Vitamin D - The sunshine Vitamin

In the UK, you won’t make much vitamin D during the winter months due to the distance from the equator and the strength of the sun’s rays. From mid-October to the beginning of April there is no ambient ultraviolet sunlight of the appropriate wavelength [Source: NICE] so the body relies on vitamin D stores acquired during the summer months and dietary sources to maintain healthy vitamin D status.

If your vitamin D levels are low in the autumn months, it is unlikely any remaining vitamin D stores will last through the winter, which can result in low vitamin D status or even deficiency.

The Department of Health has identified the following groups as particularly ‘at-risk’ of vitamin D deficiency:

• Pregnant and breastfeeding women. During pregnancy, the foetus relies solely on the mother’s vitamin D levels. Breast milk is a poor source of vitamin D

• Babies and children under the age of five

• Adults over the age of 65. The skin becomes less efficient at synthesising vitamin D from the sun, and the kidneys are less able to convert the vitamin into its active form

• People with limited exposure to sunlight

• People who have darker skin such as people of African, African-Caribbean and South Asian origin, because the skin is less able to convert vitamin D from the sun

There is also evidence to suggest a link between increasing body mass index (BMI) and falling vitamin D levels. It is thought that vitamin D can become trapped inside fat tissues and so is unable to circulate in the blood.

In children, a vitamin D deficiency results in rickets, a condition which affects the formation and growth of bones. In severe cases bones become soft and malformed, and vulnerable to fractures and breaks.

In the UK, the number of cases of rickets has quadrupled over the past fifteen years, which experts attribute to several contributing factors; children are spending more time playing indoors which limits their exposure to sunlight; the rising use of sunscreen which reduce the body’s ability to synthesise vitamin D from the sun; and poor diets. It is estimated that between 8 and 24% of children in the UK have low vitamin D level depending on the time of year - reaches the higher end during the winter months.

In adults, vitamin D deficiency is referred to as osteomalacia, which again, causes soft and fragile bones. Many adults also experience pain in their bones and muscle weakness. Vitamin D deficiency has also been linked to several other health conditions in adults and is thought to increase the risk of heart disease, diabetes, certain cancers, osteoporosis and other bone-weakening diseases. The most recent large-scale survey released by NICE in 2014 found that 1 in 5 adults in the UK - around 10 million people - have low vitamin D levels and are at risk of complications from vitamin D deficiency.

During the winter months, nearly 75% of adults from Asian or African and Caribbean backgrounds have low vitamin D levels. The researchers involved in the survey advised that the current Nutrient Reference Values (NRVs) need to be reviewed.

Fortunately, many of the effects of vitamin D deficiency are reversible over time. Increasing your vitamin D intake will gradually improve bone density and strength. If severe, your doctor may prescribe high intermittent doses until vitamin D status reaches a normal range.