What foods are high in selenium and what are the health benefits?

Selenium is an essential trace element that has many important functions in the body, including supporting a healthy immune system, and maintaining a healthy thyroid function. Selenium is also used by an enzyme system in the body (called the glutathione peroxidase system) to protect structures inside the cell from oxidative damage by free radicals.

Food sources that are high in selenium include:

• Brazil nuts: Just one or two nuts can provide a significant amount of selenium
• Cottage cheese
• Seafood: Oysters, clams, crab, tuna, halibut, and lobster are all rich in selenium
• Meat: Beef, chicken, pork, ham, and turkey are all good sources of selenium
• Eggs: Both the yolk and white eggs contain selenium
• Grains: Some whole grains, such as wheat, barley, and rice, are good sources of selenium

The selenium content of food can vary depending on the selenium content of the soil in which the food was grown or raised.

Selenium exists in inorganic forms in soils (selenate and selenite) and organic forms in plants (selenomethionine and selenocysteine).

What are the health benefits of selenium?

Some people take selenium supplements to protect against cancer and heart disease, although the effectiveness of selenium for this purpose is not well established. Trials looking at the benefits of selenium have mostly been small and larger trials are needed.

An adequate intake of selenium may help:

• Support a healthy immune system: Selenium is involved in the production of cytokines, which are signaling molecules that help regulate the immune system
• Maintain healthy thyroid function: Selenium is a key component of the enzymes that help regulate thyroid hormone metabolism
• Protect cells from oxidative damage: Selenium is a component of antioxidant enzymes that help protect cells from oxidative damage caused by free radicals
• Reduce the risk of certain types of cancer, such as that of the skin, prostate, and lung.

Although one area of China that has a deficiency in selenium has a higher rate of cardiomyopathy, called Keshan's disease, similar associations have not been seen in other countries, such as New Zealand, where selenium is also deficient in the soil. The rates of coronary artery disease, high blood pressure, and cancer in New Zealand are similar to other Western countries that have higher selenium intakes.

It's important to note that while selenium has many health benefits, too much selenium can be toxic. Symptoms of toxicity may include garlic-smelling breath, tiredness, diarrhea or nausea, hair loss, or nerve pain in the feet. There is no antidote to selenium, but symptoms usually resolve quickly if selenium supplements are withheld.

What are the signs of deficiency?

Selenium deficiency is relatively uncommon, particularly in North America where soils tend to be rich in selenium. Deficiency is more likely to occur in those with malnutrition, who live in regions with selenium-deficient soil, or with gastrointestinal problems that affect their ability to absorb nutrients.

Signs and symptoms of selenium deficiency include:

• Fatigue, low energy levels, and weakness
• Muscle wasting and heart problems
• Impaired immune function
• Infertility
• Mood changes
• Nail changes.

Doctors can perform a blood test to determine your selenium levels and provide advice on how to increase your intake of this mineral.

What about selenium supplements?

Selenium supplements can be a good option for people who are unable to get enough selenium from their diet, or for those who have a medical condition that affects their ability to absorb selenium from food. However, it's important to talk to a doctor before taking selenium supplements, as getting too much selenium can be toxic and cause health problems.

According to Harvard University, the recommended daily allowance (RDA) for selenium in adults is 55 micrograms per day. The recommended dosage of selenium supplements may vary depending on a person's age, sex, health status, and other factors. For example, women who are pregnant or breastfeeding have higher requirements, so it's important to get a doctor's advice. Selenium can be toxic if too much is taken.

When taking selenium supplements, it's important to follow the recommended dosage and to talk to a doctor regularly to monitor your health.