Every 20 microgram increase in dietary selenium consumption was associated with a 0.42% longer telomere in leukocytes in middle-aged and older adults, according an analysis of data from the National Health and Nutrition Examination Survey (NHANES) in 1999–2000 and 2001–2002.
The findings, published in the Clinical Nutrition, show correlation and not causation, but could have implications for our understanding of healthy aging.
“Our findings showed a significant correlation between dietary selenium intake and telomere length among all participants, and this association was more prominent among females and non-obese participants,” reported scientists from Guangdong Medical University and Huazhong University of Science and Technology in China.
The aging and lifespan of normal, healthy cells are linked to the so-called telomerase shortening mechanism, which limits cells to a fixed number of divisions. During cell replication, the telomeres function by ensuring the cell's chromosomes do not fuse with each other or rearrange, which can lead to cancer.
Elizabeth Blackburn, a telomere pioneer at the University of California San Francisco, likened telomeres to the ends of shoelaces, without which the lace would unravel.
With each replication the telomeres shorten, and when the telomeres are totally consumed, the cells are destroyed (apoptosis). Previous studies have also reported that telomeres are highly susceptible to oxidative stress and inflammation. Some experts have noted that telomere length may be a marker of biological aging.
The authors of the new paper explained that consumption of foods with antioxidant and anti-inflammatory properties have previously been linked with longer telomere length.
They added: “Selenium, consumed as part of a normal diet, participates in antioxidant and anti-inflammatory effects in the form of selenoproteins, such as glutathione peroxidases (GPx), thioredoxin reductases, and selenoprotein P. Therefore, it is natural to hypothesize that the increases in dietary selenium intake could be related to longer telomere length.”
The study is reportedly the first to explore the relationship between dietary selenium intake and leukocyte telomere length among middle-aged and older adults in the US.
Dietary data from 3,194 American adults older than 45 were analyzed with respect to leukocyte telomere length.
While higher dietary selenium intake was associated with longer telomeres for all of the participants, when the researcher drilled down into specific subgroups, the data revealed a stronger association between dietary selenium intake and longer telomere length for women and non-obese adults.
“Better antioxidant status of females might contribute to this sex-specific effect,” wrote the scientists. “The marked sex-dependent difference in the GPxs (selenoproteins such as GPx-1, GPx-3) activity has been demonstrated in earlier studies, suggesting that females may have higher antioxidant enzyme activity than males.
“Additionally, previous study indicated that a positive correlation was observed between estradiol and GPx activity, which emphasized that the estrogen may contribute to higher GPx activity in females.”
The researchers called for more prospective studies to corroborate the study’s findings.
Selenium is an essential micronutrient, and is considered to be an antioxidant. The mineral is included in 25 selenoproteins in the body, with diverse roles including immune support, thyroid function and healthy sperm. The issue for selenium, as for other nutrients, is that you can get too much of a good thing.
A review paper by Joyce McCann and Bruce Ames from the Nutrition and Metabolism Center at Children’s Hospital Oakland Research Institute in Oakland (CHORI) indicated that moderate deficiency in selenium may have long-term detrimental effects (FASEB Journal, 2011, Vol. 25, pp. 1793-1814).
Source: Clinical Nutrition
Published online ahead of print, doi: 10.1016/j.clnu.2020.01.014
“Association of dietary selenium intake with telomere length in middle-aged and older adults”
Authors: Y. Shu et al.