Kiwis have a very fragile relationship with the sun. We need it to keep us healthy but too much sun is bad for our skin. The sun’s rays are crucial for our body’s synthesis of vitamin D and a little exposure goes a long way in summer. In winter, however, we need to be wary of developing a deficiency, because this sun-activated vitamin is responsible for many important functions of the body, as our nutritionists explain.
How much exposure to the sun do we need to produce sufficient vitamin D?
“We have a huge [vitamin D] deficiency problem in New Zealand,” says natural fertility and women’s health expert Rene Schliebs. Vitamin D is synthesised by sunlight and you’ll usually only need 15-20 minutes of sunlight when summer is in full swing, but this increases to more than four hours in winter, explains Schliebs. Limited sunlight means limited production of vitamin D.
What are the symptoms of vitamin D deficiency and what problems does it cause?
Depending on the severity, symptoms of a vitamin D deficiency can range from “loss of appetite, a burning sensation in the mouth and throat, diarrhoea, depression, insomnia, visual problems and weight loss”, says Renée Leonard-Stainton, naturopath and nutritionist at Renée Naturally. In the worst cases, it can even lead to bone diseases like rickets and osteomalacia. Schliebs adds that a deficiency in this vitamin can also cause “softening of bones and teeth, cramps, and hypoparathyroidism” as well as raising your cancer risk.
What is the main benefit of vitamin D?
Vitamin D is crucial for good bone health, explains Leonard-Stainton. It can also help to prevent depression and is involved in “regulation of the heartbeat”. Our bodies need it to absorb and use calcium and phosphorous, and it is “especially important for normal growth and development of bones and teeth in children”. Schliebs adds that it acts more like a hormone than a vitamin by regulating more than 2,000 genes and says it’s “vital for immune system function”.
What are the sources of vitamin D found in supplements?
Vitamin D takes two main forms in supplements. The first is vegetable-based D2, which Schliebs explains is made by “irradiating fungus”. The second, and the kind produced naturally by the body, is animal-based D3, which is “derived from either fish oil or lanolin from sheep’s wool, which is exposed to sunlight to activate it”. Schliebs says D3 is the most potent type. Leonard-Stainton describes a third, synthetic form: vitamin D5. She adds: “The form of vitamin D that we get from food or supplements is not fully active. It requires conversion by the liver and then by the kidneys before it becomes fully active. This is why people with liver or kidney disorders are at a higher risk of developing osteoporosis.”
Why is vitamin D important for bone health?
Good bone strength and health is dependent on sufficient levels of vitamin D in the body. Without this they become brittle, because “they stop absorbing calcium and phosphorous adequately”, explains Schliebs.
Are vegetarians and vegans more at risk of vitamin D deficiency?
Vegetarians and vegans living in areas with plenty of sunlight hours are unlikely to experience any greater risk. However, “it is more difficult for them to obtain adequate levels from food sources,” warns Schliebs.
Good dietary sources of vitamin D include:
• Egg yolk
• Chicken liver
• Milk
• Sprouted seeds
• Fish liver oils
• Fatty saltwater fish
• Dairy products
• Butter
• Dandelion greens
• Oatmeal
• Kumara
• Vegetable oils
Words by: Rachael Harwood
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