Selenium is a trace mineral that the body requires for several important processes. Found in soil, water, and a variety of foods, its presence in the diet has prompted scientific inquiry into its effects on health, including its relationship with blood pressure.
The Role of Selenium in the Body
Selenium is a component of more than two dozen specialized proteins known as selenoproteins. These proteins are involved in processes such as DNA synthesis, reproduction, and protecting the body from infection. The body’s antioxidant defense systems rely heavily on certain selenoproteins, like glutathione peroxidases, which help neutralize damaging molecules and reduce cellular stress.
Beyond its antioxidant capabilities, selenium is necessary for proper thyroid function. The thyroid gland has a higher concentration of selenium than any other organ, where it aids in the metabolism of thyroid hormones. These hormones regulate metabolism throughout the body. The immune system also depends on adequate selenium levels to operate effectively, as selenoproteins are involved in responding to infections.
The Complex Relationship Between Selenium and Blood Pressure
The connection between selenium and blood pressure is not straightforward, with research indicating that the mineral’s effect is highly dependent on dosage. Adequate selenium levels are thought to support cardiovascular health. Selenoproteins may help prevent the oxidative modification of fats in the blood, a process that can lead to inflammation and the buildup of platelets in blood vessels. This protection helps maintain the flexibility and function of blood vessels.
Conversely, an excessive intake of selenium, particularly through supplements, has been associated with different outcomes. The specific mechanisms are still under investigation, but it is believed that very high concentrations of selenium can disrupt cellular processes. Research findings often vary based on the initial selenium levels of participants, making it difficult to draw a single conclusion. For instance, taking selenium may reduce the risk of high blood pressure during pregnancy.
Selenium Deficiency and Toxicity
The amount of selenium in the body must be maintained within a narrow range. A deficiency can lead to health issues, including a heart muscle disease known as Keshan disease, and a bone and joint disorder called Kashin-Beck disease. Insufficient selenium can impair the body’s ability to combat oxidative stress, potentially placing a greater burden on the cardiovascular system.
Consuming too much selenium results in a condition called selenosis, or selenium toxicity. Chronic overconsumption can cause a range of symptoms, including a metallic taste in the mouth, hair loss, nail brittleness, fatigue, and gastrointestinal distress. Neurological problems can also occur. In the context of cardiovascular health, some evidence suggests that chronically high selenium levels may contribute to elevated blood pressure as one of its toxic effects.
Safe Selenium Intake and Dietary Sources
The Recommended Dietary Allowance (RDA) for adults is 55 micrograms (mcg) per day, with pregnant and lactating women needing slightly more, around 60 and 70 mcg respectively. To prevent toxicity, a Tolerable Upper Intake Level (UL) has been set at 400 mcg per day for adults. Consuming amounts above this level daily increases the risk of adverse health effects.
Selenium can be obtained from a variety of foods. Brazil nuts are famously rich in selenium, but other sources include:
- Seafood
- Meats
- Poultry
- Eggs
- Whole grains
The selenium content in plant-based foods can vary significantly depending on the concentration of the mineral in the soil where they were grown. For most people, a balanced diet provides sufficient selenium, and supplementation is not needed unless advised by a healthcare professional to address a specific deficiency.