Workout Prevents Winter Vitamin D Crash

Exciting new research from the University of Bath, University of Birmingham, University of Cambridge, and others, published in Advanced Science, reveals a powerful way to support vitamin D during winter: regular, moderate-intensity exercise.

In the study, people with overweight and obesity who followed a 10-week indoor workout routine during winter had a much smaller drop in vitamin D levels compared to those who didn’t exercise. Remarkably, this happened even though participants didn’t lose weight and didn’t take any vitamin D supplements.

The exercise program included four sessions per week: two brisk treadmill walks, one steady bike ride, and one high-intensity cycling session. This simple routine made a significant difference.

What really stood out was how exercise preserved the body’s active form of vitamin D, known as 1,25(OH)2D3. This form is essential for healthy bones, a strong immune system, and overall wellness. Earlier research has shown that supplements alone don’t maintain this active version as effectively.

Lead author Dr. Oly Perkin from the Centre for Nutrition, Exercise and Metabolism, Department for Health at the University of Bath said:

“This is the first study to show that exercise alone can protect against the winter dip in vitamin D. It’s a powerful reminder that we still have lots to learn about how exercise benefits our health.”

Key Findings:

People who exercised saw a smaller drop in their overall vitamin D levels over winter, about 15%, compared to a 25% drop in those who didn’t exercise.

Importantly, those who exercised kept healthy levels of the active form of vitamin D, which helps support the immune system and bone health.

In the non-exercising group, levels of this active form fell by 15%.

Weight was kept stable throughout the study, proving the effect was due to exercise, not weight loss.

To ensure sunlight didn’t skew results, the study ran between October and April, when natural vitamin D production from sunlight is minimal in this part of the UK, and participants were asked to avoid supplements.

A previous study from the team showed that a single workout can briefly boost vitamin D levels; this is the first to show that regular cardio exercise can maintain basal circulating vitamin D levels and offer lasting protection during the winter months.

Prof Dylan Thompson, Principal Investigator for the VitaDEx study, said:

“Collectively, the findings from the VitaDEx project show that exercise increases the concentrations of vitamin D metabolites each time you are active, and, on top of this, doing regular activity helps to maintain your basal resting levels of vitamin D during winter. This means exercise gives you a double benefit to your vitamin D – firstly in and around each exercise bout, and secondly through changing your baseline levels.”

With over 50 adults taking part in this sophisticated and carefully designed randomised controlled trial, the study offers compelling evidence that exercise could be an effective winter vitamin D strategy, especially for those who are overweight or obese, for whom vitamin D supplements are less effective.

Liam Kilawee, who took part in the study, said: “I was impressed by how thorough the process was and how the team engaged with me during the research period. The results were pleasing as I could see that my actions had a positive reaction.”

Dr. Oly Perkin added: “If you’re worried about your vitamin D levels in the winter, keeping up regular exercise every week will help, and offer a load of health benefits that vitamin D supplements cannot.”

Prof Thompson added: “These findings have implications for policymakers and healthcare professionals. Exercise should be part of any strategy to improve vitamin D status and metabolism during winter.”

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