Long associated with the prevention of rickets in children and of osteoporosis in pregnant women, Vitamin D is becoming ever more essential for our wellbeing.
Article written by Ariane Monnami, nutritionist with degrees in Micro-nutrition and Neuro-nutrition.
Vitamin D — A short history…
Similarly to the way in which a lack of Vitamin C can cause scurvy, a lack in Vitamin D can be the cause of rickets. Rickets is a bone disease which affects both bone strength and structure, causing limb and spinal deformity.
In 1782, it was discovered that cod liver oil enabled prevention and treatment of this illness — Vitamin D however was only later identified in the 1920s.
A little anecdote: Long regarded as medicine to be taken “whilst holding one’s nose” (that well-known medicine that Mary Poppins had to give to the children…), cod liver oil does not owe its unpleasant taste to Vitamin D but to the oxidisation of the Omega-3 molecules which occurs once the cod liver oil remains exposed to air. It is for this reason that cod liver oil was designed to be sold in capsule form.
Close up on Vitamin D — what are its purposes?
Vitamin D is essential for calcium metabolism in our bodies — it encourages the intestinal absorption of calcium and its consequent reabsorption by the kidneys.
Essential for bone growth in children, Vitamin D contributes to good bone and dental strength.
From rickets to osteoporosis
Similar to rickets, osteoporosis is a disease linked to poor calcium fixation amongst an entirely different age group; menopausal women. Along with Vitamin D, calcium has therefore also been used as a preventive treatment against osteoporosis.
Less of a vitamin..
Vitamin D is not necessarily to be defined as a vitamin since we are in fact very well able to produce it ourselves.
In effect, when exposed to ultraviolet light, 7-Dehydrocholesterol (from the family of cholesterols) is converted by the body into Vitamin D3.
One week’s exposure to sunshine is enough to increase the concentration of Vitamin D3 by ten times — in 1865, Trousseau in fact recommended sun exposure for children suffering from rickets.
However, dermal synthesis of Vitamin D covers only 50 to 70% of our needs.
..and more of a hormone
Over the last decades, it has been revealed that Vitamin D plays the role of ‘messenger’ in numerous physiological functions. Its biochemical structure in fact contains a sterol nucleus which is very similar to the structure of steroid hormones. Just like these hormones, Vitamin D comes from cholesterol and its creation can therefore be disturbed by medication against high cholesterol.
Vitamin D and calcium
Vitamin D is not only used for calcium fixation in our bones, it also allows for a better digestive absorption of this element and reduces its urinary excretion.
Essential for our immune system
Vitamin D is key for a strong immune system and allows us to not only defend ourselves against infection but also against cancerous cells.
Here is a particularly enlightening story that Professeur Rapin, my Micro-nutrition professor, often enjoyed telling his students —
“Medical statistics for the American army having shown a greater proportion of skin cancer amongst marines compared to other army divisions, we initially assumed that this increase was linked to sun exposure whilst aboard ship… However further analysis of the statistics showed that it was in fact not those above water, but those who spent the most time underwater who were most affected, and that the increase in skin cancer frequency was not due to sun exposure but due to a lack of Vitamin D.”
A role to play in depression and mood regulation
A study carried out in the Netherlands confirmed the link between Vitamin D concentration in the blood and levels of depression.
Another study has shown close links between a lack in Vitamin D, chronic fatigue and fibromyalgia.
And plenty of ongoing research…
Numerous studies are regularly being published with regards to the role of Vitamin D in obesity, diabetes, multiple sclerosis, diabetic neuropathy, cancer, sleep apnea and much more.
What are our needs in Vitamin D?
For adults, the recommended daily amount is between 400 and 600 IU (international units). For a growing child, multiply this by two or even by three.
Be careful not to overdose!
Vitamin D’s particularity is that it can be stocked very efficiently in our fatty tissue and contrary to water-soluble vitamins (Vitamin C, Vitamin B), which are excreted in the urine in the case of excessive consumption, this is not the case with Vitamin D. This can therefore lead to an overdose.
How to know if you are lacking in Vitamin D
Disorders and illnesses linked to a lack of Vitamin D tend to develop slowly — it can take several years before rickets, osteoporosis and immune system disorders begin to show. Waiting until you start experiencing symptoms can therefore be leaving things too late for most effective prevention and treatment.
Unlike the test for magnesium, blood testing for Vitamin D is simple to do, affordable and very reliable.
How to calculate your concentration of ‘25 OH Vitamin D’
– Deficiency: 25-OH-D inferior to 25 nmol/l (10 ng/ml)
– Deficit: 25-OH-D between 25 to 75 nmol/l (10-30 ng/ml)
– Normal: 25-OH-D between 75 and 250 nmol/l (30-100 ng/ml0
Dietary sources of Vitamin D
Cod liver oil remains the best dietary source of Vitamin D with 250 µg per 100g (or 100ml). and is now sold in capsule form. Oily fish is next, with between six and 23 µg of Vitamin D per 100g and then egg yolk, with between 2 and 3,2 µg of Vitamin D per 100g.
References
Brouwer-Brolsma EM et coll. : Low vitamin D status is associated with more depressive symptoms in Dutch older adults.Eur J Nutr., 2015; early online publication, 4th July. doi:10.1007/s00394-015-0970-6
Vitamin D status and the efficacy of high-dose intramuscular cholecalciferol on musculoskeletal pain and morning fatigue in patients with chronic rheumatic diseases. B. Y. Choi et al. Eular 2015, Rome, 10-13th June 2015
