Serum selenium concentrations show a U-shaped association with all-cause mortality and with cardiovascular mortality in individuals with hypertension [Tan 2021].
This conclusion is based on an analysis of data from 929 individuals diagnosed with hypertension [Tan 2021].
- The average age of the individuals was 63 years plus/minus 13 years.
- Slightly more than half of the individuals were male: 53%.
- The researchers followed the individuals for a mean period of slightly more than ten years: 121 months plus/minus 41 months.
- During the follow-up period, 307 individuals died, including 56 individuals who died from cardiovascular disease.
Quartiles of Serum Selenium Status
For purposes of analysis, the researchers categorized the individuals with hypertension into quartiles of serum selenium concentration [Tan 2021]:
Q1: equal to or less than 124 mcg/L
Q2: 125-135 mcg/L
Q3: 136-147 mcg/L
Q4: greater than 148 mcg/L
Optimal Serum Selenium Levels in Individuals with Hypertension
The researchers compared the data from the serum selenium quartiles and found that the risk of death from all causes and death from heart disease were lowest in the third quartile (serum selenium concentrations between 136 and 147 mcg/L) [Tan 2021].
In that third quartile of serum selenium concentrations, the risk of death from all causes was 43% lower, and the risk of death from heart disease was 67% lower than in the first quartile [Tan 2021].
The lowest points on the U-shaped graphs in the Tan study depict the lowest risk of mortality as related to serum selenium concentration. The lowest risk was were found at the points indicated below [Tan 2021]:
All-cause death risk lowest at 136 mcg/L of serum selenium.
Death from heart disease risk lowest at 130 mcg/L of serum selenium.
The Tan graphs of the relationship between selenium status (the independent variable on the x-axis) and mortality risk (the dependent variable on the y-axis) seem to show increasing mortality risk in individuals with hypertension who have serum selenium concentrations below 100 mcg/L or above 175 mcg/L.
Conclusion: Serum Selenium Status and Mortality in Hypertension
The Tan analysis [2021] shows that too low and too high levels of serum selenium may be linked to elevated all-cause and cardiovascular mortality.
Tan et al. [2021] suggest several potential biological mechanisms to explain the U-shaped relationship between serum selenium status and mortality risk in individuals with hypertension:
- Hypertension is associated with a decrease in the bioavailability of antioxidants and with excessive production of harmful free radicals. Thus, hypertension is associated with oxidative stress and cellular and tissue damage.
- Selenium through its incorporation into antioxidant seleno-enzymes such as the glutathione peroxidases and the thioredoxin reductases provides protection against oxidative damage.
- Low selenium intakes and low selenium status limit the synthesis of selenoproteins, resulting a lessened antioxidant and anti-inflammatory effect and resulting in an elevated risk of death.
- With increasing selenium status, the antioxidant seleno-enzyme activity increases directly until it reaches a plateau. At some point, there can be an oversupply of selenium, and the beneficial health effects of selenium supply will begin to decline.
- Excessive exposure of selenium may also be associated with harmful effects such as preventing proper protein folding, inducing the unfolded protein response, and causing production of superoxide radicals doing angiogenesis damage.
Sources
Tan QH, Huang YQ, Liu XC, Liu L, Lo K, Chen JY, Feng YQ. A U-shaped relationship between selenium concentrations and all-cause or cardiovascular mortality in patients with hypertension. Front Cardiovasc Med. 2021 Jul 30;8:671618.
The information presented in this review article is not intended as medical advice and should not be used as such.
15 December 2021