Can we get enough Vitamin D from sun exposure without risking melanoma?
Vitamin D is a required by the body to maintain healthy bone and muscle function. Low levels are linked to bone conditions such as rickets in children and osteoporosis and osteomalacia in adults. There is also growing evidence of an association between low vitamin D levels and other health issues such as colorectal cancer, cardiovascular disease and all-cause mortality… even skin cancer!
Vitamin D is available to your body through 3 main sources:
- Exposure of the skin to ultraviolet B (UVB) from sunlight is the main source of vitamin D for most people. With sufficient exposure to UVB, a healthy person can synthesise all of their vitamin D requirements in their skin.
- The food supply also contributes to vitamin D status. Vitamin D3 is found in small quantities in a few foods such as fatty fish (North Sea salmon, herring, tuna and mackerel). Few products are fortified with vitamin D in New Zealand. It would be hard to reach acceptable blood levels of vitamin D through diet alone.
- Supplementation is available for groups at risk of insufficient levels – such as the elderly who are unable to get outside.
Given the main source of Vitamin D in New Zealand is from the sun, how do we safely get adequate Vitamin D when it is widely accepted that we need to cover up and avoid UV radiation?
Below are a few guidelines from the Ministry of Health:
- Sunburn should always be avoided.
Deliberate sun exposure during peak ultraviolet radiation periods between September and April is not recommended because this increases the risk of skin cancer, eye damage and photo ageing (wrinkles).
Between September and April, sun protection (shade, cover-up clothing and hats, sunscreen, sunglasses) is recommended, especially between 10 am and 4 pm.
- For the general population, some sun exposure is recommended for vitamin D synthesis. Physical activity is associated with increased vitamin D levels.
Between September and April, in the early morning or late afternoon, a daily walk or some other form of outdoor physical activity is recommended.
Between May and August, sun protection is generally not required unless at high altitudes or near highly reflective surfaces, such as snow or water. During this time some sun exposure, especially in the hours around noon when UVB levels are highest, is advised for vitamin D synthesis. A daily walk or other outdoor activity is recommended at this time.
- Individuals at high risk of skin cancer include those: with a history of skin cancer, who are highly sun sensitive, who have received an organ transplant, or who are taking medicines that increase photosensitivity. These people should discuss their vitamin D requirements with their health practitioner to determine whether dietary supplementation with vitamin D would be a preferable alternative to sun exposure.
- When the Ultraviolet Index is 3, in those with sensitive skin (eg, fair-skinned people), skin damage occurs after about an hour, but optimal vitamin D can still be produced in a few minutes if at least the face, arms and legs are exposed. Even during winter in southern New Zealand (when the UVI reaches only 1 at midday) there should be sufficient UV radiation available to help maintain vitamin D, though people need to expose larger areas of skin and this may not be practicable in low temperatures.
- There are two sources of information that provide advice to the public on the Ultraviolet Index.
The daily Sun Protection Alert www.sunsmart.org.nz outlines the times of day when the Ultraviolet Index is over 3.A more detailed daily Ultraviolet Index regional forecast service for New Zealand is available on the National Institute for Water and Atmospheric Research (NIWA) website www.niwa.co.nz
- Sun protection should be used throughout the year when at high altitudes or near highly reflective surfaces, such as snow or water.
- Use of sunbeds and solaria is not recommended because they are associated with increased risk of early-onset melanoma. The risk increases with greater use and an earlier age at first use.