Getting D from the Sun, Safely If sun burning always occurs at any exposure level or there is prior incidence of skin cancer you may not want to use sunlight to maintain D. Test and use a supplement. To use sunlight in lieu of supplementation refer to the skin pigmentation guide. The guide provides an estimate of the time needed to optimal levels of D. These exposure times are sufficient but remember they are calculated on UV-B intensity. Longer exposure will increase vitamin D production beyond optimal levels in some locations and will increase the danger of skin damage in all locations. This guide applies in seasons, latitudes, and altitudes of UV-B production. Please see the latitude and altitude information for UV-B levels or consider a UV-B meter. Remember, UV-B does not penetrate glass, smog, fog, some haze or clouds. UV-B Exposure Guidelines For the optimal daily dose of D from sunlight 80% of skin must be exposed for the full time, that is the time just prior to any skin changes (pinkness). In most locations in the US significant UV-B is present only during mid-day and only during summer months. Exposure must take place when UV-B is present, between 10AM and 2PM during the summer for most of the United States, on cloud and smog free days. Near noon is best. Before 10AM or after 2PM burning may occur before optimal D is produced. The closer to noon the less time needed to achieve D production. Do not over sun. The time needed to produce adequate D depends on skin color. Table 1 UV Guidelines Skin Type Time Needed for Daily D Production Type 1- Always burns easily, never tans, extremely sun-sensitive skin. Examples: Red-haired, freckles, Celtic, Irish-Scots. 5-7 minutes per side, 10 minutes full body at UV Index 9-10, above 10 less time is needed. Type 2- Always burns easily, tans minimally, very sun-sensitive skin. Examples: Fair-skinned, fair haired, blueeyed, Caucasians 10-15 minutes per side, 20 minutes full body at UV Index 9-10, above 10 less time is needed. Type 3- Sometimes burns, tans gradually to light brown, sun-sensitive skin. Examples: Darker Caucasians 20-30 minutes per side, 25 minutes full body at UV Index 9-10, above 10 less time is needed. Type 4- Burns minimally, always tans to moderate brown, minimally sun-sensitive. Examples: Mediterranean type, Caucasians. 40 minutes per side, 70-80 minutes full body at UV Index 9-10, above 10 less time is needed. Type 5- Rarely burns, tans well, suninsensitive skin. Examples: Middle Eastern, some Hispanics, some Blacks 50 minutes per side, 90-100 minutes full body at UV Index 9-10, above 10 less time is needed. Type 6- Never burns, deeply pigmented, sun-insensitive skin. Example: Blacks 60 minutes per side, 120 minutes full UVIndex 9 or above body at UV Index 9-10, above 10 less time needed. For type 1-3 skins sunbathing near noon will assure enough UV-B to produce D before burning occurs. For skin types 4-6 UV intensity is critical. Many parts of the US may not provide adequate UV-B to optimize D. A note about the UV IndexThe weather service puts out daily bulletins estimating the UV intensity. Go to http://iwin.nws.noaa.gov/iwin/us/ultraviolet.html. The problem with these ratings is that they do not actually look at the local UV-B but estimate from ‘sources’. I prefer to use my Sunsor™ UV-B meter. It is battery free and about the size of a small calculator. I carry it with me and can know instantly how much time I need to produce my daily D or if UV-B is too low to make sunning worth my while. UV-B meters are available but expensive. Table 2 UV Index and Sun Exposure National Weather Service’s UV Index. Note UV-B is present during primarily mid-day in locations with values of <10. Time is for mid-day exposure. Index readings are for the mid-day value when UV is highest. Most of the day values will be lower than that indicated by the UV Index. 0 - 2 (Minimal) - An Index reading of 0 - 2 indicates minimal danger from the sun’s UV radiation for the average (Type 2) person. Most people can stay in the noon sun for up to an hour without burning. Sufficient vitamin D will not be produced at this level before skin damage would occur. (No D all skin types) 3 - 4 (Low) - An index reading of 3 -4 indicates low risk of harm to the skin from the sun’s radiation. Type 2 individuals can experience a burn in 30 -60 minutes. It would be necessary to stay in the sun for longer than 60 minutes to activate D and burning may occur before D was produced. (No D all skin types) 5 -6 (Moderate) - An index reading of 5 - 6 indicates some significant risk of skin damage due to the sun. Unprotected exposure can result in a burn in only 20 - 30 minutes. At this level burning or skin damage would also occur before adequate D production. (D in light skin types only, but not much) 7 -9 (High) - An index reading of 7 - 9 indicates high risk of harm from unprotected exposure to the sun. Time in the sun should be limited during midday (10:00 A.M. - 4:00 P.M.) as skin may burn in as little as 13 - 20 minutes. Enough D would be generated in 10-20 minutes (before burning) in type 1 and 2 skins. (D in light and medium skins midday, very little D in dark skins) 10+ (Very High) - An index reading of 10 - 15 indicates very high risk of harm from unprotected sun exposure. Between 10:00 A.M. and 4:00 P.M. the length of time to burn may be less than 13 minutes without protection. Enough D would be generated in 10 minutes (before burning) in type 1 and 2 skins. (D all skin types, very little time needed for light skins, use caution.) While some D might be produced in light skins at the lower UV Index readings the damage from excess exposure to UV-A would out weigh the worth of sunning. At higher latitudes, most of the US, the UV Index is for midday, not morning or afternoon. Only Hawaii, Florida, south Texas, Southern Arizona, and some higher elevations, have significant UV-B for a longer stretch of the day. If sun exposure is or must be limited or avoided, use supplements. Testing is critical. We are all different and our responses are unique. Tropical sun must not be judged by these values. As little as a few minutes may be needed for persons with very light skin in subtropical or tropical locations. Sunlight and supplementation should not be mixed. Cases of elevated D have occurred by persons supplementing and sunning. BUT if the sun you sun in is far to the north rarely will it have much UV-B and sunning and supplements may work together. This mix of sunlight and D should not be attempted without testing. Several persons over the last few summers found themselves having excess levels of D by combining D and sunlight. Others have found sunlight exposure altered their need for supplementing D very little. TEST. This is particularly important in the US where during much of the year, in many locations, UV-B is not present in amounts able to produce D before burning. Depending on latitude this variable ranges from 2-3 months in San Diego and other cities of similar latitudes to 8 months in Portland, OR, upstate New York and other locations at higher latitudes. The exact time needed, varying with skin types at various US latitudes and altitudes, is not yet adequately understood. A UV meter used with sunbathing and initial frequent testing of 25(OH)D may be useful to determine your optimal use of sun and supplements. Genetics, both skin coloring and genes related to vitamin D response, strongly play a role in your need for D. Vitamin D receptor polymorphisms, genetic alterations of how we absorb and process D, are only recently being studied and the information applied to D sufficiency. (180)
