Abstract
BackgroundLeafy vegetables are good sources of folates and food shops nowadays offer an increasing number of lettuce varieties.ObjectiveTo obtain data on the folate content and forms in common lettuce varieties and spinach sold in the Nordic countries, and to investigate effects of different storage conditions and preparations in the consumer's home or at lunchtime restaurants.DesignFolate was analysed in eight different lettuce varieties and spinach using a validated high-performance liquid chromatographic method and the detected forms of folates were confirmed by a mass spectrometric detector [liquid chromatography–mass spectrometry (LC-MS)] following heat extraction, deconjugation with rat serum and purification by solid-phase extraction.ResultsFolate content, expressed in folic acid equivalents, in the lettuce samples varied six-fold, from 30 to 198 µg 100 g−1 on a fresh weight basis. The folate content was decreased by 14% after storage at 4°C for 8 days and by 2–40% after storage at 22°C for 2–4 h, depending on whether samples were stored as whole leaves, or small torn or cut pieces. LC-MS confirmed the identity of the folate forms: H4folate, 5-CH3-H4folate, 5-HCO-H4folate and 10-HCO-H4folate.ConclusionThe considerable variation in folate content between varieties of lettuce in this pilot study, with one variety reaching the level found in spinach, indicates the potential to increase folate intake considerably by choosing folate-rich varieties of lettuce and storing at low temperatures.
Highlights
Leafy vegetables are common food items in a well-balanced diet, and increased consumption of fruit and vegetables is a general goal in public health work in Western countries
The total folate concentration expressed in folic acid equivalents and calculated from the sum of H4folate, 5-CH3H4folate and 5-HCO-H4folate varied from 30 to 198 mg 100 g(1 on a fresh weight (FW) basis
Data on the concentration of individual forms of folates (H4folate, 5-CH3-H4folate and 5-HCO-H4folate) were obtained for eight different lettuce varieties and spinach sold in different wrappings and as whole lettuce heads or loose leaves
Summary
Leafy vegetables are common food items in a well-balanced diet, and increased consumption of fruit and vegetables is a general goal in public health work in Western countries. In a review [6], plant foods (vegetables, fruit and potatoes) were stated to be predominant contributors to folate intake in Europe. Even in countries from Northern Europe, where plant food consumption is lower than in the various Mediterranean diets, plant foods are estimated to contribute approximately 40% of the total folate intake among adults [6]. Despite the importance of folate in human nutrition, data on folate content in different vegetables, including lettuce varieties, are limited. Leafy vegetables are good sources of folates and food shops nowadays offer an increasing number of lettuce varieties. Objective : To obtain data on the folate content and forms in common lettuce varieties and spinach sold in the Nordic countries, and to investigate effects of different storage conditions and preparations in the consumer’s home or at lunchtime restaurants. Conclusion : The considerable variation in folate content between varieties of lettuce in this pilot study, with one variety reaching the level found in spinach, indicates the potential to increase folate intake considerably by choosing folate-rich varieties of lettuce and storing at low temperatures
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