Mixed
Conventional dietary-report instruments (FFQs, 24-hour recalls, food records) contain systematic measurement errors that invalidate their use as reference standards for adjusting nutritional epidemiology data, leading to severe underestimation of diet-disease associations.
If you are reading nutritional studies that rely on self-reported food diaries or questionnaires to determine health risks, be aware that these studies likely underestimate the true strength of the relationship between diet and disease. The tools used to measure what people eat are flawed in predictable ways, often masking real health benefits or risks. Do not assume a 'no association' finding means there is no link; it may simply mean the measurement tool was too noisy to detect it.
In assessing protein intake, all conventional dietary-report reference methods violated the critical requirements for a valid reference instrument for evaluating, and adjusting for, dietary measurement error in an FFQ. They displayed systematic bias that depended partly on true intake and partly was person-specific, correlated with person-specific bias in the FFQ. Using the dietary-report methods as reference instruments produced substantial overestimation (up to 230%) of the FFQ correlation with true usual intake and serious underestimation (up to 240%) of the degree of attenuation of FFQ-based log relative risks.
Why this rating
Based on eight validation studies using urinary nitrogen biomarkers, providing strong empirical evidence of systematic bias, though limited to protein/nitrogen intake.
Source
Bias in dietary-report instruments and its implications for nutritional epidemiology
Victor Kipnis et al. · Public Health Nutrition · 2002
DOI 10.1079/phn2002383
Related findings · Mixed
- Bariatric surgery (VSG and RYGB) is the most effective and sustainable treatment for obesity, producing marked and sustained weight loss that non-surgical interventions cannot match.Strong
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