Could Sunshine Be Good for Your Heart? What Researchers Are Learning About Sunlight and Blood Pressure
For years, most conversations about sunlight and health have focused on two things: vitamin D and skin cancer.
We know that sunlight helps our bodies produce vitamin D. We also know that too much ultraviolet (UV) exposure damages the skin and increases the risk of skin cancer.
However, researchers are studying another fascinating possibility: sunlight may affect our cardiovascular system through the skin—and vitamin D may not be the main reason why.
Research into nitric oxide and compounds stored in our skin is raising interesting questions about sunlight, blood pressure, aging, and heart health.
The science is still developing, and this certainly isn’t a reason to start tanning for your heart. But it is a fascinating example of just how complex the human body can be.
It May Not Be About Vitamin D
Researchers have known for years that people with lower vitamin D levels tend to have higher rates of cardiovascular disease.
At first glance, the explanation seems obvious: perhaps vitamin D protects the heart.
But there is a problem.
Large studies of vitamin D supplementation have generally failed to show the cardiovascular benefits we might expect if vitamin D deficiency were the primary explanation.
In other words, taking vitamin D doesn’t appear to reproduce all of the potential cardiovascular effects associated with sunlight exposure.
That raises an interesting question:
What if sunlight is doing something else?
Your Skin Is More Than a Protective Covering
Most of us think of our skin primarily as a barrier protecting everything underneath it. However, the skin is a biologically active organ.
One particularly interesting area of research involves nitrogen-containing compounds stored in the skin, including nitrate (NO₃⁻) and nitrite (NO₂⁻).
These compounds are connected to nitric oxide, an important signaling molecule throughout the body.
When ultraviolet light—particularly UVA—reaches the skin, research suggests that it can mobilize nitric-oxide-related compounds from the skin and increase nitric oxide activity in the circulation.
Why does that matter?
Because nitric oxide plays an important role in controlling our blood vessels.
Nitric Oxide Helps Your Blood Vessels Relax
Our blood vessels aren’t rigid pipes. They constantly expand and contract in response to signals from the body.
Nitric oxide is one of the signals that tells blood vessels to relax and widen, a process called vasodilation.
When blood vessels widen, blood can flow more easily and blood pressure can decrease.
That connection matters because high blood pressure is one of the most important risk factors for cardiovascular disease.
Over time, uncontrolled high blood pressure can increase the risk of:
- Heart attack
- Stroke
- Heart failure
- Kidney disease
- Damage to blood vessels throughout the body
Therefore, even relatively modest changes in blood pressure across a large population could potentially have meaningful effects on cardiovascular health.
Could Sunlight Help Lower Blood Pressure?
Dermatologist and researcher Dr. Richard Weller has spent years investigating this question.
His research suggests that exposure to UVA light can release nitric-oxide-related compounds stored in the skin, producing effects on blood vessels and blood pressure.
This is particularly interesting because it provides a possible explanation for something vitamin D alone hasn’t been able to explain.
If sunlight’s cardiovascular effects came entirely from vitamin D, we might expect vitamin D supplements to produce similar cardiovascular benefits.
So far, they generally haven’t.
That suggests that our skin’s interaction with sunlight may involve biological processes that we are still learning to understand.
Why Could This Become More Important as We Age?
Some of the observations surrounding sunlight and cardiovascular health appear particularly interesting in older adults.
Scientists are still investigating why.
One possibility involves lifestyle. As people get older, many spend more time indoors. Changes in mobility, retirement, health conditions, transportation, living arrangements, and activity levels can all reduce the amount of time someone spends outside.
However, that may not be the entire explanation.
Aging also changes our skin, cardiovascular system, and blood vessels. Blood vessels generally become less flexible with age, while the body’s ability to produce and use nitric oxide can change as well.
At the same time, high blood pressure and cardiovascular disease become increasingly common as we get older.
Researchers are still trying to determine how all these pieces fit together.
For now, we can’t say that older adults should deliberately increase UV exposure to lower their blood pressure. But the research raises an intriguing question:
Could some of the biological effects of sunlight become increasingly important as we age?
But What About Skin Cancer?
This is where the story becomes complicated.
We have strong evidence that excessive UV exposure damages skin and increases the risk of skin cancer. That hasn’t changed.
At the same time, researchers are investigating whether completely avoiding sunlight could mean missing some of its potential physiological benefits.
We don’t yet know exactly where the ideal balance lies.
There is currently no medically established amount of unprotected sunlight that people should receive specifically to improve cardiovascular health. Individual skin type, age, medications, medical history, geography, season, and previous skin cancers can also dramatically change the risks associated with UV exposure.
So this research should not be interpreted as advice to start tanning, intentionally get sunburned, or stop using appropriate sun protection.
Instead, researchers are asking a more nuanced question:
How do we protect our skin from excessive UV exposure while also understanding the potentially beneficial ways our bodies interact with sunlight?
We may learn much more about that balance in the years ahead.
Minnesota Makes the Question Even More Interesting
Here in Minnesota, our relationship with sunlight changes dramatically throughout the year.
Long summer days can keep us outside well into the evening. Several months later, winter brings short days, cold temperatures, heavy clothing, and considerably less time outdoors.
We already know that these seasonal changes can influence vitamin D production and our circadian rhythms. Researchers continue to investigate whether changes in sunlight exposure may affect cardiovascular health in additional ways as well.
Again, that doesn’t mean Minnesotans should start sunbathing in January—or July.
It simply reminds us that our environment interacts with our bodies in ways that science is still discovering.
Getting Outside Has Benefits Beyond UV Exposure
Fortunately, we don’t have to settle the sunlight-and-nitric-oxide question before recognizing the benefits of spending time outdoors.
Getting outside often means moving more.
A walk around the neighborhood, gardening, playing with your grandchildren, hiking, fishing, biking, or simply working in the yard can increase physical activity.
Outdoor light exposure during the day also helps regulate our circadian rhythm, which can support healthy sleep patterns.
And those things already have well-established benefits for our health.
The goal isn’t to chase UV exposure. It’s to avoid becoming unnecessarily disconnected from the outdoors while continuing to protect our skin appropriately.
Heart Health Is Bigger Than One Molecule
The connection between sunlight, nitric oxide, and cardiovascular health is fascinating, but we shouldn’t lose sight of what we already know.
Some of the most effective ways to protect your heart remain remarkably straightforward:
- Know your blood pressure.
- Stay physically active.
- Don’t smoke or use tobacco.
- Manage cholesterol and blood sugar.
- Eat a balanced, nutritious diet.
- Maintain a healthy weight.
- Get adequate sleep.
- Keep up with preventive healthcare.
And perhaps there is another simple habit worth remembering:
Get outside once in a while.
Not because we can promise that sunlight will prevent a heart attack. We can’t.
Rather, spending time outdoors can encourage movement, support healthy sleep patterns, and reconnect us with an environment that our bodies have interacted with throughout human history.
Science Is Still Asking Questions
One of the most exciting things about medicine is that our understanding continues to change.
We once thought the cardiovascular relationship between sunlight and health might primarily involve vitamin D. Now researchers are exploring whether nitric oxide and nitrogen compounds stored in our skin may be part of the story.
We also know that excessive UV exposure can cause real harm.
Both things can be true.
The next question for researchers is not simply whether sunlight is “good” or “bad.” Instead, it is understanding how sunlight affects the body, who may benefit from those effects, and how we can balance potential cardiovascular benefits with protecting our skin.
At Aslan Health, we believe understanding your health helps you make better decisions about it. If you have questions about blood pressure, heart disease risk, vitamin D, or other preventive health concerns, talk with your healthcare provider.
Sometimes the most interesting discoveries in medicine begin with a simple question:
What if there is more to the story?
Caring for our Neighbors.