Dr. Ron’s Research Review – June 11, 2014

© 2014

This week’s research review focuses on flax for men and women.

Breast Cancer

A food frequency questionnaire showed that consumption of flaxseed is associated with reduced breast cancer risk (odds ratio (OR) = 0.82, 95 % confidence interval (CI) 0.69-0.97), as was consumption of flax bread (OR = 0.77, 95 % CI 0.67-0.89). (Lowcock et al., 2013)

2/16 Ratio

A study of postmenopausal women (n = 46) compared placebo, soy (25 g soy flour), or flaxseed (25 g ground flaxseed) muffin for 16 weeks. Urinary concentrations of 2-hydroxyestrone, but not of 16alpha-hydroxyestrone, increased significantly in the flaxseed group (P = 0.05). In the flaxseed group, the ratio of 2-hydroxyestrone to 16alpha-hydroxyestrone was positively correlated with urinary lignan excretion (r = 0.579, P = 0.02). In the soy and placebo groups, no significant correlation was observed. No significant change in serum hormones or biochemical markers of bone metabolism was observed within or between the treatment groups. (Brooks et al., 2004)

Prostate Cancer

Flaxseed supplementation reduces prostate cancer proliferation rates in men pre-surgery. Prostate cancer patients (n = 161) scheduled at least 21 days before prostatectomy were randomly assigned to one of the following arms: (a) control (usual diet), (b) flaxseed-supplemented diet (30 g/d), (c) low-fat diet (<20% total energy), or (d) flaxseed-supplemented, low-fat diet. Men were on protocol an average of 30 days. Proliferation rates were significantly lower (P < 0.002) among men assigned to the flaxseed arms. (Demark-Wahnefried et al., 2008)

Dr. Ron


 

Articles

Supplementation with flaxseed alters estrogen metabolism in postmenopausal women to a greater extent than does supplementation with an equal amount of soy
            (Brooks et al., 2004) Download
BACKGROUND: Phytoestrogens, which are abundant in flaxseed and soy, have chemical structures resembling those of endogenous estrogens and have been shown to exert hormonal effects, thereby affecting chronic diseases. OBJECTIVE: We compared the effects of consuming equal amounts of flaxseed or soy on estrogen metabolism and biochemical markers of bone metabolism in postmenopausal women. DESIGN: In a parallel design, the diet of postmenopausal women (n = 46) was supplemented with either a placebo, soy (25 g soy flour), or flaxseed (25 g ground flaxseed) muffin for 16 wk. Blood and 24-h urine samples were collected at baseline and at the endpoint. Urine samples were analyzed for phytoestrogens, estrogen metabolites (2-hydroxyestrone, 16alpha-hydroxyestrone), and serum hormones (estradiol, estrone, estrone sulfate). Serum and urine samples were also analyzed for biochemical markers of bone metabolism. RESULTS: Urinary concentrations of 2-hydroxyestrone, but not of 16alpha-hydroxyestrone, increased significantly in the flaxseed group (P = 0.05). In the flaxseed group, the ratio of 2-hydroxyestrone to 16alpha-hydroxyestrone was positively correlated with urinary lignan excretion (r = 0.579, P = 0.02). In the soy and placebo groups, no significant correlation was observed. No significant change in serum hormones or biochemical markers of bone metabolism was observed within or between the treatment groups. CONCLUSIONS: Supplementation with flaxseed modifies urinary estrogen metabolite excretion to a greater extent than does supplementation with an equal amount of soy. This modification by flaxseed is associated with an increase in urinary lignan excretion. Despite the shift in estrogen metabolism to favor the less biologically active estrogens, a negative effect on bone cell metabolism was not observed.

Flaxseed supplementation (not dietary fat restriction) reduces prostate cancer proliferation rates in men presurgery
            (Demark-Wahnefried et al., 2008) Download
BACKGROUND: Prostate cancer affects one of six men during their lifetime. Dietary factors are postulated to influence the development and progression of prostate cancer. Low-fat diets and flaxseed supplementation may offer potentially protective strategies. METHODS: We undertook a multisite, randomized controlled trial to test the effects of low-fat and/or flaxseed-supplemented diets on the biology of the prostate and other biomarkers. Prostate cancer patients (n = 161) scheduled at least 21 days before prostatectomy were randomly assigned to one of the following arms: (a) control (usual diet), (b) flaxseed-supplemented diet (30 g/d), (c) low-fat diet (<20% total energy), or (d) flaxseed-supplemented, low-fat diet. Blood was drawn at baseline and before surgery and analyzed for prostate-specific antigen, sex hormone-binding globulin, testosterone, insulin-like growth factor-I and binding protein-3, C-reactive protein, and total and low-density lipoprotein cholesterol. Tumors were assessed for proliferation (Ki-67, the primary endpoint) and apoptosis. RESULTS: Men were on protocol an average of 30 days. Proliferation rates were significantly lower (P < 0.002) among men assigned to the flaxseed arms. Median Ki-67-positive cells/total nuclei ratios (x100) were 1.66 (flaxseed-supplemented diet) and 1.50 (flaxseed-supplemented, low-fat diet) versus 3.23 (control) and 2.56 (low-fat diet). No differences were observed between arms with regard to side effects, apoptosis, and most serologic endpoints; however, men on low-fat diets experienced significant decreases in serum cholesterol (P = 0.048). CONCLUSIONS: Findings suggest that flaxseed is safe and associated with biological alterations that may be protective for prostate cancer. Data also further support low-fat diets to manage serum cholesterol.

Consumption of flaxseed, a rich source of lignans, is associated with reduced breast cancer risk.
            (Lowcock et al., 2013) Download
PURPOSE: To investigate the association between intake of flaxseed-the richest source of dietary lignans (a class of phytoestrogens)-and breast cancer risk. METHODS: A food frequency questionnaire was used to measure the consumption of flaxseed and flax bread by 2,999 women with breast cancer and 3,370 healthy control women who participated in the Ontario Women's Diet and Health Study (2002-2003). Logistic regression was used to investigate associations between consumption of flaxseed and flax bread and breast cancer risk. Confounding by established and suspected breast cancer risk factors, as well as dietary factors, was assessed. RESULTS: Flaxseed or flax bread was consumed at least weekly by 21 % of control women. None of the 19 variables assessed were identified as confounders of the associations between flaxseed or flax bread and breast cancer risk. Consumption of flaxseed was associated with a significant reduction in breast cancer risk (odds ratio (OR) = 0.82, 95 % confidence interval (CI) 0.69-0.97), as was consumption of flax bread (OR = 0.77, 95 % CI 0.67-0.89). CONCLUSIONS: This Canadian study is, to our knowledge, the first to report on the association between flaxseed alone and breast cancer risk and has found that flaxseed intake is associated with a reduction in breast cancer risk. As dietary intake of flaxseed is modifiable, this finding may be of public health importance with respect to breast cancer prevention.


 

References

Brooks, J. D., et al. (2004), ‘Supplementation with flaxseed alters estrogen metabolism in postmenopausal women to a greater extent than does supplementation with an equal amount of soy’, Am J Clin Nutr, 79 (2), 318-25. PubMedID: 14749240
Demark-Wahnefried, W., et al. (2008), ‘Flaxseed supplementation (not dietary fat restriction) reduces prostate cancer proliferation rates in men presurgery’, Cancer Epidemiol Biomarkers Prev, 17 (12), 3577-87. PubMedID: 19064574
Lowcock, EC, M Cotterchio, and BA Boucher (2013), ‘Consumption of flaxseed, a rich source of lignans, is associated with reduced breast cancer risk.’, Cancer Causes Control, 24 (4), 813-16. PubMedID: 23354422