Researchers studied over 5,400 Chinese men to see if the amount of selenium in their blood affected their sex hormones. Selenium is a mineral found in foods like nuts and fish. The study found that men with higher selenium levels had slightly lower testosterone levels and a lower ratio of testosterone to estrogen. However, the differences were small, and scientists aren’t sure yet if this matters for men’s health. This research helps us understand how minerals in our diet might affect our bodies, but more studies are needed before making any changes to how much selenium you eat.

The Quick Take

  • What they studied: Whether the amount of selenium (a mineral) in men’s blood is connected to their testosterone and estrogen levels
  • Who participated: 5,414 Chinese men aged 18-79 years old, with an average age of about 47. Most were married and of Han ethnicity. Researchers measured their selenium levels and sex hormones from blood samples
  • Key finding: Men with higher selenium levels had slightly lower testosterone levels and a lower testosterone-to-estrogen ratio. The effect was small but showed a clear pattern as selenium levels increased
  • What it means for you: This suggests selenium might play a role in male hormone balance, but the changes are modest. If you’re concerned about your hormone levels, talk to your doctor rather than changing your selenium intake on your own

The Research Details

This was a cross-sectional study, which means researchers took a snapshot of 5,414 men at one point in time (2017-2018) and measured their selenium levels and sex hormones. They collected information about the men’s age, education, smoking habits, alcohol use, diet, weight, and health conditions through questionnaires and blood tests.

The researchers used a special statistical method that accounts for the complex way the study participants were selected from across China. They adjusted their analysis for many factors that could affect hormone levels, including age, smoking, alcohol consumption, seafood intake, soy product consumption, protein supplements, body weight, and diabetes status.

This approach helps isolate the connection between selenium and hormones by removing the influence of other factors that might also affect hormone levels.

Understanding how minerals like selenium affect our hormones is important because hormones control many body functions including energy, mood, muscle growth, and reproduction. By studying a large, representative group of Chinese men, the researchers could see if this relationship exists in real-world populations. The careful adjustment for other factors makes the findings more reliable than if they hadn’t accounted for diet, smoking, and other lifestyle factors

Strengths: Large sample size (5,414 men), national survey with diverse participants, careful measurement of both selenium and hormones from blood samples, adjustment for many confounding factors. Limitations: This is a snapshot study, so we can’t prove selenium causes the hormone changes; it only shows an association. The study was conducted in China, so results may not apply equally to other populations. The hormone changes observed were small in magnitude

What the Results Show

The study found that men with higher blood selenium levels had lower testosterone levels. When comparing men in the highest selenium group to those in the lowest group, testosterone was about 0.06 units lower (on a standardized scale). The testosterone-to-estrogen ratio also decreased with higher selenium, dropping about 0.03 units in the highest selenium group.

These changes might sound small, but they showed a clear pattern: as selenium levels went up, testosterone went down in a predictable way. The effect was consistent even after accounting for age, smoking, diet, weight, and other factors that could influence hormone levels.

The study also found that the selenium-hormone connection was stronger in certain groups: non-smoking men and men with obesity (BMI of 28 or higher) showed more pronounced associations between selenium and testosterone levels.

The researchers measured estradiol (a form of estrogen) separately but found no significant direct association between selenium and estradiol levels alone. However, because testosterone decreased while estradiol stayed relatively stable, the ratio between them changed. This ratio is important because it reflects the balance of male and female hormones in the body. The median selenium level in the study group was 97.80 micrograms per liter, which is considered normal for healthy adults

This is one of the first large studies to examine the relationship between selenium and sex hormones in adult men. Previous research has shown that selenium is important for reproductive health and thyroid function, but the specific connection to testosterone levels hasn’t been well studied. This research adds new information to our understanding of how this mineral affects male hormones, though it doesn’t contradict earlier findings about selenium’s importance for health

The biggest limitation is that this study shows association, not causation—we can’t prove that selenium causes lower testosterone. The study captured only one moment in time, so we don’t know if these relationships stay the same over months or years. The study was conducted in China, and results might differ in other populations with different diets and genetics. The hormone changes observed were small, and we’re not sure if they’re large enough to affect men’s health. The study didn’t measure selenium intake from food, only blood levels, so we don’t know exactly how much selenium men were consuming

The Bottom Line

Based on this research alone, there’s no reason to change how much selenium you eat. Current dietary guidelines recommend 55 micrograms per day for adult men, and most people get enough selenium from a balanced diet. If you have concerns about your testosterone levels or hormone balance, consult your doctor for proper evaluation and advice. Don’t take selenium supplements based on this study without medical guidance

Men concerned about hormone levels, particularly those interested in reproductive health or muscle development, should be aware of this research. However, this study is most relevant to researchers and doctors, not necessarily to the general public. Men with obesity or who don’t smoke may want to pay closer attention to this finding, as the effect was stronger in these groups

This is a single-point-in-time study, so there’s no timeline for seeing benefits or changes. If you were to change your selenium intake, it would likely take weeks to months to see any hormonal shifts, but again, this isn’t recommended without medical supervision

Want to Apply This Research?

  • Track your selenium intake from food sources (Brazil nuts, seafood, eggs, whole grains) and log it weekly. Note your energy levels, mood, and any changes in physical performance to see if there’s a personal pattern
  • If you’re interested in optimizing your mineral intake, focus on eating a balanced diet with natural selenium sources rather than supplements. Include 2-3 Brazil nuts daily (which are very high in selenium), eat fish 2-3 times weekly, and include whole grains and eggs in your diet
  • Over 3-6 months, track your overall diet quality and general wellness markers (energy, sleep quality, mood) rather than obsessing over selenium specifically. If you have specific hormone concerns, work with a healthcare provider who can order appropriate blood tests and monitor changes over time

This research shows an association between blood selenium levels and testosterone in Chinese men, but does not prove that selenium causes changes in testosterone. Individual hormone levels are influenced by many factors including age, genetics, overall health, and lifestyle. Do not change your selenium intake or take supplements based on this study alone. If you have concerns about your testosterone levels or hormone balance, consult with a qualified healthcare provider who can evaluate your individual situation, order appropriate tests, and provide personalized recommendations. This information is for educational purposes and should not replace professional medical advice.