Winter brings its own brand of challenges. 

Possibly the most overlooked is the substantial decrease in sunlight. And while that means shorter days, it also means decreased opportunity to support one of the most forgotten foundational support nutrients, vitamin D. 

As daylight shrinks and layers stack up, the body produces less of this key compound. Without compensating for those changes, deficiencies are more than just a possibility.

And when deficiency starts to rise, performance starts to drop.

Our MTN OPS Vitamin D3+K2 gummy has been a customer favorite for over a year now as a convenient way to boost your Vitamin D intake. But why are people taking it? What does Vitamin D actually do?

Strength and Endurance Performance

Strength and endurance are the two physical foundations to success in the backcountry. Vitamin D plays an integral role in both.

Vitamin D influences the activation of muscle fibers and the neural communication that influences their contraction (source). 

This is more than mechanistic. Associations have been drawn between low vitamin D concentrations and reduced strength performance, even in elite athletes (source). 

One step further, a 2024 meta-analysis demonstrated that vitamin D supplementation promoted both optimal vitamin D concentrations and strength performance,

The performance benefits don’t stop there. 

Vitamin D levels are also strongly associated with measures of endurance performance, with those who have higher vitamin D concentrations also demonstrating better VO2max scores (source). 

Again, this is not just a mechanistic claim. The same 2024 meta-analysis mentioned above also showed that vitamin D supplementation helped to promote aerobic performance.  

Bone Durability

Movement does not happen without structure. Strong physical structure requires durable bones.

Vitamin D is probably best known as a bone support compound. Vitamin D helps the body absorb and use calcium, making it an integral part of bone strength and long-term durability (source).

Maintaining bone health is a paramount cornerstone of optimal performance. When bones cannot absorb and transfer force, breakdown starts to happen. 

Too much breakdown without adequate repair leads to substantial injury. 

Immune Support

The negative effects of deficiency don’t stop at muscles and bones. Vitamin D is a key regulator of immune cell activity and supports a balanced inflammatory response (source). When vitamin D concentrations suffer, so does the immune system.

However, a 2017 review suggests that vitamin D supplementation can help bolster this crucial system and help stave off the sniffles and chicken soup. 

Recovery

Performance can only be sustained as long as recovery can support it. 

Supporting recovery means supporting performance. Another area where vitamin D shines. 

Vitamin D supports recovery by helping the body manage stress and rebuild tissue after long hours of work (source).

Don’t get it twisted. Vitamin D does not replace sleep, calories, or other nutrients, but it does support the systems that allow recovery to happen when those basics are in place.

Sourcing Vitamin D

Supporting these processes means getting enough vitamin D into the system, making sourcing critical.

Interestingly, this is one of the few micronutrients that has two ways to support adequate blood concentrations.

Vitamin D is affectionately known as the “sunshine vitamin,” and for good reason. The body uses sunlight to make this crucial nutrient in the body. This is great news for the avid outdoorsmen or women, especially those who are exposing ample amounts of skin while spending hours outside. 

But there are some key notes in that sentence that many people miss:

• “Outside”-- Inside next to a window doesn’t count. UVB radiation (a driving part of vitamin D synthesis in the skin) does not penetrate glass.
• “Ample amounts of skin”-- jackets, gloves, balaclava… all great for warmth, terrible for vitamin D. 
• “Hours”-- Brief exposure doesn’t move the needle. Synthesis requires repeated AND meaningful time in the sun. 
  
  

Miss these nuances, and miss out on natural vitamin D production.

When exposure to sunlight decreases, as it does in the winter months, vitamin D consumption must increase to sustain optimal levels. 

That being said, the list of foods containing meaningful amounts of vitamin D is pretty paltry and tends to be animal-based:

• Salmon, sardines, mackerel, other fatty fish
• Cod Liver Oil
• Egg Yolks
• Beef Liver
  
  

Because of this scarcity, many foods like cereal and orange juice have been fortified with vitamin D to help boost levels. This short list also supports arguments for adequate supplementation. 

MTN OPS Vitamin D3+K2 gummies provide a quick and convenient way to supplement your Vitamin D, packing 5,000 IU in a single gummy.

Supporting Foundational Support

Vitamin D is quite possibly the most systemically relevant micronutrient in physiology, especially performance physiology. 

The short winter days and increased layering cut adequate sunlight exposure, challenging blood concentrations, resulting in hindered processes across multiple bodily systems.

Finding ways to maintain optimal vitamin D concentrations is crucial to preventing setbacks in the winter months and promoting optimal performance year-round.