Iodine and Cancer

A Comprehensive Review of the anti-cancer actions of iodine.

Researched and written by Keith Bishop, clinical nutritionist, cancer coach, and retired pharmacist.

Iodine, an essential trace element, has garnered significant attention for its potential anticancer properties. This blog post delves into iodine's anticancer activity, its mechanisms, other health benefits, cancers at higher risk due to deficiency, interactions with medications, top food sources, potential side effects of excess iodine, testing methods, and supplement sources.

Consult your health care team before making changes to your health program.

Anticancer Activity of Iodine

Research has shown that iodine exhibits significant anticancer effects, particularly in breast cancer. Molecular iodine has been found to diminish proliferation and invasive potential and activate the immune response in mammary cancer xenografts. Iodine induces apoptosis (programmed cell death) and inhibits angiogenesis (formation of new blood vessels) in cancer cells, thereby preventing tumor growth and metastasis. In one research study, 88% of people with cancer were found to have severe iodine deficiency.[i]

Iodine supplementation increases the number of white blood cells and lymphocytes inside cancer cells, suggesting an activation of antitumor immune responses. [ii] Researchers found that tumors with a low iodine density ratio had an increased rate of recurrence.[iii]

Iodine neutralizes free radicals, increases antioxidant enzymes, and inactivates proinflammatory pathways. In cancer cells, Iodine activates apoptosis (normal cancer cell death) and decreases the markers related to cancer stem cell maintenance, chemoresistance, and survival.[iv]

Iodine is vital in promoting cellular differentiation and maintaining normal cell function. Research has shown that iodine contributes to the regulation of gene expression, which is essential for cells to develop specialized functions. This differentiation process is crucial in preventing the' uncontrolled growth of undifferentiated cells, a cancer hallmark. Additionally, iodine's antioxidant properties help protect cells from oxidative stress, further supporting their normal function.[v]

Other Health Benefits of Iodine

Beyond its anticancer properties, iodine offers several other health benefits:

• Thyroid Health: Iodine is crucial for producing thyroid hormones, which regulate metabolism, growth, and development.
• Brain Development: Adequate iodine intake during pregnancy is essential for fetal brain development and can prevent cognitive impairments.
• Detoxification: Iodine helps detoxify the body by competing for absorption and removing heavy metals and halogens like fluoride, chlorine, and bromine.
• Immune Support: Iodine has antimicrobial properties that support the immune system.

Iodine's antiviral, antifungal, and anti-yeast properties may significantly affect cancer prevention and treatment. Its ability to combat pathogens reduces the risk of infections contributing to chronic inflammation, a known factor in cancer development. Additionally, iodine's antimicrobial action supports a healthier immune system, crucial for identifying and eliminating abnormal cells. Research also suggests that iodine can induce apoptosis in cancer cells and inhibit their proliferation, further highlighting its potential role in cancer therapy.[vi]

The Prevalence of Iodine Deficiency

Iodine deficiency occurs worldwide. Implementing salt iodization has reduced its deficiency.[vii] However, with the current popularity of consuming un-iodized salt, iodine deficiency and related health concerns may increase.

Cancers at Higher Risk Due to Iodine Deficiency

Iodine deficiency and the risk of cancer have not been well studied. At the time of publication, only five cancers have been evaluated. We need more research. Iodine deficiency has been linked to an increased risk of:

• Thyroid Cancer, particularly follicular and anaplastic thyroid cancer[viii] [ix]
• Breast Cancer[x] [xi]
• Stomach Cancer[xii]
• Prostate Cancer[xiii]
• Endometrial and Ovarian Cancer[xiv]

Iodine may play a protective role in decreasing cancer concerns for those with BRCA1.[xv]

Excessive iodine intake is associated with some types of papillary thyroid cancer, while adequate iodine intake is protective against papillary thyroid cancer.[xvi]

Iodine Interactions with Medications, Chemotherapy, and Radiation

Iodine can interact with certain medications and treatments:

• Medications: Iodine can interact with lithium, which is used to treat bipolar disorder, potentially leading to hypothyroidism.
• Chemotherapy: Iodine may decrease the level or effect of baloxavir marboxil. For additional potential interactions, visit https://www.drugs.com/drug_interactions.html.
• Radiation Therapy: Supplementing iodine during Radioactive iodine (I-131) treatment of thyroid cancer may decrease the effectiveness of I-131.

Iodine Excess and Toxicity

Iodine excess can cause thyroid dysfunction. Iodine toxicity may lead to thyroiditis, low thyroid function, high thyroid function, and papillary cancer. Mild iodine toxicity symptoms include gastrointestinal upset, nausea, vomiting, and diarrhea, which may progress to more severe manifestations of delirium, confusion, fatigue, and shock.[xvii]

Top 10 Food Sources of Iodine

Incorporating iodine-rich foods into your diet is essential for maintaining adequate iodine levels. Here are the top 10 food sources of iodine:

• Seaweed (Kombu Kelp): Up to 2,984 mcg per gram
• Cod: 99 mcg per 3-ounce serving
• Dairy Products (Milk): 94 mcg per cup
• Iodized Salt: 71 mcg per 1.5 grams
• Shrimp: 35 mcg per 3-ounce serving
• Tuna: 17 mcg per 100 grams
• Eggs: 24 mcg per large egg
• Prunes: 13 mcg per 5 prunes
• Lima Beans: 8 mcg per 1/2 cup
• Baked Potatoes (with skin): 60 mcg per medium potato

Potential Side Effects of Too Much Iodine

While iodine is essential, excessive intake can lead to adverse effects:

• Hyperthyroidism: Excess iodine can cause overactive thyroid, leading to symptoms such as rapid heartbeat, weight loss, and anxiety.
• Iodine Poisoning: Symptoms include nausea, vomiting, diarrhea, and abdominal pain.
• Thyroiditis: Inflammation of the thyroid gland can occur with high iodine intake.

How to Test for Iodine

Testing for iodine levels can be done through various methods:

• Urine Test: Measures the amount of iodine excreted in the urine, indicating recent iodine intake. Click here to learn how to do a urine test for iodine, bromine, selenium, lithium, arsenic, cadmium, and mercury.
• Blood Test: Measures iodine levels, offering a snapshot of current iodine status.
• Iodine Patch Test: A preliminary at-home test where iodine tincture is applied to the skin and monitored for absorption. Click here to learn how to do the Iodine Paint Test.

Supplement Sources of Iodine

If dietary intake is insufficient, iodine supplements can help maintain adequate levels:

• Iodized salt
• Potassium Iodide: Commonly used in supplements and iodized salt.
• Lugol’s solution: potassium iodide and elemental/molecular iodine.
  Click here to learn more about the iodine capsules I take.
• Sodium Iodide: Available in supplement form.
• Kelp Supplements: Derived from seaweed, these supplements are rich in iodine.

In conclusion, iodine is vital in cancer prevention and overall health. Ensuring adequate iodine intake through diet or supplements, while being mindful of potential interactions and side effects, can help harness its numerous benefits.

Iodine and Cancer Reference Sources

[i] Kargar S, Shiryazdi SM, Atashi SR, Neamatzadeh H, Kamali M. Urinary Iodine Concentrations in Cancer Patients. Asian Pac J Cancer Prev. 2017;18(3):819-821. Published 2017 Mar 1. doi:10.22034/APJCP.2017.18.3.819  https://pmc.ncbi.nlm.nih.gov/articles/PMC5464505/

[ii] Mendieta, I., Nuñez-Anita, R.E., Nava-Villalba, M. et al. Molecular iodine exerts antineoplastic effects by diminishing proliferation and invasive potential and activating the immune response in mammary cancer xenografts. BMC Cancer 19, 261 (2019). https://doi.org/10.1186/s12885-019-5437-3

[iii] Tanaka M, Koji I, Fujioka I, et al. Impact of low iodine density tumor area ratio on the local control of non-small cell lung cancer through stereotactic body radiotherapy. J Radiat Res. 2021;62(3):448-456. doi:10.1093/jrr/rrab015 https://pmc.ncbi.nlm.nih.gov/articles/PMC8127655/

[iv] Aceves C, Mendieta I, Anguiano B, Delgado-González E. Molecular Iodine Has Extrathyroidal Effects as an Antioxidant, Differentiator, and Immunomodulator. Int J Mol Sci. 2021;22(3):1228. Published 2021 Jan 27. doi:10.3390/ijms22031228 https://pmc.ncbi.nlm.nih.gov/articles/PMC7865438/

[v] Lennartz, S., Cao, J., Pisuchpen, N. et al. Intra-patient variability of iodine quantification across different dual-energy CT platforms: assessment of normalization techniques. Eur Radiol 34, 5131–5141 (2024). https://doi.org/10.1007/s00330-023-10560-z

[vi] Eggers, M. Infectious Disease Management and Control with Povidone Iodine. Infect Dis Ther 8, 581–593 (2019). https://doi.org/10.1007/s40121-019-00260-x

[vii] Winder M, Kosztyła Z, Boral A, Kocełak P, Chudek J. The Impact of Iodine Concentration Disorders on Health and Cancer. Nutrients. 2022;14(11):2209. Published 2022 May 26. doi:10.3390/nu14112209 https://pmc.ncbi.nlm.nih.gov/articles/PMC9182735/

[viii] Winder M, Kosztyła Z, Boral A, Kocełak P, Chudek J. The Impact of Iodine Concentration Disorders on Health and Cancer. Nutrients. 2022; 14(11):2209. https://doi.org/10.3390/nu14112209

[ix] Zimmermann, M.B., Galetti, V. Iodine intake as a risk factor for thyroid cancer: a comprehensive review of animal and human studies. Thyroid Res 8, 8 (2015). https://doi.org/10.1186/s13044-015-0020-8

[x] appaport, J. (2017). Changes in Dietary Iodine Explains Increasing Incidence of Breast Cancer with Distant Involvement in Young Women. Journal of Cancer, 8(2), 174-177. https://doi.org/10.7150/jca.17835.

[xi] Aceves C., García-Solís P., Arroyo-Helguera O., Vega-Riveroll L., Delgado G., Anguiano B. Antineoplastic effect of iodine in mammary cancer: Participation of 6-iodolactone (6-IL) and peroxisome proliferator-activated receptors (PPAR) Mol. Cancer. 2009;8:33. doi: 10.1186/1476-4598-8-33.

[xii] Behrouzian R, Aghdami N. Urinary iodine/creatinine ratio in patients with stomach cancer in Urmia, Islamic Republic of Iran. East Mediterr Health J. 2004;10:921-924

[xiii] Cann SA, Qiu Z, van Netten C. A prospective study of iodine sta[xiii]tus, thyroid function, and prostate cancer risk: follow-up of the first National Health and Nutrition Examination Survey. Nutr Cancer. 2007;58:28-34

[xiv] Stadel BV. Dietary iodine and risk of breast, endometrial, and ovarian cancer. Lancet. 1976;1(7965):890-891. doi:10.1016/s0140-6736(76)92102-4 https://pubmed.ncbi.nlm.nih.gov/58152/ 

[xv] Kiljańczyk A, Matuszczak M, Marciniak W, Derkacz R, Stempa K, Baszuk P, Bryśkiewicz M, Cybulski C, Dębniak T, Gronwald J, et al. Blood Iodine as a Potential Marker of the Risk of Cancer in BRCA1 Carriers. Nutrients. 2024; 16(11):1788. https://doi.org/10.3390/nu16111788

[xvi] Zhang X, Zhang F, Li Q, et al. The relationship between urinary iodine concentration and papillary thyroid cancer: A systematic review and meta-analysis. Front Endocrinol (Lausanne). 2022;13:1049423. Published 2022 Oct 31. doi:10.3389/fendo.2022.1049423 https://pmc.ncbi.nlm.nih.gov/articles/PMC9659619/

[xvii] Southern AP, Anastasopoulou C, Jwayyed S. Iodine Toxicity. In: StatPearls. Treasure Island (FL): StatPearls Publishing; May 2, 2024. https://www.ncbi.nlm.nih.gov/books/NBK560770/