The effect of oral contraceptives on folate metabolism

Association Between Use of Oral Contraceptives and Folate Status: A Systematic Review and Meta-Analysis

OBJECTIVE

To conduct a systematic review and meta-analysis of the effect of oral contraceptive use on plasma and red blood cell (RBC) folate concentrations.

METHODS

We searched Medline, EMBASE, Web of Science, and the Cochrane library for human studies published from inception to June 2013 evaluating oral contraceptive use and folate status. Case-control studies, cohort studies, and clinical trials were included. A random-effects model of outcomes was used for the meta-analysis.

RESULTS

A total of 2831 women in 17 studies were included in the analysis. In those whose plasma folate concentrations were available, there was a significant folate-lowering effect of oral contraceptives observed (mean reduction 1.27 µg/L; 95% CI 1.85 to 0.69, P < 0.001). Similarly, after analyzing data from 1389 women in 12 studies whose RBC folate concentrations were available, significantly lower folate status was observed among oral contraceptive users (mean reduction 59.32 µg/L; 95% CI 58.03 to 23.04, P < 0.001).

CONCLUSION

Because of the reduction in blood folate concentrations associated with the use of oral contraceptives, it is critical for women of childbearing age to continue folate supplementation during oral contraceptive use.

Effects of oral and transdermal 17 beta-estradiol combined with progesterone on homocysteine metabolism in postmenopausal women: a randomised placebo-controlled trial

Mild hyperhomocysteinemia is a risk factor for both ischaemic heart disease and venous thromboembolism. The effects of transdermal estrogen replacement therapy (ERT) on homocysteine metabolism in postmenopausal women have scarcely been investigated. This clinical trial aimed to estimate the effects of combined hormone replacement therapy on the fasting total homocysteine levels according to the estrogen route of administration. We enrolled 196 postmenopausal women, who were randomly allocated to receive on a continuous basis either 1mg of 17 beta-estradiol orally (n = 63) or 50 microg transdermally (n = 68) per day, both combined with a daily intake of 100 mg progesterone, or placebo (n = 65) over a period of 6 months. Neither oral nor transdermal ERT significantly affected total plasma homocysteine levels or red-blood cell folate levels. However, oral ERT significantly decreased plasma vitamin B12 levels compared to placebo (mean relative variation difference over 6 months between oral ERT and placebo: -11.7% (95%CI, -21 to -2%) whereas transdermal ERT did not display any significant effects. Our data show that transdermal ERT as well as low dose of oral ERT does not significantly affect the homocysteine metabolism. This finding does not support a role for transdermal estrogen in the prevention of ischaemic heart disease in postmenopausal women.

Effects of hormone replacement therapy and methylenetetrahydrofolate reductase polymorphism on plasma folate and homocysteine levels in postmenopausal Japanese women

OBJECTIVE

To evaluate the relationships among the methylenetetrahydrofolate reductase (MTHFR) polymorphism, plasma folate, total homocysteine (Hcy) levels, lipids, and the reduction of Hcy levels resulting from hormone replacement therapy (HRT).

DESIGN

Clinical study.

SETTING

Outpatient department of obstetrics and gynecology in a general hospital.

PATIENT(S)

Two hundred seventeen postmenopausal Japanese women.

INTERVENTION(S)

Of the 217 women, 172 patients were under continuous treatment with oral conjugated equine estrogen and medroxyprogesteron acetate.

MAIN OUTCOME MEASURE(S)

Fasting Hcy, folate, methionine, lipids, and apolipoproteins were measured before and after 3 months of HRT.

RESULT(S)

The plasma Hcy concentration was significantly higher in the low folate than in the high-folate group only in patients with the homozygous (T/T) mutant. Plasma Hcy concentrations were significantly correlated with age (R = 0.64, P=.02) or years since menopause (R = 0.73, P=.02) only in the low-folate group with T/T. The plasma Hcy concentration decreased significantly in all genotypes after 3 months of HRT, but the levels of serum folate and methionine remained unchanged.

CONCLUSION(S)

The MTHFR polymorphism was associated with a higher Hcy concentration, and this association was related to the serum folate level. Hormone replacement therapy reduced the plasma Hcy concentration independently of the MTHFR polymorphism.

The effect of estrogen replacement therapy on total plasma homocysteine in healthy postmenopausal women

OBJECTIVE

To clarify the effect of estrogen on total plasma homocysteine concentration and on the concentration of vitamins required for homocysteine metabolism (folate, vitamin B12, and vitamin B6).

METHODS AND RESULTS

We measured total fasting plasma homocysteine in 16 healthy postmenopausal women before and 6 hours after a methionine load (100 mg/kg); fasting concentrations of folate, vitamin B12, vitamin B6, total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol were also determined. After 6 months of estrogen replacement therapy with estradiol, 2 mg daily, and 1 cycle of quarterly methoxyprogesterone acetate, 5 mg daily administered on the 91st through 100th days, measurements were repeated. There was no significant change in mean +/- SD fasting homocysteine concentration (8.8+/-2.5 vs 8.5+/-2.0 micromol/L; P=.30); homocysteine concentrations after methionine load increased from 38.8+/-12.3 to 51.1+/-12.5 micromol/L (P=.01). During this time period, no significant changes occurred in the concentrations of folate (11.7+/-4.4 vs 9.8+/-4.1 nmol/L; P=.06), vitamin B12 (394+/-182 vs 411+/-155 pmol/L; P=.40), or vitamin B6 (pyridoxal phosphate) (26+/-21 vs 36+/-25 nmol/L; P=.15). The mean +/- SD concentration of low-density cholesterol declined 20% (from 147+/-32 to 118+/-37 mg/dL) and high-density lipoprotein increased 16% (from 40+/-13 to 46+/-19 mg/dL) during the study period.

CONCLUSIONS

Six months of estrogen replacement therapy did not lower fasting plasma total homocysteine concentrations and raised homocysteine concentrations following a methionine load. Lipid profiles improved significantly during the study period. A reduction in homocysteine concentrations is not likely to contribute to the reduction in cardiovascular events seen with estrogen replacement therapy.

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.

Oral contraceptives, sociocultural beliefs and psychiatric symptoms

The occurrence of psychiatric symptoms as detected by the General Health Questionnaire was examined in three groups of Moslem women. Those who used oral contraceptives were compared to those who used local contraceptives and those using no contraceptives in relation to their beliefs about prohibition of contraception by the Islamic religious code and/or about possible health hazards of contraception. Those who held one or both sets of adverse beliefs had significantly more symptoms. However the fact that women on oral contraceptives had most symptoms has been attributed to the repetitive nature of pill-taking acting as a reminder of the presumed adversity and/or to the biochemical effects of oral contraceptives.

A comparative study of two estrogen dosages in combined oral contraceptives among Sudanese women

A prospective study of two combined oral contraceptives was conducted in the Sudan. No pregnancies occurred. Overall incidence of side effects was low. Headache was most frequently reported. Elevations were observed for weight, systolic and diastolic blood pressures, and SGOT and SGPT values while a decrease was seen for hemoglobin levels. Menstrual irregularities were not a problem for the users. Total 6-month use discontinuation rates were low for both pill groups.

The effect of oral contraceptive therapy and of pregnancy on serum folate levels of rural Sri Lankan women

Serum folate level, packed cell volume and haemoglobin concentration of apparently healthy rural Sri Lankan women, between 20 and 45 years and earning up to Rs. 500 (Sri Lankan Rs. 35 congruent to 1 pound Sterling) per month, were estimated during pregnancy and when on oral contraceptive (OC) treatment with Ovulen 50 (ethinyl oestradiol 0.05 mg, ethinodiol diacetate 1 mg). Ovulen 50 administration led to a fall in serum folate levels which occurred very rapidly during the first 6 months and more slowly thereafter, stabilizing at 2.2 ng/ml in women of very low economic status and at 2.9 ng/ml in the more privileged. There was a steady fall in serum folate concentrations during pregnancy, the levels at the end of pregnancy being higher than those in women under OC treatment for 9 months. The need for folate supplementation during OC treatment is stressed.

Effect of orange juice, folic acid, and oral contraceptives on serum folate in women taking a folate-restricted diet

The effect of folate intake from orange juice on serum folate was evaluated in 60 women (age 20-39) during 9 weeks of a folate-restricted diet. Twenty-one were users of oral contraceptives (OCA). Folate intake from the restricted diet was 159 +/- 5 micrograms/day, as assessed by dietary surveys. Serum folate of women taking OCA was lower than in nonusers at the inception of the study (P less than 0.01). During the initial 2 weeks of restricted diet, serum folates decreased significantly (13.8 +/- 1.8 to 8.5 +/- 0.4 ng/ml; P less than 0.002). This decrease was further prevented by supplementation of the diet for 7 weeks with 100 micrograms/day of total folate from reconstituted frozen orange juice or synthetic folic acid (PteGlu). Both folate supplements were effective (P less than 0.05) in increasing serum folate (9.4 +/- 1.0 to 14.5 +/- 1.4 ng/ml, orange juice; 8.4 +/- 0.7 to 20.5 +/- 5.8 ng/ml, folic acid). Serum folates were similar in women taking either orange juice or folic acid. Serum folate of nonsupplemented women decreased from 10.2 +/- 0.8 to 8.3 +/- 0.4 ng/ml (P less than 0.05). No difference between serum folates of OCA users and nonusers was detected during the restricted diet or folate supplementation. These data indicate that folate in reconstituted orange juice was as available as folic acid, and that utilization of both folate forms and folate in a mixed diet was unaffected by oral contraceptives.

Time-course studies on the effects of oestradiol administration on the activity of some folate-metabolizing enzymes in chicken liver

1. The specific activities of some enzymes of folate metabolism were measured in the liver of folate-treated and folate-deficient immature female chickens at intervals up to 9 days after an initial administration of 17 beta-oestradiol dipropionate. 2. An increase in dihydrofolate reductase activity after 3 days and decreases in 10-formyltetrahydrofolate synthetase and 5,10-methylenetetrahydrofolate dehydrogenase activities after 2 days became evident as a result of oestradiol treatment. 3. After 9 days, oestradiol caused a small decrease in glutamate formiminotransferase activity. 4. In folate-deficient chickens the activity of dihydrofolate reductase was decreased and that of serine hydroxymethyltransferase, 10-formyltetrahydrofolate synthetase and 5,10-methylenetetrahydrofolate dehydrogenase was increased in both non-hormone-treated and oestradiol-treated animals.

Serum 25-hydroxycholecalciferol levels in women using oral contraceptives

A study has been made of the serum 25-hydroxycholecalciferol (25-HCC) levels in six groups of women. Significant differences were found between the one pregnant group and the two reference groups as well as between the one pregnant group and two of the three groups using oral contraceptives. No significant differences were found between the reference groups and the ones taking oral contraceptives with oestrogenic concentrations of 0.05 mg or 0.03 mg ethinyl oestradiol for more than one year. It can therefore be concluded that in contrast with most other vitamins, the serum 25-HCC levels are not influenced by the use of oral contraceptives with different oestrogenic concentrations, even over a long period of time.

[Metabolic studies under administration of oral contraceptives. A review]

The use of oral contraceptives can produce changes in the metabolism of carbohydrates, lipids, proteins, vitamins, and minerals. Responsible for the alterations seems to be the used oestrogen- and gestagen derivative and not so much the type of the contraceptive. The most frequent findings are raised serum-glucose-, insulin-, and triglyceride levels; disturbances in protein-metabolism increase the risk of developing thrombosis and hypertonia. Little is known about the significance of oral contraceptives on the vitamin- and mineral metabolism--yet extreme deficiencies have not been observed so far. Oral contraceptives can become an extra risk factor when given to women with metabolic disturbances.

Effect of oral contraceptives on blood folate levels in pregnancy

An investigation was carried out to assess residual effects of oral contraceptives on the folate status of pregnant women who had discontinued intake of these drugs within six months of conception. The sample population of middle class women consisted of users and nonusers of oral contraceptives of similar age groups. Subgroups were those studied initially during the summer (May to July) or winter (October to January). Red blood cell folate values showed seasonal variability and were lower in the winter months. Oral contraceptive users had lower plasma and red blood cell folate values than did the respective control subjects. Red blood cell folate values were more affected by previous drug use in the winter group than in the summer group. Dietary folate was found to have a significant effect on plasma and red cell folate; such for any one level of intake, blood folate values were significantly lower in oral contraceptive users.

Effusions into body cavities in hypothyroidism

Effusions into body cavities secondary to hypothyroidism, though rare, are well recognised. They may precede the more specific and typical manifestations of the disease, thereby misleading the clinician.

Anemia in adolescence. 2. Hemoglobinopathies and other causes

Many complex forces are at work during adolescence which can contribute to the occurrence of anemia. Careful consideration of the entire patient should enable a physician to identify the unusual as well as the more common causes of anemia in this age group. Anemia in teenage girls is primarily due to menstrual iron loss. In boys, borderline diets and the demands of rapid growth predominate as causative factors. Hemoglobinopathies (thalassemia, sickle cell disease), G6PD deficiency, infectious mononucleosis, and illicit drug use account for small proportions of cases.

Oral contraceptives and vitamins: a review

The literature concerning the influence of estrogen-containing oral contraceptives on vitamins is reviewed. The appearance of an elevated plasma concentration of vitamin A is probably without clinical importance, while there seems to be a clear connection between disturbances of vitamin B6 metabolism and mental symptoms. Low levels of folic acid and vitamin B12 have also been noted. Despite this, it is very rare that hematologic abnormalities develop during hormonal contraception. A reduced concentration of vitamin C in plasma and blood corpuscles has been reported. The clinical significance of these alterations is unknown.