Widespread selenium deficiency predicts a higher risk of colorectal cancer

The trace mineral selenium is an essential component of several selenium-containing proteins that support overall health. A new meta-analysis published in BMC Public Health found that selenium deficiency is associated with a higher risk of several diseases, including colorectal cancer, one of the leading causes of cancer-related deaths worldwide.

Colorectal cancer develops from benign polyps in the lining of the colon or rectum. The disease often causes no symptoms in its early stages, but as it progresses, symptoms may include changes in bowel habits, abdominal pain, fatigue, blood in the stool, and anemia. Nearly two million people worldwide are diagnosed with colorectal cancer each year, and the number continues to rise. Even when the disease is detected early and treated by surgically removing the tumor, the risk of recurrence remains high, and only about half of all patients are still alive five years after diagnosis.
These facts underscore the importance of prevention, particularly through healthy diet and lifestyle choices. Because selenium is already known to possess several cancer-protective properties, and selenium deficiency is common throughout Europe and many other parts of the world, researchers wanted to determine whether low selenium status could predict the risk of developing colorectal cancer.
Using relevant search terms in databases including PubMed, Embase, and Web of Science, the researchers identified 16 studies examining the relationship between selenium and colorectal cancer risk. The meta-analysis included nearly 200,000 participants and evaluated both dietary selenium intake and selenium concentrations in blood and various tissues.

Higher selenium intake may help prevent colorectal cancer

Overall, the analysis found that higher selenium intake was significantly associated with a lower risk of colorectal cancer. Two large population-based studies and several case-control studies consistently showed an inverse relationship between selenium intake and colorectal cancer risk.
Subgroup analyses also revealed a significant inverse association between selenium intake and colon cancer risk among populations in Europe and Australia.
The researchers therefore concluded that higher selenium intake is associated with a lower risk of developing colorectal cancer and that selenium may play a valuable role in colorectal cancer prevention.

Selenium supports gut health and helps protect against cancer

In the introduction to the new meta-analysis, as well as in another relevant study by Jinzhong Cai and colleagues (2022), previously discussed on this website, the authors describe the many ways selenium-containing proteins contribute to intestinal health and help protect against colorectal cancer and other forms of cancer. In summary, these proteins:

• Support the body's utilization of coenzyme Q10 and normal cellular energy production in the mitochondria
• Help regulate cell signaling pathways that are essential for normal cell function
• Regulate apoptosis, the natural process by which damaged or worn-out cells undergo programmed cell death—a mechanism that cancer cells are able to evade
• Form part of important antioxidant enzymes such as glutathione peroxidases (GPx) and thioredoxin reductase (TrxR), which protect cells, DNA, and mitochondria against oxidative damage caused by free radicals
• Support healthy immune function, enabling the body to combat harmful bacteria, foodborne toxins, an imbalanced gut microbiome, and abnormal cells
• Help regulate chronic inflammation, which increases the risk of colorectal cancer and many other chronic diseases
• Support the enzyme activity of certain beneficial gut bacteria, including the selenium-rich probiotic strain Lactobacillus rhamnosus SHA113, which helps protect the intestinal lining by producing a protective compound

Dietary sources of selenium and supplementation for colorectal cancer prevention

Good dietary sources of selenium include organ meats, meat, fish, eggs, grains, and Brazil nuts. However, because the soil in Europe and many other regions is naturally low in selenium, crops grown there also contain relatively little selenium. This is a major reason why selenium deficiency remains so widespread.
In Denmark, the recommended daily intake of selenium is 55 micrograms, yet many people do not obtain this amount through their diet. Moreover, several studies suggest that an intake of approximately 100–200 micrograms per day may be needed to fully optimize all selenium-dependent proteins.
The authors of the new meta-analysis refer to several supplementation studies. One of the most important is the Nutritional Prevention of Cancer (NPC) Study, which found that participants with low blood selenium levels (≤113.4 ng/mL) who took 200 micrograms of selenium yeast daily for several years reduced their risk of several common cancers, including colorectal cancer, by about 50%.
By contrast, the later SELECT trial found no cancer-preventive effect of selenium supplementation. However, this was largely because participants already had relatively high blood selenium levels before entering the study. In addition, the researchers used selenomethionine, a different form of selenium than selenium yeast.
These findings suggest that selenium supplementation is most relevant for people with low selenium status who wish to prevent or correct a deficiency. They also indicate that selenium yeast is the preferred supplement because it has demonstrated superior bioavailability and utilization.
At the same time, excessive selenium intake should be avoided. According to the World Health Organization, the tolerable upper intake level for adults is 400 micrograms per day.

• Selenium deficiency is common throughout Europe, largely because the soil is naturally low in selenium.
• According to the landmark NPC study, selenium yeast supplementation in people with low blood selenium levels reduced the risk of colorectal cancer and several other common cancers by approximately 50%.

References:

Jiacheng Ying et al. Low level of selenium predicts high incidence of colorectal cancer. BMC Public Health. 2026 Springer Nature

Jinzhong Cai et al. Advances in the study of selenium and human intestinal bacteria. Frontiers in Nutrition. 14 December 2022.