Precaution
1. Soy lacks the amino acids cysteine and methionine
2. Combine with rice, corn or wheat
  1. To supply all essential amino acids
Mechanism
1. Weak Estrogen and anti-Estrogen effects
  1. Weaker than estradiol by factor of 1/1000
2. Phytoestrogen Sources
  1. Lignan in seeds and grains
  2. Isoflavone (genistein, daidzein) in legumes
    1. Soybeans
    2. Red Clover
3. Inhibit tumor growth in culture
Dietary sources
1. Soy-rich foods (richest sources)
  1. Soy milk (1 cup): 3-10 grams Soy Protein (90-140 cal)
  2. Tofu (3 oz): 10 grams Soy Protein (90 cals)
  3. Soy flour (1/2 cup): 20 grams Soy Protein (220 cals)
  4. Soy Protein (2 tbs): 25 grams Soy Protein (110 cals)
2. Licorice
3. Red clover
4. Thyme
5. Tumeric
6. Hops
7. Verbena
8. Alfalfa
9. Beans
Potential Benefits
1. Associated with significant reduced Breast Cancer risk
  1. Initial Retrospective Studies (needs confirmation)
2. Decreased Lipid
  1. Decreases LDL (10%)
  2. Decreases Total Cholesterol (13%)
3. May increase Bone Mineral Density
Variable Benefits
1. Hot Flushes
  1. Some studies show benefit in Hot Flushes
    1. Faure (2002) {a 8005} 9:329
    2. Han (2002) Obstet Gynecol 99:389
  2. Other studies suggest no benefit in Hot Flushes
    1. Nikander (2003) Obstet Gynecol 101:1213
  3. Requires large, often intolerable doses (60 g/day)
    1. Albertazzi (1998) Obstet Gynecol 91:6
Adverse Effects
1. Thyroid suppression may occur
2. Recent flawed study showed adverse neurologic effects
  1. Further well performed studies required
3. Unknown longterm effects on Estrogen receptors
  1. Caution in Estrogen receptor positive Breast Cancer
  2. Does not appear to increase endometrial thickness
    1. Penotti (2003) Fertil Steril 79:1112
Dosing: Sources of dietary Soy Protein and isoflavone
1. Recommended doses for Hot Flashes in Menopause
  1. Soy Protein 25-60 g/day
  2. Isoflavone 60 mg/day
2. Equivalent sources to meet 25-60 gram daily intake
  1. Soy Milk (4 glasses)
  2. Tofu 2 portions or one third brick
  3. Edamame 1/2 cup
  4. Soy Protein powder in shake (1 serving)
References

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This page was written by Scott Moses, MD, and was last revised 1/27/2008. Please send comments and questions to the editor. Contact information may be found on the page About the Family Practice Notebook. These pages are best viewed with Microsoft Internet Explorer 5.0.