Post on 18-Jan-2016
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Selenium
By: Danielle Roller
What Is Selenium?
• Trace Mineral
• Essential in good health
• Small amounts• 55-400 micrograms
• Selenoproteins = antioxidant enzymes
http://ods.od.nih.gov/factsheets/selenium.
Selenium Sources
Amount in food depends on amount in the soil
• Nuts• Fish• Beef• Chicken • Turkey • Grains• Eggs
http://ods.od.nih.gov/factsheets/selenium.
6 whole nuts (1 oz)= 544 mcg
What About Selenium?• Improves brain function: protects brain cells
• Inhibit genetic damage
• Anti-viral
• Anti Heart Disease & Anti-Diabetes:
• Deficiency Keshan Disease in China
• Proteins provide antioxidant effectsMale fertility Anti asthma, arthritis, muscular Thyroid function dystrophy & cystic fibrosisSupports immune function Reduces cancer riskAnti-aging Zeng, Huawei (2009)
“What is the relationship between selenium & cancer?”
Types Of Cancers
Breast
Colon Head
Prostate
Lymphatic Neck
Lung
Zeng, Huawei (2009)
Cancer Prevention“ANTI-TUMORIGENIC”
Vitamin C, E & beta carotene
• Antioxidant
• Cofactor to scavenge free radicals
(cancer and chemotherapy)
• Glutathione peroxidase enzyme
• Cell Apoptosis Zeng, Huawei (2009)
Defining the optimal selenium dose for prostate cancer risk reduction: insights from the u-shaped
relationship between selenium status, DNA damage, and apoptosis
Bostwick, D., Chiang,E., Combos, G., Kengeri, S., Morris, S., Shen, S., Waters, D. and Xu, H.
Objective
To provide further research based on the dietary intake of selenium providing a decreased risk in the onset of
prostate cancer
Study Design
• Experimental Study
• 69 male beagle dogs
• 7 months
• control & experimental
Methods• Control group (n=20): Nutritionally adequate with selenium from the
start and was fed a adequate selenium diet.
• Experimental group (n=29): Nutritionally adequate with selenium but received daily supplemetation
– 3 mcg/kg/day– 6 mcg/kg/day
• Once 7 months complete– Low = <6.7 ppm– Medium = 0.67-0.92 ppm– High = >0.92 ppm
• Observed “hot spots” (cells that went through apoptosis)• Rate of DNA damage in the cells of the prostate.
Descriptive Statistics
• Range
• Mean apoptotic index
• Median
Inferential Statistics
• 95% confidence interval
• Odds Ratio
• Multivariate analysis
• Chi-Square
• T-test
Results
Moderate Selenium Status
• Less DNA damage by 84%
• 4.1x more apoptotic “hot spots”
• Selenium exposure = positive outcome
• Normal Distribution Curve
Low & High Selenium Status
Slight increase in epithelial cell apoptosis
More DNA Damage
Selenium supplementation was not beneficial
Selenium status vs. epithelial cell apoptosis
LOW (<0.67 ppm)
MODERATE(0.67-0.92)
HIGH(>0.92 ppm)
Toenail Selenium Concentration
(ppm)Range 0.43-0.66 0.67-0.88 0.94-1.22
Mean 0.56 0.76 1.03
# of dogs 23 26 12
Mean apoptotic index
1.0 ± 1.3 2.6 ± 3.1 2.2 ± 2.1
Likelihood of apoptotic hot spotsOdds Ratio (95% CI) 1.0 (reference) 4.1 (1.1-15.3) 1.6 (0.3-8.6)
Strengths
• Population used
• Clear evidence of planning and organization in methods
• Internal Validity: Confounding Variables
• Suggestions of further research
• In vivo Study
Weaknesses• In vivo
• Sample size of population used
• External Validity
• Not clear which group received selenium supplementation
(How much?)
Support
Reduces cancer risks by halting damaged DNA molecules from reproducing (cell growth)* Inducing apoptosis - “hot spots”• Prevents tumors from
developing• Slows cancer progression in
patients who already have it
Zeng, Huawei (2009)
Selenium substitution during radiotherapy of solid tumors
Bruns, F., Buntzel, J., Glatzel, M., Kisters, K., Kundt, C., Micke, O., Mucke, R., Schafer, U., and Schanekaes, K.
What is the relationship between selenium and cancer?
ChemotherapyTreatment involving the use of chemical agents to stop cancer cells from growing
• Increases free radicals because of toxic drugs involved in the process
• Increases amount of damaged DNA
http://www.chemotherapy.com/
Objective
Determining what the sufficient selenium dose is in supportive therapy.
Study Design
• Experimental study
• 81 gynecological cancer patients
• 48 head and neck cancer patients
• Control & Experimental Group
Methods
• Group 1(Experimental) 500 micrograms SE
• Group 2 (Control) Received no Se supplementation
• Blood samples collected before, half way through, after, and 6 weeks after radiotherapy
• Results sent to laboratory
Descriptive statistics
• Mean
• Standard Error
• P-value
Inferential statistics
• Leven’s test
• T-test
• Chi-Square test
• Fisher’s exact test
• Mann-Whitney u-test
Results
• No differences with location of tumors
• Mann-Whitney u-test 50% significant differences in Se concentrations in the blood at the end of radiotherapy (p<0.001)
• No significant difference between groups before and 6 weeks after
Selenium concentrations (whole blood) during radiotherapy
Büntzel, J (2010)
Additional Results
• Se provided as therapeutic option• GYN: diarrheas• Head & Neck: improved loss of taste & “dysphagia”
• Both trials showed clinical effects with toxicity of anti-cancer treatments
• 500 microgram dose blood concentrations after 3 weeks• Se dose either increased more or started earlier (10-15
weeks prior) to have earlier effects in reducing toxicity during first part of radiotherapy.
Strengths• Accepted their hypothesis
• Evidence of planning & organization
• Research Questions (Objective) clearly stated
• Internal validity: Chance
• Population used
Weaknesses
• Internal Validity: confounding variables
Support
• Blocks chemical reactions that produce free radicals gluthione peroxidase enzyme
• recognition of DNA damage DNA repair & DNA repair synthesis.
• Minimizing potential damage to normal cells from free radicals
• Enhancing effectiveness of radiation process by• 3.) toxicity of chemotherapy drugs• 4.) Therapy = “selective toxin”
Büntzel, J. (2010)