Is There a Role for N-of-1 Trials in Nutrition Research?
Author: Dr Veronique Chachay
As a key component of evidence-based healthcare, nutrition research provides insight into a number of significant issues: the metabolic consequences of under- and over-nutrition; the food constituents with health-promoting properties; and the complex diet-disease relationships that underlie conditions such as cardiovascular disease, diabetes and cancer. However, nutrition research is often considered a “soft” field of research. This is due to the limitations of instruments used to investigate the dietary intake of individuals, and the difficulty in demonstrating causality when many nutrition-associated biomarkers are slow to progress, or may be influenced by other factors. For example, while an antioxidant-promoting diet is correlated with cardiovascular health, the benefits of this in a controlled research trial may not be visible for several years. Surrogate biomarkers are often used to assess the effect of the diet, such as metabolites of oxidative stress (F2-isoprostanes), as indicators of the imbalance between free radicals and antioxidant compounds.
Scholarly investigation of a patient’s diet-disease relationship requires a thorough record of their usual dietary intake, which is subsequently analysed with food composition software. A number of methods are used, including:
24-hour recall, in which individuals verbally report their dietary intake over the previous 24 hours.
A diet diary, in which an individual records their food and beverage consumption over a specified period, often 3-7 days.
A diet history interview, in which a nutrition professional aims to capture patients’ long-term eating habits and patterns, including cooking methods.
A food frequency questionnaire, through which patients report their long-term frequency and quantity of intake of specific foods.