1. VITAMIN D IS IMPORTANT FOR YOUR BONES
Vitamin D is a fat soluble vitamin that plays an essential role in the maintenance of normal calcium levels in the body. Without sufficient vitamin D, maintenance of the integrity of the skeletal system is impaired. This can affect bone development in children and bone strength in adults.
People often do not experience symptoms of Vitamin D deficiency, but without treatment there can be significant health effects. Very low vitamin D levels can cause poor bone
mineralisation. This can result in rickets in children, a condition that causes bone and muscle weakness and bone deformities. In adults, vitamin D deficiency can cause bone and muscle pain and can contribute to osteopenia and osteoporosis (brittle bones) thereby increasing the risk of falls and bone fractures.
2. IN AUSTRALIA, MORE THAN 1 IN 5 ADULTS DO NOT GET ENOUGH VITAMIN D
Studies have indicated that there is a high prevalence of vitamin D deficiency worldwide. In Australia, more than 1 in 5 adults do not get enough vitamin D. There are some reports that over 30% of Australian adults have mild, moderate or even severe vitamin D deficiency.
Older adults are particularly at risk of vitamin D deficiency due to the age-related decline in the skin’s ability to synthesise vitamin D from the sun. Many Australians are found to be particularly low in vitamin D during winter due to reduced sun exposure, so it is important to find the time to expose yourself to some sun which can help increase and maintain your Vitamin D levels and also help your sleep quality, mood and general well-being.
3. SOME PEOPLE ARE AT A GREATER RISK OF VITAMIN D DEFICIENCY
Some people are at a greater risk of vitamin D deficiency, including:
People with naturally very dark skin. The pigment in skin (melanin) acts as a filter to UVB radiation and reduces synthesis of vitamin D in the skin
People with little or no sun exposure, including:
o People who avoid the sun due to previous skin cancers, immune suppression or sensitive skin
o People in occupations with limited sun exposure – office workers, taxi drivers, factory workers, night-shift workers
o People who wear covering clothing or concealing clothing
o People who spend a lot of time indoors, such as those who are housebound, hospitalised or institutionalised long term
People with medical conditions or people who are on medications affecting vitamin D metabolism. For example, obesity, liver disease, kidney disease, malabsorption conditions (cystic fibrosis, coeliac disease, inflammatory bowel disease)
Babies and in particular, breast-fed babies of vitamin D deficient mothers. Breastmilk contains little vitamin D. Infants depend initially on maternal stores of vitamin D (formula milk is fortified with vitamin D) and are at risk of low vitamin D if their mother has low vitamin D.
4. VITAMIN D PLAYS A KEY ROLE IN IMMUNE FUNCTION
Low vitamin D levels have been associated with a number of medical conditions. Although studies have not confirmed whether there is a causal relationship between vitamin D and certain medical conditions, preliminary studies suggest that there are some potentially significant health benefits of maintaining adequate vitamin D levels.
Vitamin D plays a key role in immune function and can modulate the innate and adaptive immune responses. Vitamin D deficiency is associated with increased autoimmunity and an increased susceptibility to infection and in particular, vitamin D deficiency has been linked to respiratory infections such as pneumonia and tuberculosis.
5. LOW VITAMIN D IN PREGNANT WOMEN CAN CAUSE THEIR BABY TO DEVELOP MUSCLE WEAKNESS AND BONE DEFORMITIES
As vitamin D is required for the maintenance of normal calcium levels in the body, a deficiency in vitamin D can cause low calcium levels. In neonates and infants, low calcium is a potentially severe problem and can cause seizures.
Vitamin D deficiency during pregnancy has also been associated with impaired growth and bone development in the foetus. During pregnancy, vitamin D levels may be checked by your doctor to ensure that any vitamin D deficiency is corrected in order to minimise the risk of vitamin D related complications.
Discuss with your doctor whether you need to be tested for vitamin D deficiency particularly if you are in a high risk group for vitamin D deficiency.
6. THERE IS A RELATIONSHIP BETWEEN VITAMIN D AND COVID-19 (SARS-CoV-2)
More recently, evidence has emerged suggesting a relationship between low vitamin D levels and worsening outcomes of SARS-CoV-2 (the COVID-19 virus) infection.
A cross-sectional study across Europe showed that mortality from COVID-19 was significantly associated with vitamin D levels in different populations. The study found that countries at lower altitude that are typically sunny, such as Spain and Northern Italy, had high rates of vitamin D deficiency. These countries experienced the highest COVID-19 infection and death rates in Europe.
There have been low mortality rates in countries like Norway, Finland and Sweden, however, as people were found to have higher vitamin D levels despite less UVB sunlight exposure because supplementation and fortification of foods is more common.
In addition, studies have shown that African American people, and minority ethnic people who are more likely to have vitamin D deficiency due to naturally darker skin, appear to be more affected by COVID-19. African American people in England and Wales are more than four times more likely to die from COVID-19 and African American people in the United States are three times as likely to die from COVID-19 when compared with Caucasian people.
7. REGULAR DOSES OF VITAMIN D EARLY IN LIFE CAN REDUCE THE RISK OF DEVELOPING TYPE 1 DIABETES
Research has shown that regular doses of vitamin D early in life can reduce the risk of developing Type 1 Diabetes. Studies have also shown that vitamin D is important in the prevention of damage to cells in the pancreas that are associated with Type 1 Diabetes and can improve the production of insulin. Also, Vitamin D treatment has been shown to improve diabetic control in people with Type 1 and Type 2 Diabetes and in normal individuals.
8. LOW LEVELS OF VITAMIN D ARE ASSOCIATED WITH CARDIOVASCULAR DISEASE
Vitamin D deficiency has also been associated with hypertension (high blood pressure), hyperlipidaemia (high cholesterol), heart disease, heart failure and stroke. Studies have suggested that vitamin D protects against cardiovascular disease through inhibiting inflammation, regulating blood pressure and regulating glucose metabolism.
9. VITAMIN D MAY PREVENT CANCER
Many studies have investigated whether vitamin D can prevent cancer or if it can improve cancer treatment outcomes. The cancers for which human data are available are colorectal, breast, prostate and pancreatic cancer. There is increasing evidence that vitamin D helps to regulate cellular growth and may reduce the aggressiveness of cancer cells. At this stage, however, the available data are not comprehensive enough to establish whether taking vitamin D can prevent cancer.
10. LOW LEVELS OF VITAMIN D MAY INCREASE THE RISK OF DEVELOPING MULTIPLE SCLEROSIS
An association has also been shown between vitamin D and Multiple Sclerosis (MS). Current evidence supports that vitamin D deficiency increases the risk of developing MS, shown by a higher prevalence of MS in geographic areas that are further from the equator, where people are exposed to less sunlight. In addition, studies suggest that for people who already have MS, vitamin D may affect disease activity. Studies show that with adequate vitamin D levels in people with MS there are fewer relapses, lower risk of development of new lesions in the brain, reduced disability and reduced disease severity.
11. PEOPLE WITH AUTOIMMUNE THYROID DISEASE ARE MORE LIKELY TO HAVE VITAMIN D DEFICIENCY
Studies have shown that people with autoimmune thyroid disease (Grave’s disease and Hashimoto’s thyroiditis) were more likely to have vitamin D deficiency and some studies have shown that vitamin D deficiency is significantly associated with the severity of thyroid disease. This association may be related to the significant role that vitamin D plays in modulation of the immune system, enhancing the innate immune response while exerting an inhibitory action on the adaptive immune system.
12. VITAMIN D HAS BEEN FOUND TO PLAY AN IMPORTANT ROLE IN BRAIN DEVELOPMENT AND BRAIN FUNCTION
Vitamin D has been found to play an important role in brain development and brain function. Vitamin D deficiency has been found to be common in patients with Parkinson’s disease, Alzheimer’s disease, schizophrenia, depression, anxiety disorders, dementia and older adults with cognitive decline. Vitamin D receptors are widespread in brain tissue and the biologically active form of vitamin D has been shown to have protective effects on the nervous system. Associations have been noted between vitamin D and Alzheimer’s Disease and dementia in Europe and in the United States. Cognitive impairment was up to four times greater in older adults who were severely vitamin D deficient in comparison to individuals with adequate levels of vitamin D.
13. NOT EVERYONE SHOULD TAKE VITAMIN D SUPPLEMENTS
Although there is mounting research into the relationship between vitamin D and a number of medical conditions, there is currently insufficient data to inform nutritional requirements. As such, further research is needed before specific recommendations can be made.
At this stage, it is not recommended that you take vitamin D supplements unless you have been advised to do so by your doctor. It is our recommendation that you ensure you have your daily requirement of vitamin D through diet and/or sun exposure and if you are in an at risk group or are concerned about your vitamin D levels, see your doctor to discuss this further.
Vitamin D supplements are not recommended for healthy people who are not vitamin D deficient. It is not recommended to take vitamin D supplements unless you are advised to do so by your doctor. As vitamin D is a fat-soluble vitamin, it is absorbed through the small intestine with dietary fat and is excreted slowly. Too much vitamin D can therefore cause toxicity, as the body is unable to rapidly excrete vitamin D. High levels of vitamin D can also cause high calcium levels, which can lead to nausea, dehydration and constipation.
14. YOU NEED 200-800IU OF VITAMIN D PER DAY
Assuming a person has minimal sunlight exposure, the recommended daily intake of vitamin D in Australia is:
5 micrograms (200IU) for children, adolescents and adults 19-50 years
10 micrograms (400IU) for adults aged 51-70 years
15 micrograms (600IU-800IU) for adults over 70 years
Vitamin D is found in small amounts in animal-sourced foods such as oily fish (salmon, trout, swordfish, mackerel, tuna, herring, sardines), eggs and meat. Vitamin D is also added to fortified foods such as fortified milk and margarine.
For most Australians, however, it is difficult to obtain enough vitamin D from diet alone. Most people only get 5-10% of their vitamin D from food. The main source of vitamin D is through the direct action of sunlight on the skin.
15. IT IS IMPORTANT TO BALANCE YOUR NEED FOR SUN EXPOSURE WITH THE RISK OF SUN DAMAGE
The amount of sun needed to produce enough vitamin D depends on the time of day, the season, location, a person’s skin type and the area of skin exposed. There is minimal transmission of UVB radiation through normal clear windows, so sun exposure should be outdoors.
In summer, 5-10 minutes of sun exposure is best in mid morning or mid afternoon (outside peak UV times). In winter, 7-30 minutes of sun exposure is needed, preferably around midday. (Figure 1) For people with darker skin types, 3-6 times longer exposure times are required.
Figure 1.
It is important to balance the need for sun exposure to produce adequate vitamin D and at the same time avoid the risk of skin damage from too much exposure. Your body can only absorb a limited amount of vitamin D at a time, therefore prolonged sun exposure does not cause vitamin D levels to continue to increase but it will increase your risk of skin cancer. Around 2 in 3 Australians will be diagnosed with skin cancer in their lifetime and around 2000 Australians die each year as a result, so protection against excessive UV exposure remains vital.
When the UV index is above 3, you should use sun protection measures (hat, sunscreen, clothing, sunglasses and staying in the shade) if you are outdoors for more than a few minutes. When the UV index is below 3, sun protection is generally not required. (Figure 2)
Figure 2.
16. A BLOOD TEST CAN CHECK VITAMIN D LEVELS IF YOU ARE AT RISK OF VITAMIN D DEFICIENCY
Your vitamin D level can be determined with a blood test. The test measures the total concentration of vitamin D, 25-hydroxyvitamin D (25-OHD) in a person’s blood. Not everyone, however will require a blood test. If you are at risk of vitamin D deficiency or at risk of the medical conditions that result from vitamin D deficiency, your doctor may recommend that you check your vitamin D level. If you are found to be vitamin D deficient, your doctor may recommend that you take supplements for a specified period of time. Vitamin D deficiency can be mild 30-49nmol/L, moderate 12.5-29nmol/L or severe <12.5nmol/L.
If you are concerned about your vitamin D levels, see your doctor for further advice.
Dr Lufi and Dr Leah
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