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Here’s why, and how to fix it
Vitamin D is free - from sunshine, yet amazingly vitamin D deficiency is the most common nutritional deficiency worldwide (2019).
This deficiency is terrible for our health, and neglectful, considering how easy it is to get the optimum dose.
Vitamin D deficiency is associated with:
Vitamin D deficiency is also associated with muscle aches and bone pain.
People who have fibromyalgia, chronic fatigue syndrome, and depression have been found to have low vitamin D. That's not to say that low vitamin D causes those things - but a significant proportion of people with those diagnoses were deficient in vitamin D.
The elderly and the obese are at risk
One estimate is that 40 to 100% of older people in Europe and the US living in the community (not nursing homes) have vitamin D deficiency.
Vitamin D improves our ability to absorb calcium and phosphorous - hence why it is said to be good for bone health. Without vitamin D, only 10 to 15% of dietary calcium is absorbed. Deficiencies of calcium signal the body, via the kidneys, to start absorbing calcium back from our bones. Needless to say, this is disastrous as we get older.
At the same time that calcium is being removed from our bones as we age, we are simultaneously losing muscle mass and strength, and our balance is deteriorating. These degradations are made worse by older people exercising less.
The combination of poor bone health, fragility, and loss of muscularity significantly increases the risk of fractures and falls. Over 65, a fall resulting in ER admission will typically reduce your remaining life span by 5 years.
Other risks - obesity and not enough sunshine
Obesity is a risk factor for chronic vitamin D deficiency, and hence all the problems mentioned above. Researchers found that the absorption of dietary vitamin D (D3) was 57% lower in obese than in nonobese subjects.
Unfortunately, health advice about preventing skin cancer has resulted in whole populations avoiding sunshine, e.g. in Australia. Estimates are that 30 to 50% of children and adults in Australia have vitamin D deficiency.
Although there have been no trials of the high-SPF sunscreens that are now widely recommended, there is little evidence that sunscreen decreases vitamin D concentration. Therefore the need to get out in the sunshine for vitamin D should not negate skin cancer prevention advice.
The obese and the inactive were deficient
In one part of Australia, a study in 2014 found almost one-quarter of the population to be deficient in vitamin D. That study also found levels were lower in those classified as obese and those undertaking none or less than 150 minutes/week of physical activity.
Thus, obesity and insufficient physical activity (inadequate to obtain a health benefit) were significantly associated with the prevalence of vitamin D deficiency.
Should you up your dose in winter?
Winter is especially a problem as one study found (2015) that 70% of one Australian sample had inadequate vitamin D levels during winter.
Because COVID-19 is more potent in winter, a concurrent deficiency of Vitamin D is a risk factor since vitamin D supports immune system health.
This research (Apr 2020) recommends that to reduce the risk of infection, people vulnerable to influenza or COVID-19 should consider taking 10,000 IU per day of vitamin D3 for a few weeks to raise concentrations, followed by 5000 IU per day until winter or the risk of the virus has passed.
Be aware though, that single large single doses of vitamin D appear to worsen the risk of falls. So you best seek medical advice before significantly increasing your dosage.
Where does our Vitamin D come from?
We get vitamin D from exposure to sunlight, from our diet, and dietary supplements. Our liver processes it, then passes it to the kidneys which produce the active form which is needed by our metabolism.
There are two forms of vitamin D: vitamin D3 and vitamin D2.
Vitamin D3 is synthesised via sunlight on the skin (ultraviolet B radiation) and found naturally in oily fish and cod liver oil. (Because sunlight destroys any excess vitamin D3, overexposure does not cause Vitamin D3 intoxication.)
Vitamin D2 is synthesised from ergosterol - a compound found in yeast and mushrooms. When commonly consumed mushroom species are exposed to a source of ultraviolet (UV) radiation, such as sunlight or a UV lamp, they can generate nutritionally relevant amounts of vitamin D2.
Vitamin D is fat-soluble. Fat-soluble vitamins are absorbed along with fats in the diet and can be stored in the body's fatty tissue. Oddly enough, very little is known about the bioavailability of Vitamin D and how it interacts with other foods in the gut, e.g. dietary fibre and proteins.
Recommendations for your daily dose
Eat foods that provide vitamin D such as:
Cod liver oil is also one of the best food sources of vitamin D and can provide nearly all of your daily requirements for vitamins A and D. See: 9 Science-Backed Benefits of Cod Liver Oil
Many supplements will provide your correct daily dose, generally for a relatively modest price - about $10 for 100 tablets according to what I found on Google.
It would be best if you also exercised as regular exercise boosts the effects of vitamin D on skeletal muscle, according to a very recent research report in the Journal of Bone and Mineral Research (2020).
Get out in the sun - use sunscreen then the UV index is 3 and above, otherwise below 3 is safe from cancer risk. Being active while you're outside — for example, by walking or gardening — will boost the value as you are getting exercise and UV exposure.
Here's a tip - expose as much of your skin as possible (safely). For example, exposing your upper body produces 10X more Vitamin D than just exposing your hands and face (according to this research).
In summary, lose weight, exercise regularly, find a dietary solution of your choice, and expose as much of your whole body to the sun as possible.
That's simple and enjoyable right?
So please do your bit to improve your health and to reduce the worldwide population deficiency of vitamin D.
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Since I was diagnosed at 50 with Type 2 diabetes I've been learning how to do bone-building fitness training which lowers my age. You can too. It's your choice. Walter