Guest guest Posted February 22, 2004 Report Share Posted February 22, 2004 [i just posted this to the Kefir Making list and I figured I should cross-post it here. For those on both lists, just delete one (or both) because it's the same post.] @@@@@@@@ I have read that kefir increases the folic acid content of milk. I have been taking folic acid supplements prior to conceiving, but would like to rely on my diet for this. Does anyone know how much folic acid is in kefir? Is it enough to stop taking supplements (as probably they don't get absorbed anyway!!). Helen @@@@@@@@ The short answer is that milks are not good folate sources, even with the increase due to fermentation in some cases. If you're eating plenty of veggies and some liver, then supplementing folate is completely unnecessary, but in any case your milk intake (unless it's a gallon a day or something) wouldn't have any bearing on a decision to supplement. By the way, folate supplements (generally in the folic acid form) are absorbed much better than food sources, and absorption is almost 100% in-between meals, which is not to suggest they should be taken that way or at all. The difference in absorption is the whole reason that the " dietary folate equivalents (DFE) " notation was introduced. I'll give a slightly longer answer because this has reminded me to follow up a little on the general topic of vitamin synthesis in fermentation, which intrigued me when I was reading the two-volume Microbiology of Fermented Foods a few months ago and came across H. Steinkraus' article " Bio-enrichment: Production of Vitamins in Fermented Foods " . Even though the particular case of milk and folate is not especially significant, this general topic is fascinating, as Steinkraus gives data suggesting that alcoholic fermented beverages are crucial sources of certain B-vitamins for some societies, like the kaffir (sorghum) beer of the Bantu, the palm wine of Southern Nigeria, the pulque of Mexico, and the chicha of the Andes. He also gives some data for the ketan and tempe of Indonesia and the idli of India that follow a similar pattern of nutritional enhancement due to fermentation. By the way, these books are wonderful and there is a 30 page chapter on fermented milks. Keep in mind that this is generally a matter of taking nutritionally mediocre foods relied upon by poor people and making them more valuable with the help of bacteria; none of these foods even come close to veggies and meat for nutritional value, especially leaves (e.g. kale, spinach), organs, and shellfish. I did a little PubMed surfing about folate and pasted some brief non- technical excerpts of particular interest below, but I'll make my own summary of the milk folate issue here. Essentially, milks are only moderate sources of folate; they can make a useful contribution when they are major parts of the diet, as is the case in many societies, but other sources of folate are much more important. However, there are two very interesting twists to the milk folate story. One is that all the folate is milks is bound to folate-binding proteins (FBP) that apparently play a role in preserving the folate and making it more bioavailable. Studies on the enhancement of folate availability due to FBP are not entirely conclusive, but mostly point towards a positive effect in unprocessed milks, and it seems clear they play a critical role in ensuring adequate folate for the nursing offspring the milk is designed for. Since milks are milks, we shouldn't be so surprised that there are unique nutritional mechanisms at play here, especially for something as labile and critical as folate. It is important to realize that, like other proteins, FBP is affected by heat processing. There are two issues to consider in the effect of heating on FBP. One is that any form of pasteurization causes a subtle chemical change in the binding- capacity of FBP (the binding " cooperativity " ; see below for technical details), even if the FBP itself is mostly intact. The second issue is that the temperatures of pasteurization are in the same neighborhood as the ones that cause FBP to be destroyed, so some lower temperature pasteurizations leave most of the FBP intact (except for the change in binding capacity), while other pasteurizations destroy significant amounts. At the higher temperatures of UHT and commercial yogurt-making, very little FBP survives. The second interesting twist is a special case of the general topic of vitamin synthesis in fermentation. Depending on the strains of bacteria and the conditions, folate levels are often higher in fermented milks like yogurt and kefir. Streptococci like S. Thermophilus are present in kefir and synthesize folate, while Lactobacilli, also present in kefir, generally don't synthesize folate and in fact have the opposite effect of consuming folate. In the real world practical conditions of homemade kefir-making, the high numbers for folate increase in some studies may not actually be realized due to variations in the composition of grains and bacterial interactions over the course of fermentation and storage. One of the studies below found maximal levels after about 6 hours, but of course the culture involved was not the same as that in kefir. Even though folate levels may be higher in fermented milks, it's possible that positive effects from FBP may be lost. I haven't been able to find any information about this, but it's definitely possible that the FBP is hydrolyzed during fermentation or during gastric passage. It appears that FBP can only impact absorption to the extent it survives gastric passage and recombines with folate in the higher PH of the duodenum. FBP and folate dissociate at the lower PHs of fermented milks and the stomach, but whether this is relevant I don't know. The role of FBP in fermented milks is not clear, but these are the issues I've been able to identify. Keep in mind that in fermented milks like typical yogurt where the milk is heated to the point of destroying FBP in the first place, this is a non-issue. Even if kefir roughly doubles the folate content of unprocessed milk, you'd have to drink one quart of kefir to get the same amount of folate you'd get (about 100mcg) from 12g (=0.4 ounces) of simmered chicken liver or 50g (less than 2 ounces) of mixed greens like spinach, turnip, mustard, and romain lettuce. That's an extremely small amount of liver and not a lot of greens either. So eat the liver and the greens, eat some other veggies, and don't worry about how much is in the milk. Also keep in mind that a deficiency in zinc (one of the best reasons to eat meats) could interfere with folate absorption. Just in case you missed it at the time, at the bottom of this email I pasted some old posts from the Native Nutrition list when we had a short thread on folate last fall. My list of folate density is in there, and while preparing this email I discovered that asparagus and okra had been unfairly omitted from the list, so it is new and improved. The last thing at the bottom is an abstract about folate status in infants and mothers, which is not strictly the topic here, but still interesting. Mike SE Pennsylvania ------------------------------------------------------ Synthesis and utilisation of folate by yoghurt starter cultures and probiotic bacteria Crittenden R.G.; ez N.R.; Playne M.J. International Journal of Food Microbiology, 15 February 2003, vol. 80, no. 3, pp. 217-222(6) Elsevier Science Abstract Thirty-two bacterial isolates from species commonly used in yoghurts and fermented milks were examined for their ability to synthesise or utilise folate during fermentation of skim milk. The organisms examined included the traditional yoghurt starter cultures, Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus, and probiotic lactobacilli, bifidobacteria, and Enterococcus faecium. Folate was synthesised by S. thermophilus, bifidobacteria, and E. faecium. S. thermophilus was the dominant producer, elevating folate levels in skim milk from 11.5 ng g-1 to between 40 and 50 ng g-1. Generally, lactobacilli depleted the available folate in the skim milk. Fermentations with mixed cultures showed that folate production and utilisation by the cultures was additive. Fermentations using a combination of Bifidobacterium animalis and S. thermophilus resulted in a six-fold increase in folate concentration. Although increased folate levels in yoghurts and fermented milks are possible through judicious selection of inoculum species, the folate levels remain relatively low in terms of recommended daily allowance. ------------------------------------------------------ M.Y. Lin, C.M. Young Folate levels in cultures of lactic acid bacteria International Dairy Journal 10 (2000) 409}413 Abstract The folate levels in cultures of the lactic acid bacteria Bixdobacterium longum B6 and ATCC 15708, Lactobacillus acidophilus N1 and ATCC 4356, Lactobacillus delbrueckii ssp. bulgaricus 448 and 449, and Streptococcus thermophilus MC and 573 was investigated. All lactic acid bacteria had higher folate levels in reconstituted milk than in complex media. B. longum B6 had the highest level of folate and S. thermophilus 573 had the lowest level of folate. The time course curves show that all strains tested had the maximum folate levels in 6 h. These strains varied in their abilities to accumulate tetrahydrofolate (THF), 5-methyltetrahydrofolate (5-MeTHF), and 5-formyltetrahydrofolate (5-FmTHF); however, strains of B. longum, L. bulgaricus, and S. thermophilus accumulated more 5-MeTHF than THF or 5-FmTHF. Folate levels decreased 2-16% for the " rst week and continued to decrease gradually throughout the 3-week period for fermented milk stored at 43C. Folate contents of milk fermented with L. acidophilus ATCC 4356 and S. thermophilusMCremained the most stable and decreased only about 8% in 2 weeks and 12% in 3 weeks. However, folate level of milk fermented with L. bulgaricus 449 decreased approximately 27% in 2 weeks and 39% in 3 weeks. 2000 Elsevier Science Ltd. All rights reserved. @@@@ Although all 8 strains of lactic acid bacteria tested demonstrated folate synthesizing ability, strain selection is important for folate content in fermented dairy foods. The incubation time is also one of the signi " cant factors in#uencing the folate levels. Rao, Reddy, Pulusani, and Cornwell (1984) have demonstrated that lactic cultures do not only synthesize but also utilize folic acid. This is consistent with what was observed in this study. All 8 strains of lactic acid bacteria had the maximum levels of folate in 6 h when incubated at 37 [degrees] C. Folate levels decreased as fermentation continued. Lactic acid bacteria were, therefore, propagated in reconstituted milk at 37 [degrees] C for 6 h for folate synthesis. The folate level was about 100 ng mL-1 for B. longum B6 grown under these conditions. According to our previous studies (Lin, Savaiano, & Harlander, 1991; Lin, Yen, & Chen, 1998), it is reasonable to expect a significant number of lactic acid bacterial cells to lyse during transit through the gastrointestinal tract. Therefore, the folate should be available to our bodies whether or not it is inside the cells. According to data provided by the Food and Nutrition Board of the National Research Council (US), the Recommended Dietary Allowance for folate is 50 lg for children age 1-3. One cup of milk fermented with B. longum B6 would provide 24 mcg of folate, which is about half of that RDA. @@@@ @@@@ Folate stability of fermented milk during the storage in#uences the folate levels in the products. Strains of B. longum had the highest levels of folates; however, folate levels for these strains decreased by more than 18% during 2 weeks of refrigerated storage. Although S. thermophilus 573 had the lowest level of folate, this dropped by only 9% in 2 weeks. As mentioned previously, lactic acid bacteria do not only synthesize but also utilize folates. Although lactic acid bacteria had very low metabolism at 4 [degrees] C, the rate of folate utilization was higher than synthesis at this refrigeration storage temperature. These strains also varied in levels of folate utilized during refrigerated storage at 4 [degrees] C. @@@@ ----------------------------------------------- Wilbert Sybesma,1 Marjo Starrenburg,1 Tijsseling, Marcel H. N. Hoefnagel,1,3 and Jeroen Hugenholtz1* Effects of Cultivation Conditions on Folate Production by Lactic Acid Bacteria APPLIED AND ENVIRONMENTAL MICROBIOLOGY, Aug. 2003, .69.8.4542- 4548.2003 @@@@ Several species and strains from the lactic acid bacterial genera Lactococcus, Lactobacillus, Streptococcus, and Leuconostoc were screened for folate production. The lactic acid bacteria L. lactis MG1363 and S. thermophilus B119 were further analyzed for folate production under different growth conditions. L. lactis, S. thermophilus, and Leuconostoc spp. produced folate in the range of 5 to 291 g/liter. Lactobacillus strains, with the exception of Lactobacillus plantarum, did not produce folate. In several strains, folate analysis performed after deconjugation resulted in detection of higher folate levels. This indicates that part of the folate is present as polyglutamyl folate with more than three glutamate residues. All folate-producing strains showed partial excretion of fo- late into the external medium. In L. lactis, up to 90% of the total produced folate remained in the cell and was identified as 5,10-methenyl tetrahydrofolate and presumably 10-formyl tetrahydrofolate, both with four, five, or six glutamate residues. In S. thermophilus, much less of the total produced folate remained in the cell and was identified as 5-formyl tetrahydrofolate and 5,10-methenyl tetrahydrofolate, both with three glutamate residues. The difference in distribution can probably be explained by the different length of the polyglutamyl tail of the two microorganisms. One of the functions of the polyglutamyl tail is believed to be the retention of folate within the cell (22, 30). The longer polyglutamyl tail identified in L. lactis improves the retention of folate. @@@@ @@@@ The observation that the level of folate produced is influenced by the specific lactic acid bacterium, growth conditions, and medium used could have a large impact on the manufacture of dairy products. For instance, by specifically selecting high-folate-producing strains as part of the starter culture, yogurt with elevated levels of folate could be produced (35, 41). Furthermore, it is expected that in combination with specific growth conditions and metabolic engineering approaches (36), the current contribution of yogurt of 10 to 20% to the average daily intake for folate could be substantially increased. @@@@ ------------------------------------------------------------ Karin M. Forsse´n, MSc, Margaretha I. Ja¨gerstad, PhD, Karin Wigertz, PhD, and Cornelia M. Wittho¨ft, PhD Folates and Dairy Products: A Critical Update. Journal of the American College of Nutrition, Vol. 19, No. 2, 100S- 110S (2000) Published by the American College of Nutrition @@@@ Folate deficiency is developed in the presence of malnutrition, due to low intake of folate-containing foods, or as a result of severe alcoholism. A more important risk factor is malabsorption, especially for diseases affecting either intestinal pH or the jejunal mucosa, e.g., celiac disease. Secondary folate deficiency (also giving rise to megaloblastic anaemia) may be due to vitamin B12 deficiency.@@@@ @@@@ Several studies over time indicate higher folate values for cow's milk during summer (May-September) than winter, ranging between 4mg and 10mg folate per 100g on an annual basis [23,40-42]. However, Hoppner and Lampi [44] found no significant variation of folate content in skim milk obtained from local stores in Canada. A seasonal change in milk folates seems logical considering that folate is an unstable vitamin with highest concentrations occurring in fresh green plants fed to the cows during the summer compared to longer stored winterfodder. @@@@ @@@@ Pasteurisation has only minor effects on the folate content of milk, causing losses of less than 10% [22,40,45]. According to a study by Andersson & Oste [14], folate levels in pasteurised milk were not reduced during storage beyond the expiration date. The milk, packaged in commercial paperboard cartons, was stored open in a refrigerator to simulate household conditions and was exposed to daylight at room temperature for two 30-minute periods per day [14]. @@@@ @@@@ Several review articles on the nutritive value of cultured dairy products, e.g., buttermilk and yogurt, have reported that the folate content of such milk products vary widely, ranging from 4mg to 19mg/100g [39,40,47-50]. Food composition tables based on microbiological assays report total folate values of between 5mg and 18mg per 100g for various fermented milk products (Table 1). A few studies based on HPLC analyses support the data obtained with microbiological assays (Table 2). In addition, one study using RBPA found plain yogurt to contain 5.4mg folate per 100g [23]. A recent study based on HPLC found buttermilk and yogurt to contain 9.7mg and 4.7mg 5-methyl-THF/100g, respectively [44]. The plain yogurt in their study consisted of a culture of Streptococcus salivarius ssp. thermophilus and Lactobacillus delbrueckii ssp. bulgaricus, which could continuously alter the composition and concentration of folate. However, the significantly lower levels of 5-methyl-THF found in plain yogurt compared with buttermilk (inocculated with Lactococcus lactis ssp. lactis, Lactococcus lactis ssp. cremoris, Lactococcus lactis ssp. lactis biovar. diacetylactis and Leuconostoc mesenteroides ssp. cremoris) seemed to be in accordance with observations by Rao & Shahani [51]. They found that the total folate levels in skimmed milk fermented by L. bulgaricus decreased from 9.8mg to 1.6mg/100g within 36 hours of incubation, while S. thermophilus and L. acidophilus increased the total folate levels substantially. In the presence of both L. bulgaricus and S. thermophilus (see plain yogurt) the former might have consumed the folates produced by the latter. @@@@ @@@@ Bound folate and free folate are absorbed in different ways in the gastro-intestinal tract. While free monoglutamic folate is absorbed in the jejunum, the protein- bound folate is mainly absorbed in the ileum and at a much slower rate than free folate [61]. A slower rate of transport, coupled with protection from intestinal bacteria, may improve the bioavailability of folate when bound to proteins in milk. In fact, breastfed babies have been reported to have a better folate status than bottlefed babies. While breastfed babies sustain their folate status on an intake of 55mg folate per day, bottlefed babies need 78mg/day. It has been suggested that the discrepancy is due to the occurrence of folate-binding proteins in human milk which are not present in the heat-processed milk formula [62,63]. @@@@ @@@@ A possible explanation of these conflicting results might be that the conditions used for pasteurisation are very close to those at which denaturation of FBP takes place. Thus, small fluctuations in the processing conditions may have a relatively large impact on the denaturation state of FBP. @@@@ @@@@ However, even if the heating step in yogurt production had been omitted, folate in fermented milk would most likely have occurred in the free form, since low pH such as that found in yogurt is known to cause dissociation between FBP and the folate [68]. @@@@ @@@@ All three methods show similar ranges for folate concentrations in cow's milk, 5-10mg per 100g, taking into consideration seasonal variations. In addition, data on folates in fermented milk products (buttermilk and yogurt) are comparable by these methods. Different starter cultures, however, might explain some of the variations in folate content and folate forms determined. An overall trend suggests that fermented milk contains slightly higher amounts of folates, sometimes double, depending on the starter culture used. @@@@ @@@@ Considering the bioavailability of dairy folates, HPLC studies indicate that approximately half of the folates in milk and dairy products occur as polyglutamic folates which require intestinal hydrolysis before they can be absorbed. In respect to the suggested role of folate-binding proteins in facilitating the absorption of folates from milk, new data on actual concentrations in different dairy products are now available. These data clearly show folate-binding proteins to occur in unprocessed milk, but also in pasteurised milk, spray-dried skim milk powder and whey. In contrast, UHT milk, fermented milk and most cheeses only contain low levels or trace amounts of FBP. The role of FBP, if any, requires further elucidation. One question that needs to be answered is whether FBP can resist gastrointestinal proteolysis, thereby acting like an " intrinsic factor " for folates. For example, if unsaturated FBP binds dietary folates, pasteurised milk, with its excess of FBP, could be used as a means of enhancing the bioavailability of not only milk folates but also dietary folates in general. @@@@ ------------------------------------------------------------ Int J Food Sci Nutr. 1996 Jul;47(4):315-22. Effect of milk processing on the concentration of folate-binding protein (FBP), folate-binding capacity and retention of 5- methyltetrahydrofolate. Wigertz K, Hansen I, Hoier-Madsen M, Holm J, Jagerstad M. Department of Applied Nutrition and Food Chemistry, Lund University, Sweden. The main objective of this study was to investigate the effects of pasteurisation, UHT processing and fermentation on the concentration of folate-binding proteins (FBP) and their folate binding capacity in comparison with the retention of the most predominant folate from, 5- CH3THF. The amount of folate-binding protein (FBP) was analysed using enzyme-linked immunosorbent assay (ELISA). Unprocessed milk and pasteurised milk were found to contain similar amounts, 211 and 168 nmol/l, of FBP, respectively. UHT-processed milk and Yoghurt naturelle, both processed at temperatures above 90 degrees C, contained only 5.2 and 0.2 nmol/l FBP, respectively. As an indication of the protein-binding capacity free and protein-bound folates were analysed after charcoal treatment using the radio-protein binding assay method (RPBA). These results indicated that all folates in unprocessed milk and pasteurised milk were protein-bound, while folates in UHT-processed milk and Yoghurt naturelle occurred freely which is supported by our findings on FBP. High-performance liquid chromatography analysis indicated that unprocessed milk, pasteurised milk, UHT-processed milk and Yoghurt naturelle contained 44.8 +/- 2.1 (n = 10), 41.1 +/- 0.9 (n = 10), 36.1 +/- 1.8 (n = 10) and 35.6 +/- 9.1 micrograms/l (n = 10) 5-methyltetrahydrofolates (5-CH3THF), respectively, after deconjugation. Corresponding values for total milk folates analysed using radio-protein binding assay were 80.4 +/- 0.9 (n = 10), 64.2 +/- 2.7 (n = 10), 48.2 +/- 1.8 (n = 10) and 54.0 +/- 8.2 micrograms/l (n = 10), respectively. Hence, both methods indicated significant (P < 0.05) losses of 5-CH3THF as a result of pasteurisation, UHT processing and fermentation, compared with unprocessed milk. In spite of apparent discrepancies in folate concentrations obtained using the two different methods, these results support the equimolar ratio of FBP and folates in unprocessed and pasteurised milk when data on 5-CH3THF, obtained using HPLC were corrected for differences in recovery. Thus, heat processing of milk not only reduced the amount of 5-CH3 THF significantly, but also changed the concentration of FBP and the folate-binding capacity of FBP, which may have implications on the bioavailability of milk folates. PMID: 8844253 [PubMed - indexed for MEDLINE] ---------------------------------------------------------- Folate and folate-binding protein content in dairy products. J Dairy Res. 1997 May;64(2):239-52. Wigertz K, Svensson UK, Jagerstad M. Department of Applied Nutrition and Food Chemistry, University of Lund, Sweden. Recent findings suggest a protective role for folates in the reduction of neural tube defects and possibly also coronary heart disease and cancer. Consequently, an increase in the daily intake of folates is warranted, which emphasizes the need for quantitative as well as qualitative measurements of dietary folates. Milk plays an important part in the food chain in many Western countries today. Several studies suggest that folate-binding proteins might have an impact on folate absorption and therefore their concentrations are also important. The mean concentration of the predominant form of folate, 5-methyltetrahydrofolate (5-CH3THF), was determined using HPLC in thirteen selected dairy products; skim milk powder, two pasteurized milks, UHT milk, two fermented milks, three whey products and four different cheeses. All results were corrected for recovery by spiking the samples with 5-CH3THF. Effects of storage of dairy products on 5-CH3THF concentrations were also investigated; generally small and insignificant fluctuations were found, except for hard cheese, in which 5-CH3THF decreased significantly. There was a significant seasonal variation in the folate concentration of pasteurized milk which peaked in the summer months. The concentrations of folate-binding protein in skim milk powder and pasteurized milk analysed using an enzyme-linked immunosorbent assay were similar. UHT milk and fermented milk, both of which are processed at temperatures > 90 degrees C, contained significantly lower concentrations of folate-binding protein. PMID: 9161916 [PubMed - indexed for MEDLINE] --------------------------------------------------------- Karin Arkbåge,3 Miriam Verwei,* Havenaar† and Cornelia Wittho¨ ft. Bioaccessibility of Folic Acid and (6S)-5-Methyltetrahydrofolate Decreases after the Addition of Folate-Binding Protein to Yogurt as Studied in a Dynamic In Vitro Gastrointestinal Model1,2 J Nutr. 2003 Nov;133(11):3678-83. @@@@ The lower pH of yogurt (pH 4.2) compared with milk (pH 6.8) (14) might affect the FBP binding activity and its stability during gastrointestinal transit. At a pH 5, FBP loses its folate-binding capacity, allowing dissociation between FBP and folate in yogurt. Moreover, the starter culture might have proteolytic enzymes that hydrolyze FBP during the gastrointestinal transit. This could result in a different folate bioaccessibility from yogurt compared with milk. @@@@ @@@@ Our results seem to agree in part with an in vivo study performed on 6-d-old goat kids (26). That study showed that gastric acidity and gastrointestinal digestive enzymes only slightly affected the folate-binding capacity of FBP in goat's milk. In addition, Tani et al. (10) found in rats that the folate binding activity of FBP recovered fully in jejunum after being reversibly inactivated under the gastric acidic conditions. However, contradictory results were obtained in an in vitro study (27) in which half of the folic acid-binding capacity was lost during pepsin treatment and all of the folic acid-binding capacity was lost after further digestion with trypsin. @@@@ @@@@ Folate bioaccessibility did not differ between folate-fortified yogurt and folate-fortified pasteurized milk (P 0.10). In contrast, the addition of FBP to both dairy matrices resulted in a lower (P 0.05) folate bioaccessibility in yogurt compared with milk. This was accompanied by a 2- to 16-fold higher ileal excretion of intact FBP from yogurt compared with the corresponding pasteurized milk. Thus, it seems that FBP is more stable in yogurt. The TIM protocols were identical for yogurt and milk, excluding that pH might have had an effect. Interestingly, the viable starter culture in yogurt seemed to have no degradable effect on FBP, nor did the microorganisms affect the folate content during the TIM experiment. @@@@ @@@@ In conclusion, both folic acid and (6S)-5-CH3-H4folate in fortified yogurt are highly bioaccessible (82%). The addition of FBP to yogurt (P 0.05) decreased the folate bioaccessibility with a more pronounced effect in yogurt fortified with folic acid than in yogurt fortified with (6S)-5-CH3-H4folate. In addition, the inhibiting effect of FBP on folate bioaccessibility was higher (P 0.05) in yogurt compared with milk. The stability of FBP during gastrointestinal transport of yogurt depended on the folate form used for fortification, and ranged between 17 to 34%; it appeared to be higher than the FBP stability in pasteurized milk (0-15%). @@@@ ------------------------------------------------------------------ Miriam Verwei,*‡2 Karin Arkbåge,†† Hans Mocking,† Havenaar* and Groten. The Binding of Folic Acid and 5-Methyltetrahydrofolate to Folate- Binding Proteins during Gastric Passage Differs in a Dynamic In Vitro Gastrointestinal Model1 J Nutr. 2004 Jan;134(1):31-7. @@@@ In untreated milk, 5-CH3-H4folate occurs bound to folatebinding proteins (FBP) (14 -16). The role of FBP in folate bioavailability is unclear. It has been suggested that FBP protects folate from bacterial uptake and degradation (17,18) or may play a role in sequestering folate from the blood plasma into the mammary glands, thereby supplying folate to the newborn (19). FBP could also affect mucosal folate transport, although both inhibition and enhancement have been reported (20 -23). The influence of FBP on folate absorption might depend on its binding to folate after gastric passage. @@@@ @@@@ (bioaccessibility is, in these studies, defined as the free folate fractions that are available for absorption during gastrointestinal passage). The bioaccessibility of folic acid from folic acid-fortified milk and yogurt was lower (P 0.05), i.e., 11-14 and 47%, respectively, after the addition of FBP to the fortified milk (13) and yogurt (25). However, FBP did not lower the bioaccessibility of 5-CH3-H4folate from fortified milk (13) and lowered the bioaccessibility of 5-CH3-H4folate from fortified yogurt by 26% (25). These findings indicate that FBP in whey powder, milk and yogurt have different binding characteristics for folic acid and 5-CH3-H4folate. @@@@ @@@@ It appeared that bovine FBP in a dairy matrix was less stable in combination with 5-CH3-H4folate (0-17%) than with folic acid (13- 34%). Thus, a major portion of FBP passed through the stomach intact and was largely digested by pancreatic enzymes along the passage through the small intestine. Apparently, this further digestion of FBP in the small intestine was dependent on the folate compound, folic acid or 5-CH3-H4folate, present in the dairy matrix. @@@@ @@@@ We conclude that a major part of folic acid is still bound to FBP after gastric passage, whereas a large portion of 5-CH3- H4folate is released from FBP. This difference in extent of binding to FBP for the two folate compounds can influence the folate bioavailability (i.e., release from the food matrix and intestinal transport) from milk products. To examine this further, studies are underway in our laboratory concerning the effect of FBP on intestinal transport of folic acid and 5-CH3- H4folate. @@@@ ------------------------------------------------------------------ a L. , Tony Treloar and F. Nixon Dietary interactions influence the effects of bovine folate-binding protein on the bioavailability of tetrahydrofolates in rats. J Nutr. 2003 Feb;133(2):489-95. @@@@ The folate in milk is entirely bound by an excess of folatebinding protein (FBP).4 The function of FBP in milk is unclear, but it may ensure the folate content of milk by sequestering folate from the blood plasma into the mammary gland (5). It is also very effective in stabilizing the very labile tetrahydrofolate (H4folate) and moderately labile 5- methyltetrahydrofolate (5-CH3H4folate) in vitro (6). FBP is resistant to gastric digestion, and although it releases folate at the pH of the stomach, the two recombine in the more alkaline environment of the small intestine (7,8). FBP binds folates in a 1:1 molar stoichiometry (9), and folate bound to FBP is less available to microorganisms that inhabit the intestinal tract (10), making more folate available for absorption. A few studies have investigated whether FBP has a direct effect on folate absorption. Several investigators have observed that although free folic acid is rapidly absorbed from the jejunum, absorption of folic acid, either bound to purified FBP or in the presence of crude milk, occurs primarily in the ileum 8,11,12,13). Whether overall absorption is affected by FBP is unclear; some investigators observed an increase (12,14), some observed no difference (8) and some observed less overall absorption (11,15) of folate when bound to FBP. Tani and Iwai (16) observed lower excretion of folate into the urine of rats when folic acid was administered with bovine FBP, and attributed this result to a more gradual absorption of folic acid, thereby decreasing the blood folate peak and reducing urinary folate loss. One study, using crude milk rather than purified FBP, examined the period after absorption and found that kidney and plasma folate levels were higher after 4 wk in rats fed a milk-containing diet than in rats fed a milk-free diet, despite the diets having equal folic acid content (17). @@@@ @@@@ The physical properties of FBP appear to be affected also by heat treatment. Raw cow's milk FBP binds folic acid with positive cooperativity, whereas that property is lost under selected conditions after pasteurization (49) without greatly affecting binding capacity or binding affinity. Whatever properties are altered by pasteurization might be associated with the observation (12) that pasteurized bovine and goat milk did not affect the uptake of folic acid into isolated intestinal cells, whereas uptake was enhanced by unheated human and goat milk. @@@@ @@@@ Our results suggest that FBP-rich foods could be combined with folate-rich foods to enhance the bioavailability of natural folates in human diets. However, these results also indicate that the effects of FBP depend upon other dietary components in complex interactions, making it impossible to extrapolate to full diets and other species with any confidence. @@@@ ------------------------------------------------------------------ J Nutr. 1982 Jul;112(7):1329-38. Denaturation of the folacin-binding protein in pasteurized milk products. JF 3rd. The folacin-binding characteristics and chromatographic properties of the folacin-binding protein (FBP) of commercial pasteurized skim milk and whey protein concentrate were compared with those of fresh raw cows' milk. Native state FBP recently has been shown to enhance the intestinal absorption of folacin, whereas the FBP of pasteurized milk is ineffective. Anion-exchange chromatography indicated no major electrostatic differences in the FBP of these products, although gel- filtration chromatography provided evidence of enhanced FBP aggregation in the pasteurized whey protein concentrate. Analysis of folic acid binding kinetics by using Scatchard and Hill plots indicated that pasteurization or subsequent processing induces alterations in binding cooperatively, its pH dependence, or both. These results suggest that partial denaturation during pasteurization alters the folacin-binding characteristics and extent of molecular interaction of FBP. These changes may be responsible for the reported differences between raw and pasteurized milk products in their ability to enhance folacin absorption. Further research is needed to clarify the biological significance of these findings with respect to potential differences in folacin bioavailability from breast milk, pasteurized cows' milk and infant formulas. PMID: 7097350 [PubMed - indexed for MEDLINE] ------------------------------------------------------------------ From old Native-Nutrition posts: ------------------------------------------------------------------- the RDA is 400 mcg (600 mcg for pregnancy). if 1/2 of a 2000 calorie diet contains decent (i'll pick .4 as a random cutoff) sources of folate, then that gives **at least** 400 mcg. in addition, if 20% of this diet contains excellent sources of folate (i'll pick 1.0 as a random cutoff), then that gives **at least** 640 mcg. throw in a few blowout sources, and it's not too hard to double or triple the RDA. here's my personal list for folate-density. folate (mcg/cal): (from the usda database) endive 8.4 spinach 8.4 lettuce, cos or romain 8.0 chrysanthemum leaves 7.4 turnip greens 7.2 mustard greens 7.2 chicken liver 5.9 lettuce, butterhead (includes boston and bibb) 5.6 lettuce, iceberg 5.6 collard 5.5 goose liver 5.5 duck liver 5.4 pak-choi 5.1 pe-tsai 4.9 veal liver 4.8 chicory 4.8 arugula 3.9 cabbage, savoy 3.0 okra 2.8 coriander 2.7 celery 2.6 radicchio 2.6 asparagus 2.6 beets 2.5 broccoli stalks 2.5 cress (garden) 2.5 lettuce, green leaf 2.5 cabbage, " common " 2.4 spearmint 2.4 sweetpotato greens 2.3 lettuce, red leaf 2.3 radish sprouts 2.2 mung beans, sprouted 2.0 scallions 2.0 moth beans 1.9 broccoli 1.9 mung beans 1.8 beef liver 1.7 lamb liver 1.7 pork liver 1.6 peppermint 1.6 daikon 1.6 chickpeas 1.5 lentils 1.3 alfalfa, sprouted 1.2 beef kidneys .99 lentils, sprouted .94 watercress .82 pepper, sweet .81 beet greens .80 swiss chard .74 tomato .71 lambsquarters .70 dandelion greens .60 cabbage, red .60 kale .58 crab .52 chicken heart .47 peanuts .42 pork kidneys .42 sunflower seeds .40 egg, yolk .40 egg, whole .30 lamb kidneys .30 veal kidneys .21 cuttlefish .20 octopus .20 sesame seeds .17 oats .14 wheat .12 lobster .10 milk .08 coconut .07 almonds .05 beef brain .03 beef heart .02 lamb heart .02 remarks: some common foods with virtually no folate content were included for reference, like milk and grains. other than some organs, no meat (land or sea) has any signficant folate content. some of this data is suspicious... keep in mind the limitations of the usda data... check out the HUGE variation in folate content among different greens in the usda database!! could it really be true that turnip greens have 12 times the concentration of folate as kale, even though they're from the same family??? here's an interesting passage from a website (the bit about masking b12 deficiency is misleading i think--i don't think it CAUSES the deficiency, only makes it difficult to recognize): @@@@@ The synthetic form of folate is more easily absorbed by the body than the natural folate. Consequently, 1 mcg food folate = 0.6 mcg of synthetic folic acid from a fortified food or a supplement when consumed at a meal or snack. When taken on an empty stomach, only 0.5 mcg is needed to equal 1 mcg of food folate. The upper limit, (its UL or tolerable upper limit) is 1 mg (1000 mcg). Intakes of 1 mg folate or more can mask vitamin B12 deficiency resulting in permanent nerve damage. This is another instance of " more is not necessarily better. " @@@@@ mike parker ------------------------------------------------------------------ @@@@@ Filippa: Thank you! So is folate destroyed by heat then? And what does " water soluble " mean? I know the literal meaning but what is the relevance in terms of consumption? @@@@@@@@@@@@@@@@@@@@@@ i guess the relevance of water-solubility is that if you soak/boil something, some of it will be leached into the water. it's one of the reasons why steaming is often recommended over boiling, unless your goal is to get rid the thing, like the tannins in acorns, water- soluble oxalates, etc. higher volumes of water leach more. @@@@@@@@@@@@ I'm making chicken liver pate tommorrow. Do you think if I leave the centre of the pieces of liver pink, I will leave some folic acid intact. Joanne @@@@@@@@@@@@ keeping in mind the limitations of the usda data, especially the fact that we don't know what conditions things were tested under, how long they were stored, what the animal ate, etc, here's a comparison of the data for chicken liver for different processing, expressed as percentage of folate of raw form. in other words, the percentage retained. simmered 83% pan-fried 55% canned pate 27% here's similar comparison for beef liver: braised 78% pan-fried 60% and for pork liver: braised 62% and some non-liver foods to get a better feel for it: boiled spinach / raw spinach 76% boiled frozen spinach / raw frozen spinach 90 % boiled turnip greens / raw turnip greens 82% boiled chickpeas / raw chickpeas 70% and to close out these citations of *****usda data******, here's this piece of exciting news: boiled lentils / raw lentils 120% !!!!!! so you can see that quite a bit of folate is retained despite cooking. of course, raw gives you more, but i wouldn't worry about it too much if you have other reasons for cooking it and you're eating a variety of veggies. of course, there may be other nutrients that are affected more dramatically; i really don't know! since folate is heat-labile, independent of being water-soluble, i'm guessing that the disparity between the simmered and pan-fried data comes from greater temperatures in frying. mike parker ----------------------------------------------------- Salmenpera L, Perheentupa J, Siimes MA. Folate nutrition is optimal in exclusively breast-fed infants but inadequate in some of their mothers and in formula-fed infants. J Pediatr Gastroenterol Nutr. 1986 Mar-Apr;5(2):283-9. Plasma concentrations of folate were studied in a group of exclusively breast-fed infants and their mothers (their numbers gradually decreased from 200 at birth to 7 at 12 months) and in infants completely weaned to a cow's milk formula (containing 35 micrograms of folate/L) and solid foods. The exclusively breast-fed infants were in no danger of folate deficiency; their plasma levels were elevated after the age of 2 months and, on average, were 2.0-3.3- fold higher than maternal levels throughout the study. None of these infants had an inadequate plasma concentration, whereas up to 5% of the mothers had values less than or equal to 3 micrograms/L, despite supplementation during lactation with 0.1 mg folate/day. In the formula-fed infants, 69-94% of the plasma folate concentrations lay below the lowest concentration for the breast-fed infants. Although no infant had signs of anemia or macrocytosis in red cell indices, the infants weaned earliest had the lowest hemoglobin concentrations (p = 0.09) and the highest mean corpuscular volume (MCV) values (p = 0.06) at 9 months of age. Thus, an infant fed a formula containing the recommended amount of folate runs a risk of folate deficiency. PMID: 3958855 [PubMed - indexed for MEDLINE] -------------------------------------------------------- Quote Link to comment Share on other sites More sharing options...
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