Potischman N, Weed D L
National Cancer Institute, Bethesda, Maryland, USA.
Am J Clin Nutr. 1999 Jun;69(6):1309S-1314S. doi: 10.1093/ajcn/69.6.1309S.
Making nutrition recommendations involves complex judgments about the balance between benefits and risks associated with a nutrient or food. Causal criteria are central features of such judgments but are not sufficient. Other scientific considerations include study designs, statistical tests, bias, confounding, and measurement issues. At a minimum, the set of criteria includes consistency, strength of association, dose response, plausibility, and temporality. The current practice, methods, and theory of causal inference permit flexibility in the choice of criteria, their relative priority, and the rules of inference assigned to them. Our approach is as follows. Consistency across study designs is compelling when the studies are of high quality and are not subject to biases. A statistically significant risk estimate with a > 20% increase or decrease in risk is considered a positive finding. A statistically significant linear or otherwise regularly increasing trend reinforces the judgment in favor of a recommendation. A plausible hypothesis likewise reinforces a recommendation, although the rules of inference for biological evidence are highly variable and depend on the situation. Temporality is, for nutrition recommendations, more a consideration of the extent to which a dietary factor affects disease onset or progression. Evidence supporting these criteria provides a strong basis for making a nutrition recommendation, given due consideration of the balance between presumed benefits and presumed harms. Recommendations should make clear their breadth of application; a narrow recommendation involves a single disease or condition whereas a broad recommendation involves all relevant diseases or conditions.
制定营养建议需要对与营养素或食物相关的益处和风险之间的平衡进行复杂的判断。因果标准是此类判断的核心特征，但并不充分。其他科学考量包括研究设计、统计检验、偏差、混杂因素和测量问题。该标准集至少包括一致性、关联强度、剂量反应、合理性和时间顺序。当前因果推断的实践、方法和理论允许在标准选择、它们的相对优先级以及赋予它们的推断规则方面具有灵活性。我们的方法如下。当研究质量高且不受偏差影响时，不同研究设计之间的一致性很有说服力。风险估计在统计学上显著且风险增加或降低超过20%被视为阳性结果。统计学上显著的线性或其他有规律增加的趋势会强化支持建议的判断。一个合理的假设同样会强化建议，尽管生物证据的推断规则高度可变且取决于具体情况。对于营养建议而言，时间顺序更多地是考虑饮食因素对疾病发生或进展的影响程度。在适当考虑假定益处和假定危害之间的平衡的情况下，支持这些标准的证据为制定营养建议提供了有力依据。建议应明确其适用范围；狭义的建议涉及单一疾病或状况，而广义的建议涉及所有相关疾病或状况。
