Asthma patients' intake of selenium and manganese affects mortality

Asthma is characterized by chronic inflammation and oxidative stress. Smoking, air pollution, heavy metals, and various environmental allergens also increase the risk. However, it appears that an optimal level of selenium and manganese in the blood can potentially improve health and survival in asthma patients. This is partly because selenium and manganese function as antioxidants that counteract oxidative stress and chronic inflammation. At the same time, selenium helps eliminate heavy metals, according to a study published in Scientific Reports.

Asthma is a chronic lung disease that is neither caused by bacteria nor viruses. The local irritation is the result of chronic, unwanted inflammation that causes swelling of the mucous membranes in the airways, labored breathing, and coughing. Asthma is a complex disease that appears in varying degrees of severity and is responsible for several hundred thousand deaths worldwide. It is widely known that genetic factors, smoking, ageing, overweight, and allergies increase the risk. This is also the case with heavy metals such as lead, cadmium, and mercury. Although manganese is an essential trace element involved in a powerful antioxidant (SOD), excessive amounts of manganese from industry, pesticides, and certain water sources can have a toxic effect that increases the risk.
Various heavy metals are widespread in the environment, and they can enter the lungs and bloodstream through food, water, or air pollution. This exposure can provoke the immune system, leading to chronic inflammation. The condition can also trigger oxidative stress because the immune system releases cascades of free radicals. These are aggressive molecules that can cause cell damage, destroy lung tissue, and result in early death.
In contrast to the dangerous heavy metals, selenium is an essential trace element that plays a crucial role in the immune system and the regulation of inflammation. Selenium also functions as a powerful antioxidant (GPXs) that counteracts oxidative stress caused by too many free radicals. Additionally, selenium can neutralize heavy metals such as mercury. It also appears that having low selenium levels in the blood can increase the risk of developing asthma. On the other hand, too much selenium can also be harmful. Therefore, the researchers behind this new study aimed to closely examine the blood levels of heavy metals and whether the blood levels of manganese and selenium affect overall mortality in adult asthma patients.

Higher selenium levels have the greatest effect on asthma patients' survival

The researchers used data from a large U.S. study, NHANES (National Health and Nutrition Examination Survey), which monitored the nutritional status and other parameters of the population from 2011 to 2018. The researchers identified 2,432 adult asthma patients and collected data on the patients' blood levels of heavy metals such as lead, cadmium, and mercury, as well as blood levels of manganese and selenium. Data on mortality among the participants during the study period was also collected.
The analysis revealed that mortality among asthma patients is generally associated with old age, low education, low social status, smoking, and comorbidities such as cardiovascular diseases and lung diseases.
The study showed that higher selenium levels in the blood are statistically and significantly associated with lower mortality among adult asthma patients due to all diseases. The same was true for the manganese content in the blood of asthma patients.
The lowest mortality was observed in asthma patients with a blood selenium level of 188.66 micrograms per liter and a manganese level of 8.47 micrograms per liter. Blood selenium levels had the greatest impact on survival in asthma patients.
The researchers also found that very high levels of selenium and manganese could increase mortality, indicating a "U-shaped" relationship where both too little and too much are harmful.
However, the researchers found no significant link between the blood levels of lead, cadmium, and mercury and the mortality of asthma patients due to all diseases.
The study suggests that an optimal level of selenium and manganese in the blood can potentially improve the health and life expectancy of adult asthma patients. The results contribute to a better understanding of how selenium and manganese affect the health of asthma patients.

Where can you find manganese and selenium – and why is selenium deficiency so widespread?

Manganese is found in whole grains, nuts, seeds, vegetables, herbs, and fruits. The official daily recommended intake is 2 mg, and it is relatively easy to obtain enough through the diet.
Selenium is found in fish, organ meats, meat, eggs, grains, dairy products, and Brazil nuts. The selenium content of the soil varies greatly around the world, affecting the entire food chain. According to the WHO, selenium intake is too low in Europe, parts of the U.S., and several other regions, primarily due to selenium-poor soil conditions. This means that selenium deficiency is a serious health issue in our part of the world.
According to the Nordic Nutrient Recommendations (NNA), men and women should consume 90 and 75 micrograms daily, respectively, but there is no guarantee that this optimizes blood levels of the nutrient. Many studies have been conducted using 200 micrograms daily to optimize blood selenium levels, which should ideally be around 125 micrograms per liter. As the new study shows, asthma patients achieve the best effect when the level is as high as 188 micrograms per liter. As there is also a toxic threshold for selenium, the European Food Safety Authority (EFSA) has set an upper daily limit of 300 micrograms.

References:

Liao J. Association between blood heavy metal element and all-cause mortality in asthmatic adults: a cohort study. Scientific Reports. 2024

Sanchari Sinha Dutta. Selenium and manganese levels significantly impact mortality risk in asthma patients. News Medical Life Sciences. 2024