Vitamin D

We all associate Vitamin D with bone health but it’s also blazing a trail of interest for its other effects on the body. Vitamin D aids the absorption of calcium from the gut and calcium is essential for strong bones so it has long been used as part of treatment for and prevention of rickets, osteoporosis, osteopaenia and osteomalacia. But Vitamin D can also trigger gene expression, i.e change the way we respond and work. It does this by attaching itself to DNA receptors in the cell nucleus and signalling them to produce proteins that affect the functioning of many systems and organs in the body.

The conclusions have been published after a new review of 195 studies involving more than 168,000 patients. Vitamin D’s effects have been noted on the immune system, in cellular growth and death, in detoxification, the regulation of calcium and neurotransmitters. One particularly large study of 858 adults over the age of 65 showed Vitamin D deficiency to be related to a decline in brain function with the most severely deficient showing the most substantial decline. A 2008 Dutch study of 1282 adults between 65 and 95 showed higher levels of depression amongst those with the lowest levels of vitamin D. 28 of the studies based in the UK showed that middle aged and elderly adults have a 33% greater chance of avoiding heart disease if their Vitamin D levels were sufficiently high. The review also revealed a 55% reduction in type 2 diabetes and a 51% reduction in the risk of metabolic syndrome compared to those with the lowest levels. Those with the highest levels had no diabetes at all.

The survey reveals enormous potential for its use. None more relevant than Vitamin D’s potential to reduce the size of existing cancer tumours due to its anti-proliferative role which means it encourages natural cell death (apoptosis) and may stop tumours from spreading.

So why are a third of us, 37.3% of the population, deficient in Vitamin D and how can we correct this? Perversely one of the reasons may be the advice to cover up against the sun and use sun screens to reduce the incidence of sun cancer. The production of Vitamin D starts in the skin and the chemical produced is then activated by the liver and the kidneys. We can make up to 20,000 international units (i.u.s) per exposure to the sun. But the body has its own system of stopping production at about 10,000 i.us to prevent toxicity. But this is the catch… the sun, or rather UVB rays… have to be strong enough (50 degrees above the horizon) and between September and April in the UK they’re not. So unless you can holiday abroad in winter it seems that food sources and/or supplements are a good alternative. The recommended daily allowance (RDA) is 200 i.us and the suggested safe upper limit for supplementing is 4,000 i.us.

Unless we eat wild salmon where a 3oz portion provides 1000 i.us we get very little from food sources. In comparison farmed salmon provides 375 i.us. One cup of mushrooms provides 12.6 i.us and one egg provides 26 i.us. Our blood levels of Vitamin D are deemed to be sufficient if they are above 50nmol/L.

There has been recent controversy cast over blanket supplementing to the over 50s as a preventative measure as bone mineral density didn’t significantly improve. But this study was testing bone mineral density and we don’t know about non recorded improvements to the immune system and respiratory health and mental health as a result.

It would seem that the best way to ensure good levels is to expose 40% of your body to the sun daily during the summer months of May to August for 15 to 20 minutes or until your skin turns slightly pink and then cover up. Little and often is the advice given. And then between September and April to take a daily supplement along with good dietary sources of calcium which is contained naturally in all fruits and vegetables but particularly green, leafy vegetables.

A good nutritional expert will help you decide on a suitable supplement and where and how to get your blood levels taken. A what about cod liver oil I hear you ask? It has historically been used to ensure adequate levels during the winter months but the oil must be cold-pressed and clean if it is worth taking and most supermarket shelf products won’t be good enough.

Unless you have symptoms of bone disease most GPs won’t routinely test your levels of Vitamin D. Considering its potential therapeutic uses to other systems in the body, mentioned above, this may change. There are home kits available but it is always worth talking to your GP first. They may agree to perform the test if you pay to have the blood taken by the surgery nurse and can provide the kit.

Anna Pugh, Nutritional Therapist

Categories: Nutrition.