Nutritional biomarkers may more accurately assess FV intake than traditional assessment methods. Combining potential biomarkers of intake to better predict overall FV intake has not been tested. Furthermore, urinary biomarkers as novel non-invasive alternatives to predict FV intake are underexplored. Few interventions have examined novel biological effects of increased FV that could potentially be used to encourage increased intake. Examining the effects of increased exposure to FV on liking, and whether increased FV intake impacts indirectly on disease risk via weight loss, also remain unexamined. Thus, this thesis aimed to develop and assess novel biomarkers of FV intake. Secondly, it aimed to assess biological effects of increased FV consumption and, thirdly, to determine the effect of incorporation of increased FV into the diet on liking, and success of weight loss. Findings from a supervised and other less intensive RCTs showed that a combined biomarker approach may more accurately predict overall FV intake than a single biomarker. An observational study showed that an adjusted combined biomarker model did not perform better at predicting FV intake than single biomarker models. No effect of increasing FV consumption on urinary pH or potassium was demonstrated. However, urinary vitamin C increased linearly with increasing FV consumption. Increased FV intake had no effect on oxidised LDL or appearance. Finally, a web-based program, providing no specific advice on dietary weight loss strategies, indicated that individuals trying to lose weight consumed more FV and that eating more FV may aid successful weight loss. This thesis indicates improved methods of accurately measuring FV intake that will aid the study of biological and health effects of increased intake, the measurement of compliance with interventions and allow better evaluation of the effects of public health campaigns to increase intake, which is still low in the UK.