Biochemical validation of a food frequency questionnaire measuring immune modulating nutrient intake in patients with peripheral arterial disease

Background and aims: Peripheral arterial disease (PAD) is a cardiovascular disease affecting approximately 6 % of the population. The condition is associated with claudication, non-healing ischemic ulceration, and a systemic pro-inflammatory and pro-oxidative state. Recently, nutrition therapy is exploring immunonutrition as a novel dietary strategy to reduce the progression of atherosclerosis. A 21-item food frequency questionnaire (FFQ) has been developed and previously validated in the PAD population against a dietitian collected seven-day diet history method showing good agreement. The aim of this study was to determine whether the FFQ accurately predicts serum levels of six routinely analysed immune-modulating nutrients (vitamins A, C, D, and E, zinc, iron). 

Methods and results: Dietary intake measured by the validated FFQ was compared to fasting serum blood levels of their respective biomarkers. Correlation coefficients and quartile agreements were performed to determine the relationship between dietary intake and serum levels. The mean age of participants (n = 100) was 75 years with 76 % being male. Correlation coefficients and quartile agreements indicated poor agreement between intake measured by FFQ and serum biomarkers and were not statistically significant. 

Conclusion: These results suggest that intake measured by the FFQ is not an accurate reflection of serum levels of these immune-modulating nutrients in this population, possibly due to endogenous physiological processes specific to PAD. Further research into the utilisation of nutrients is warranted to inform dietary recommendations in this population.