Can Exercise Prevent the Winter Drop in Vitamin D?

December 17, 2025 •

4 min read

According to research, many adults experience a significant decline in vitamin D levels during the winter months due to reduced sunlight exposure. While supplementation is a common remedy, a groundbreaking study suggests regular exercise may offer a natural and effective way to counteract this seasonal drop.

Quick Summary

A recent study suggests that exercise can significantly reduce the seasonal decline of vitamin D. Regular physical activity, particularly endurance training, helps maintain the body's vitamin D levels and supports mood, immunity, and overall winter health.

Key Points

Exercise can mitigate vitamin D loss: A recent study shows regular exercise can prevent the typical winter decline in the active form of vitamin D.
Metabolism is a key factor: The benefits of exercise for vitamin D levels are linked to improvements in how the body processes the vitamin, not just increased sun exposure or weight loss.
All types of activity help: Moderate-intensity cardio, such as cycling or brisk walking, has been shown to be effective in preserving vitamin D levels.
Supports mental health: By helping to maintain vitamin D and boosting feel-good neurotransmitters, exercise provides a dual-action defense against seasonal mood dips and SAD.
Combines well with other methods: Exercise is a powerful complement to other vitamin D strategies, including a nutritious diet, safe sun exposure, and doctor-recommended supplements.

The Winter Vitamin D Challenge

For many, the winter season brings with it shorter days, less sunlight, and a greater risk of vitamin D deficiency. The 'sunshine vitamin' is primarily synthesized in the skin through exposure to UVB rays, which are less potent and frequent during winter, especially at higher latitudes. This seasonal drop can impact everything from immune function to mood regulation, with low levels being linked to conditions like Seasonal Affective Disorder (SAD). While diet and supplementation are traditional strategies for maintaining levels, recent research highlights a powerful and previously underappreciated tool: exercise.

The Science Behind Exercise and Vitamin D Metabolism

A recent randomized controlled trial, known as VitaDEx, provided compelling causal evidence that regular physical activity can prevent the typical winter decline in the body’s active vitamin D metabolite, 1,25(OH)2D3. This is significant because the active form is crucial for the healthy function of bones, muscles, and the immune system. The study found that regular exercise, even without weight loss, preserved the active form of vitamin D in overweight and obese individuals, suggesting exercise influences metabolism rather than just relying on fat-related release. Professor Dylan Thompson, a lead researcher, noted that exercise provides a 'double benefit,' both transiently boosting vitamin D metabolites after a workout and improving baseline levels over time.

Exercise vs. Supplements: A Comparison

While supplements are an effective way to boost vitamin D, exercise provides a unique set of benefits. The VitaDEx study indicated that exercise influences vitamin D metabolism in a way that supplementation does not, particularly regarding the active metabolite.


Feature	Regular Exercise	Vitamin D Supplements
Mechanism of Action	Influences metabolic pathways; mobilizes stored vitamin D; provides transient boosts.	Provides a direct influx of vitamin D to be metabolized by the body.
Impact on Active Vitamin D	Shown to maintain levels of 1,25(OH)2D3 (the active form) throughout winter.	Does not directly impact circulating levels of the active form.
Associated Health Benefits	Boosts mood (endorphins), improves cardiovascular health, enhances muscle strength, and supports immunity.	Primarily impacts bone health and immune function by addressing deficiency.
Application	Must be regular and consistent, such as aerobic activities like walking or cycling.	Can be easily incorporated through daily or weekly capsules; dosage must be monitored with a healthcare provider.
Potential Side Effects	Risk of injury if not performed correctly; overtraining is a risk.	Excessive intake can be toxic and lead to hypercalcemia.

A Holistic Approach to Winter Wellness

To effectively combat the winter slump, a combination of strategies is often best. Regular physical activity should be considered a core component, not just a bonus. For those living with conditions like MS or SAD, where vitamin D plays a critical role, consistent movement is especially important. Combining regular exercise with other healthy habits can significantly mitigate the negative effects of reduced sunlight.

Prioritize Regular Movement: Aim for consistent activity, even if it's moderate. Indoor cardio, like walking on a treadmill or cycling, proved effective in the VitaDEx study.
Maximize Safe Sunlight: When possible, spend time outdoors around midday to maximize your exposure to limited UVB rays. A short walk in the park can be beneficial.
Eat Vitamin D-Rich Foods: Incorporate foods like fatty fish, eggs, and fortified dairy or cereals into your diet to support your body’s vitamin D intake.
Consult a Healthcare Provider: Talk with your doctor about your vitamin D levels and whether a supplement is right for you. They can determine the appropriate dosage and monitor your progress.

The Mood-Boosting Connection: Vitamin D, Exercise, and SAD

Beyond its role in physical health, vitamin D is also linked to mental well-being. It helps regulate neurotransmitters like serotonin and dopamine, which are key for mood and happiness. The winter drop in vitamin D can exacerbate the symptoms of SAD. Fortunately, exercise is a known mood booster that can also improve mental health days by nearly 50%. By helping to maintain vitamin D levels and releasing mood-elevating endorphins, exercise provides a dual-action defense against seasonal sadness.

Conclusion

While sunlight remains the primary source of vitamin D, and supplements offer a reliable alternative, recent research confirms that exercise can play a crucial role in preventing the natural winter decline. The VitaDEx study provides clear evidence that regular physical activity helps preserve the body’s active vitamin D levels, offering a powerful, natural strategy, especially for those at higher risk of deficiency. By incorporating consistent exercise, prioritizing nutrient-rich foods, and seeking professional advice on supplementation, you can develop a comprehensive plan to safeguard your health and well-being throughout the colder, darker months.

For more detailed findings from the primary research, consider exploring the study published in Advanced Science.

Frequently Asked Questions

Yes, a study found that a 10-week indoor exercise program helped adults maintain their vitamin D levels during winter, showing smaller drops compared to a control group.

Not necessarily. While exercise can significantly reduce the winter drop, it should be seen as a complementary strategy alongside diet, safe sun exposure, and potentially doctor-recommended supplementation.

The study showing protective effects used indoor aerobic exercise, such as walking and cycling. However, other types of endurance and resistance training may also have an impact.

Exercise influences the body's metabolism of vitamin D, specifically helping to maintain levels of the active form, 1,25(OH)2D3. This is a distinct effect from oral supplements, which primarily increase stored vitamin D.

Yes, some studies suggest that endurance training can significantly improve vitamin D levels in individuals who are already deficient. However, the effect may vary based on overall vitamin D status and exercise type.

Yes, exercise can help combat SAD symptoms. It not only assists in maintaining vitamin D levels, which influences mood-regulating neurotransmitters, but also boosts mood through endorphin release.

Regular and consistent activity is key. In the VitaDEx study, participants exercised regularly over a 10-week period to see a benefit. Aiming for a few moderate sessions per week is a good starting point.