Molly Knudsen, M.S., RDN is a Registered Dietician Nutritionist with a bachelor’s degree in nutrition from Texas Christian University and a master’s in nutrition interventions, communication, and behavior change from Tufts University. She lives in Newport Beach, California, and enjoys connecting people to the food they eat and how it influences health and wellbeing.
Image by Trinette Reed / Stocksy
July 10, 2025
While it seems like aging can happen overnight (don’t we all just wake up one day with back pain or a gray hair?),it’s actually a process that occurs over decades at the cellular level.
Aging itself is defined as the gradual decline of physiological function1—like how well organs work—that increases vulnerability to illness, age-related diseases, and frailty.
Now for the latter, vitamin D is an integral player in bone health. And low vitamin D levels are solidly linked to contributing to falls, fractures, fragility, and mobility issues. But vitamin D is garnering more and more attention for its role in other aging processes.
That’s because there are vitamin D receptors all over the body, including the gut, brain, kidneys, and immune cells.
The active form of vitamin D in the body (calcitriol) acts as a hormone that binds to those receptors, influencing cellular processes and regulating gene expression.
Vitamin D also acts as an antioxidant, potentially protecting cells from harmful free radicals and accumulating oxidative stress (a main driver of accelerated aging).
However, the effects of vitamin D on aging processes are far less studied in people than the vitamin’s effect on bone health.
Researchers of a review published in the journal Nutrients summarized all the available data (human, animal, and cell) on vitamin D’s role in and impact on the 12 hallmarks of aging2. Here’s what they found.
As we alluded to, aging is a complex process. Scientists use the term hallmarks of aging to refer to key characteristics (or pathways) that shape aging as a whole.
And the thing is, all these processes are connected. So if one pathway starts declining, it can hurt or accelerate the decline of another. Just as improving one process could improve others.
Below is a quick summary of the 12 hallmarks of aging this research review focused on and how vitamin D influences it:
Genomic instability: Cells in the body are always dividing, and DNA is always being replicated. So mistakes or damage to that DNA occur and even accumulate with time. High blood sugar3 (and high cholesterol) can also damage DNA. There are currently some human and cell studies showing vitamin D’s antioxidant functions protect against this instability, especially for those with Type 2 diabetes4.
Telomere attrition: Telomeres are protective caps of DNA-carrying chromosomes. Each time a cell divides, telomeres shorten. This happens until telomeres get so short they can no longer divide, turning into senescent (or zombie) cells or dying. Longer telomere length is associated with better health and longevity. Several studies on humans show a relationship between blood vitamin D levels and telomere length5, and vitamin D supplementation improves measures of telomere health6.
Epigenetic alterations: While your genetic code is constant, epigenetics (whether a certain gene is turned on or off) is influenced by lifestyle. Vitamin D has been shown to influence DNA methylation, particularly impacting the gene sites that code for immune function and inflammation.
Loss of protein balance: The body is always building and breaking down proteins. An inability to maintain proper protein balance is a sign of aging. While studies on vitamin D’s role in this are limited to cell and animal studies at this time, researchers speculate that vitamin D may impact genes that are involved in this balancing act. So an improved vitamin D status may help the body maintain proper protein balance.
Deregulated nutrient sensing: With age, cells may have trouble detecting and responding to certain nutrients, which can affect metabolism and overall health. As vitamin D is involved in many metabolic activities (including insulin sensitivity), maintaining optimal vitamin D levels can support healthy nutrient sensing.
Disabled macroautophagy: Macroautophagy is a cellular cleanup process in which the body gets rid of damaged cellular components. When this cleaning service is interrupted, junk builds up and can potentially contribute to various diseases. But vitamin D helps kick cellular cleanup processes into gear.
Cellular senescence: Aging, as well as obesity, metabolic syndrome7, and a lack of physical activity, can all increase cellular senescence and the presence of zombie cells. Vitamin D not only helps initiate macroautophagy to help get rid of those cells, but it may also help calm the underlying low-grade inflammation associated with those conditions.
Mitochondrial dysfunction: By now, we all know the mitochondria as the powerhouse of the cell. When mitochondria are struggling, energy production decreases and oxidative stress can increase. Low vitamin D levels can contribute to mitochondrial dysfunction8.
Stem cell exhaustion: The number (and function of stem cells) declines with age. Stem cells play important roles in repairing tissues and producing immune cells. Studies done on cells show that vitamin D may support stem cell maintenance with age, but human studies are needed.
Chronic inflammation: Inflammation itself is a hallmark of aging, but as you can see, it influences so many things at the cellular level. Many studies show that vitamin D supplementation helps reduce markers of inflammation9 in people with diabetes, kidney disease, and PCOS. While these conditions may be a reason for low vitamin D levels in the first place, there’s no doubt that vitamin D status and Inflammation are closely connected.
Dysbiosis: Dysbiosis refers to an imbalance of good and bad bacteria in the gut, and inflammation may be a driver of this. Vitamin D receptors are found throughout the gut, and clinical studies show that vitamin D supplementation can help strengthen the gut lining and help decrease certain types of bad bacteria that promote inflammation10.
Altered intercellular communication: Cells are in constant communication with each other, but with age, blockers arise in these communication channels—affecting tissue function and repair processes. Very early research on bone cells in a lab is starting to see how vitamin D may affect these channels. But right now, not much is known, and more research is needed.
How to get (& maintain) optimal vitamin D levels throughout your life
Research continually shows how vitamin D is a key player in many physiological processes tied to living a long, healthy, happy life.
But most people fail to get enough of this crucial vitamin. About 41% of adults in the U.S. have insufficient vitamin D11 levels (less than 30 ng/mL on a blood test), and 29% are vitamin D deficient (levels less than 20 mg/mL).
And you really want your levels to be at or above 50 ng/mL for optimal health.
So it’s difficult (basically impossible) to get enough vitamin D from food and sunshine alone (especially when trying to raise already low levels), and aging processes also make it harder to maintain vitamin D levels. So it’s a smart idea to add a high-quality vitamin D supplement to your routine.
The takeaway
Vitamin D is tied to aging beyond its role in keeping your bones strong and healthy (although that benefit should not be overlooked). Its antioxidant properties are also essential to help fight aging at the cellular level.
While more research is needed, maintaining optimal vitamin D levels is undoubtedly an important part of promoting longevity12.
