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Dr Dominik Alexander acknowledged his visit to New Zealand and Australia was jointly funded by Beef and Lamb New Zealand, and an Australian agribusiness group, but this did not compromise his views, he said.
Evidence of nutritional links to bowel cancer were "underwhelming".
Even the role of fibre in preventing bowel cancer was not firmly established, while the "jury is still out" on fruit and vegetables.
There was emerging evidence for a protective role played by vitamin D, as well as calcium.
Isolating the role food played in cancer was notoriously difficult, far more than Dr Alexander's other area of expertise, occupational and environmental epidemiology.
The biggest factors in developing bowel cancer were shown to be body weight and exercise, showing people needed a balanced, active lifestyle, he said.
He acknowledged there was concern in the United States about the role red meat played in cancer development, but the science did not back up the perception of harm, he said.
Some studies showing a link had been "over-hyped".
Dr Alexander said that employing a meta-analysis - weighing up all studies - revealed no discernable increased risk.
Otago and Southland have New Zealand's highest incidence of bowel cancer, while New Zealand's rates are some of the highest in the world.
Asked about that, Dr Alexander said causes were not necessarily environmental, and people often overlooked the fact cancers could take decades to develop.
Dr Alexander lives in Boulder, Colorado, where he works for an epidemiology consulting firm.