Think you’re getting enough? Think again, says naturopath Teresa Mitchell-Paterson.

Your first association for vitamin D is probably the role it plays in maintaining strong bones by boosting the body’s ability to absorb calcium; it is well known that vitamin D supplementation reduces the risk of bone loss and fracture, especially in the elderly. However, its many other functions are less well known, including its ability to help prevent diabetes, hypertension, and autoimmune diseases, like multiple sclerosis, as well as reducing the risk for certain cancers, including of the colon, breast, and prostate. More conditions influenced by a lack of vitamin D are depression, seizures, migraines, polycystic ovary syndrome, and inflammatory problems, including lower back pain: clinical trials show that, in some cases, vitamin D supplementation can actually cure this problem.

The sunshine vitamin

A pro-vitamin that is converted in the body to its active form, vitamin D commences its journey in the bowel epithelium as ergosterol. It oxidises the cholesterol from our food in the blood in order to create activated pro-vitamin D, or 7-dehydrocholesterol, which is transported to the skin where it sits on the top of the epidermis and, through exposure to UV radiation, is converted into pre-vitamin D3, or cholecalciferol.

To achieve this conversion, we need a minimal erythemal dose (MED) of sunlight daily, about 15 minutes, morning or afternoon, at a time when we’re less likely to burn as the skin must be free of sunscreen. It doesn’t have to be the entire body: just hands, legs and face. Those with darker skin may require up to three times as long due to the natural protection endowed by their melanocytes, while anybody who lives above latitude 40 degrees north, or below latitude 40 degrees south, needs to take vitamin D via food or supplements, because they won’t get enough from sunlight outside summer.

There’s a widely held belief that in sunny Australia, we should have all the vitamin D we need - but the reality is one in three people are deficient. Despite our abundance of sunshine, the reality is up to one in three Australians are deficient. This is largely attributed to our slip-slap-slop efficiency, which is great to prevent melanoma, but unfortunately reduces our ability to convert 7-dehydrocholesterol into cholecalciferol. Office and shift workers also miss out because they’re commuting before the sun comes out and heading home as it sets. It’s critical to take breaks outside, again ensuring skin is free from sunscreen and chemical skin creams. Other factors which affect conversion are:

* Chemicals: Sodium lauryl sulphate (present in skin washes, bubble baths, mineral body lotions, fake tans, body scrubs) strips natural oils from the skin’s surface and interferes with the conversion of vitamin D to its active form. Ideally, use a mild soap to wash areas that need it, and simply rinse the rest of the body as we mostly don’t get very dirty. Practise skin brushing as it stimulates the skin’s natural oils.
* Age: The decline in the body’s ability to synthesise vitamin D through the skin starts at 20, and by the time we’re 50 it has halved. Supplements are essential after age 50; check with your healthcare provider to ensure you’re within range, which is 50-150, as we find many people are coming in at 35-43.
* Medications: Any drug that interferes with liver function and cholesterol production will decrease the conversion of vitamin D, including thiazide diuretics; statins; prednisone and corticosteroids; weight-loss drugs like Xenical, which gets rid of fat and so prevents absorption of vitamin D; Dilantin for epileptic seizures; and any heavily medicated disease, such as cancer. If you take any of these drugs, get a serum vitamin D test.
* Alcohol: Because a healthy liver is essential for the synthesis of vitamin D, binge drinking is not a good idea.
* Bowel problems: People with irritable bowel syndrome or inflammatory bowel conditions like Crohn’s and coeliac disease, which involve frequent bowel movements, will experience a lack of absorption and conversion of vitamin D.
* Obesity: People risk deficiency because their body fat actually binds to some of the vitamin D and prevents it from entering the blood.
Children are also at risk as a consequence of our slip-slop-slapping skills, so ensure they’re obtaining some vitamin D from sunlight and food. Admittedly, food sources are limited: D is found in whole milk, fortified foods, fatty fish (salmon, tuna, mackerel, sardines), and very small amounts in beef liver, cheese, and egg yolk.

Recommended doses

These vary according to age: the older you are, the more you need. A recent review suggests everybody should have 1,000 IU. Children can take up to 2,000 IU and adults up to 4,000 IU, while studies of people in aged-care facilities suggest up to 10,000 IU for a three-month period to bring levels back up to normal. There are two supplemental forms: D2 (ergocalciferol) and D3 (cholecalciferol). Both will increase vitamin D in the blood, although some claim cholecalciferol is better absorbed. Ergocalciferol perhaps takes a bit longer to boost levels. The key message with supplementation is to take as prescribed, and test in three months. The safe upper limit is 4,000 IU. Before taking more, it’s essential to have levels checked, as too much vitamin D can be toxic, causing vomiting, constipation, fatigue, and weight loss.

Naturopath Teresa Mitchell-Paterson, BHSc, MHSc, is a member of the Australian Traditional Medicine Society.