Where is the Sun?

Twenty three per cent of young adults are thought to be vitamin D deficient, and studies show that 86 per cent of the elderly living in residential care in Australia are vitamin D deficient.

Those with dark skins, and people who cover their skin, such as veiled women, are also at risk of deficiency. Breast-fed infants born to mothers within these groups are also at high risk of vitamin D deficiency.

In addition those with Coeliac disease and Crohn’s disease are at risk due to impaired lipid digestion and absorption. This includes those with cystic fibrosis.

Vitamin D deficiency is defined as less than 20–25 nmol per litre and marginal deficiency at levels between 25–50 nmol per litre.

Interesting to know too, that obese and overweight individuals have lower circulating vitamin D levels than those with BMIs less than 25. Indeed, vitamin D status has an inverse relationship to BMI, with those who have a BMI over 39.9, having vitamin D levels 24 per cent lower than those with a BMI less than 25. In other words, the fatter you are, the lower your vitamin D.

There is evidence that homeostatic control of body weight can be influenced by vitamin D, and that deficiency may result in a higher adipose tissue set point, resulting in a larger body size.

Cod, halibut liver, sardines and mackerel are the richest food sources of naturally occurring vitamin D… not foods most of us eat regularly. Eggs and butter also provide vitamin D, but due to cholesterol concerns are often restricted.

Therapeutic roles for vitamin D

Bone Health

The most well-known role of vitamin D is the maintenance of serum calcium levels. This is achieved by increasing the absorption of calcium from food in the small intestine. This facilitates the deposition of calcium from serum into the skeletal bones.
Amazingly we are seeing resurgence in the occurrence of rickets! A deficiency of vitamin D during pregnancy, breastfeeding and early childhood can result in this condition of decreased bone mineralization. And, 95–97 per cent of patients with osteoporotic fractures are vitamin D deficient.

Vitamin D and cancer

Latest research shows a clear relationship between vitamin D deficiency and an increased risk of developing several cancers, including breast, prostate and colorectal cancer.

Diabetes obesity

Obese individuals have low serum vitamin D levels which correlate with impaired insulin sensitivity. Vitamin D is an essential factor for pancreatic function and blood glucose metabolism. Deficiency of vitamin D is associated with the development of both Type 1 and Type 2 diabetes.

Fertility and reproduction

Vitamin D receptors are present in sperm and are linked to sperm survival and the ability to bind to and fertilise the ovum.
Gestational vitamin D deficiency is associated with low birth weight, small for gestational age, congenital rickets, infantile heart failure, defects in enamel and a large fontanelle.

Immune function

Several autoimmune conditions are linked to vitamin D deficiency. These include, asthma, psoriasis, MS and diabetes Type 1, rheumatoid arthritis, SLE and inflammatory bowel diseases.

Dosage recommendations

A general maintenance dose to maintain serum levels is 1000 IU of vitamin D daily.
To treat deficiency, supplementation needs to be in the range of 2000–7000 daily. Chronic disease states including autoimmune diseases, diabetes, cardiovascular disease and cancer require supplementation that maintains serum levels between 55–75 ng/mL.
It has been suggested that for every 40 IU of vitamin D3 supplemented an estimated increase of 0.04 ng/mL of 25 (OH) D may occur.
Bear in mind too that due to the natural variance in sun time and strength during autumn and winter, there is a corresponding seasonal variation of serum vitamin D levels.