Do you need a vitamin D supplement?
Vitamin D is a very special substance to me. Not because it saved my life or anything dramatic. But its special because it is an exception to my rule of no supplements. I usually don't think being reliant on supplements is helpful, but vitamin D is different. I think everyone should take vitamin D. Seriously, everyone. And not a measly dose 200 IU a day either! 4,000? 5,000? 10,000 IU even! Well maybe not that high. But you get my drift.
So let’s start at the beginning. What is it?
Vitamin D is necessary for life (that’s what vitamins mean, in case you didn’t know – they are substances that we need in order to survive). Vitamin D is special in that all other vitamins are primarily gotten through food (there is some debate about vitamin K and B12 as gut bacteria may play a role in their production, but we mostly get them from food), but Vitamin D is made through sunlight exposure (there is some present in a foods, but not much. We will go into this more later). Vitamin D is made from cholesterol (fun fact! Most of your hormones are made from cholesterol. Cholesterol is used to make estrogen, testosterone, cortisol, aldosterone and others). Cholesterol makes its way to your skin, then sunlight hits the skin (specifically UVB) and converts it to vitamin D3 (what you buy as a supplement), also written as cholecalciferol. This compound then goes to your liver and then the kidneys where it’s converted to the active form of vitamin D.
Vitamin D is also fat soluble. That means it is like a wax or oil; it doesn’t dissolve in water. What is special about fat soluble vitamins though, is that they are easily able to travel into our cells’ nuclei and change our genes. This means the vitamin D in our body is responsible for so many functions that it’s impossible to list them all. I will go through some of the big, famous functions in a little bit. Fat soluble vitamins (A,D,E and K) are also different from water soluble vitamins in that they can become toxic at lower doses than water soluble ones. With water soluble vitamins, you have to ingest a lot to get a toxic reaction, because you can’t really store these vitamins for a long time in the body. Fat soluble vitamins on the other hand can be stored for very long amounts of time in the body, which means you can get a toxic dose of the vitamin if you have a moderately high dose over a long period of time. In other words, if you take too much vitamin C, you get diarrhea but then the extra vitamin C is gone. You don’t have any other problems. With vitamin D, if you take too much (what is “too much” is defined in the next blog post), you don’t just get diarrhea, you have symptoms of hypercalcemia, such as abdominal pain, constipation, nausea, vomiting, confusion, delirium, psychosis, and muscle weakness. This can go on for a long time if you don’t get treatment (provided you have stopped taking vitamin D). The reason the effects last so long is because the vitamin D has accumulated in your fat stores.
What does it do?
Vitamin D is famous for its role in bone formation and maintenance. It does this by increasing how much calcium you absorb and improving mineralization of bones, which therefore helps children develop strong bones and helps adults maintain strong bones. Osteomalacia and Ricket’s are severe bone disorders caused by vitamin D deficiency that helped by vitamin D supplementation. However vitamin D regulates over 1,000 genes in our body, impacting our sugar metabolism, immune system (by improving our ability to fight infections, but also reduces the risk of autoimmune disorders), cardiovascular system and oncogenic (cancer-causing) cells, and more.
In the immune system, vitamin D makes the process of recognizing pathogens and destroying them before they create an infection (called the innate immune system, think of it as a guard dog for your body) more efficient (“deadly” for the pathogen) and plays a role in antibody production. Low vitamin D increases infection rates and autoimmune disease rates. Supplementation seems to help decrease rates of infection and improve the symptoms of some autoimmune diseases. Some people believe the reason the winter is the “flu season” is due to the fact that people become vitamin D deficient in the winter, when sun exposure no longer triggers vitamin D production.
The cardiovascular system is also potently affected by vitamin D, although the mechanisms are not well understood. Vitamin D dramatically decreases the hormones that control blood pressure (even though in one study, only a 4 mmHg change was shown. Meaning the average person dropped from 150/80 mmHg to 145/80 mmHg for example. This is a small change for most people, so it’s not too exciting a finding). Vitamin D also decreases inflammation in arteries themselves, which may decrease the risk of atherosclerosis and blockages.
A lot of the vitamin D excitement right now is in the cancer arena. Specifically, prostate, breast ( by as much as 50% in a couple of studies) and colon cancer have been found to be linked to vitamin D deficiency. One study even found a 15% reduction in risk of all advanced cancers if the person had normal vitamin D levels.
But why do I need to take a pill?
Vitamin D is synthesized in response to sunlight, as I said before. If you are a light skinned person “a half-hour in the summer sun in a bathing suit can initiate the release of 50,000 IU vitamin D into the circulation…this same amount of exposure yields 20,000–30,000 IU in tanned individuals and 8,000–10,000 IU in dark-skinned people” (read more here). For context, the recommended amount to take in a supplement every day for adults in Canada is 600 IU with the “high but only slightly dangerous level” (aka tolerable upper intake level) amount being 4,000 IU – even though we obviously make much more than that naturally.
We can only synthesize vitamin D when the UV index is 3 or above. Most weather apps include the UV index, so you can find out how strong the UV light is where you are on any given day. However, you can also judge this by looking at your shadow – when you shadow is longer than you are, you are not synthesizing vitamin D. For different areas of the world, you will synthesize vitamin D at different times of the year. I am near Toronto, and here vitamin D can only be synthesized in March-September.
If you are cleverly paying rapt attention, you will now know that vitamin D is stored, and so why would we need a supplement over the winter if we made lots of extra during the summer?
The reason is not well known or researched. However Dr. Vieth, a vitamin D researcher in Toronto, has noticed that there are papers that show for people who live where there is a vitamin D “winter” (a long time in the year when vitamin D cannot be produced), the people with high vitamin D levels are at an increased risk of certain conditions. He says this seems to be true only for people who live in northern climates – why would this be? He believes that people in northern climates who are outdoors all summer (and therefore are the ones with high vitamin D levels) are the people with the greatest variation in vitamin D. He believes the variation is very damaging. In other words, not taking any vitamin D after spending a whole summer outdoors will cause your vitamin D levels to fall quite a bit over the next few months. Then summer comes, and they spike again. This yo-yoing may be detrimental to health. Therefore “desirable [vitamin D] concentrations are ones that are both high and stable”.
Food also is notoriously poor in vitamin D, if you want more than the RDA (600 IU). This is true even if you are eating fortified eggs or milk. Traditionally, people in a vitamin D winter got vitamin D from cod liver oil and/or other fatty fish. Theoretically this is still possible, but cod liver is still a supplement and to get enough from fish, you would need roughly a pound of blue fish, 4 oz of wild salmon, a pound of farmed salmon, or 2 lbs of cod a day to get 4000 IU. That’s a lot of fish! And I think we all know there are massive issues with the environmental impact of fishing on the world’s ecosystems.
So it would seem the best way to get stable vitamin D levels these days is to supplement. But how much is too much? Read on in the next post.