Ultraviolet Radiation Type A
Ultraviolet rays can be broken down into three parts: UVA, UVB, and UVC. UVA rays are 320-400 nm in wavelength, UVB rays are 280-320 nm, and UVC rays are 100-280nm. UVA rays can be further broken down into long UVA-1 rays (340-400nm) and short UVA-2 rays (320-340nm).
Ultraviolet A (UVA) radiation can be very harmful. While UVA rays do not cause the characteristic red sunburns like its UVB counterpart, UVA rays still penetrate the skin to cause DNA damage. This DNA damage can result in skin aging and cancer, which is why protecting yourself against UVA radiation is important. UVA blockers, clothing, and certain oral supplements can provide effective UVA sun protection.
Sunscreen is the classic way to shield yourself from the sun’s harmful rays. However, not all sunscreens provide protection against UVA radiation. Only sunscreens that contain UVA blockers can absorb UVA rays. The SPF value on sunscreens only indicates the level of UVB protection, so look for sunscreens labeled “broad spectrum” or “PA+”, which indicates the presence of a UVA blocker.
Common UVA blockers include chemical sunscreens, like Avobenzone, Oxybenzone, Emcamsule, and Tinosorb, and physical sunscreen ingredients, like Titanium dioxide and Zinc oxide.
Zinc oxide vs titanium dioxide
Zinc oxide has a broader protective ability compared to titanium dioxide. While both of these sunscreens are considered physical sunscreens, zinc oxide has broader coverage of all of UVA.
- Zinc oxide: blocks UVB and all of UVA
- Titanium dioxide: blocks UVB and UVA2 most effectively
Table 1. Sunscreen ingredients that block all UVA
||Physical or Chemical
||Is it Available in the United States
||What Wavelength Does it Block?
||290-400 nm (all UVA and UVB)
||310-400 nm (all UVA)
||290-400 nm (all UVA and UVB)
||280-400 nm (all UVA and UVB)
||Chemical and Physical
||280-400nm (all UVA and UVB)
UVA Sun Protection Clothing
Because sunscreen application is not perfect (i.e. missing spots, not applying enough, forgetting to reapply, or sweating it off), clothing is an excellent and superior form of sun protection. However, not all clothes provide the same amount of UVA sun protection.
The material, thickness, and color of the clothing are important factors in how well an article of clothing protects against UV rays. Studies have shown that synthetic fabrics, like polyester, provide higher levels of sun protection. In addition, thicker, darker-colored clothing are more effective against UVA radiation compared to thin, white or light-colored clothing.[1,2]
Table 2. Clothing factors that affect sun protection
|Different Factor in Clothing
||What’s Better for Sun Protection
||White cotton T-shirts do not provide much UV protection, and its protection is decreased when it is wet.
||Try to wear darker or more vivid colored clothing but avoid black as you may overheat.
||Thicker clothing like denim blocks more UV rays than thin or sheer clothing.
||Avoid loose weave fabrics such as linens since they transmit more UV radiation to the skin. Prewash cotton T-shirts to shrink them so that they have a tighter weave.
Aside from clothing, another preventative measure against UVA that has been gaining in popularity is oral supplements.
1. Polypodium leucotomos
When taken orally, the extract of the tropical cabbage palm fern, Polypodium leucotomos, has been shown to have photoprotective effects by reducing phototoxicity in skin cells exposed to UVA.[3,4] Research has shown that a 240mg dose of Polypodium leucotomos extract taken twice a day was effective in reducing UV-induced skin damage.
Carotenoids, such as lycopene, β-carotene, and Astaxanthin, have also been shown to have photoprotective effects against UV rays by acting as antioxidants.[6,7] UV radiation can create reactive oxygen species, which can cause damage to cells and DNA. Antioxidants are molecules that can prevent against oxidative damage caused by UV radiation.
Foods that are rich in lycopene have a red coloring, such as guavas, watermelon, and tomatoes. β-carotene gives foods, like carrots, sweet potatoes, and squash, a characteristic orange color. However, β-carotene can also be found in some green leafy vegetables. Astaxanthin is naturally found in algae, yeast, salmon, trout, krill, shrimp and crayfish.
Need for More Research
While there have been many promising studies about natural botanicals that have UV protective effects, more research should be done about the efficacy of these oral supplements in humans for actual UV protection. These oral supplements should not be used alone; they should supplement other sun protection methods, like broad-spectrum sunscreen and clothing, to most effectively protect you from harmful UV rays.
- Make sure that your sunscreen is labeled “broad spectrum” or lists UVA blockers in the ingredients
- Wear thicker, darker, tightly woven, synthetic fabric clothing that will provide better UVA sun protection
- Do not rely on oral supplements alone to provide adequate protection against UV rays