What is Soy

1
What is Soy?

• Soybeans are legumes
• The most widely eaten plant in the world
• Higher in protein and fat than most other legumes
• CHO- 26, Protein- 37, Fat 37

2
What is Soy, cont.

• Complete protein
• Primary fat source polyunsaturated (54)
• Source of omega-3 fatty acid (linolenic acid)

3
What is Soy, cont.

• Contains weak estrogens- phytoestrogens or
  isoflavones
• Isoflavones may be in foods or extracted and used
  in supplements
• Isoflavones SERM (selective estrogen receptor
  modulators)

4
Possible Benefits of Soy in

• Menopausal Symptoms
• Breast Cancer
• Osteoporosis/ Bone Health
• Cardiovascular Disease

5
Menopausal Symptoms and Soy

• Hot flashes and night sweats
• Cultural differences in severity of symptoms
• Research studies with mixed results

6
Menopause and Soy, cont.

• Individual responders/ placebo effect/
  inconclusive results with clinical trials
• General conclusion from 13 studies
• Hot flashes ? 5/day- soy may be effective
• Hot flashes lt 5/day- soy has little effect
• According to Am. College of OB and GYN, soy may
  be beneficial in short term (? 2 yrs)

7
Breast Cancer and Soy

• American women 4x more likely to die from Breast
  CA as Chinese or Japanese women
• Due to diet/ life long consumption?
• Early soy consumption (pre-pubertal) may be key
  to ?d risk

8
Breast Cancer and Soy, cont.

• Research focus- phytoestrogens
• 1000 x weaker than endogenous estrogen
• Focus on ER positive breast cancer
• Some ? if antiestrogenic or estrogenic effects in
  breast cells

9
Breast Cancer and Soy, cont.

• More recent studies ?d breast density and
  breast inflammation with soy (risk factors for
  breast CA)
• Recommendations
• Moderation if h/o breast cancer (3-4 servings/wk
  of soy food no supplements)
• ? Encourage earlier consumption of soy

10
Bone Health and Soy

• Osteoporosis- prevention is key
• Bioavailability of calcium from soy
• Soy protein ?d calcium excretion
• Isoflavones- inhibit bone resorption and
  stimulate bone formation (femur and lumbar spine)

11
Bone Health and Soy, cont.

• Journal of Bone and Mineral Research study (2002)
• Measured change in BMD
• Placebo vs. genistein (54 mg) vs. HRT (estradiol
  E2 norethisterone acetate)

12
Heart Disease and Soy

• Research has focused on soy protein vs.
  isoflavones
• Protein may ? cholesterol by interfering with LDL
  oxidation
• Genistein may ? clot formation and plaque
• Blood pressure

13
Heart and Soy, cont.

• FDA claim (1999)
• Guidelines (per serving)
• 6.25 g soy protein or more
• Low fat (? 3 grams) low sat. fat (? 1gram)
• Low cholesterol (? 20 mg)
• Whole soybean if no additional fat

14
Heart and Soy, cont.

• Current rec. for cholesterol lowering- 25 g/d
• Results related to initial cholesterol levels
• Initial expected response (-10 in LDL) may be
  overestimated
• Ave. ? in LDL with soy protein 6
• Each 1 ? in chol ? risk of CHD as much as 3-4
  !

15
Recommendations for Soy foods

• 2 servings soy per day
• 15 grams soy protein (range 10-25 grams)
• 50 mg isoflavones (range 30-100 mg)
• Choose soy foods first!

16
Recommendations for Soy-containing Supplements

• Data is generally not strong
• Hot flashes- likely no better than placebo
• Cholesterol lowering- focus on soy protein rather
  than phytoestrogen extracts may have other CVD
  benefits
• Bone- suggestive benefit
• Breast CA- conflicting results. Avoid until
  safety in established, esp. if Breast CA