Vitamin D
D2 & D3
At some point in your life, you may have heard of the bone deforming disease called rickets(bowed legs). Amazingly, this disease has been described going all the way back to ancient times. It wasn’t until 1918 that scientists discovered they could cure dogs that had rickets by feeding them cod liver oil. Once the discovery of vitamin D was made, millions of children began taking a daily dose of cod liver oil to prevent bone deformities.
Vitamin D is quite interesting in that there are two forms D2 & D3 and in the presence of sunlight skin cells can synthesize a sufficient supply from a form of cholesterol. The internal making sounds simple but there are many factors that can prevent people from being able to make adequate amounts of vitamin D.
Vitamin D2 comes from food sources, the richest sources being fatty fish (salmon, herring, mackerel & sardines), cod liver oil, some fortified cereals and starting in 1933 fortified milk. From this list of food, you can probably understand why they had to find a commonly eaten food source to fortify, otherwise most American’s would never get enough vitamin D. As a nation, we simply don’t eat enough fatty fish. Also, if you’ve ever tasted cod liver oil, you know how horrible it is. My mom and dad used to make us take a teaspoon of that as a form of punishment when we were bratty. I was shocked when I saw a big bottle of it at a breakfast buffet in Sweden, alongside it sat little shot glasses you could fill up and toss back. Uggghhhhh, again we aren’t accustomed to fatty fish like other countries.
Vitamin D3 synthesis is fascinating but complicated. Several things have to align in order for someone to be able to synthesize enough to support their bodies need. The process begins with a precursor of cholesterol being synthesized in the skin, following that the skin must be exposed to sunlight for a chemical transformation to happen which forms D3. The vitamin D3 then enters the bloodstream where it is transported to the liver and kidneys where it undergoes yet another transformation to its active form. Whhhewwww…see what I mean about it being complicated. But wait, we’re not done yet.
Some people could get 80 to 100% of their vitamin D3 through sun exposure but the percentage greatly depends on the time of day, what season it is, geographic location, age, skin color and if the person is wearing sunscreen. The further away you get from the equator, the less availability of UV light there is. The more pigment a persons skin has (darker), more UV light is blocked, preventing vitamin D3 synthesis. By the time someone reaches the age of 70, their ability to synthesize D3 has decreased by 70%, so supplements are usually prescribed to prevent deficiency. Wearing sunscreen with SPF 8 or higher prevents synthesis from occurring.
It’s believed that in order to synthesize D3, you must expose a large portion of skin (hands, face & arms) without sunscreen 2 or 3 times a week for at least 10 to 15 minutes. Darker skin may need 30 minutes or more sun exposure. There’s a problem with this scenario, what about sun damage and skin cancer? Thankfully, we have multiple options to get our vitamin D and we don’t have to rely on sun exposure. Adults in North America need 600 IU of vitamin D each day (remember our sun exposure is affected due to our geographic location). This amount is based on minimal sun exposure.
Vitamin D is very important in maintaining the body’s concentration of calcium and phosphorus (bone & heart health). Bone deformities are caused when blood calcium and phosphorus levels fall or stay low for prolonged periods of time. Vitamin D and parathyroid hormone (PTH) release minerals from the bone to restore blood levels, which are necessary for basic bodily functions. This is why you will usually see calcium and vitamin D together in supplements, they go hand in hand.
Toxicity can occur, and an upper limit of 4000 IUs has been set for people 9 years of age and older. Too much vitamin D can cause overabsorption of calcium which can lead to deposits of calcium in the kidneys, heart and lungs. It can also cause nausea, vomiting, bone demineralization, weakness, joint pain and kidney dysfunction. If caught early it is treatable but if overuse continues it can be fatal.
In children, deficiencies can cause bones to weaken and bow (rickets). Other signs of rickets are enlarged heads, joints and rib cages and a deformed pelvis. In adults, deficiency is called osteomalacia, which means soft bones. This can result in fractures of the hip, spine and other bones. This is seen mostly in adults with liver or kidney disease or other intestinal diseases that impair fat absorption (remember vitamin D is a fat-soluble vitamin). The elderly are also at risk because of low sun exposure, poor diets and impaired kidney function.
It is important to understand that for most of us, there are very few sources of vitamin D, especially if we are wary of sun exposure and spend a lot of time indoors. If you don’t drink milk, you may want to speak with your doctor about taking a supplement.