Is summer sunshine enough to fix low vitamin D?
No. In this Newcastle University study, low vitamin D stayed common all year, even through the summer. More than half of older adults and nearly three quarters of adults from minoritized ethnic backgrounds had low levels, and warm sunny months did not raise them.
Many people assume that vitamin D problems only happen in winter. The thinking is simple: less sun means less vitamin D, so summer should fix it. This new study from Northern Britain shows that assumption falls apart for the people who need protection most. For older adults and for people with darker skin, the sun did not do the job in any season.
Why vitamin D matters
Vitamin D helps your body absorb calcium and other minerals that keep bones strong. It also plays a role in your immune system and has been linked to lower risk of heart disease and diabetes. Your body makes vitamin D when sunlight hits your skin, and you also get smaller amounts from food like oily fish and fortified products.
The problem is that sunlight does not work equally for everyone. As people get older, their skin makes less vitamin D from the same amount of sun. People with darker skin have more melanin, which acts like a natural sunscreen and slows vitamin D production. Northern Britain also sits far from the equator, so the sun is weak for much of the year.
What the data show
Researchers screened 299 adults between December 2024 and August 2025. They used a simple finger-prick blood spot test and a precise lab method to measure 25-hydroxyvitamin D, the standard marker of vitamin D status. A level below 50 nmol/L counts as insufficient or deficient.
Among the 168 older adults aged 65 and over, 54.8% had low vitamin D. Among the 147 adults from minoritized ethnic backgrounds, the rate was even higher at 72.1%. The most important finding was about timing. These rates barely moved across the calendar. Winter, spring, and summer all looked about the same. The extra daylight of summer did not pull people out of the low range.
Dr. Kumar’s Take
This study confirms something I see often in practice. We tell people to get more sun, but for many patients that advice quietly fails. An older adult with thin, aging skin and a person with darker skin in a cloudy northern climate are both fighting biology that sunlight cannot overcome. I find the flat seasonal pattern striking, because it removes the easy excuse that “things will be fine by summer.” For these groups, things were not fine by summer. The honest limitation here is that this is a screening snapshot, not proof that supplements fixed the problem. But the screening alone makes a strong case that we should stop treating sunshine as a reliable treatment for high-risk people.
Who is most at risk
The study points to two clear groups. The first is anyone aged 65 and older, regardless of background, because aging skin simply produces less vitamin D. The second is adults of any age with darker skin tones, described in the study as Fitzpatrick classes 4, 5, and 6. People in these groups carried the highest burden, with almost three out of four testing low. Living far north, spending more time indoors, and covering the skin for cultural or personal reasons can add to the risk.
Practical Takeaways
- If you are over 65 or have darker skin, ask your doctor for a simple vitamin D blood test rather than assuming summer sun has topped you up.
- Consider year-round vitamin D from food or a daily supplement, since this study suggests sunlight alone did not keep at-risk groups in the healthy range.
- Do not increase sun exposure as a fix, because more time in weak northern sun carries skin cancer risk without reliably solving low vitamin D.
- Talk to your doctor about the right dose for you, especially if you take other medicines or have kidney or other health conditions.
Related Studies and Research
- Vitamin C deficiency: clinical features, risk factors, and modern lessons from scurvy
- How much vitamin C do we need for tissue saturation? Blood vs. leukocyte levels explained
- Does warfarin increase the risk of bone fractures in older adults?
- Glycine improves daytime performance after sleep restriction: clinical trial
FAQs
How much summer sun do I need to make enough vitamin D?
There is no single safe answer, and that is part of the lesson from this study. The amount depends on your age, your skin tone, the time of day, and how far north you live. In Northern Britain, even summer sun was not strong or consistent enough to raise levels in older adults and people with darker skin. Rather than chasing a sun target, it is safer to check your blood level and use food or supplements to fill the gap.
What vitamin D level is considered healthy?
In this study, a blood level above 50 nmol/L counted as sufficient. Levels between 31 and 49 nmol/L were classed as insufficient, and anything below 30 nmol/L was deficient. These cutoffs use the marker called 25-hydroxyvitamin D, which is the form doctors measure to judge your status. A simple blood test, including a finger-prick spot test like the one used here, can tell you where you stand.
Can I get enough vitamin D from food instead of sun or pills?
It is hard for most people to reach healthy levels from food alone. Vitamin D is found in only a few foods, mainly oily fish such as salmon and sardines, egg yolks, and products that have vitamin D added to them. For people at high risk, like older adults and those with darker skin in northern climates, food usually needs to be paired with a supplement. Your doctor can help you decide the right combination based on your test results.
Bottom Line
This Newcastle University study screened nearly 300 adults in Northern Britain and found low vitamin D in 54.8% of older adults and 72.1% of adults from minoritized ethnic backgrounds. The rates stayed high in every season, which means summer sunshine did not correct the problem for the people most at risk. The clear message is that older adults and people with darker skin should not rely on the sun. Year-round vitamin D from food or supplements, guided by a blood test, is the safer path.
