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.

为什么证明基于营养素的干预措施能降低疾病风险如此困难？往往是一份报告称某种营养干预措施降低了疾病风险，不久之后就会有另一份出版物指出，在不同人群中，该营养治疗的效果无法重现。例如，一项临床试验的荟萃分析得出结论，维生素D3降低了养老院及依赖护理的老年女性的死亡率。随后，其他研究人员发现，在患有维生素D缺乏症的重症患者中，与安慰剂相比，给予高剂量维生素D3并没有降低死亡率。不一致的结果加剧了人们对于维生素A或E是否会降低患肺癌风险的困惑。一些临床试验结果显示有效，但其他大型随机试验报告称这些维生素会增加肺癌风险。还有许多其他看似营养矛盾的例子。