Submitted to: Advances in Experimental Medicine and Biology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/20/2001
Publication Date: 1/20/2003
Citation: Novotny Dura, J., Britz, S.J., Caulfield, F.A., Beecher, G.R., Clevidence, B.A. 2003. Intrinsic labeling of plants for nutrient bioavailability studies. Advances in Experimental Medicine and Biology.537:131-140. Interpretive Summary: Fruits and vegetables which are high in beta-carotene and other carotenoids are associated with promotion of health and decreased risk of many diseases. However, the availability of these nutrients from fruits and vegetables is affected by the plant structure and other compounds present in the plant. It is crucial that the availability of carotenoids and other nutrients from plants be known so that health professional can make appropriate recommendations for nutrient intakes. The difficulty in studying nutrient availability in plants rests in the difficulty in discerning newly eaten nutrients from those already present in the body. The present study describes a novel technique for measuring nutrient availability from green, leafy vegetables. The technique involves labeling all the nutrients in the vegetable with a stable (safe) isotope called carbon-13. Since carbon-13 is uncommon in nature, the nutrients which are absorbed after eating a carbon-13 vegetable can be detected in the blood. Without the carbon-13 tag, the nutrients mix with those already in the body pool, and it is very difficult to measure nutrient absorption. The present study describes a first attempt at this method. Kale was successfully grown in a carbon-13 environment, and beta-carotene was subsequently analyzed for carbon-13 accumulation. It was found that 99% of carbon atoms associated with beta-carotene from the kale were carbon-13. Therefore, we have shown that nutrients in green, leafy vegetables can be fully tagged with carbon-13 for nutrition studies. These results will be useful for scientist whose research is aimed at evaluating availability of nutrients from plant foods.
Technical Abstract: Bioavailability of nutrients from fruits and vegetables is a crucial value for making recommendations for nutrient intakes sufficient to provide health benefits. Successful bioavailability studies require that recently ingested nutrients can be discerned from endogenous nutrients. Stable isotopic labeling of plants allows the nutrients in the plant food to be labeled in situ, so that when the nutrients from that plant food are ingested, those nutrients can be distinctly identified. The objective of this study was to produce carbon-13 labeled kale to meet the requirements of a clinical bioavailability study. Kale was grown in an environmental chamber to be entirely labeled with carbon-13. The growth chamber was sealed, and the only source of carbon available to kale plants during the growth cycle was carbon-13. Beta-carotene was analyzed for extend of labeling, and it was found that 99% of carbon sites contained carbon-13 molecules. The plants grew equally well in the carbon-13 dioxide environment compared to plants grown in a carbon-12 dioxide environment. In conclusion, labeling of green, leafy vegetables with carbon-13 is a feasible way to study bioavailabiltiy of nutrients from plant foods.