How Exercise Helps Maintain Healthy Vitamin D Levels in the Wintertime

Dr. Joseph Mercola - Take Control of Your Health

Briana Mercola

Alternative Health, Health & Fitness

4.6 • 1.6K Ratings

🗓️ 11 October 2025

⏱️ 7 minutes

🔗️ Recording | iTunes | RSS

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Summary

During winter in northern climates, sunlight is too weak to trigger vitamin D production, leaving many people — especially those with excess body fat — at risk for deficiency
A 10-week study found that exercise alone, without supplements or weight loss, helped maintain levels of active vitamin D in overweight or obese adults
Physical activity altered enzyme activity in fat tissue, boosting the body's ability to convert stored vitamin D into its usable form and preventing it from being broken down
People with the most fat tissue saw the biggest improvements in vitamin D activation, showing that exercise is especially important if you're carrying extra weight
Exercise trains your body to activate and protect the vitamin D it already has, offering a natural way to help maintain vitamin D levels through winter when sun exposure is limited

Transcript

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0:00.0	Are you losing vitamin D every winter, even when you think you're doing everything right?
0:04.6	And could a simple training plan help you hold the line without supplements or sun?
0:09.9	Welcome to Dr. Mercola's cellular wisdom.
0:12.8	Stay informed with quick, easy-to-listen summaries of our latest articles, perfect for when you're on the go.
0:18.1	No reading required.
0:19.4	Subscribe for free at Mercola.com for the latest health insights.
0:23.6	Hello and welcome to Dr. Mercola's cellular wisdom.
0:26.7	I'm Ethan Foster, and today we're unpacking how consistent exercise
0:30.3	helps you maintain active vitamin D through the darker months,
0:33.9	especially if you carry extra weight.
0:36.0	I'm Alara Sky.
0:39.0	You'll hear what a 10-week winter study uncovered in adults with overweight or obesity, why active vitamin D matters more than total
0:45.1	vitamin D, how fat and muscle enzymes respond to movement, and what type of routine helps
0:50.9	you preserve your levels when sunlight is too weak to help. You need ultraviolet B from direct sunlight to make vitamin D, but in northern climates,
0:59.0	winter UVB is often too low for months. That's when deficiency risk rises, and excess
1:06.0	body fat amplifies it, because vitamin D gets sequestered in fat tissue, making it harder to access the form your cells actually use.
1:13.6	The most active form of vitamin D binds to receptors across your body,
1:17.6	influencing immune function, inflammation, insulin sensitivity, and muscle health.
1:23.6	If active levels slip, you're more likely to face fatigue, poorer blood sugar
1:29.0	control, depressed mood, chronic pain, and less resilience to infection. The question the study
1:35.8	asked was direct. Can exercise alone, without supplements or weight loss, preserve active
1:41.8	vitamin D in winter? Participants were inactive adults with overweight
	...

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