Estradiol-Levonorgestrel

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Drug Information

Common brand names:

Climara Pro

Summary of Interactions with Vitamins, Herbs, & Foods

Types of interactions: Beneficial Adverse Check

Replenish Depleted Nutrients

  • Folic Acid

    Oral contraceptive use can cause folic acid depletion.1 In a double-blind trial of oral contraceptive users with cervical dysplasia, supplementation with very large amounts (10 mg per day) of folic acid improved cervical health.2 Women with cervical dysplasia diagnosed while they are taking oral contraceptives should consult a doctor. Mega-folate supplementation should not be attempted without a doctor’s supervision, nor is there any reason to believe that folic acid supplementation would help people with cervical cancer.

  • Vitamin B6

    A review of literature suggests that women who use oral contraceptives may experience decreased vitamin B1, B2, B3, B12, C, and zinc levels.5 , 6 , 7 Oral contraceptive use has been associated with increased absorption of calcium and copper and with increased blood levels of copper and vitamin A.8 , 9 , 10 Oral contraceptives may interfere with manganese absorption.11 The clinical importance of these actions remains unclear.

  • Magnesium

    Women using oral contraceptives were found to have significantly lower serum magnesium levels in a controlled study.12 In a preliminary study, blood levels of magnesium decreased in women taking an oral contraceptive containing ethinyl estradiol and levonorgestrel.13 Although the importance of this interaction remains somewhat unclear, supplementation with 250 to 350 mg of magnesium per day is a safe and reasonable supplemental level for most adults.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Vitamin B1

    A review of literature suggests that women who use oral contraceptives may experience decreased vitamin B1, B2, B3, B12, C, and zinc levels.16 , 17 , 18 Oral contraceptive use has been associated with increased absorption of calcium and copper and with increased blood levels of copper and vitamin A.19 , 20 , 21 Oral contraceptives may interfere with manganese absorption.22 The clinical importance of these actions remains unclear.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Vitamin B12

    A review of literature suggests that women who use oral contraceptives may experience decreased vitamin B1, B2, B3, B12, C, and zinc levels.28 , 29 , 30 Oral contraceptive use has been associated with increased absorption of calcium and copper and with increased blood levels of copper and vitamin A.31 , 32 Oral contraceptives may interfere with manganese absorption.33 The clinical importance of these actions remains unclear.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Vitamin B2

    A review of literature suggests that women who use oral contraceptives may experience decreased vitamin B1, B2, B3, B12, C, and zinc levels.41 , 42 , 43 Oral contraceptive use has been associated with increased absorption of calcium and copper and with increased blood levels of copper and vitamin A.44 , 45 Oral contraceptives may interfere with manganese absorption.46 The clinical importance of these actions remains unclear.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Vitamin B3 (Niacin)

    A review of literature suggests that women who use oral contraceptives may experience decreased vitamin B1, B2, B3, B12, C, and zinc levels.54 , 55 , 56 Oral contraceptive use has been associated with increased absorption of calcium and copper and with increased blood levels of copper and vitamin A.57 Oral contraceptives may interfere with manganese absorption.58 The clinical importance of these actions remains unclear.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Vitamin C

    A review of literature suggests that women who use oral contraceptives may experience decreased vitamin B1, B2, B3, B12, C, and zinc levels.69 , 70 , 71 Oral contraceptive use has been associated with increased absorption of calcium and copper and with increased blood levels of copper and vitamin A.72 , 73 , 74 Oral contraceptives may interfere with manganese absorption.75 The clinical importance of these actions remains unclear.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Zinc

    A review of literature suggests that women who use oral contraceptives may experience decreased vitamin B1, B2, B3, B12, C, and zinc levels.82 , 83 , 84 Oral contraceptive use has been associated with increased absorption of calcium and copper and with increased blood levels of copper and vitamin A.85 , 86 , 87 Oral contraceptives may interfere with manganese absorption.88 The clinical importance of these actions remains unclear.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Reduce Side Effects

  • Folic Acid

    Oral contraceptive use can cause folic acid depletion.95 In a double-blind trial of oral contraceptive users with cervical dysplasia, supplementation with very large amounts (10 mg per day) of folic acid improved cervical health.96 Women with cervical dysplasia diagnosed while they are taking oral contraceptives should consult a doctor. Mega-folate supplementation should not be attempted without a doctor’s supervision, nor is there any reason to believe that folic acid supplementation would help people with cervical cancer.

  • Vitamin B6

    Oral contraceptives have been associated with vitamin B6 depletion and clinical depression. In a small, double-blind study of women with depression taking oral contraceptives, vitamin B6 (20 mg twice per day) improved depression.99 Half of the women in the study showed laboratory evidence of vitamin B6 deficiency.

Reduces Effectiveness

  • none

Potential Negative Interaction

  • Grapefruit

    In a small, controlled study of women with surgically removed ovaries, estradiol levels in the blood were significantly higher after estradiol was taken with grapefruit juice than when estradiol was taken alone.103 These results have been independently confirmed,104 suggesting that women taking oral estradiol should probably avoid grapefruit altogether.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Pomegranate

    Pomegranate juice has been shown to inhibit the same enzyme that is inhibited by grapefruit juice.105 , 106 The degree of inhibition is about the same for each of these juices. Therefore, it would be reasonable to expect that pomegranate juice might interact with estradiol in the same way that grapefruit juice does.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Quercetin

    Studies have shown that grapefruit juice significantly increases estradiol levels in the blood.107 , 108 One of the flavonoids found in grapefruit juice is quercetin. In a test tube study, quercetin was found to change estrogen metabolism in human liver cells in a way that increases estradiol levels and reduces other forms of estrogen.109 This effect is likely to increase estrogen activity in the body. However, the levels of quercetin used to alter estrogen metabolism in the test tube were much higher than levels found in the body after supplementing with quercetin.

    There is evidence from test tube studies that another flavonoid in grapefruit juice, naringenin, also has estrogenic activity.110 It has yet to be shown that dietary or supplemental levels of quercetin (or naringenin) could create a significant problem.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • St. John’s Wort

    Eight cases reported to the Medical Products Agency of Sweden suggest that St. John’s wort may interact with oral contraceptives and cause intramenstrual bleeding and/or changes in menstrual bleeding.111 One reviewer has suggested that St. John’s wort may reduce serum levels of estradiol.112 It should be noted, however, that only three of the eight Swedish women returned to normal menstrual cycles after stopping St. John’s wort. Women taking oral contraceptives for birth control should consult with their doctor before taking St. John’s wort.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Explanation Required 

  • Copper
    A review of literature suggests that women who use oral contraceptives may experience decreased vitamin B1, B2, B3, B12, C, and zinc levels.115 , 116 , 117 Oral contraceptive use has been associated with increased absorption of calcium and copper and with increased blood levels of copper and vitamin A.118 , 119 , 120 Oral contraceptives may interfere with manganese absorption.121 The clinical importance of these actions remains unclear.
  • Iron

    Menstrual blood loss is typically reduced with use of oral contraceptives. This can lead to increased iron stores and, presumably, a decreased need for iron in premenopausal women.122 Premenopausal women taking oral contraceptives should have their iron levels monitored and talk with their prescribing doctor before using iron-containing supplements.

  • Vitamin A

    A review of literature suggests that women who use oral contraceptives may experience decreased vitamin B1, B2, B3, B12, C, and zinc levels.124 , 125 , 126 Oral contraceptive use has been associated with increased absorption of calcium and copper and with increased blood levels of copper and vitamin A.127 , 128 , 129 Oral contraceptives may interfere with manganese absorption.130 The clinical importance of these actions remains unclear.

  • Calcium
    A review of literature suggests that women who use oral contraceptives may experience decreased vitamin B1, B2, B3, B12, C, and zinc levels.138 , 139 , 140 Oral contraceptive use has been associated with increased absorption of calcium and copper and with increased blood levels of copper and vitamin A.141 , 142 , 143 Oral contraceptives may interfere with manganese absorption.144 The clinical importance of these actions remains unclear.
    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Manganese
    A review of literature suggests that women who use oral contraceptives may experience decreased vitamin B1, B2, B3, B12, C, and zinc levels.145 , 146 , 147 Oral contraceptive use has been associated with increased absorption of calcium and copper and with increased blood levels of copper and vitamin A.148 Oral contraceptives may interfere with manganese absorption.149 The clinical importance of these actions remains unclear.
    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
The Drug-Nutrient Interactions table may not include every possible interaction. Taking medicines with meals, on an empty stomach, or with alcohol may influence their effects. For details, refer to the manufacturers’ package information as these are not covered in this table. If you take medications, always discuss the potential risks and benefits of adding a new supplement with your doctor or pharmacist.

References

1. Lindenbaum J, Whitehead N, Reyner F. Oral contraceptive hormones, folate metabolism, and the cervical epithelium. Am J Clin Nutr 1975;28:346-53.

2. Butterworth CE Jr, Hatch KD, Gore H, et al. Improvement in cervical dysplasia associated with folic acid therapy in users of oral contraceptives. Am J Clin Nutr 1982;35:73-82.

3. Lindenbaum J, Whitehead N, Reyner F. Oral contraceptive hormones, folate metabolism, and the cervical epithelium. Am J Clin Nutr 1975;28:346-53.

4. Butterworth CE Jr, Hatch KD, Gore H, et al. Improvement in cervical dysplasia associated with folic acid therapy in users of oral contraceptives. Am J Clin Nutr 1982;35:73-82.

5. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

6. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

7. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197-8.

8. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

9. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

10. Berg G, Kohlmeier L, Brenner H. Effect of oral contraceptive progestins on serum copper concentration. Eur J Clin Nutr 1998;52:711-5.

11. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197.

12. Olatunbosum DA, Adeniyi FA, Adadevoh BK. Effect of oral contraceptives on serum magnesium levels. Int J Fertil 1974;19:224-6.

13. Blum M, Kitai E, Ariel Y, et al. Oral contraceptive lowers serum magnesium. Harefuah 1991;121:363-4 [in Hebrew].

14. Olatunbosum DA, Adeniyi FA, Adadevoh BK. Effect of oral contraceptives on serum magnesium levels. Int J Fertil 1974;19:224-6.

15. Blum M, Kitai E, Ariel Y, et al. Oral contraceptive lowers serum magnesium. Harefuah 1991;121:363-4 [in Hebrew].

16. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

17. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

18. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197-8.

19. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

20. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

21. Berg G, Kohlmeier L, Brenner H. Effect of oral contraceptive progestins on serum copper concentration. Eur J Clin Nutr 1998;52:711-5.

22. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197.

23. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

24. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

25. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197-8.

26. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

27. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197.

28. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

29. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

30. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197-8.

31. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

32. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

33. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197.

34. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

35. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

36. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197-8.

37. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

38. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

39. Berg G, Kohlmeier L, Brenner H. Effect of oral contraceptive progestins on serum copper concentration. Eur J Clin Nutr 1998;52:711-5.

40. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197.

41. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

42. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

43. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197-8.

44. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

45. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

46. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197.

47. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

48. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

49. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197-8.

50. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

51. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

52. Berg G, Kohlmeier L, Brenner H. Effect of oral contraceptive progestins on serum copper concentration. Eur J Clin Nutr 1998;52:711-5.

53. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197.

54. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

55. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

56. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197-8.

57. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

58. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197.

59. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

60. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

61. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197-8.

62. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

63. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

64. Berg G, Kohlmeier L, Brenner H. Effect of oral contraceptive progestins on serum copper concentration. Eur J Clin Nutr 1998;52:711-5.

65. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197.

66. Adams PW, Folkard J, Wynn V, Seed M. Influence of oral contraceptives, pyridoxine (vitamin B6), and tryptophan on carbohydrate metabolism. Lancet 1976;1:759-64.

67. Adams PW, Wynn V, Rose DP, et al. Effect of pyridoxine hydrochloride (vitamin B6) upon depression associated with oral contraception. Lancet 1973;I:897-904.

68. Adams PW, Wynn V, Seed M, Folkard J. Vitamin B6, depression, and oral contraception. Lancet 1974;2:516-7.

69. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

70. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

71. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197-8.

72. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

73. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

74. Berg G, Kohlmeier L, Brenner H. Effect of oral contraceptive progestins on serum copper concentration. Eur J Clin Nutr 1998;52:711-5.

75. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197.

76. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

77. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

78. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197-8.

79. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

80. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

81. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197.

82. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

83. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

84. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197-8.

85. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

86. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

87. Berg G, Kohlmeier L, Brenner H. Effect of oral contraceptive progestins on serum copper concentration. Eur J Clin Nutr 1998;52:711-5.

88. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197.

89. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

90. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

91. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197-8.

92. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

93. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

94. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197.

95. Lindenbaum J, Whitehead N, Reyner F. Oral contraceptive hormones, folate metabolism, and the cervical epithelium. Am J Clin Nutr 1975;28:346-53.

96. Butterworth CE Jr, Hatch KD, Gore H, et al. Improvement in cervical dysplasia associated with folic acid therapy in users of oral contraceptives. Am J Clin Nutr 1982;35:73-82.

97. Lindenbaum J, Whitehead N, Reyner F. Oral contraceptive hormones, folate metabolism, and the cervical epithelium. Am J Clin Nutr 1975;28:346-53.

98. Butterworth CE Jr, Hatch KD, Gore H, et al. Improvement in cervical dysplasia associated with folic acid therapy in users of oral contraceptives. Am J Clin Nutr 1982;35:73-82.

99. Adams PW, Wynn V, Rose DP, et al. Effect of pyridoxine hydrochloride (vitamin B6) upon depression associated with oral contraception. Lancet 1973;I:897-904.

100. Adams PW, Folkard J, Wynn V, Seed M. Influence of oral contraceptives, pyridoxine (vitamin B6), and tryptophan on carbohydrate metabolism. Lancet 1976;1:759-64.

101. Adams PW, Wynn V, Rose DP, et al. Effect of pyridoxine hydrochloride (vitamin B6) upon depression associated with oral contraception. Lancet 1973;I:897-904.

102. Adams PW, Wynn V, Seed M, Folkard J. Vitamin B6, depression, and oral contraception. Lancet 1974;2:516-7.

103. Schubert W, Cullberg G, Edgar B, Hedner T. Inhibition of 17 beta-estradiol metabolism by grapefruit juice in ovariectomized women. Maturitas 1994;20:155-63.

104. Weber A, Jager R, Borner A, et al. Can grapefruit juice influence ethinylestradiol bioavailability? Contraception 1996;53:41-7.

105. Sorokin AV, Duncan B, Panetta R, Thompson PD. Rhabdomyolysis associated with pomegranate juice consumption. Am J Cardiol 2006;98:705-6.

106. Summers KM. Potential drug-food interactions with pomegranate juice. Ann Pharmacother 2006;40:1472-3.

107. Schubert W, Cullberg G, Edgar B, Hedner T. Inhibition of 17 beta-estradiol metabolism by grapefruit juice in ovariectomized women. Maturitas 1994;20:155-63.

108. Weber A, Jager R, Borner A, et al. Can grapefruit juice influence ethinylestradiol bioavailability? Contraception 1996;53:41-7.

109. Schubert W, Eriksson U, Edgar B, et al. Flavonoids in grapefruit juice inhibit the in vitro hepatic metabolism of 17 beta-estradiol. Eur J Drug Metab Pharmacokinet 1995;3:219-24.

110. Kuiper GG, Lemmen JG, Carlsson B, et al. Interaction of estrogenic chemicals and phytoestrogens with estrogen receptor beta. Endocrinology 1998;139:4252-63.

111. Safety of St. John's wort (Hypericum perforatum)[letters to the editor from various authors]. Lancet 2000;355:575-7.

112. Ernst E. Second thoughts about safety of St. John's wort. Lancet 1999;354:2014-6 [letter].

113. Safety of St. John's wort (Hypericum perforatum)[letters to the editor from various authors]. Lancet 2000;355:575-7.

114. Ernst E. Second thoughts about safety of St. John's wort. Lancet 1999;354:2014-6 [letter].

115. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

116. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

117. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197-8.

118. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

119. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

120. Berg G, Kohlmeier L, Brenner H. Effect of oral contraceptive progestins on serum copper concentration. Eur J Clin Nutr 1998;52:711-5.

121. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197.

122. Frassinelli-Gunderson EP, Margen S, Brown JR. Iron stores in users of oral contraceptive agents. Am J Clin Nutr 1985;41(4):703.

123. Frassinelli-Gunderson EP, Margen S, Brown JR. Iron stores in users of oral contraceptive agents. Am J Clin Nutr 1985;41(4):703.

124. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

125. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

126. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197-8.

127. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

128. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

129. Berg G, Kohlmeier L, Brenner H. Effect of oral contraceptive progestins on serum copper concentration. Eur J Clin Nutr 1998;52:711-5.

130. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197.

131. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

132. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

133. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197-8.

134. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

135. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

136. Berg G, Kohlmeier L, Brenner H. Effect of oral contraceptive progestins on serum copper concentration. Eur J Clin Nutr 1998;52:711-5.

137. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197.

138. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

139. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

140. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197-8.

141. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

142. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

143. Berg G, Kohlmeier L, Brenner H. Effect of oral contraceptive progestins on serum copper concentration. Eur J Clin Nutr 1998;52:711-5.

144. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197.

145. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

146. Wynn V. Vitamins and oral contraceptive use. Lancet 1975;1:561-4.

147. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197-8.

148. Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997, 210-1 [review].

149. Holt GA. Food & Drug Interaction. Chicago: Precept Press, 1998, 197.