Recommended Target Range (optimum health): 124-200 nmol/l
Deficient level: <50 nmol/l
Insufficient level: 50-74 nmol/l
Sufficient level: 75-250 nmol/l
Excessive level: >250 nmol/l
Vitamin D is a fat-soluble vitamin, sometimes called the “sunshine vitamin” because it’s produced in your skin in response to sunlight. Your body naturally produces Vitamin D upon sun exposure and can also be derived from certain foods and supplements.
Vitamin D has several important functions, including the regulation of calcium and phosphorus absorption (bones & teeth) and immune function (resistance against disease). Vitamin D has other roles in the body, including modulation of cell growth, neuromuscular and immune function, and reduction of inflammation Many genes are also modulated in part by vitamin D.
In addition to its primary benefits, research suggests that vitamin D may also play a role in:
- In one study, people taking a daily vitamin D supplement were able to lose more weight than subjects taking a placebo supplement. The scientists said the extra vitamin D had an appetite-suppressing effect.
- In another study, overweight people who took a daily vitamin D supplement improved their heart disease risk markers.
- Reducing your risk of multiple sclerosis, according to a 2006 study published in the Journal of the American Medical Association
- Decreasing your chance of developing heart disease, according to 2008 findings published in Circulation
- Helping to reduce your likelihood of developing the flu, according to 2010 research published in the American Journal of Clinical Nutrition
Research has shown that vitamin D might play an important role in regulating mood. In one study, scientists found that people with depression who received vitamin D supplements noticed an improvement in their symptoms. Other studies have shown that Vitamin D deficiency was more common in those suffering with anxiety and depression.
So, who is at risk of deficiency?
- Living in an area with high pollution
- Regular users of sunscreen
- Those spending more time indoors
- Living in big cities where buildings block sunlight
- Having darker skin. (The higher the levels of melanin, the less vitamin D the skin can absorb.)
These factors contribute to vitamin D deficiency in an increasing number of people. That’s why it’s important to get some of your vitamin D from sources besides sunlight.
What are some of the notable symptoms of a vitamin D deficiency?
- Tiredness, aches and pains, and a general sense of feeling unwell
- Severe bone or muscle pain/weakness that may cause difficulty climbing stairs or getting up from the floor
- Stress fractures, especially in your legs, pelvis, and hips
It’s very common in Australia to be deficient in Vitamin D. This is likely due to being a sun-smart nation, increases in body weight, reduced milk intake and greater time spent indoors.
Nutrient deficiencies are usually the result of dietary inadequacy, impaired absorption and use, increased requirement, or increased excretion. A vitamin D deficiency can occur when usual intake is lower than recommended levels over time, exposure to sunlight is limited, the kidneys cannot convert 25(OH)D to its active form, or absorption of vitamin D from the digestive tract is inadequate. Vitamin D-deficient diets are associated with milk allergy, lactose intolerance, ovo-vegetarianism, and veganism.
Older adults are at increased risk of developing vitamin D insufficiency in part because, as they age, skin cannot synthesize vitamin D as efficiently, they are likely to spend more time indoors, and they may have inadequate intakes of the vitamin.
People with limited sun exposure
Homebound individuals, women who wear long robes and head coverings for religious reasons, and people with occupations that limit sun exposure are unlikely to obtain adequate vitamin D from sunlight.
People with dark skin
Greater amounts of the pigment melanin in our skin results in darker skin and reduce the skin’s ability to produce vitamin D from sunlight.
People with inflammatory bowel disease and other conditions causing fat malabsorption
Because vitamin D is a fat-soluble vitamin, its absorption depends on the gut’s ability to absorb dietary fat. Individuals who have a reduced ability to absorb dietary fat might require vitamin D supplementation. Fat malabsorption is associated with a variety of medical conditions, including some forms of liver disease, cystic fibrosis, celiac disease, and Crohn’s disease.
People who are obese or who have undergone gastric bypass surgery
A body mass index ≥30 is associated with lower Vitamin D levels compared with non-obese individuals; people who are obese may need larger than usual intakes of vitamin D to achieve healthy levels. In obese individuals, a greater amounts of body fat sequester more of the vitamin and alter its release into the circulation. Obese individuals who have undergone gastric bypass surgery may become vitamin D deficient, as part of the small intestine where vitamin D is absorbed is bypassed.
Risks from Excessive Vitamin D
Vitamin D toxicity can cause non-specific symptoms such as anorexia, weight loss, polyuria, and heart arrhythmias. More seriously, it can also raise blood levels of calcium which leads to vascular and tissue calcification, with subsequent damage to the heart, blood vessels, and kidneys.
Interactions with Medications
Vitamin D supplements have the potential to interact with several types of medications. A few examples are provided below. Individuals taking these medications on a regular basis should discuss vitamin D intakes with their healthcare providers.
Corticosteroid medications such as prednisone, often prescribed to reduce inflammation, can reduce calcium absorption and impair vitamin D metabolism. These effects can further contribute to the loss of bone and the development of osteoporosis associated with their long-term use.
Both the weight-loss drug orlistat and the cholesterol-lowering drug cholestyramine can reduce the absorption of vitamin D and other fat-soluble vitamins. Some drugs used to prevent and control epileptic seizures, increase liver metabolism of vitamin D to inactive compounds and reduce calcium absorption.
Which foods contain Vitamin D?
Very few foods in nature contain vitamin D. The flesh of fatty fish (such as salmon, tuna, and mackerel) and fish liver oils are among the best sources.
Small amounts of vitamin D are found in beef liver, cheese, and egg yolks.
Fortified foods, such as milk, provide most of the vitamin D in the Western diet. Other dairy products, such as cheese, are generally not fortified.
If your blood test indicates a Vitamin D deficiency, a daily ongoing supplement may be your best option to ensure your levels reach and remain in a healthy range. Speak to your GP or local pharmacist about your best options.
Most people meet at least some of their vitamin D needs through exposure to sunlight. It has been suggested by some vitamin D researchers, that approximately 5–30 minutes of sun exposure between 10 AM and 3 PM at least twice a week to the face, arms, legs, or back without sunscreen usually lead to sufficient vitamin D synthesis. Individuals with limited sun exposure need to include good sources of vitamin D in their diet and/or take a supplement to achieve recommended levels of intake.