U.S. flag

An official website of the United States government

Dot gov

Official websites use .gov
A .gov website belongs to an official government organization in the United States.


Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.


Main content area

Directions in nutritional assessment: Biomarkers and bio-indicators - providing clarity in the face of complexity

Daniel J. Raiten, Gerald F. Combs Jr.
Sight and Life 2015 v.29 no.1 pp. 39-44
biomarkers, classification, disease prevention, health care workers, health promotion, human development, nutrients, nutrition assessment, risk, vitamin A, xerophthalmia, zinc
Among the greatest challenges facing the nutrition community is integrating nutrition into all aspects of global efforts in health promotion and disease prevention. Despite compelling evidence of its importance to human development, a full appreciation of how nutrition affects health is still lacking throughout the continuum of health care providers, programmers and policymakers. In large part, this disconnect is the result of relying on evidence that is often not directly or specifically linked to the biology of nutrition in a meaningful manner. Over the years, attempts have been made to put the differential responses due to inadequacy of individual nutrients into a classification scheme based on specificity of response. The classification of Type 1 and Type 2 nutrients offered by Golden et al is a widely accepted application of this approach. Type 1 nutrients (e.g., vitamin A) are directly and inextricably linked to explicitly defined outcomes, e.g., xerophthalmia, by a well described biological relationship. By contrast, Type 2 nutrients, such as zinc, are not directly linked to particular outcomes. In fact, the categorization of nutrients by this paradigm is dependent on context. For example, vitamin A is clearly a Type 1 nutrient with respect to its role in preventing xerophthalmia, but it appears to be a Type 2 nutrient with respect to its activity in reducing risk of infection. This is more than a semantic issue, as addressing such physiological impacts calls for an understanding of the actual root causes. That challenge requires tools capable of identifying relationships between nutrients and specific outcomes. It necessitates a clear appreciation of the functions of nutrients within relevant biological systems (e.g., immune, neurological). Further, it requires evidence that changes in nutrient status will, in fact, have functional consequences. These are the domains of nutritional assessment.