Want to prevent premature aging? Then take care of your telomeres!
New findings link higher intakes of selenium — an essential trace mineral — to that anti-aging effect.
The protective factor affected by selenium is your cells' telomeres, which form the “caps” found at the ends of our chromosomes.
Those telomere caps consist of short, repeating, protein-sheathed DNA sequences that protect the genetic material in chromosomes from premature decay.
Good evidence links shorter telomeres to worse health and faster aging, and longer telomeres to slower aging and lower risks for chronic conditions like heart disease.
Before we get to the findings of the new study, let’s quickly review what’s known about telomeres, aging, and nutrition.
Diet and lifestyle factors can affect our telomeres and “biological age”
Professor Elizabeth Blackburn, PhD, and two colleagues won the 2009 Nobel Prize for their discoveries about telomeres.
Their landmark research illuminated the role of telomeres — including their length — in the aging process, and what causes them to lengthen or shorten.
Here’s how Dr. Blackburn described the importance of telomeres to The Guardian: “During our lives they tend to wear down and … [this] … sets up physiological changes which increase risks of the major conditions and diseases of ageing: cardiovascular disease, diabetes, cancer, a weakened immune system, and more.”
When a cell divides (replicates), the telomeres on its chromosomes help prevent them from fusing with each other or rearranging, which can lead to cancer.
The aging and lifespan of normal, healthy cells are linked to the so-called telomerase shortening mechanism, which causes telomeres to shorten with each replication, and cells to die when they wear away completely.
Telomeres erode faster under pressure from oxidative stress — which generally results from an excess of free radicals in the body — and by chronic inflammation, which results from and worsens oxidative stress.
Since they promote oxidative stress and inflammation, it's perhaps unsurprising that diets high in processed foods, sugars, and foods made from refined white flour — such as the standard American diet — have been linked to having shorter, unhealthier telomeres.
Conversely, Dr. Blackburn points to growing evidence that we can lengthen our telomeres — or at least prevent their premature shortening — by managing chronic stress, exercising, eating better, and getting enough sleep.
Indeed, the available evidence suggests that balanced, whole-foods diets high in nutrients and antioxidants and multivitamin supplements help prevent telomeres from eroding prematurely: see Vitamin Studies Paint a More Positive Prevention Picture and Tea May Yield Younger Cells.
And as Dr. Blackburn told The Guardian, “Having adequate omega-3 fatty acids really seems to relate to better telomere maintenance, and the easiest way to ensure that may be a [fish oil] supplement.”
We reported on some of the evidence for that in Omega-3s’ DNA-Telomere Effects vs. Heart Disease and Aging and in Omega-3s May Slow Aging, in which we summarized a study showing that people whose ratios of omega-3 to omega-6 fats were raised by taking fish oil supplements had longer telomeres and lower levels of oxidation-related blood markers.
Now, an analysis of data from America’s most comprehensive diet-lifestyle survey suggests that higher intakes of selenium also protect telomeres — and the DNA they protect — from decay.
U.S. health data reveals link between selenium and longer/healthier telomeres
The new findings come from Chinese scientists, who conducted the first study designed to look for links between Americans' selenium intake and the length of their telomeres (Shu Y et al. 2020).
They analyzed diet and blood-sample data collected from 3,194 Americans aged 45 years or older who’d participated in the U.S. National Health and Nutrition Examination Survey (NHANES) for 1999–2000 and 2001–2002.
The Chinese team compared those Americans' intakes of selenium to the lengths of the telomeres in their leukocytes (immune system cells) — a measure called leukocyte telomere length or LTL.
Longer LTLs have previously been linked to lower proportions of body fat (adiposity), to positive markers of health in several body systems, and to reduced risks for developing cardiovascular disease.
When the researchers compared the survey participants’ estimated selenium intakes to their LTLs, the results linked higher selenium intakes to longer, “healthier” telomeres — regardless of people’s age, gender, diets, or lifestyles.
Specifically, the analysis linked every 20mcg (microgram) rise in dietary selenium to a substantial, 0.42% rise in average leukocyte telomere length (LTL).
Interestingly, the Chinese team’s data analysis revealed that women and non-obese people displayed the strongest links between higher selenium intakes and longer telomeres.
Why would selenium protect telomere lengths?
Selenium is critical to the body’s ability to control oxidation and inflammation, to thyroid health, and to sperm health.
That’s because this trace mineral is a key component in more than two dozen selenoprotein compounds critical to the body’s own “antioxidant network”, including glutathione peroxidases (GPx), thioredoxin reductases, and selenoprotein P.
Given the evidence that oxidation and inflammation shorten telomeres, it’s reasonable to presume that higher selenium intakes — which could optimize the body’s antioxidant/anti-inflammatory capacities — would help protect telomeres from erosion by those forces.
Several years ago, renowned biologist Bruce Ames, PhD, and his colleague Joyce McCann, PhD, published an evidence review in which they concluded that even a moderate deficiency and dietary selenium can have serious consequences.
Seafood scores high for selenium
Albacore tuna (canned) – 60
As they wrote, “… age-related diseases and conditions, including cancer, heart disease, and immune dysfunction, are … associated with modest Se [selenium] deficiency …” (McCann JC, Ames BN 2011). For more on that, see Selenium Seen as Key Anti-Aging Ally.
It’s important to note that you can get too much of a good thing, because selenium can produce toxic effects at very high intake levels. However, it’s very rare for people to suffer from selenium toxicity, unless they’ve accidentally overdosed on supplemental selenium.
How much selenium do we need, and where can we get it?
People's selenium levels vary, depending on soil selenium levels where most of the produce and grains they consume is grown.
For example, when some European countries switched from generally selenium-rich U.S. grains to generally selenium-poor European grains, their citizens’ average selenium levels dropped.
Wild fish and shellfish are some of the best food sources of selenium: see our sidebar, “Seafood scores high for selenium”.
It's worth noting that virtually all commercial species of ocean fish, including tuna, contain more selenium than mercury, which likely explains their well-documented safety: for more on that, see Most Fish Rank as Very Safe on New, Selenium-Based Standard. The only commonly sold exceptions are swordfish, shark, tilefish, and king mackerel. (In contrast, freshwater fish are much more likely to contain more mercury than selenium, depending on where they are caught.)
Outright selenium deficiency is rare in the U.S. and Canada — if you define it as falling short of the adult RDA of 55 micrograms (mcg) — but it’s quite common in China, which has selenium-poor soils.
However, the US RDA (55mcg) may be too low for optimal immunity. The results of at least one clinical study suggest that the amount needed to raise body levels of selenoprotein P — a key compound in the body’s antioxidant network — into the range associated with reduced cancer rates is 105mcg per day (Hurst R et al. 2010).