Selenium may protect against breast cancer

- other cancers, and premature death

The incidence of breast cancer has been rising in recent years. Diet, lifestyle, and genetic predisposition all play a role. There is also evidence that the trace element selenium helps protect against cancer, including breast cancer, through several mechanisms. According to a Polish population study published in the International Journal of Molecular Sciences, this appears to apply even among the many women with breast cancer who have high levels of the genotype HRG (histidine-rich glycoprotein).

Today, approximately one in eight women will develop breast cancer, and the trend has not yet reversed - quite the opposite. Familial breast cancer, caused by mutations in the so-called BRCA genes, accounts for around 30% of all cases. In addition, high levels of the genotype HRG (histidine-rich glycoprotein) may act as a genetic growth factor. HRG can bind to specific proteins (HER3 and HER4) expressed in several types of breast cancer, thereby promoting aggressive tumor growth.
Elevated HRG levels are also associated with treatment resistance and poorer prognosis.
In addition to genetic predisposition, diet and lifestyle play crucial roles in determining the risk of developing breast cancer. Since selenium is already known to help protect against breast cancer and early mortality through multiple mechanisms, the aim of this new population study was to investigate whether selenium may also regulate levels of the growth factor HRG.

The risk of breast cancer and early death depends on blood selenium levels

The study included 2,782 healthy women from families with a history of breast cancer, registered at the Hereditary Cancer Centre in Szczecin, Poland. The participants, aged 40 – 82 years, were recruited between September 2010 and March 2024. Women carrying the BRCA1 mutation, which is associated with particularly high breast cancer risk, or those already diagnosed with cancer were excluded.
Participants’ blood selenium levels were measured using plasma mass spectrometry, and they were divided into four groups (quartiles) based on selenium status. Molecular analyses of the HRG growth factor were also performed.
During a follow-up period of six years and two months, researchers identified 210 new cancer cases, including 106 cases of breast cancer. There were 82 deaths in total, of which 44 were cancer-related.
The study revealed significant differences depending on blood selenium levels, including their impact on HRG levels, cancer risk, and overall mortality. These associations were particularly evident among women over the age of 50.
Regardless of HRG levels, the group with the lowest selenium levels (quartile 1) had a significantly higher overall risk of cancer and all-cause mortality compared with the group with the highest selenium levels (quartile 4).
The researchers therefore conclude that the risk of cancer and early death from all causes depends on both HRG levels and blood selenium status.

Selenium has multiple cancer-protective mechanisms

In the study’s introduction, the authors note that selenium is a component of several selenoproteins that play key roles in immune function, antioxidant defense, and thyroid hormone metabolism. Through these mechanisms, selenium helps protect cells from damage caused by oxidative stress and chronic inflammation, both of which are major factors involved in the development of cancer and tumor growth.
Higher blood selenium levels are generally associated with a lower risk of several cancers and cancer-related mortality, including cancers of the breast, prostate, lungs, colon and rectum, bladder, stomach, liver, and pancreas.

Official selenium recommendations vs. actual requirements

In Denmark, the official recommended daily selenium intake is 55 micrograms. The revised Nordic Nutrition Recommendations are higher, though, suggesting 75 micrograms for women and 90 micrograms for men.
The authors of the population study also refer to a large Vietnamese study indicating that an even higher intake (around 110–124 micrograms daily) may be needed to reduce the risk of several cancers. As noted, these levels are more than double the Danish recommendations and far above the average European intake of approximately 40 micrograms. In several cancer studies, supplements with 200 micrograms of selenium per day have been used.
Nonetheless, excessive selenium intake should be avoided. According to the European Food Safety Authority (EFSA), the upper safe intake level is set at 300 micrograms per day.

• Selenium is found in foods such as fish, organ meats, meat, eggs, and Brazil nuts
• The selenium content of grains and crops depends on soil conditions
• European soils are relatively low in selenium, which is a major reason for widespread deficiency

References:

Krzysztof Lubinski et al. All-Cause Mortality and Cancer Risk Depend on Blood Se Level and HRG rs10770 Genotypes on a Prospective Cohort of Women with Familial Breast Cancers. International Journal of Molecular Sciences. 2026 Mar.

Christina Pfister, Joerg Schoenemann. Selenium in Cancer Rehabilitation – A Retrospective Study from a Specialized Clinic. Nutrients 2023 Sep.

Nordic Council of Ministers. Nordic Nutrition Recommendations 2023