Accounting for differences in the bioactivity and bioavailability of vitamers

Jesse F Gregory

doi:10.3402/fnr.v56i0.5809

Abstract

Essentially all vitamins exist with multiple nutritionally active chemical species often called vitamers. Our quantitative understanding of the bioactivity and bioavailability of the various members of each vitamin family has increased markedly, but many issues remain to be resolved concerning the reporting and use of analytical data. Modern methods of vitamin analysis rely heavily on chromatographic techniques that generally allow the measurement of the individual chemical forms of vitamins. Typical applications of food analysis include the evaluation of shelf life and storage stability, monitoring of nutrient retention during food processing, developing food composition databases and data needed for food labeling, assessing dietary adequacy and evaluating epidemiological relationships between diet and disease. Although the usage of analytical data varies depending on the situation, important issues regarding how best to present and interpret the data in light of the presence of multiple vitamers are common to all aspects of food analysis. In this review, we will evaluate the existence of vitamers that exhibit differences in bioactivity or bioavailability, consider when there is a need to address differences in bioactivity or bioavailability of vitamers, and then consider alternative approaches and possible ways to improve the reporting of data. Major examples are taken from literature and experience with vitamin B6 and folate.

Highlights

All vitamins exist with multiple nutritionally active chemical species often called vitamers
In spite of this modern analytical power, the following questions illustrate the complexity of this area, including: (a) In which cases of food analysis is there a need to consider differences in vitamer bioactivity and/or bioavailability? (b) Does the analytical method being used allow measurement of all biologically active vitamers? (c) Is our understanding of the bioactivity and bioavailability of particular vitamers sufficient to allow reliable adjustments of food composition data to reflect nutritional properties? (d) Can nutritional requirements and food labeling be expressed in a way that incorporates the differences in bioavailability or bioactivities among vitamers?
Full activity and bioavailability Approximately equivalent to pyridoxine; occasionally reported to have slightly lower bioactivity Similar to bioavailability to nonphosphorylated vitamers Approximately 50% bioavailability Catabolic product inactive A protein bound complex of vitamin B6 formed during food processing/storage

Summary

Vitamin D

Lower content but higher bioavailability than parent (nonhydroxylated) vitamin D compounds. Vitamin E a-Tocopherol a-Tocopheryl acetate b-tocopherol d-tocopherol g-tocopherol Tocotrienols a-Tocopherol exhibits primary in vivo activity. Greatest activity in natural RRR stereochemical form Acetate and other esters are fully available Á common form used in fortification Primarily contributes antioxidant activity Primarily contributes antioxidant activity Primarily contributes antioxidant activity Primarily contributes antioxidant activity

Vitamers have equivalent activity and bioavailability

Findings

Cyanocobalamin Methylcobalamin Adenosylcobalamin Aquacobalamin