How Nutrigenetics Can Help Prove that Nutrient-Based Interventions Reduce Disease Risk

Why is it so hard to prove that nutrient-based interventions reduce risk for disease? All too often, a report that a nutritional intervention reduced disease risk is followed shortly thereafter by another publication observing that, in a different population, the effect of the nutritional treatment could not be replicated. For example, a metaanalysis of clinical trials concluded that vitamin D3 decreased mortality in elderly women who are in institutions and dependent care.1 Subsequently, other investigators observed that, in critically ill patients with vitamin D deficiency, admin¬istration of high-dose vitamin D3 compared with placebo did not reduce mortality.2 Inconsistent results fueled confusion about whether vitamins A or E lower the risk for developing lung cancer. Some clinical trials produced results suggesting efficacy, but other large randomized trials reported that these vitamins increased lung cancer risk.3–6 There are many other examples of what appear to be nutritional contradictions.