You may have noticed a lot more information in the media about vitamin D of late. The Cancer Society tells us to “slip, slop, slap and wrap” to minimise sunburn and reduce the harmful effects of the sun’s rays – which are linked to skin cancers. But we also obtain most of our vitamin D, required for good health, through our exposure to the sun. So how do we ensure that we achieve healthy vitamin D levels without risking our skin’s health?
Vitamin D plays a critical role in healthy calcium metabolism (required for strong bones) as well as muscular function. There is now growing research into its role in a surprising array of health conditions including: internal cancers, heart disease, immunity, diabetes, strokes and mood disorders. You may have heard of S.A.D. (seasonal affective disorder) as being linked to lower levels of vitamin D. We can get small amounts of this fat-soluble vitamin from our diet – although few foods contain significant amounts. It’s found primarily in oily fish (and is included in our Fish Oil Supplements), salmon, sardines, mackerel, tuna, egg yolks, butter, some cheeses and oysters, as well as fortified foods like margarine, some cereals and soy milk. But at various stages of our lives, the amount we require varies significantly.
How much vitamin D do we need?
Current Ministry of Health guidelines recommend 5mcg (200IU) of vitamin D per day from birth up to the age of 50 years, but our need increases with age. The below adequate intakes (AI) are based on little or no exposure to sunlight. Adults: Men and Women 1 9-50 yr 5 mcg/day (200 IU) 51-70 yr 10mcg/day (400 IU) >70 yr 15mcg/day (600 IU) NB: These amounts don’t take into account any underlying health conditions or concerns, and fall below the amount some health practitioners would term “optimal”. Most people under 50 years of age can store approximately six months’ worth of vitamin D after regular sun exposure – enough to carry us through winter when production slows. As we age, our skin synthesis and production of vitamin D declines. As Holick (1996) states: “Vitamin D insufficiency and vitamin D deficiency is now being recognized as a major cause of metabolic bone disease in the elderly.” So supplementation of vitamin D may be even more important for obtaining optimal bone health and wellbeing as we age.
Have you been tested recently? As a fair-skinned person, I always use sunscreen as I burn easily. There have been times – in the morning or afternoon during the warmer months – where I have soaked up a few rays at the beach, feeling that I was topping up my (already sufficient) vitamin D levels. Towards the end of the last winter I had my vitamin D levels tested. I was genuinely shocked to learn that my blood test results showed me as very deficient, with a vitamin D reading of 17! (See the chart below).
What should our vitamin D levels be? National Nutrition Survey (NNS) data classifies the range of serum vitamin D levels in NZ as: 50-150nmol/L= healthy range <50nmol/L = insufficiency <17.5nmol/L of serum 25-hydroxyvitaminD = deficiency NB: It is worth noting that a vitamin D test is quite expensive, so it is not done as part of a standard blood test.
Who’s at risk of vitamin D insufficiency or deficiency?
• People over the age of 50 and the elderly
• People who are housebound or in institutional care
• Office workers or healthy people who spend most of their time indoors
• Those who cover their skin extensively (for religious or cultural reasons)
• Exclusively breast-fed babies of vitamin D-deficient mothers (especially if they are dark-skinned, wear a veil and/or have limited exposure to sunlight)
• Those with darker skin types (due to the higher amount of melanin pigment in the skin)
• Those with gut absorption problems
• Those with chronic kidney and liver diseases
• People with fat malabsorption disorders
• People with a high risk of skin cancer who avoid the sun
Making a vitamin D-posit
Vitamin D levels can be a bit like a bank account. If we don’t deposit funds to top up what we have taken out of the account, we can end up with decreased amounts over a period of time. Exposure of the hands, arms and face for 10-15 minutes of noon summer sun will produce approximately 1000IU (or 25mcg) of vitamin D, but it is generally recommended sun is taken before 11am and after 4pm to reduce the risk of skin cancer. As vitamin D is produced in the body by exposure to UVB rays, the use of sunscreen or sunblocking clothing may reduce the synthesis of vitamin D in the skin by 99 per cent.
The New Zealand vitamin D position statement has assessed this risk and acknowledges, “A balance is required between avoiding an increased risk of skin cancer and maintaining adequate vitamin D levels.” During winter months – and especially in the South Island – when UV levels are lower, vitamin D status may drop below adequate levels and additional vitamin D intake via supplementation may be required. As always, those who are at high risk of skin cancer should discuss supplemental vitamin D requirements with a health professional.
