Summer is the best time to enjoy the outdoors and connect with the healing power of nature. For most of us, this is the time of year we get the most exposure to sunlight, which comes with pros and cons. We need to find balance to prevent overexposure to harmful ultraviolet (UV) rays—which increase the risk of sunburn, skin aging, and skin cancer. While at the same time, we should maximize the beneficial aspects of sunlight that influence levels of vitamin D and enhance mood, energy, and sleep.
Vitamin D: The Sunshine Vitamin
Vitamin D is a fat-soluble essential vitamin that plays multiple roles in the body. In addition to maintaining bone health, vitamin D can protect against heart disease, diabetes, and cancers of the breast, prostate, and colon. Vitamin D is necessary for healthy immune function and may reduce inflammation, pain, depression, and sleep. Vitamin D also enhances absorption of other key nutrients such as calcium, iron, magnesium, phosphate, and zinc.
Known as the sunshine vitamin, the body can synthesize vitamin D3 (cholecalciferol) in the skin from a cholesterol precursor when exposed to adequate UVB (ultraviolet B) rays. Vitamin D synthesis in the body depends on multiple factors including:
- Time of day
- Length of sun exposure
- Cloud and smog cover
- Skin pigment
- Body fat
- Usage of sunscreens
In order to synthesize vitamin D, you need UVB sunlight between 290 and 300 nm. This only occurs when the UV index is above 3, which is not consistent outside of the sun belt. This means that if you live 37 degrees north of the equator (north of San Francisco, St. Louis, and Richmond in the U.S.) or 37 degrees south of the equator, you’re probably not getting enough sun exposure year-round. It also means that summer is a great time to catch up on some rays.
Studies have found that between five and 30 minutes of sun exposure to your unprotected face, arms, legs, or back between the hours of 10 a.m. and 3 p.m. two to three times per week can significantly increase your vitamin D levels. Those with darker skin pigment, higher body fat, and those over 70 years-old do not produce as much vitamin D, and therefore have increased needs. Using UVB-blocking sunscreen will decrease skin production of vitamin D. For example, a sunscreen with an SPF of 8 decreases vitamin D synthetic capacity by 95% and an SPF of 15 reduces synthesis by 98%.
You can also get your Vitamin D from food and dietary supplements of cholecalciferol (D3). It’s naturally found in egg yolks, fatty fish, and certain mushrooms, and is sometimes added to fortified milk and juices. The RDA for vitamin D is 600 to 800 IU daily, but new research suggests that adults may actually need at least 2,000 IU daily for optimal health and wellness. Serum levels of 25-hydroxy-vitamin D can be measured to determine a person’s vitamin D status with optimal levels between 40 and 60 ng/ml.
Melatonin and Serotonin: Sleep and Mood
Our natural rhythm is programmed for us to be outdoors while the sun is shining, and in bed at night. In addition to producing vitamin D, exposure to bright sunlight interacts with our pineal gland and regulates melatonin production, which influences our sleep cycles.
Melatonin also plays an important role in regulating inflammation and immune function, and suppressing skin damage from UV rays. Serotonin—a neurotransmitter related to mood that is a precursor to melatonin—is also affected by exposure to daylight. Getting outside during the day and sleeping in complete darkness can boost our sleep, energy levels, and mood.
Skin Aging, Sunburn, and Skin Cancer
While exposure to sunlight has its health benefits, UV radiation from the sun can also have harmful effects, contributing to skin damage including:
- Akin cancer
- Eye diseases, including cancer, cataracts, age-related macular degeneration, and eye growths
Skin cancer is the most common cancer worldwide, and the three main forms of skin cancer (melanoma, basal cell carcinoma, and squamous cell carcinoma) are largely attributed to excess UV radiation.
In the US, an estimated that 1.5 million skin cancers and 8,000 deaths due to metastatic melanoma occur annually. Current estimates are that one in five Americans will develop skin cancer in their lifetime. Although certain skin types are more prone to skin damage, anyone can get skin cancer, therefore it is important to protect yourself while having fun in the sun.
Sun Protection Factor
Brief repeated exposures to sunlight may be beneficial for our vitamin D and melatonin levels, however longer sun exposures do not further increase vitamin D production and can result in skin and eye damage. So those spending more time outdoors should to take precautions to protect against the sun’s damaging effects.
Sun Protection Factor (SPF) was a term introduced in the early 1960’s to describe a sunscreen’s effect against UVB rays. For example, if you sunburn after 10 minutes without sunscreen, then using an SPF of 8 should allow you to be exposed to the sun for 10 x 8 = 80 minutes before burning. Results, of course, vary depending on how much sunscreen you apply, how thoroughly you apply it, and how quickly it degrades after applying. Sunscreens are now available ranging from an SPF of 2 to an SPF of 70 and the American Academy of Dermatology recommends using an SPF of at least 30. Remember, it may take up to 20 minutes after application for the SPF to be active.
Tips to Safely Enjoy Summer Sunlight
- Spend a short amount of time (under 30 minutes) in the mid-day sun with exposed and unprotected arms and legs to increase your body’s synthesis of vitamin D
- Use a mineral-based sunscreen and/or UPF-rated clothing to protect yourself during longer sun exposures. Find out more about what’s in your sunscreen.
- Use UV-blocking sunglasses to protect your eyes with brief unprotected eye exposures (10-15 minutes per day) to daylight or bright full-spectrum light to influence your pineal gland
- Consume antioxidant-rich foods such as turmeric, artichoke, deeply pigmented fruits (such as purple or red grapes, blueberries), celery, parsley, and dark chocolate to help protect against skin cancer
- Consult with a dermatologist if you have new growths on your skin, a sore that doesn’t heal, or a mole or other skin lesion that changes in size, shape, or color
- Ask your doctor to check your level of vitamin D. If you are deficient, take a supplement of vitamin D3 (cholecalciferol)
As with everything, getting a healthy sun intake is just a balancing act.
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