Chlorophyll-bound Magnesium in Commonly Consumed Vegetables and Fruits: Relevance to Magnesium Nutrition |
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Authors: | T Bohn T Walczyk S Leisibach RF Hurrell |
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Affiliation: | Authors are with Inst. ofFood Science and Nutrition, Laboratory for Human Nutrition, Swiss Federal Inst. of Technology Zurich, Seestrasse 72,8803 Rueschlikon, Switzerland. Direct inquiries to author Bohn (E-mail: ). |
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Abstract: | ABSTRACT: Magnesium is bound as the central atom of the porphyrin ring of the green plant pigments chlorophyll a and b . It has been suggested that chlorophyll-bound magnesium may play an important role in magnesium nutrition because when iron is similarly bound in the porphyrin ring of heme, it is absorbed to a greater extent than non-heme iron. We have analyzed 22 frequently consumed fruits and vegetables for the chlorophyll content by high-pressure liquid chromatography and for magnesium with atomic absorption spectroscopy. Chlorophyll concentrations ranged from 6 μg/g (grape) to 790 μg/g (spinach) (median 63 μg/g). Magnesium concentrations ranged from 48 μg/g (grape) to 849 μg/g (spinach) (median 122 μg/g). In the green leafy vegetables, such as spinach and lettuce, chlorophyll-bound magnesium represented 2.5% to 10.5% of total magnesium whereas other common green vegetables, pulses and fruits contained < 1% chlorophyll-bound magnesium. The chlorophyll content of spinach was further decreased by about 35% on thawing frozen spinach or on chopping fresh spinach, and this degradation increased to about 50% after boiling and steaming. Based on the present results and published food consumption data, we estimate that chlorophyll-bound magnesium represents a very low fraction of total magnesium intake in industrialized countries, less than 1% in the case for data obtained from Switzerland. Thus, chlorophyll-bound magnesium is of little relevance to magnesium nutrition. |
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Keywords: | magnesium chlorophylls chlorophyll-bound magnesium vegetables and fruits pigment degradation |
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