How Does Iodine Inhibit Cancer: Introduction, Studies, and Evidence

In human physiology, one of the essential elements is iodine, with many recent studies and ongoing epidemiological evidence suggesting its role in preventing different types of cancer. It is critical to the production of thyroid hormone and the maintenance of the thyroid gland.

At Paul Ehline Ride, we offer insights into the relevant legislature and review research papers for affected veterans with service-related cancer and other diseases. Here, we will go over dietary iodine and iodine supplementation and its effect on the cell cycle, thyroid cells, breast cancer cell lines, and other cancers.

Introduction to Iodine

According to a 2009 study published in the Nutrition and Health journal, the total Iodine content in the human body varies between 25 mg and 50 mg, with up to 70% of the iodine found in extrathyroidal tissues. The small intestines absorb most of the iodine consumed, which enters the bloodstream as iodide (I-), and the remaining gets excreted in urine or feces.

To overcome the electrochemical gradient, iodine requires two molecules of sodium and the combination of iodine and sodium that transport into enterocytes, the epithelial cells which line the inner surface of the small and large intestines, similar to what is found in the membrane of thyroid follicular cells.

Other body organs or glands have a combination of Iodine and Sodium (NIS), including stomach mucosa, salivary glands, and the lactating mammary gland. A study carried out in 2006 and published in the European Journal of Endocrinology also provides evidence of high concentrations of NIS in different tissues, including the choroid plexus, lacrimal gland, ovary, and many other tissues.

Iodine found in the lactating mammary gland helps provide the mineral to the developing child, whereas the iodine found in tissues acts as an antioxidant, antibacterial, and anti-inflammatory.

After iodine gets transported into the bloodstream with the help of sodium, it reaches the mouth and stomach, where it deposits in and around the mucosa. This reserve of iodine replenishes the gastro-salivary pool of iodine, which accounts for more than 20% of iodine content in the body.

Although the organs and tissues mentioned above contain iodine for various purposes, many studies dating back to 1968 suggest that iodine may be in every tissue in the human body. There may be other receptors that can aid in uptaking iodine and transporting it into many other tissues.

Over the years, humans have slowly grasped the importance of iodine, not just to the human body but also to the environment. 

Iodine in algae helps remove carbon dioxide from the atmosphere and turn it into biomass and oxygen. On the other hand, the intake of iodine in the human body positively helps with the serum antioxidant status. It also aids in the removal of hydroxyl radicals, which attack the cell membrane, causing damage.

Iodine also has excellent anti-inflammatory properties in the human body. After suffering wounds, medical professionals recommend applying povidone-iodine to prevent inflammation. During abdominal surgeries, the anti-inflammatory effect of iodine reduces the risk of cancer cells spreading.

Evidence of Iodine Inhibiting Cancer Cells

Let’s review some of the research evidence that suggests iodine’s positive role in inhibiting the following types of cancer.

Breast Cancer

Iodine has somewhat of a therapeutic effect on benign breast conditions, which helps maintain healthy breast tissues in the body. In a study that reviewed the results of three clinical trials, the findings suggested that molecular iodine (I2) played a crucial role in the reduction of fibrocystic symptoms.

Another study published in the breast cancer res journal uses a sample size of 111 women who suffered from cyclic mastalgia, breast pain related to the hormonal variations associated with the menstrual cycle. The study divided the sample into three groups: two received different doses of combination iodide/iodate (I-/IO3-), and the third received a placebo. The study’s findings revealed that over half of the women who received a daily dose of more than 6 mg showed a reduction in their mastalgia symptoms at six months.

While human tissues uptake iodine, the cancerous breast tissue takes in more molecular iodine (I2) than normal tissues. A pioneering study showed NIS prevalent in 87% of the breast tissue compared to normal tissue. In another study on rodent samples, the mammary carcinogenesis molecular iodine showed positive signs of breast cancer prevention.

Plenty of evidence suggests molecular iodine (I2) plays a vital role in the prevention of carcinogenic processes. In a study involving Sprague-Dawley rats, the mammals had unrestricted access to a water source containing 0.05% Iodine. The study showed that the rats with access to iodine water had 37.5% less risk of mammary tumors than rats drinking regular water.

A recent 2020 study on the impact of iodine on breast cancer revealed that high levels of iodine led to a lower risk of breast cancer. In women with low selenium levels, there was a positive correlation between iodine and breast cancer in women diagnosed early on. The study revealed a 25% lower risk of breast cancer in women with high levels of iodine than those with lower levels of iodine. The association between iodine and breast cancer was only negative in cases with higher age or later diagnosis.

Although iodine has a positive effect on cancer, patients with Thyroid cancer cells intaking iodized salt have shown an increased risk of breast cancer. There is a 21%–89% increase in breast cancer risk following thyroid cancer in patients consuming iodized salt. Patients treated with radioactive iodine for hyperthyroidism (thyroid disease) were more susceptible to breast and stomach cancer than others.

Gastric Cancer

Several studies have been conducted across the world that suggests that iodine levels are much lower in patients with gastric cancer. 

A study conducted in Iran assessed the Iodine levels in 100 patients suffering from gastric cancer and found that the levels in the urine of the patients were much lower than in healthy humans, suggesting a severe iodine deficiency.

A study conducted in Turkey assessed iodine levels in gastric cancer tissues and found that the levels of iodine in the cancer tissues were much lower than those in the surrounding tissues.

Many studies have revealed lower or limited NIS levels in patients with gastric cancer or a later stage of Barrett’s esophagus. What’s surprising is that a European Journal of Nutrition 2007 study found that salt (containing iodine) in Poland contributed to lower incidences of gastric or stomach cancer between the 1900s and 2000s.

The United Nations Nutritional Policy Board recognizes iodine as integral to maintaining healthy cells in the stomach lining and is required for proper immune functions.

Prostate Cancer

Japan and its people have a higher intake of iodine, which may suggest why there are lower incidences of prostate cancer than in the United States. Although there may be other factors that have led to lower incidents of prostate cancer in Japan, the Japanese diet is exceptionally high in iodine, almost 25 times the regular intake of the United States population. Research suggests that people with higher levels of iodine have a 29% lower risk of prostate cancer than those with lower levels of Iodine intake.

In a study on animals, a 0.05% molecular iodine (I2) intake reduced the signs of benign prostatic hyperplasia, also called prostate gland enlargement, suggesting that the prostate absorbs iodine.

The following are the results of different studies carried out to determine iodine and its effects on the prostate:

• Improved urine flow and reduced Prostate-Specific Antigen (PSA) values across eight months.
• 52% of the sample size suffering from prostate adenocarcinomas, the most common type of prostate cancer, had NIS.
• Unlike normal cells that require NIS for Iodine intake, prostate cancer cell lines absorb iodine without support from sodium.
• Prostate cancer cells are most susceptible to the intake of molecular iodine (I2), which showed that it prevented the growth of xenografts of prostate cancer in mice.

Other Cancers

Studies show that Molecular iodine (I2) and 6-iodolactone (6-IL) inhibit the following cell lines in the human body:

• Four mammary cancer lines
• Lung cells
• Two glioblastoma cell lines
• Two pancreatic cell lines
• Neuroblastoma

The neuroblastoma cells were the ones that showed complete inhibition, followed by the MCF-7 breast cancer cells. According to the studies, the I2 and 6-IL inhibit endothelial growth factor contradicting previous studies that suggested that the inhibition of changes in mitochondrial membrane potential inhibits the growth factor.

There is a need for more research to determine whether the 6-IL inhibits colon cancer cells, as studies suggest that it induces apoptosis in the colon cancer cell.

How Does Iodine Inhibit Cancer: Discussing the Role of Iodine in the Human Body

Iodine plays a crucial role in cellular renewal and proper health of the human body due to its many properties as an antioxidant, anti-inflammatory, and others. When manipulated, appropriate amounts of iodine and Type 3 deiodinase (DOI3) can attack or inhibit cancer cells.

The concrete evidence of iodine deficiency in populations and its implications on the growth of cancer cells suggests that we must replenish our body’s iodine pool by changing our diet or taking supplements. There are safe limits to taking iodine; for example, adults should only take about 1,100 mcg/day, but these limits do not apply to those who take iodine for medical reasons.

Iodine salts affect the thyroid by shutting down thyroid hormone synthesis. Although this effect may be temporary, some studies suggest a permanent impairment of thyroid function. The National Institutes of Health (NIH) recommends 4.0 mg/100 lb body weight to prevent the spread of benign breast diseases. However, higher doses of molecular iodine and intracellular 6-iodolactone may induce transient hypothyroidism and other side effects, which dissipate after the discontinuance of iodine.

The supplements on the market provide potassium iodide, which is safe for replenishing iodine reserves in the body, but it does lead to increased interference with thyroid functions. According to research, the best consumption of iodine should include molecular iodine with very little iodide.

The best way to consume iodine to reduce benign breast diseases and inhibit certain cancers is to consume seaweed and fish moderately. Studies exploring whether seaweed prevents breast cancer reveal that seaweed can lead to the death of human breast cancer cells.

The dosage of iodine in seafood varies significantly, which may make it challenging to get the right amount of iodine nutrition to maintain proper health. For example, depending on the type of seaweed and where it comes from, the iodine content may vary between 16 mcg to 2,984 mcg iodine/g.

Conclusion – Is Consuming Iodine Risk-free?

Molecular iodine doesn’t come without risks. When intaking molecular iodine, people with antithyroid antibodies may exacerbate their symptoms, which is why all patients need to test for autoantibodies before taking any Iodine supplements. 

The results from the benign breast disease samples did not show any adverse reactions to iodine supplements because the sample did not have women with autoimmune diseases.

There is vast data and evidence that substantiate the claim that iodine is great for health and that deficiency of iodine is a common factor in most cancers, suggesting that an intake could inhibit cancer, especially stomach or gastric cancer. 

You may consider adding whole sea vegetables to your diet to get the benefits of good iodine, but if you’re looking for therapeutic use, it is best to reach out to a medical professional and start the treatment under their guidance.