Which nutrient is effective in cancer treatment?

Selenium has a proven antitumor potential. Its action is associated with several biochemical mechanisms that affect the growth and survival of tumor cells.

Involvement in the activity of glutathione peroxidase. Selenium is a key component of the enzymes of the glutathione peroxidase family. These enzymes protect cells from oxidative stress, which causes DNA damage and can trigger oncogenesis.

• At sufficient selenium levels, the enzymatic system actively neutralizes peroxides and free radicals.
• Tumor cells that have already undergone mutations tolerate high levels of antioxidant activity poorly, as it disrupts their atypical metabolism.

Induction of apoptosis in tumor cells. Some forms of selenium (e.g., methylseleninate, selenomethionine) can induce apoptosis (programmed cell death) in malignant cells:

• They increase the intracellular level of hydrogen peroxide and other ROS specifically in tumor cells, as their antioxidant defense is impaired.
• This leads to the activation of caspases and the destruction of tumor cell structures.

Modulation of gene expression. Selenium affects the activity of genes related to DNA repair, immune response, and antitumor proteins:

• It increases the expression of p53 (the main "guardian" of DNA, suppressing the division of mutated cells).
• It decreases the expression of pro-oncogenic growth factors (VEGF, bFGF), which suppresses tumor angiogenesis.

Enhancement of immune response. Selenium stimulates the activity of NK cells and cytotoxic T lymphocytes that attack tumor cells. This is especially important in the therapy of cancers where immune surveillance is weakened (e.g., liver, prostate, breast cancer).

Evidence of effectiveness

Clinical studies and meta-analyses show:

• Prostate cancer: high efficacy of selenium (especially with vitamin E) in reducing the risk of progression and recurrence.
• Liver cancer: in patients with chronic hepatitis B/C, selenium supplements reduce the incidence of hepatocellular carcinoma and slow its development.
• Breast and lung cancer: selenium supportive therapy improves prognosis and reduces the toxicity of chemotherapy and radiotherapy.
• Colon cancer: there is evidence of reduced adenoma size and risk of malignancy with long-term selenium intake.

Doses

Therapeutic doses are usually higher than preventive ones: 200–400 mcg/day (organic forms, most often selenomethionine).

In oncological diseases, short-term courses of up to 800 mcg/day are sometimes used under medical supervision.

Selenium overdose is toxic (risk of selenosis: hair loss, brittle nails, nervous system damage).