How can iodine help you? What the research says

As an essential nutrient, iodine is needed for thyroid function, and a deficiency is linked to higher risk of thyroid and stomach cancers. Some evidence shows that treatment with molecular iodine before breast cancer surgery may improve tumor response and reduce some side effects.

How can iodine help you? What the research says

We summarize the clinical evidence for each medical benefit here. We begin with our assessment of the strength of evidence within each category, followed by a brief summary of individual studies or reviews of several studies. In assessing the strength of evidence, we consider the study design, number of participants, and the size of the treatment effect (how much outcomes changed with treatment).

To see more details, click the plus sign to the right of any section.

Our assessments of evidence for each medical benefit fall into one of these categories:

Strong evidence: consistent, significant effects in several large (or at least one very large) well designed clinical studies or at least two meta-analysesa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of clinical studies of moderate or better quality (or one large meta-analysis) finding similar results
Good evidence: significant effects in one large or several mid-sized and well-designed clinical studies ( randomized controlled trialsa study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects with an appropriate placebo or other strong comparison control or observational studies that control for confounds)
Modest evidence: significant effects in at least three small but well-designed randomized controlled trials (RCTs), or one or more well-designed, mid-sized clinical studies of reasonably good quality (RCTs or observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods studies), or several small studies aggregated into a meta-analysis
Preliminary evidence: significant effects in small or poorly designed clinical studies OR conflicting results in adequate studies but a preponderance of evidence of an effect
Weak evidence: one or more case studies, supported by animal evidence OR small treatment effects of limited clinical significance OR studies with no controls OR weak trends of effects
Insufficient evidence: preclinical evidence only OR clinical studies with such poor or unclear methodology that no conclusion can be drawn OR conflicting findings across clinical studies with no preponderance of evidence in one direction; conflicting evidence occurs when studies find conflicting effects (positive effect vs no effect or negative effect) with the same treatment and the same general study population (same cancer type, for example)

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Improving treatment outcomes

Is iodine linked to improved survival? Is it linked to less cancer growth or metastasis? Does it enhance the anticancer action of other treatments or therapies? We present the evidence.

Breast cancer

Preliminary evidencesignificant effects in small or poorly designed clinical studies OR conflicting results in adequate studies but a preponderance of evidence of an effect (this is the CancerChoices definition; other researchers and studies may define this differently) of better survival and tumor response rates among women with breast cancer treated with molecular iodine before and after surgery compared to after surgery alone

Higher 5-year disease-free survivalthe time during and after successful treatment of a disease during which there are no signs and symptoms of the disease that was treated; this is the same as recurrence-free survival, tumor response rates, and other anticancer markers among women with early (stage 2) breast cancer treated with 5 mg molecular iodine (I2) per day for 7–35 days before surgery compared to placeboa pill, medicine, or procedure—thought to be both harmless and ineffective—prescribed for the psychological benefit to the patient or as a sham treatment in a study to allow a comparison to a therapy of interest, and then all treated with neoadjuvanttherapy used before a main treatment, such as chemotherapy, radiation therapy, and hormone therapy before surgery therapy (5-fluorouracil/epirubicin/cyclophosphamide or taxotere/epirubicin) and iodine after surgery for 170 days (4 to 6 cycles of chemotherapy) in a small RCTrandomized controlled trial, a study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects¹Moreno-Vega A, Vega-Riveroll L et al. Adjuvant effect of molecular iodine in conventional chemotherapy for breast cancer. Randomized pilot study. Nutrients. 2019 Jul 17;11(7). pii: E1623.
Substantially higher 5-year disease-free survival, tumor response rates, and other anticancer markers among women with advanced (stage 3) breast cancer treated with with 4 to 6 cycles neoadjuvant chemotherapy (5-fluorouracil/epirubicin/cyclophosphamide or taxotere/epirubicin) plus 5 mg molecular iodine (I2) per day before surgery compared to chemotherapy and placebo, and then after surgery all treated with iodine to make a total of 170 days in a small RCT²Moreno-Vega A, Vega-Riveroll L et al. Adjuvant effect of molecular iodine in conventional chemotherapy for breast cancer. Randomized pilot study. Nutrients. 2019 Jul 17;11(7). pii: E1623.

Thyroid cancer

Preliminary evidence of comparable radioiodine consumption after radioiodine ablation therapy following a total thyroidectomy among Korean people following either a low-iodine diet (less than 50 µg iodine) or a restricted-iodine diet (50–100 µg)

Managing side effects and promoting wellness

Is iodine linked to fewer or less severe side effects or symptoms? Is it linked to less toxicity from cancer treatment? Does it support your quality of life or promote general well-being? We present the evidence.

Blood-related side effects

Preliminary evidencesignificant effects in small or poorly designed clinical studies OR conflicting results in adequate studies but a preponderance of evidence of an effect (this is the CancerChoices definition; other researchers and studies may define this differently) of less neutropeniaan abnormally low number of neutrophils in the blood, leading to increased susceptibility to infection from chemotherapy among women with breast cancer treated with molecular iodine before and after surgery compared to after surgery alone

Cardiovascular side effects

Preliminary evidence of less cardiotoxicity from chemotherapy among women with breast cancer treated with molecular iodine before and after surgery compared to after surgery alone

Gastrointestinal symptoms

Preliminary evidence of less nausea, vomiting, and diarrhea from chemotherapy among women with breast cancer treated with molecular iodine before and after surgery compared to after surgery alone

Pain

No evidence of an effectoverall, one or more studies did not demonstrate that a treatment or intervention led to an expected outcome; this does not always mean that there is no effect in clinical practice, but that the studies may have been underpowered (too few participants) or poorly designed. Larger, well-designed studies provide more confidence in making assessments. on muscle pain among women with stage 2 or 3 breast cancer treated with molecular iodine

Skin and tissue side effects

Preliminary evidence of less hand-foot syndrome from chemotherapy among women with breast cancer treated with molecular iodine before and after surgery compared to after surgery alone

Reducing cancer risk

Is iodine linked to lower risks of developing cancer or of recurrence? We present the evidence.

An iodine deficiency is linked to higher risk of stomach and thyroid cancers. Among nonpregnant people, an iodine deficiency is less than 100 μg/L urine.¹⁰Iodine: Fact Sheet for Health Professionals. National Institutes of Health Office of Dietary Supplements. October 13, 2023. Viewed April 19, 2024. Higher levels are recommended during pregnancy.

Gastrointestinal cancer

Modest evidencesignificant effects in at least three small but well-designed randomized controlled trials (RCTs), or one or more well-designed, mid-sized clinical studies of reasonably good quality (RCTs or observational studies), or several small studies aggregated into a meta-analysis (this is the CancerChoices definition; other researchers and studies may define this differently) of a link between iodine deficiency and risk of stomach cancer

Thyroid cancer

Modest evidence of a link between iodine deficiency and risk of thyroid cancer

Helpful link

Iodine: Fact Sheet for Consumers ›

Keep reading about iodine

See all our reviews of complementary therapies

Authors

Nancy Hepp, MS

Lead Researcher

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Laura Pole, MSN, RN, OCNS

Senior Clinical Consultant

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Reviewer

Susan Yaguda, MSN, RN

Manager at Atrium Health’s Levine Cancer Institute and CancerChoices Clinical Consultant

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Last update: April 19, 2024

Last full literature review: April 2023

We are grateful for research support from Adriana Gutierrez Galvis.

CancerChoices provides information about integrativein cancer care, a patient-centered approach combining the best of conventional care, self care, and evidence-informed complementary care in an integrated plan cancer care. We review complementaryin cancer care, complementary care involves the use of therapies intended to enhance or add to standard conventional treatments; examples include supplements, mind-body approaches such as yoga or psychosocialtherapy, and acupuncture therapies and self carelifestyle actions and behaviors that may impact cancer outcomes; examples include eating health-promoting foods, limiting alcohol, increasing physical activity, and managing stress practices to help patients and professionals explore and integrate the best combination of conventionalthe cancer care offered by conventionally trained physicians and most hospitals; examples are chemotherapy, surgery, and radiotherapy and complementary therapies and practices for each person.

Our staff have no financial conflicts of interest to declare. We receive no funds from any manufacturers or retailers gaining financial profit by promoting or discouraging therapies mentioned on this site.

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Berberine

Integrative Cancer Care

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Complementary Therapies and Cancer: How Much Evidence Is Enough?

References[+]

1, 2, 5, 6	Moreno-Vega A, Vega-Riveroll L et al. Adjuvant effect of molecular iodine in conventional chemotherapy for breast cancer. Randomized pilot study. Nutrients. 2019 Jul 17;11(7). pii: E1623.
3	Cooper DS, Doherty GM et al; American Thyroid Association Guidelines Taskforce. Management guidelines for patients with thyroid nodules and differentiated thyroid cancer. Thyroid. 2006 Feb;16(2):109-42.
4	Lim CY, Kim JY et al. Effect of a low iodine diet vs. restricted iodine diet on postsurgical preparation for radioiodine ablation therapy in thyroid carcinoma patients. Yonsei Medical Journal. 2015 Jul;56(4):1021-7.
7, 8, 9	Moreno-Vega A, Vega-Riveroll L et al. Adjuvant effect of molecular iodine in conventional chemotherapy for breast cancer. randomized pilot study. Nutrients. 2019 Jul 17;11(7). pii: E1623.
10	Iodine: Fact Sheet for Health Professionals. National Institutes of Health Office of Dietary Supplements. October 13, 2023. Viewed April 19, 2024.
11	Gołkowski F, Szybiński Z et al. Iodine prophylaxis—the protective factor against stomach cancer in iodine deficient areas. European Journal of Nutrition. 2007 Aug;46(5):251-6.
12	Behrouzian R, Aghdami N. Urinary iodine/creatinine ratio in patients with stomach cancer in Urmia, Islamic Republic of Iran. East Mediterranean Health Journal. 2004 Nov;10(6):921-4.
13	Gulaboglu M, Yildiz L, Celebi F, Gul M, Peker K. Comparison of iodine contents in gastric cancer and surrounding normal tissues. Clinical Chemistry and Laboratory Medicine. 2005;43(6):581-4.
14	Zhang YL, Li P et al. Does relatively low iodine intake contribute to thyroid cancer? An ecological comparison of epidemiology. Medicine (Baltimore). 2019;98(41):e17539.