Fruit, folate

Brevick A, Vollset S, Tell G, Refsum H, Ueland P, Locken E, Drevon C and Andersen L. 2005. Plasma concentration of folate as a biomarker for the intake of fruit and vegetables the Hordaland Homocysteine Study. Am J Clin Nutr 81 434 139. 

Eolates are present in nearly all natural foods. Those with the highest folate content include yeast, liver and other organ meats, fresh green vegetables and some fresh fruits. The term folic acid arose from its first identification in leafy vegetables (e.g. spinach). 

The major sources of folate are green vegetables, citrus fruits, legumes, egg yolk, wheat germ, and yeast [417]. This vitamin can be added only in the form of pteroylmonoglutamic acid [402]. The multiplicity of forms, low stability, low concentration, and the complex extraction and detection techniques make the analysis of folate in food a difficult task. 

Determination of folate and folic acid in vegetables and fruits... 

Folic acid (or folate) deficiency, one of the most common vitamin deficiencies in the population consuming few dietary fruits and vegetables, causes chromosome breaks in humans,34 analogous to those caused by radiation. Folate supplementation above... 

Vitamins and minerals, whose main dietary sources are other than fruits and vegetables, are also likely to play a significant role in the prevention and repair of DNA damage, and thus are important to the maintenance of long-term health. Vitamin B12 is found in animal products, and deficiencies of B12 cause a functional folate deficiency, accumulation of the amino acid homocysteine (a risk factor for heart disease),46 and chromosome breaks. B12 supplementation above the RDA was necessary to minimize chromosome breakage.47 Strict vegetarians are at increased risk for developing vitamin B12 deficiency. 

Vitamins B6, B12, and folate An elevated plasma homocysteine level is associated with increased cardiovascular risk (see p. 263). Homocysteine, which is thought to be toxic to the vascular endothelium, is converted into harmless amino acids by the action of enzymes that require the B vitamins—folate, B6 (pyridoxine), and B12 (cobalamin). Ingesting foods rich in these vitamins can lower homocysteine levels and possibly decrease the risk of car diovascular disease. Folate and B6 are found in leafy green veg etables, whole grains, some fruits, and fortified breakfast cereals. B12 comes from animal food, for example, meat, fish, and eggs. 

L Vahteristo, K Lehikoinen, V Ollilainen, P Varo. Application of an HPLC assay for the determination of folate derivatives in some vegetables, fruits and berries consumed in Finland. Food Chem 59 589-597, 1997. 

Another vitamin which is of interest in fruit juices is folate, which can be found in low, but significant, levels in some juices, such as orange. However, the analysis of natural levels of this vitamin is very difficult and is best performed using microbiological methods. 

Its natural occurrence is unique in citrus fruits (4-6J. Furthermore, by employing triple lumen perfusion techniques, it was shown that diphenylhydantoin does not influence the absorption of citrus folate in human volunteers. This may be clinically significant, since diphenylhydantoin in dosages sufficient to control epileptic seizures influences absorption of forms of folate present in other food sources. 

Evidence that a diet rich in fruits and vegetables may protect against coronary heart disease is accumulating. It is unclear exactly which substances in fruits and vegetables are responsible for the observed inverse association with cardiovascular disease. The inverse association may be attributed to folate, antioxidant vitamins, or other constituents such as fiber, potassium, fla-vonoids, or other phytochemicals. The protective effect of folate may be attributed to its role as a cosubstrate in homocysteine metabolism (Eichholzer et al., 2001). 

The observed associations between folate, antioxidant vitamins, and cardiovascular disease may be confounded by other substances in fruits and vegetables, as the following examples of studies show Flavonoids (see Chapter 31) are naturally occurring, water-soluble antioxidants found widely distributed in vegetables, fruits, tea, and wine. There is an inverse relationship between flavonoids and decreased risk of coronary heart disease. Lycopene, the key antioxidant in tomatoes, shows an inverse association with myocardial infarctions. There is an inverse association between folate and cardiovascular disease. 

Eichholzer, M. et al., The role of folate, antioxidant vitamins and other constituents in fruit and vegetables in the prevention of cardiovascular disease the epidemiological evidence, Int. J. Vitam. Nutr. Res., 71, 5-17, 2001. 

NCSDCc,f 6.3 yr 3405 3692 1074 M-F Dietary or supplemental intake of vitamin A, C, E, folates and carotenoids are not associated with bladder risk of cancer inverse association were found between the intake of vitamins, carotenoids, and dietary fibers and risk of gastric carcinoma inverse association with lung cancer is found both for vegetables and fruit intake. (148,212) (213)... 

Fruits and vegetables provide vitamins A and K, ascorbic acid, riboflavin, and folate. 

Tetrahydrofolate (THF) The active form of the vitamin folic acid. THF is one of the major carriers of one-carbon units at various oxidation states for biosynthetic reactions. It is required for the synthesis of the nucleotide thymidylate (dTMP). Although bacteria can synthesize folic acid, eukaryotes must obtain folate from the diet. Dietary sources of folate include leafy green vegetables (e.g., spinach and turnip greens), citrus fruits, and legumes. Many breakfast cereals, breads, and other grain products are fortified with folate. 

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