Why You Still Need Vitamin D After Summer Ends

As summer fades and the days grow shorter, many assume they’ve stored enough of the “sunshine vitamin” to last through the darker months. But unless you’ve been exposing large areas of your skin to sunlight multiple times a week for 5–30 minutes without sunscreen, chances are your vitamin D levels may already be on the decline. And even if you did reach optimal levels during the summer, you’re now heading into autumn and winter—when natural sun exposure plummets and vitamin D stores begin to drop.

Vitamin D is essential for more than just bone health. Deficiency can increase your risk of common cancers, osteopenia, osteoporosis, fractures, autoimmune disease, hypertension, type 2 diabetes, infections, and muscle weakness. So why is it so hard to maintain adequate levels?

There are several reasons. First, we’re conditioned to use sunscreen at all times, which blocks UVB rays required for vitamin D synthesis. While protecting against burns is important, overuse of sunscreen can prevent necessary exposure. Secondly, many people don’t get enough natural sunlight due to lifestyle, age, or cultural habits that limit skin exposure. Diet also plays a role. Few people eat enough vitamin D–rich foods like fatty fish, fish liver oil, or vitamin D–enriched eggs. And finally, most people aren’t taking high enough doses of vitamin D3 supplements to maintain optimal levels year-round.

That’s why it’s vital to take responsibility for your own vitamin D health. The best place to start is with testing. Use an accredited home blood spot test (available in many countries) to measure your 25(OH)D levels at the end of summer or winter—these are typically your highest and lowest points. If your levels fall below 100 nmol/L (40 ng/ml), consider taking a high-dose vitamin D3 supplement (around 4000 IU [100 mcg] or more daily) under the guidance of a qualified practitioner. Retest after 3 months to assess your progress.

Be smart with the sun. Don’t fear it—respect it. Allow safe exposure without burning. Let kids play in the sun before applying sunscreen, and avoid midday intensity. Our ancestors thrived under the sun for millennia without SPF 50. It's time to find a balanced, informed approach again.

While oily fish and fish oil can help, they’re often not potent enough to correct deficiency alone. Supplements and regular monitoring remain your most reliable tools.

Vitamin D is not just a seasonal concern—it’s a year-round necessity for vibrant health, resilience, and longevity. Take it seriously, and your body will thank you.