The research was done as part of a high-value nutrition national science challenge led by AgResearch and co-funded by First Light Wagyu beef company.
Its 50 participants were put on diets consisting of either 500g a week of Wagyu beef, conventional beef or soy protein spread over three portions a week for eight weeks. At the end of the trial all three groups had reduced their cholesterol.
The outcome prompted study leader Professor David Cameron-Smith to conclude eating New Zealand grass-fed Wagyu with its high level of fat does not affect heart disease, including cholesterol and blood pressure levels.
But fellow Auckland University academic, epidemiologist Professor Rod Jackson has challenged the veracity of the research, claiming there are issues in the study that make such conclusions fraught.
Interventions using the serving sizes in the study are weak and such research work offers no control over most of what else the subjects ate.
“What if those on the meat had more non-meat/dairy meals on the other days than those on the soy?” he said.
He also raised concerns linked to other general dietary studies, including a recent international study claiming reductions in red meat had negligible effects on individual health. Issues around length of trial and the number of participants also apply to the Wagyu research.
But Cameron-Smith said the servings of 170g of meat three times a week were not a weak intervention but aligned with health recommendations and as a major dietary intervention.
The servings per week was based on the NZ, Australian and World Cancer Research Fund guidelines for weekly red meat consumption. It was also on par with data on the average quantities of meat consumed by Australian males.
Cameron-Smith said researchers are still analysing the subjects’ entire diet over the trial and the information remains meaningful and relevant to real world dietary behaviour.
Jackson said all participants had lower cholesterol and fatty acids after the study, something that is a feature of all intervention studies in nutrition.
He also noted all participants changed their overall diet, all losing weight regardless of diet.
“I am not surprised they showed nothing. In these types of studies you have to completely control participants’ diet.”
But Cameron-Smith said complete control is not the real world.
“A balance between reality and control is never easy.”
AgResearch research directdor Trevor Stuthridge said AgResearch stands by the research and welcomes the academic interest and discussion it has sparked.
Firstlight Wagyu director and co-founder Jason Ross said the company was keen to find out what it could about heart health, particularly relating to a common perception red meat damages the heart.
“We had some idea of what the outcome might be but, of course, what we didn’t anticipate was that if you put a group of middle-aged Kiwi men in a study measuring cholesterol at the beginning and at the end of the study, some of them might begin to change or manage other risk factors in their lives too.”
