Introduction:​ A novel method of dietary assessment was introduced in a field study with wildland firefighters, published in 2017. The purpose of this thesis was to validate this novel, audio-video method of dietary assessment, and to determine whether it can be integrated into clinical practice, to replace written food journals. The validation process was completed in two phases and is presented as two manuscripts within this thesis.

Manuscript One:​ Phase one was designed to validate the audio-video method in comparison to the gold standard:​ weighed food assessment;​ in a free-living setting. With the exception of Vitamin E (mg) and total weight (g), kilocalories, macro and micronutrient values were highly correlated between the audio-video diary recorded estimations and weighed food items. We concluded that the novel method was able to make accurate estimations of energy and nutrient intake, and may therefore be a meaningful alternative to diary recording in a free-living setting.

Manuscript Two:​ Phase Two was designed to assess the application of the 3-day, audio-video method in a clinical setting, to replace the current method of 3-day, written food journaling. We found that the diet assessments, as performed by a Registered Dietitian for the same participants, were comparable between written and audio-video diaries. In consultation with the Registered Dietitian, we conclude that the audio-video method is acceptable for use in clinical practice.

Conclusion:​ The audio-video method is a suitable method for assessing food items, when the portion sizes from the video are estimated by persons with training on portion sizing (i.e. researchers or Registered Dietitians). In addition, the AV method was determined to be an acceptable method for use in clinical practice, to replace written food journals. Participants indicated that if the method was developed into a mobile phone application, for use on their personal device, they would be more likely to accept it as a food journaling method, when compared to the written method of food journaling.