from a traditional, lower-fat diet to a westernised one containing more fat, there could be potential harmful health effects. This seems to have been the point of the research: to investigate how changes in the makeup of the diet might be affecting gut and therefore general health.
But this trial didn't compare a healthy diet with an unhealthy diet. It didn't compare healthy diets with each other, either. And it wasn't about comparing people on popular low-carb diets with people eating according to traditional healthy eating guidelines.
I don't think any nutrition expert would consider a diet of mainly white rice, wheat flour and soybean oil a healthy one. (I'm sure they ate other food too, but we can assume not many plants, since all three diets were just 14 per cent fibre).
Those high ratios of fat, carbs and protein don't really mimic what proponents of low-carb diets would recommend; they're more akin to western eating patterns, apart from the protein, which is low by any measure.
It's worth noting that people on keto-style diets are more likely to be eating over 70 per cent of energy from fat and perhaps as little as 5 per cent from carbohydrate. So this trial does not prove that keto-bashing headline.
There is minimal research, so far, to show benefit or harm from long-term keto-style eating. People on both sides of that philosophical divide can point to studies supporting their arguments. This particular research – while suggesting further research into gut health effects is warranted - doesn't help much in that debate. Perhaps the main thing we can learn here is not to take those headlines at face value.
• Niki Bezzant is editor-at-large for Healthy Food Guide www.healthyfood.co.nz