Maternal folic acid and multivitamin supplementation: International clinical evidence with considerations for the prevention of folate-sensitive birth defects.

More evidence is available for maternal intake, absorption, distribution, tissue specific concentrations, and pregnancy outcomes with folic acid (fortification/supplementation) during preconception - first trimester. This Quality Improvement prevention review used expert guidelines/opinions, systematic reviews, randomized control trials/controlled clinical trials, and observational case control/case series studies, published in English, from 1990 to August 2021. Optimization for an oral maternal folic acid supplementation is difficult because it relies on folic acid dose, type of folate supplement, bio-availability of the folate from foods, timing of supplementation initiation, maternal metabolism/genetic factors, and many other factors. There is continued use of high dose pre-food fortification 'RCT evidenced-based' folic acid supplementation for NTD recurrence pregnancy prevention. Innovation requires preconception and pregnancy use of 'carbon one nutrient' supplements (folic acid, vitamin B12, B6, choline), using the appropriate evidence, need to be considered. The consideration and adoption of directed personalized approaches for maternal complex risk could use serum folate testing for supplementation dosing choice. Routine daily folic acid dosing for low-risk women should consider a multivitamin with 0.4 mg of folic acid starting 3 months prior to conception until completion of breastfeeding. Routine folic acid dosing or preconception measurement of maternal serum folate (after 4-6 weeks of folate supplementation) could be considered for maternal complex risk group with genetic/medical/surgical co-morbidities. These new approaches for folic acid oral supplementation are required to optimize benefit (decreasing folate sensitive congenital anomalies; childhood morbidity) and minimizing potential maternal and childhood risk.

Lower dietary vitamin E intake during the second trimester is associated with insulin resistance and hyperglycemia later in pregnancy.

BACKGROUND/OBJECTIVES: Beneficial effects of vitamin E on insulin sensitivity have been reported in observational and short-term intervention studies in non-pregnant populations. We aimed to investigate whether dietary vitamin E intake during the second trimester would be associated with glucose metabolism later in pregnancy and whether this association would be influenced by an insulin-sensitizing hormone adiponectin. SUBJECTS/METHODS: Women with singleton pregnancies (n=205) underwent a 3-h oral glucose tolerance test at 30 weeks gestation and were asked to recall second trimester dietary intake. RESULTS: Higher dietary vitamin E intake was associated with lower fasting glucose, lower HOMA insulin resistance, and higher Matsuda insulin sensitivity index after covariate adjustment including serum adiponectin among women consuming daily multivitamin supplements (all P≤0.03). CONCLUSIONS: Lower dietary vitamin E intake during the second trimester is associated with hyperglycemia and insulin resistance later in pregnancy among women consuming daily multivitamin supplementations. Further, these associations are not influenced by adiponectin.

Effect of pasteurization on selected immune components of donated human breast milk.

OBJECTIVE: Pasteurized, donated milk is increasingly provided to preterm infants in the absence of mother's own milk. The aim of this study was to determine the effect of pasteurization on the concentration of selected components in donated human breast milk. STUDY DESIGN: Donated milk from 34 mothers was pooled into 17 distinct batches (4 mothers per batch). Aliquots of each batch were then Holder pasteurized (62.5 °C for 30 min). Interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß), IL-2, IL-4, IL-5, IL-8, IL-10, IL-12p70 and IL-13 were measured in a multiplex enzyme-linked immunosorbent assay (ELISA). Granulocyte colony-stimulating factor (G-CSF), heparin-binding epidermal-like growth factor (HB-EGF) and hepatocyte growth factor (HGF) were measured by ELISA. Lipids were assessed by gas chromatography and gangliosides by the resorcinol-HCl reaction. RESULT: IFN-γ, TNF-α, IL-1ß, IL-10 and HGF were significantly reduced by pasteurization (P<0.05). Gangliosides were not affected, but the proportion of medium-chain saturated fats was increased (P<0.05) with a trend towards a decreased proportion of oleic acid (P=0.057). CONCLUSION: Pasteurization significantly reduced the concentration of several immunoactive compounds present in breast milk, but did not have an impact on others.

Characterization of folate-dependent enzymes and indices of folate status in laying hens supplemented with folic acid or 5-methyltetrahydrofolate.

The conversion of folic acid (FA) to the biologically active 5-methyltetrahydrofolate (5-MTHF) is necessary for the deposition of folate in the egg. A study was conducted to compare egg folate concentrations, indices of folate status, and activities of folate-dependent enzymes in response to equimolar intake of either FA or 5-MTHF in laying hens. Forty-eight laying hens, 24 wk of age, from 2 different strains (Shaver White and Shaver Brown) were randomly assigned to receive 1 of 3 (n = 8 per strain) dietary treatments: 1) basal diet with no supplemental folate, 2) basal diet + 10 mg/kg of FA, or 3) basal diet + 11.3 mg/kg of 5-MTHF for 3 wk. A completely randomized design with 3 dietary treatments and 2 laying hen strains in a 3 x 2 factorial arrangement was used. Data were subjected to ANOVA, using the PROC GLM procedure of SAS. Plasma homocysteine, serum, and egg folate concentrations; hepatic serine hydroxymethyltransferase; and methionine synthase activity were affected by dietary folate supplementation but not by its form (FA and 5-MTHF). Relative to control hens, plasma homocysteine was decreased (P < 0.05) by 14.2%, whereas serum and egg folate were increased (P < 0.05) by 78.3 and 61.8%, respectively, in hens consuming either folate compound. Hepatic serine hydroxymethyltransferase and methionine synthase activity were increased and decreased (P < 0.05), respectively, in folate-fed birds compared with control-fed birds. Hepatic dihydrofolate reductase was influenced by both the addition and form of dietary folate, being higher (P < 0.05) in FA-fed birds than in 5-MTHF and control-fed birds. Feed efficiency was improved (P < 0.05) in 5-MTHF-fed birds relative to FA-fed birds. Strain of hen influenced serum folate and plasma homocysteine concentrations but not other indices of folate metabolism. Overall, FA and 5-MTHF have equivalent effects in enhancing egg folate concentrations and improving folate status in laying hens. Also, supplementation and form of folate may modulate the activity of folate-dependent enzymes.

Growth and development in preterm infants fed long-chain polyunsaturated fatty acids: a prospective, randomized controlled trial.

OBJECTIVES: A randomized, masked, controlled trial was conducted to assess effects of supplementing premature infant formulas with oils containing the long-chain polyunsaturated fatty acids, arachidonic acid (AA; 20:4 n6), and docosahexaenoic acid (DHA; 22:6 n3) on growth, visual acuity, and multiple indices of development. METHODS: Infants (N = 470) with birth weights 750 to 1800 g were assigned within 72 hours of the first enteral feeding to 1 of 3 formula groups with or without long-chain polyunsaturated fatty acids: 1) control (N = 144), 2) AA+DHA from fish/fungal oil (N = 140), and 3) AA+DHA from egg-derived triglyceride (egg-TG)/fish oil (N = 143). Infants were fed human milk and/or Similac Special Care with or without 0.42% AA and 0.26% DHA to term corrected age (CA), then fed human milk or NeoSure with or without 0.42% AA and 0.16% DHA to 12 months' CA. Infants fed exclusively human milk to term CA (EHM-T; N = 43) served as a reference. RESULTS: Visual acuity measured by acuity cards at 2, 4, and 6 months' CA was not different among groups. Visual acuity measured by swept-parameter visual-evoked potentials in a subgroup from 3 sites (45 control, 50 AA+DHA [fish/fungal]; 39 AA+DHA [egg-TG/fish]; and 23 EHM-T) was better in both the AA+DHA (fish/fungal; least square [LS] means [cycle/degree] +/- standard error [SE; octaves] 11.4 +/- 0.1) and AA+DHA (egg-TG/fish; 12.5 +/- 0.1) than control (8.4 +/- 0.1) and closer to that of the EHM-T group (16.0 +/- 0.2) at 6 months' CA. Visual acuity improved from 4 to 6 months' CA in all but the control group. Scores on the Fagan test of novelty preference were greater in AA+DHA (egg-TG/fish; LS means +/- SE, 59.4 +/- 7.7) than AA+DHA (fish/fungal; 57.0 +/- 7.5) and control (57.5 +/- 7.4) at 6 months' CA, but not at 9 months' CA. There were no differences in the Bayley Mental Development Index at 12 months' CA. However, the Bayley motor development index was higher for AA+DHA (fish/fungal; LS means +/- SE, 90.6 +/- 4.4) than control (81.8 +/- 4.3) for infants

Caregiving arrangement and nutrition: good news with some reservations.

The objective of this study was to assess the impact of caregiving arrangement on the iron and folate status of infants and toddlers reared at home or enrolled in centre-based, independent home, or licensed home care. One hundred and eighty-nine children aged 2 to 29 months were assessed 1 month prior to child care entry and at 6 months after entry into child care. Dietary (24-hour records), anthropometric (height, weight, head circumference) and biochemical (red blood cell folate, hematocrit, transferrin, and serum ferritin concentrations) methods were used to assess nutritional status. Frequency of illness was determined by a series of telephone interviews. Median intake of nutrients exceeded Canadian recommendations, regardless of care arrangement. Fifteen of 65 children had hematocrit values below age-specific cutoffs at the 6-month post-entry to child care visit. Children were frequently taken to obtain medical advice (average of 4 to 6 times during the study period) and 75% of subjects were prescribed at least one course of antibiotics. In conclusion, infants and toddlers in this study were generally well nourished, regardless of child care arrangement; however, iron status may remain an issue in this sample of infants and toddlers.

A three-day weighed food record and a semiquantitative food-frequency questionnaire are valid measures for assessing the folate and vitamin B-12 intakes of women aged 16 to 19 years.

The purpose of this study was to validate a food-frequency questionnaire (FFQ) and a 3-d weighed food record (3d-WFR) by comparing nutrient intakes estimated using these methods with serum folate, RBC folate and serum vitamin B-12 concentrations in 105 females aged 16-19 y. During an early morning clinic visit, subjects completed a self-administered, 116-item FFQ, blood was collected and they were trained to complete a 3d-WFR. Folate intakes as determined by the 3d-WFR (r = 0.65, P < 0.01) exhibited a stronger association with serum folate than did intakes from the FFQ (r = 0.48, P < 0.01) (P = 0.017). The correlations between folate intakes and RBC folate as determined by the FFQ (r = 0.42, P < 0.01) and 3d-WFR (r = 0.50, P < 0.01) methods did not differ. Vitamin B-12 intakes showed only a modest association with serum vitamin B-12 when supplement users were included in the analyses (FFQ, r = 0.25, P < 0.05; 3d-WFR, r = 0.32, P < 0.05). After excluding supplement users from the analyses, the relationship between vitamin B-12 intakes as determined by FFQ and serum vitamin B-12 was no longer significant. Median daily folate intakes (346 vs. 212 microgram) and vitamin B-12 (4.9 vs. 1.9 microgram) estimated from the FFQ were higher than those obtained from the 3d-WFR. In sum, these data suggest that both the FFQ and 3d-WFR are valid measures of assessing the folate intake of young women, and both appear to be useful in determining vitamin B-12 intake when supplemental users are included. The markedly different conclusions about absolute folate and vitamin B-12 intakes obtained using these two dietary methodologies should be taken into consideration when making recommendations about optimal folate intakes in relation to disease prevention.

Oral contraceptives did not affect biochemical folate indexes and homocysteine concentrations in adolescent females.

OBJECTIVE: The study was designed to determine the impact of currently available oral contraceptive agents (OCAs), smoking, and alcohol on biochemical indexes of folate and vitamin B-12 in adolescent females. DESIGN: Subjects completed a 3-day weighed food record along with a detailed lifestyle questionnaire that included questions on OCA, cigarette, and alcohol use. After subjects had fasted overnight, blood samples were collected and analyzed for levels of serum and red blood cell (RBC) folate and serum B-12 and homocysteine. SUBJECTS/SETTINGS: Two hundred twenty-nine adolescent females (aged 14 to 20 years) were recruited from southern Ontario, Canada, by advertisements in newspapers, high schools, universities, shopping malls, adolescent drop-in centers, and community groups. STATISTICAL ANALYSES PERFORMED: Multiple regression models were used to determine the effect of lifestyle factors and covariates (e.g., dietary folate intake, supplemental folate intake, and age) on biochemical indexes. RESULTS: OCA use, alcohol use, and smoking were not significantly associated with lower serum or RBC folate levels, after controlling for folate intake. Serum homocysteine levels were not associated with smoking or OCA use; however, we estimated a 13% higher concentration among alcohol users than nonusers. Smoking and alcohol use were not associated with serum B-12 levels, but OCA use was associated with an estimated 33% lower serum B-12 level than nonuse. APPLICATIONS: Our findings provide no evidence to suggest that currently available OCAs have a negative impact on the folate status of adolescent females; thus, dietary advice designed to specifically encourage an increase in folate intake among adolescents who use OCAs is not supported. In contrast, serum B-12 levels were lower among OCA users than nonusers, which suggests that an interaction between OCA and some vitamins may persist. The suboptimal biochemical folate indexes of smokers may have more to do with the dietary quality of smokers than previously appreciated. Thus, efforts to improve dietary folate intakes of adolescents who smoke may be an important strategy for improving the folate status of young women.

PIP: The impact of oral contraceptive (OC) use, smoking, and alcohol drinking on biochemical indexes of folate and vitamin B-12 was investigated in 229 adolescents 14-20 years old recruited from advertisements in Ontario, Canada. Subjects completed a life-style questionnaire and a 3-day, weighed food record, followed by overnight fasting and the collection of blood samples. Of the 48 participants (21%) who were OC users, 30 had used the pill for more than 12 months. Only 37 adolescents (16%) smoked, but 94 (60%) had consumed alcohol in the month preceding the study. Median daily intake of folate and vitamin B-12 (including intake from supplements) was 215 mcg and 1.9 mcg, respectively. OC use, smoking, and alcohol consumption were not significantly associated with lower serum or red blood cell folate levels, after controlling for folate intake. Serum homocysteine levels were not correlated with smoking or OC use, but were 13% higher among alcohol drinkers than nondrinkers. Finally, although smoking and alcohol use were not associated with serum B-12 levels, OC use was linked with an estimated 33% lower serum B-12 level than was nonuse. These findings fail to validate concerns that OC use has a negative impact on the folate status of adolescent females, but suggest a need to improve the dietary folate intake of young women who smoke.

Association between dietary fiber intake and the folate status of a group of female adolescents.

The main objective of this study was to assess the association between dietary fiber intake and the folate status of Canadian female adolescents. We also assessed dietary folate intakes and evaluated the prevalence of biochemical folate deficiency in these subjects. Female adolescents aged 14-19 y (n = 224) were recruited and fasting blood samples were collected. Dietary intakes (3-d food record) were recorded and participants were classified as lactoovovegetarians, semivegetarians, or omnivores on the basis of food-consumption patterns assessed with food-frequency questionnaires. Fourteen percent, 17%, and 26% of lactoovovegetarians, semivegetarians, and omnivores, respectively, had dietary folate intakes below their predicted requirements; 1%, 4%, and 23%, respectively, had serum folate concentrations indicative of deficiency. Despite low dietary folate intakes and serum folate concentrations, few subjects had homocysteine concentrations indicative of deficiency, suggesting that the degree of folate depletion had not yet produced functional consequences. Most important, results suggest that the consumption of nonstarch polysaccharide is significantly associated with serum folate concentrations (P < 0.001). For each 1-g increase in nonstarch polysaccharide intake, a 1.8% increase in serum folate concentration is expected. In summary, we propose that an increase in nonstarch polysaccharide intake may promote the intestinal biosynthesis of folate, providing a complementary strategy to enhance the folate nutriture of humans.

Maternal folate status and lactation.

Folate plays an essential role in DNA, RNA, and protein biosynthesis. For this reason, the physiological need for this vitamin is increased during periods of rapid anabolic activity such as pregnancy and lactation. Although the importance of folate and the consequences of suboptimal folate status during pregnancy, especially during the periconceptional period, are well appreciated, little is known about the value of folate during lactation. The limited number of studies available on folate intake during lactation suggest that many women do not consume an adequate amount of folate and that recommended target intakes may be too low. Although inadequate maternal folate intake does not affect milk folate concentration unless maternal deficiency is severe, potential consequences of suboptimal folate nutrition to both the mother and her future offspring should also be considered.

Feeding human milk to rats increases Bifidobacterium in the cecum and colon which correlates with enhanced folate status.

The purpose of this investigation was to determine if feeding diets containing human milk resulted in increased numbers of microorganisms implicated in increased folate production and the effect on folate availability. Following a folate-depletion period (5 wk), 30 rats were fed folate-repletion diets (4 wk) with or without 20% milk solids (human, cow or goat) and containing either 906 or 4530 nmol folic acid/kg. At the end of the test period, the cecum and colon were removed in an anaerobic chamber, homogenized, diluted (10(-2) -10(-8)), and the contents of each plated on selective and nonselective media. In addition to enumeration of the total anaerobic load, five genera of bacteria were counted (Bacteroides, Bifidobacterium, Clostridium, Escherichia and Streptococcus). Rats fed human milk solids had at least a seven- and onefold mean increase in the Bifidobacterium concentration in the cecum (P < 0.006) and colon (P < 0.04), respectively, compared with rats fed other diets. The total anaerobic bacterial concentration in the cecum and the colon of rats fed human milk solids was also greater than that of rats fed the other diets (P < 0.05). The single exception was the total anaerobic count in the cecum of rats consuming goat milk solids, which did not differ from that of rats consuming human milk solids. Further, rats fed human milk solids had at least a 42 and 48% higher mean plasma folate concentration and total cecal material folate content, respectively, than rats in other dietary treatments containing 906 nmol/kg folic acid. Therefore, the improved folate status of rats fed human milk-containing diets appears to be due, at least in part, to increased folate synthesis by Bifidobacteria and other folate-synthesizing microbes in the cecum and colon.

Postpartum folic acid supplementation of adolescents: impact on maternal folate and zinc status and milk composition.

The objectives of the present study were to assess the impact of lactation on the folate status of adolescents and determine the effect of ingestion of a low-dose postpartum (PP) folic acid supplement on maternal folate and zinc status and milk composition. Pregnant adolescents (aged 14-19 y; n = 71) were recruited; those who initiated breast-feeding on delivery were randomly assigned to a folic acid supplement lactating (SL; 300 micrograms/d, n = 14) group or to a placebo lactating (PL; n = 15) group. Subjects who initiated formula feeding were given a placebo (FF; n = 18). Dietary intakes (two 24-h recalls) were recorded and blood and milk samples were collected at 4, 8, and 12 wk PP. Of the adolescents, 71%, 48%, 67%, and 60% had folate, iron, vitamin B-12, and zinc intakes, respectively, below their predicted requirements. Despite this, most blood indexes were within normal ranges, probably reflecting the subjects' use of supplements during pregnancy. Red blood cell (r = -0.49, P < 0.05) and plasma (r = -0.42, P = 0.08) folate concentrations were negatively correlated with milk zinc concentrations. Mean red blood cell folate content declined between 4 and 12 wk PP among PL (31%) and FF (34%) subjects (P < 0.05) but not among SL subjects. Hence, 300 micrograms folic acid/d was sufficient to prevent a decline in blood folate values of these adolescents PP.

Biochemical folate, B12, and iron status of a group of pregnant adolescents accessed through the public health system in southern Ontario.

PURPOSE: This study was designed to estimate the prevalence of biochemical iron, folate, and vitamin B12 depletion among a group of Canadian pregnant adolescents accessed through the Public Health system. Further, the impact of prenatal supplement use, chronologic age, gynecologic age, living arrangement, main source of income, postpartum custody plan, time of entry into prenatal care, and cigarette smoking on laboratory indices of the three nutrients were determined. METHODS: Fifty-eight adolescents (14.5-19.0 years) were interviewed and blood samples were collected at 36 +/- 2 wk gestation. RESULTS: Thirteen (22%) of the pregnant adolescents had anemia (hemoglobin < 110 g/L) and forty-five (78%) had depleted iron stores (plasma ferritin < 26.6 pmol/L or 12.0 micrograms/L). Twenty-five subjects had plasma B12 values in the sub-optimal range (< 148 pmol/L). Five of the 16 adolescents who infrequently or never consumed a folate-containing supplement had suboptimal erythrocyte folate values. Twenty-four percent of the subjects had hypersegmented neutrophils and of these, all and 71% of subjects had plasma ferritin and B12 concentrations in the suboptimal range, respectively. Self-reported folic acid and B12 supplement intakes were correlated with the corresponding blood values for these nutrients. In contrast, supplement iron use was only weakly, or not at all associated with biochemical indices of iron status. CONCLUSIONS: Data from the present study indicate that plasma B12 and ferritin levels are low in a group of pregnant adolescents. These low values appear to be associated with a high prevalence of hypersegmented neutrophils. Prenatal supplement use appears to reduce the risk of low folate and B12 blood values but not biochemical iron status.

Folate bioavailability from milk-containing diets is affected by altered intestinal biosynthesis of folate in rats.

This study was designed to assess the effect of succinylsulfathiazole on the apparent bioavailability of folate added to milk-containing diets. We also evaluated the impact of milk type on the relative bioavailability (bioavailability) of folate following pasteurization (62.5 degrees C, 30 min) and on the bioavailability of folic acid (PteGlu) vs. pteroylhexa-gamma-L-glutamic acid (PteGlu6). Following folate depletion (5 wk), 108 rats (six per group) were fed for 4 wk diets with or without 20 g milk solids/100 g diet and containing PteGlu, PteGlu + 5 g/kg succinylsulfathiazole, or PteGlu6. Folate bioavailability was determined using plasma folate concentration and a standard curve generated from rats fed milk-free diets with graded levels of PteGlu. The PteGlu and PteGlu6 bioavailability from human milk-containing diets was twice that of diets containing cow or goat milk (P < 0.05). Incorporation of a sulfa drug into diets containing human or cow milk reduced PteGlu bioavailability by one half (P < 0.05). Further, the values for bioavailability of PteGlu from diets containing human or goat milk no longer differed (0.86 and 0.75, respectively), and bioavailabilities from human milk- and goat milk-containing diets were greater than that of the cow-milk-containing diet (0.54) (P < 0.05). Pasteurization of milk did not influence folate bioavailability. The bioavailability of PteGlu6 was 49-71% that of PteGlu (P < 0.05). In summary, milk type differentially affects intestinal folate biosynthesis, and the superior folate bioavailability from human milk-containing diets is due in part to enhanced intestinal biosynthesis of folate.

Zinc status of a group of pregnant adolescents at 36 weeks gestation living in southern Ontario.

OBJECTIVE: Pregnant adolescents have very high zinc (Zn) requirements to support the developing fetus and to maintain skeletal maturation after menarche. METHODS: Sixty-six adolescents aged 17.1 +/- 0.15 years (mean +/- SEM; range 14.5-19.0 years) were recruited from three regions of Southern Ontario at 35.9 +/- 0.15 weeks gestation. Data on sociodemographic status, health, infant birth weight and birth length, smoking, alcohol consumption, and prenatal supplement use were collected. Fasting venipuncture blood was analyzed for Zn (via AAS) and alkaline phosphatase in plasma; scalp hair was analyzed for Zn by instrumental neutron activation. RESULTS: Mean (95% CI) values were: plasma Zn 10.7 (10.0-11.5) mumol/L; plasma alkaline phosphatase 46.6 (43.7-49.5) U/L; hair Zn 2.64 (2.52-2.77) mumol/g. None of the plasma and hair Zn values were indicative of suboptimal Zn status. Mean plasma Zn concentrations of subjects (n = 19) consuming a supplement with Zn sulfate were higher than those of subjects consuming a supplement with Zn oxide (n = 18) (12.2 vs 9.7 mumol/L; p < 0.02) and unsupplemented subjects (n = 11) (9.4 mumol/L). Plasma Zn concentrations correlated negatively with reported birth lengths (mean +/- SEM = 51.6 +/- 0.31 cm) while accounting for chronological age (r = 0.42; p < 0.01), but not with reported birth weights (mean +/- SEM = 3.439 +/- 0.107 kg). CONCLUSIONS: Results emphasize that the form of Zn must be taken into account when considering the impact of prenatal supplements containing Zn on plasma Zn concentrations. Suboptimal Zn status was not prevalent in these pregnant adolescents.

The impact of iron deficiency on the flux of folates within the mammary gland.

The purpose of the present study was to examine whether impaired milk folate secretion during maternal iron deficiency is due to an altered flux of folates within the mammary secretory cell. Specifically we sought to determine whether the folate substrates of methionine synthase and the products of folylpolyglutamate synthetase are altered during iron deficiency in vivo. Rats were fed diets containing 0.5, 2.0 or 7.0 mg/kg folate and 8(Fe-) or 250(Fe+)mg/kg Fe throughout gestation and lactation. On day 17 of lactation dams were milked and killed. The concentration of reduced, methylated (5-CH3-H4), nonmethylated short and long chain forms of folate in milk were determined using a differential microbiological technique. Total mean milk folate concentrations among Fe- dams fed 2.0 and 7.0 mg/kg folate were half that of Fe+ dams fed 2.0 and 7.0 mg/kg folate. Despite this, the relative proportion of reduced, 5-CH3-H4, short and long chain folates did not differ in milk from Fe+ or Fe- dams. Approximately 75% of milk folates were methylated. Only Fe+ dams fed 7.0 mg/kg folate produced milk containing significant quantities of incompletely reduced folates. In conclusion, activity of the mammary epithelial cell enzymes methionine synthase and folylpolyglutamate synthetase in vivo, are unaffected by iron deficiency and therefore are not responsible for the dramatic reduction in milk folate secretion.

Pteroylpolyglutamates in human milk.

Considerable variation exists in reported values for total folate content and the pteroylpolyglutamate (PteGlun) content of human milk. We investigated possible methodological sources of this variation. In two laboratories, milk folate content (with and without folate conjugase) was determined microbiologically. No differences in total milk folate or PteGlun (n greater than 3) content were found between laboratories. PteGlun was found to comprise a significant fraction of total milk folate (28%). Use of rennin did not alter total folate content nor the percent of PteGlun in human milk. Heating (121 degrees C for 5 min) increased folate concentrations (190%, P less than 0.0001), indicating that release of folate from binding protein is necessary for folate utilization by Lactobacillus casei. Although human milk folate conjugase, (FC) activity was approximately one-twentieth that of plasma FC activity, it was not sufficient to autolyze endogenous PteGlun. Thus, microbiological protocols that do not use folate conjugase and do not release folate from binding proteins will seriously underestimate milk folate values.

Interaction of iron and folate during reproduction.

Biochemical evidence collected from both clinical and non-institutionalized populations indicate that iron and folate deficiencies frequently occur simultaneously. Supplementation trials of iron-deficient patients with either iron or iron and folate has helped to illustrate that a complex interrelationship exists between these two nutrients. Controlled animal trials in which dietary iron and folate content has been systematically manipulated reveal that iron deficiency can cause altered folate utilization. The impact of iron deficiency on folate metabolism is most dramatic during the reproductive and neonatal stages of the life cycle. Rat pups and piglets nursed by dams fed iron-depleted diets exhibit signs of altered folate utilization. Depressed milk folate secretion is an early manifestation of iron deficiency in the rat dam and is a prime factor responsible for folate depletion in their nursing pups. Impaired milk folate secretion during iron deficiency is not due to a decrease in the amount of folate supplied to the mammary gland; rather, the defect causing this reduction is specific to the mammary gland.