II. Precaution

  1. Soy lacks the amino acids cysteine and methionine
  2. Combine with rice, corn or wheat
    1. To supply all essential amino acids

III. 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

IV. Dietary sources

  1. Soy-rich foods (richest sources)
    1. Soy milk (1 cup): 3-10 grams Soy Protein (90-140 cals)
    2. Tofu (3 oz): 10 grams Soy Protein (90 cals)
    3. Tempeh (1 ounce): 5 grams Soy Protein (55 cals)
    4. Soy flour (1/2 cup): 20 grams Soy Protein (220 cals)
    5. Soy Protein (2 tbs): 25 grams Soy Protein (110 cals)
    6. Edamame (1 cup): 22 grams Soy Protein (250 cals)
  2. Licorice
  3. Red clover
  4. Thyme
  5. Tumeric
  6. Hops
  7. Verbena
  8. Alfalfa
  9. Beans

V. Benefits: Potential

  1. Associated with significant reduced Breast Cancer risk
    1. Initial Retrospective Studies (needs confirmation)
    2. However, avoid in those with Estrogen receptor positive Breast Cancer
  2. Decreased lipid levels (Soy Protein - not subcomponents)
    1. Decreases LDL Cholesterol (up to 13%)
    2. Decreases Serum Triglycerides (up to 10%)
    3. Reynolds (2006) Am J Cardiol 98(5): 633-40 [PubMed]
  3. May increase Bone Mineral Density
    1. Soy Protein decreases Fracture risk
      1. Zhang (2005) Arch Intern Med 165(16): 1890-5 [PubMed]
    2. Soy Isoflavone decreases postmenopausal spinal bone loss
      1. Ma (2008) Clin Nutr 27:57-64 [PubMed]

VI. Benefits: Variable

  1. Hot Flushes
    1. Effectiveness appears dependent on pharmacogenomic factors
      1. Equol is a soy metabolite with Estrogenic Activity
      2. Only 40% of North American women convert Soy Isoflavone (daidzein) to equol
        1. Conversion is most common in Asian and Hispanic women
        2. The majority who lack this conversion are unlikely to see benefit from soy
      3. References
        1. Clarkson (2011) Menopause 18(7):732-53 [PubMed]
    2. Some studies show benefit in Hot Flushes
      1. Faure (2002) Menopause 9:329-34 [PubMed]
      2. Han (2002) Obstet Gynecol 99:389-94 [PubMed]
      3. Howes (2006) Maturitas 55:203-11 [PubMed]
      4. Welty (2007) J Womens Health 16:361-9 [PubMed]
    3. Other studies suggest no benefit in Hot Flushes
      1. Nikander (2003) Obstet Gynecol 101:1213-20 [PubMed]
    4. Requires large, often intolerable doses (60 g/day)
      1. Albertazzi (1998) Obstet Gynecol 91:6-11 [PubMed]

VII. Adverse Effects

  1. Most common side effects
    1. Diarrhea
    2. Menstrual irregularities (Amenorrhea or prolonged periods)
  2. Thyroid suppression may occur
  3. Recent flawed study showed adverse neurologic effects
    1. Further well performed studies required
  4. Unknown longterm effects on Estrogen receptors
    1. Caution in Estrogen receptor positive Breast Cancer
    2. Does not appear to increase endometrial thickness at typical isoflavone doses (40-80 mg)
      1. Penotti (2003) Fertil Steril 79:1112-7 [PubMed]

VIII. 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)

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Ontology: Phytoestrogens (C0071011)

Definition (NCI) Compounds from plant sources with estrogen-like activities
Definition (NCI_NCI-GLOSS) An estrogen-like substance found in some plants and plant products. Phytoestrogens may have anticancer effects.
Definition (MSH) PLANT EXTRACTS and compounds, primarily ISOFLAVONES, that mimic or modulate endogenous estrogens, usually by binding to ESTROGEN RECEPTORS.
Definition (CSP) plant chemicals that may act as fungicides, deter herbivores, regulate plant hormones, and protect plants from ultraviolet radiation; structurally resemble endogenous animal estrogens; may function as estrogen agonists or antagonists when consumed by humans.
Concepts Pharmacologic Substance (T121) , Hormone (T125) , Steroid (T110)
MSH D048789
French Agents phyto-oestrogènes, Agents phyto-estrogènes, Phytoestrogènes, Phyto-estrogènes, Agents phytoestrogènes, Phyto-oestrogènes, Phytooestrogènes
Swedish Fytoöstrogener
Czech fytoestrogeny
Finnish Kasviestrogeenit
Russian FITOESTROGENY, ФИТОЭСТРОГЕНЫ
Japanese 植物性エストロゲン, 植物エストロゲン, フィトエストロゲン
Italian Fitoestrogeno, Fitoestrogeni
English phytoestrogens, phyto-estrogen, phyto estrogens, phyto estrogen, phytoestrogen, Phyto Estrogen, Phyto-Estrogen, Phytoestrogens, Phytoestrogen
Polish Fitoestrogeny
German Phyto-Östrogen, Phytoöstrogene, Phytoöstrogen
Portuguese Fitoestrógenos
Spanish Fitoestrogenos

Ontology: Glycine max (C1262902)

Definition (CSP) food plant which contains little starch and is rich in protein; used to prepare protein supplements; also furnishes commercially important enzymes and other products.
Concepts Plant (T002)
MSH D013025
SnomedCT 76068006
English Chinese bean, Soja hispida, Glycine max (L.) Merr., soybean, glycine max, soybeans, Soybean, Glycine max (organism), Glycine max
Portuguese Glycine max
German Glycine max
French Glycine max, Soja hispida
Czech Glycine max, sója luštinatá, Glycine soja
Norwegian Glycine max
Italian Glycine max
Spanish Glycine max (organismo), soja, Glycine max
Dutch Glycine max