Vitamin D & Sun – how much is enough?

Sue Stevens

Sue has been in clinical practice for over 20 years and in that time, she has consulted and guided 1000’s of people through their healthcare journey. After studying for over 15 years, acquiring 3 post-graduate qualifications, Sue works to understand the nature of your health concerns, using traditional thinking and the best evidence-based information to create a holistic, manageable, and individualised treatment plan. Call today to step into the healthy, energetic version of yourself! Learn to live your best life!

Sunlight contains ultraviolet radiation: ultraviolet B radiation (UVB) acts on the epidermis of the skin and causes erythema (reddening). When ultraviolet radiation interacts with 7-dehydrocholesterol in the skin, vitamin D is produced. Things that can affect this conversion in the skin are – increased age, darker skin colour, the area of skin surface exposed and low levels of ultraviolet radiation (cloud cover/time of year). Although sun exposure can help increase vitamin D production, ultraviolet radiation is a risk factor for skin cancer and sun protection should be considered, especially in summer.

Minimal Erythemal Dose

Or how much sun do I need? UVB penetrates the outer layers of skin, causing temporary redness (erythema). (It is the ultraviolet radiation A (UVA) that penetrates deeper layers of the skin, causing photo-ageing and increased risk of cutaneous malignant melanoma). The minimal erythemal dose (MED) is the minimum amount of exposure to ultraviolet radiation that causes erythema (reddening) of the skin. A MED required to synthesise 1000 IU of Vitamin D would depend upon the duration of sunlight which varies by time of day, season and city. The assumption that ¼ of 1 MED directed at ¼ of the body surface area (i.e., the face, neck, hands and full arms) allows for the equivalent production of 1000 IU of oral Vitamin D. For fair-skinned people, a dose of 1000 IU of Vitamin D would be achieved by exposing 11% of the body equivalent to 0.455 MED. If 17% of the body (hands, arms, neck and lower legs) were exposed that would equal a MED of 0.294. That is the more skin exposed the less time in the sun is needed to acquire a therapeutic dose of Vitamin D. Table 1. The time required, at different times of the day and seasons for a 1000IU dose of Vitamin D – with 11% of the body exposed (hands, arms, neck) (boxes in red indicate times the Ultraviolet Index (UVI) is >3 – when sun exposure should be taken with caution)

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Published on:25 Jan, 2021

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