Dr. Sarah Brewer is a medical nutritionist, nutritional therapist and the author of over 60 popular health books. We are excited about her guest blog post on this vital topic.
At one-time, vitamin D was all about ensuring good calcium absorption from the diet to maintain healthy bones. Researchers now realize this important vitamin does a lot more than that and has beneficial effects all over the body.
What is it?
Vitamin D, or calciferol, is the collective term for five different, fat-soluble vitamins. The most important for human health is vitamin D3 (cholecalciferol) which we can make in our skin to some extent. Vitamin D3 is also obtained from animal-based foods such as liver, oily fish, meat, eggs, and dairy products and is added to some fortified foods. We also obtain small amounts of vitamin D2 (ergocalciferol) from a few plant foods such as mushrooms.
What does it do?
As well as regulating the absorption of calcium and phosphate from the diet, and helping to maintain strong bones, vitamin D helps to stimulate immune cells to reduce the susceptibility to infections such as pneumonia. It’s no coincidence that sun exposure was once a leading sanatorium treatment for tuberculosis before antibiotics were available.
Vitamin D helps to reduce calcium deposition in arteries, is involved in memory and mood, and has a strengthening effect on muscle fibres that improve stability and help reduce falls.
Studies have also found associations between good vitamin D status and reduced risks of:
- breast cancer[i]
- type 2 diabetes[ii]
- Alzheimer’s disease and Parkinson’s disease[iv]
The difficulty with making vitamin D
Even in youth, it’s difficult to make all the vitamin D3 you need, which is why it is classed as an essential micronutrient. Its synthesis depends on the presence of a cholesterol-like building block (7-dehydrocholesterol) in the skin, and exposure to sunlight when the UV index is greater than 3.
People living at a latitude of 52 degrees N (which passes through the center of the UK and Canada) are not exposed to enough UVB radiation to make vitamin D between October and April. Those living at a latitude 42 degrees N (which forms the northern limit of Spain and part of the border between Canada and North America) are unable to synthesise vitamin D3 between November to February.
Low vitamin D levels are frequently seen in people living at northern latitudes, especially in those who cover up in the sun, use high factor sun protection, or who stay indoors most of the time – which includes many older people, especially those who are frail or relatively immobile.
People who are taking a statin drug are also at risk of vitamin D deficiency as they produce less of the cholesterol-like precursor in their skin.[vi]
Skin synthesis falls with age
Over the age of 50, the ability to synthesise vitamin D3 reduces so that skin concentrations fall by at least half between the ages of 20 to 80 years. One study showed that people aged 62 and over synthesised four times less natural vitamin D than those in their 20s.[vii]
Due to a combination of less sun exposure, and less ability to make vitamin D3 even when the sun is shining, vitamin D deficiency becomes more common with increasing age.
Vitamin D3 deficiency has wide-ranging effects on health
In older people, lack of vitamin D is associated with the bone diseases, osteomalacia and osteoporosis, and has been linked with muscle weakness, falls and bone fractures.
In the Health, Aging and Body Composition study, involving 2,099 older people (average age around 75 years) who were initially well-functioning, a low vitamin D level was associated with increased risk of developing mobility limitation, disability and poor physical function. [viii]
In the United States, the CDC Injury Center estimates that the number of fatal falls in older people will rise to 100,000 per year by 2030, but that these future fatal falls could be reduced by nearly a quarter through screening for fall risks, reviewing medications, and recommending Vitamin D supplementation.[ix]
Vitamin D deficiency may also play a role in constipation and increase the risk of common age-related conditions such as type 2 diabetes, arterial calcification, hypertension and heart disease as well as some cancers.
What’s the answer?
Despite the limitations mentioned, it’s important to encourage the elderly to spend time out of doors, to obtain some sun exposure, and to eat food sources of vitamin D regularly. The most important intervention, however, is to offer them a vitamin D3 supplement.
What’s the best dose?
Opinions vary, with recommendations ranging from 10mcg to 50 mcg vitamin D3 per day. Some researchers have found that the United States, for examples, studies show that an intake of 100 mcg (4000 IU) is needed to maintain vitamin D levels in all older women. [x] This intake is equivalent to the currently suggested EU Upper Safe Level.[xi] If in doubt, blood tests can predict the best dose.
Intakes above 100mcg vitamin D3 are best taken under medical supervision. Excess can lead to side effects associated with high calcium levels, such as demineralization of bone, kidney stones, headache and weakness.
Read more about vitamin D and health here: https://drsarahbrewer.com/a-z-of-vitamins/vitamin-d
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For more information on diet and supplements, visit my Nutritional Medicine website at www.DrSarahBrewer.com. Read my general health articles at www.MyLowerBloodPressure.com and www.ExpertHealthReviews.com @DrSarahB
- [i] http://www.ncbi.nlm.nih.gov/pubmed/23807676
- [ii] http://www.ncbi.nlm.nih.gov/pubmed/23613602
- [iii] http://www.ncbi.nlm.nih.gov/pubmed/23377209
- [iv] http://www.ncbi.nlm.nih.gov/pubmed/23415143
- [v] http://www.ncbi.nlm.nih.gov/pubmed/23225498
- [vi] http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4382771/
- [vii] http://jn.nutrition.org/content/136/4/1123.full
- [viii] http://www.ncbi.nlm.nih.gov/pubmed/22573914
- [ix] http://www.ncbi.nlm.nih.gov/pubmed/26688674
- [x] http://www.ncbi.nlm.nih.gov/pubmed/18065583
- [xi] http://www.efsa.europa.eu/en/efsajournal/pub/2813.htm