April 28, 2018
A pretty intense molecule made right under our skin in broad daylight. But little do we know that Vitamin D is actually not a vitamin but a hormone. This means it does exponentially more than a nutrient nourishing our cells. Vitamin D binds to receptors in the body to produce certain functions and in fact, it is so important to our bodies that it regulates its own production. Many of the body’s organs and tissues have receptors for vitamin D so getting a sufficient amount of vitamin D is not only important for normal growth and development of bones but may improve resistance against certain diseases. Vitamin D deficiency has now been linked to breast cancer, colon cancer, prostate cancer, heart disease, depression and weight gain, although more evidence needs to emerge before we can be confident of these benefits. While scientists are teasing out vitamin D’s other possible functions, here are 11 things that you probably don’t know about it.
Vitamin D may play important roles in regulating the immune system and in preventing diseases like multiple sclerosis, infectious diseases, tuberculosis, heart diseases, the seasonal flu and even some cancers. Although these findings are still preliminary, researchers have reasonably concluded that taking moderate doses of vitamin D regularly have a strong safety record and do confer more health benefits than we know. However experts advised to avoid extremely high single doses.
Darker skin absorbs less sunlight and may need 20 to 30 times as much exposure to sunlight as fair-skinned people to generate the same amount of vitamin D. Other factors such as obesity and those aged above 65 are also at risk of vitamin D deficiency and should discuss with their physicians if vitamin D supplements will benefit them.
Few foods are naturally rich in vitamin D. The biggest, but still modest, dietary sources of vitamin D are fortified breakfast cereals and dairy products, fatty fish such as salmon and tuna.
Dose-wise, many experts view the current recommended intake guidelines of 400 IU for adults below 65 as overly conservative and do not give due weight to the latest science on vitamin D and health. For bone health and chronic disease prevention, many people are likely to need more vitamin D than the current guidelines recommend. Safety-wise, most experts acknowledged that even at 4,000 IU per day, vitamin D shows no good evidence of harm.
The sun emits three different types of radiation, UVA, UVB and UVC. UVB radiation is the one that is responsible for generating vitamin D under the skin. UVB rays cannot penetrate glass windows so in order to obtain any vitamin D from sunlight, the skin must come into direct contact with the sun’s UVB rays.
Even if you have a calcium-rich diet, without enough vitamin D, you cannot absorb the calcium into your bones and cells where it’s needed.
When ultraviolet rays from sunlight penetrate the skin, they react with 7-dehydrocholesterol which is a precursor to cholesterol. This reaction forms vitamin D3 (cholecalciferol) in the skin. However, vitamin D needs to be “activated” before it can be used. It is then quickly converted by the liver to the precursor 25(OH)D and then further converted in the kidneys to the hormone 1,25(OH)D2 – the active form of vitamin D.