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)