Ginkgo biloba (scientific name Salisburia adiantifolia) is a plant extract that has been traditionally used in Chinese medicine for thousands of years. Historically, gingko was used as a natural remedy for asthma, bronchitis, fatigue, and improving brain health.
Today, gingko biloba is gaining immense popularity as a herbal dietary supplement. It is believed to be helpful in preventing and managing a wide range of health issues such as eye problems, cognitive decline, memory issues, circulatory issues and tinnitus (ringing in the ears). In Norway, products made with ginkgo leaf extract have been approved by the Norwegian Medicines Agency for improving blood circulation. 
Gingko biloba is a powerful anti-oxidant, a property that makes it useful in various health conditions. Scientists have found yet another use for this dietary supplement: as a natural remedy to provide protection against radiation exposure.
Gingko Biloba as a radioprotective agent
Extracts made from gingko biloba leaves contain powerful antioxidant compounds (namely ginkgolides and bilobalides) that protect cells from the damage caused by free radicals – molecules with unpaired electrons that can damage cellular proteins, DNA, lipids and mitochondria.
Free radicals are naturally produced during chemical reactions when the body produces energy. They are also produced by our immune system on purpose to kill viruses and bacteria. At this level, your body is generally prepared to contain the damage caused by these free radicals, for example, by employing endogenous antioxidants (that are made internally by the body) and exogenous antioxidants (that you get through external sources like food and supplements). In addition, the body also has self-repair mechanisms to supress and even correct this damage.
The problem arises when there is an overload of free radicals. And a number of environmental triggers – such as chronic infections, poor diet, overuse of antibiotics and medications, pollution and exposure to UV rays and pesticides – can all contribute to the overwhelming production of these highly reactive molecules. Eventually, this cripples your body’s natural systems that are responsible for keeping the oxidative damage under control.
Ionizing radiation also trigger the formation of free radicals and clastogenic factors that cause genetic damage. And with its anti-oxidant and anti-clastogenic properties, ginkgo biloba works as a very effective radioprotective agent. It protects cells and their components from the effects of radiation exposure. What’s more, gingko biloba appears to be effective even long after a person has been exposed to radiation.
How it works?
Exposure to ionizing radiation, whether from nuclear accident or radiation therapy, produces clastogenic factors (CFs) in the blood. These clastogenic factors are also present in individuals with health conditions triggered by oxidative stress such as chronic inflammatory conditions, HIV and ischemia reperfusion injury.
Clastogenic factors can break apart DNA and cause chromosomal damage, leading to cell mutations and cancer formation. These chromosome-damaging substances can persist in the bloodstream for a long time and keep causing DNA and chromosomal damage even years after a person has been irradiated. CFs were found in the blood samples of survivors from both the Chernobyl nuclear accident and the atomic bomb attack on Japan, even 30 years after radiation exposure.  These factors were also detected in the plasma of Chernobyl-exposed children. 
A 2009 study published in the International Journal of Low Radiation found that antioxidant extracts of the leaves of the Gingko biloba tree may protect cells from radiation damage. Researchers believe that this discovery may become useful in decreasing the side effects of radiotherapy in cancer patients. The study, performed on healthy white blood cells, found that cells treated with gingko biloba extract were protected from gamma radiation but those untreated went through apoptosis (process of programmed cell death).
The study concluded that Gingko biloba extract (EGb) “through its free-radical scavenging and antioxidant properties, attenuates IR-induced apoptosis in radiosensitive cells, suggesting that EGb may have a potential benefit in enhancing radioprotective effects.” 
Gingko Biloba as a chemo-preventive agent
A 2006 study reported that gingko biloba, and various other natural agents such as vitamin E, vitamin C, carotenoids and selenium, can prevent skin cancer risk. The study also highlighted that gingko biloba has other cancer chemo-preventive properties :
- Promotes programmed cell death (apoptosis) of cancer cells
- Helps repair and reconstitute damaged chromosomes
- Helps in the treatment of fibrosis-related cancer
- Exerts healing effect on cancer induced by free radicals
- Works as an effective adjunct therapy to radiation therapy for cancer treatment
- Helps reduce the size of cancer tumors
Protective Effects of Gingko Biloba in Radioiodine Therapy
Data suggests that extracts from gingko biloba may also avert genetic damage caused by radioiodine therapy, that is often used in treating hyperthyroidism. 
Radioiodine therapy or I-131 therapy, is fast becoming the first line of treatment for hyperthyroidism (overactive thyroid gland). How does it work? Radioactive iodine concentrates in the thyroid gland and destroys thyroid cells, including the cancer cells.
However, recent reports indicate an increased rate of overall cancer among patients treated with radioiodine for their overactive thyroid disorders. I-131 therapy causes chromosomal damage to lymphocytes patients with Grave’s disease – an autoimmune thyroid disorder commonly responsible for hyperthyroidism.
Ionizing radiation from I-131 triggers the excessive production of free radicals – causing oxidative damage to fragile cellular structures. Additionally, free radicals also stimulate the release of clastogenic factors (CFs) in the bloodstream, which in turn promote further production of free radicals. This creates a vicious cycle of more clastogenic factors in the blood followed by increased amounts of free radicals – leading to chromosomal damage. This self-perpetuating mechanism soon spirals out of control and causes more chromosomal damage than the cells can withstand and repair on their own.
Several studies back the claims that Ginkgo biloba extracts have antioxidant properties and employ various mechanisms to dilute the oxidative stress caused by free radicals.   While the exact mechanisms through which this happens is not yet clear, studies show that gingko biloba contains antioxidant compounds that scavenge free radicals such as NO•, OH•, O2•−, and peroxyl radicals. It also inhibits the chromosomal damage by clastogenic factors.
So, this study showed for the first time that “Ginkgo biloba extracts’ supplementation is effective in reducing radiation-induced genotoxic damage in hyperthyroid patients receiving 131I therapy”.  It also noted that I-131 therapy is generally safe, but gingko biloba may prevent the genotoxicity caused by radioactive iodine.
Another 2008 study published in the Endocrine Abstracts attested to these findings. It concluded, “Although I-131 therapy is essentially safe, our data encourages the use of Ginkgo biloba extract to prevent possible harmful genetic effects, particularly in patients with metastasis who require repeated radioiodine treatments.” 
Taking gingko biloba supplements may help reduce your risk of genetic damage caused by radiation exposure. However, always consult your healthcare practitioner before you start consuming ginkgo biloba or any other natural plant extracts (such as curcumin or resveratrol) to achieve radioprotection. Although generally safe, these natural agents may interfere with any existing health condition. They may also negatively interact with medication you are already taking.
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- Emerit et al. Clastogenic factors in the plasma of children exposed at Chernobyl. Mutat Res. 1997
- Shin et al. Protective effect of Gingko biloba against radiation-induced cellular damage in human peripheral lymphocytes and murine spleen cells. International Journal of Low Radiation. Vol. 6, No. 3, 2009
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- Dardano et al. Anticlastogenic Effect of Ginkgo Biloba Extract in Graves’ Disease Patients Receiving Radioiodine Therapy. The Journal of Clinical Endocrinology & Metabolism. Volume 92, Issue 11, 1 November 2007.
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- Dardano et al. Effect of Ginkgo biloba extract supplementation on genotoxic damage after thyroid remnant ablation by 131I. Endocrine Abstracts. 2008.