March 22, 2016
There is virtually no aspect of your health that is not affected by Vitamin D. We have vitamin D receptors throughout our bodies, including the heart, kidneys, brain, colon, muscle and immune cells. This wide distribution of receptors highlights the importance of this vitamin to many of the body’s functions, and helps to explain why vitamin D deficiency affects not only bone health, but also other systems in the body. Vitamin D deficiency has been linked to various types of cancer, heart disease, depression, multiple sclerosis, lupus, high blood pressure, weight gain, diabetes, infections, colds, flu and a growing list of other illnesses.
Vitamin D is a fat-soluble vitamin that is naturally present in few foods, added to some, available as a dietary supplement and produced when ultraviolet rays from sunlight strike the skin and triggers vitamin D synthesis.
Table of Contents
- 1 How does your Body Make Vitamin D?
- 2 Do I need to take Vitamin D Supplements?
- 3 Can I get my Vitamin D from my diet?
- 4 What is the Difference Between Vitamin D2 and Vitamin D3?
- 5 How do I Know What my Vitamin D Levels Are?
- 6 How Much Vitamin D do I Need to Take?
- 7 How Much Vitamin D Should I Have in my Body?
- 8 Can I Take Too Much Vitamin D?
- 9 Vitamin D Co-Factors?
- 10 Are Doses of Vitamin D Over 5,000 IU Safe?
- 11 How Controversial are the IOM’s Recommendations?
- 12 What Does Evolutionary Anthropology Teach Us?
- 13 Benefits of Higher Vitamin D Levels
- 14 Conclusion
- 15 Share this:
How does your Body Make Vitamin D?
Vitamin D obtained from the sun, food, and supplements is biologically inert and must undergo two processes in the body to be active. The first occurs in the liver and converts vitamin D to 25-hydroxyvitamin D [25(OH)D]. The second occurs primarily in the kidney and forms the active 1,25-dihydroxyvitamin D [1,25(OH)2D] or calcitriol.
Do I need to take Vitamin D Supplements?
The simple answer is that we all need vitamin D and that most of of us are able to get at least some of the required amount from our diet and sun exposure for at least part of the year.
There is a mistaken belief that as little as ten minutes of daily sunlight exposure on your hands and face will provide you with your daily Vitamin D requirements year round. Unfortunately, there is far more to it: it depends on where you live, the time of year and even your skin type or whether you are wearing sunscreen. The NCBI (The National Center for Biotechnology Information) has determined for example, that “exposure to winter sunlight in Boston and Edmonton will not promote vitamin D3 synthesis in human skin.”(1)
Simply put, if you live anywhere cold or rainy in the winter, you will have to supplement at least to some extent, and depending on your lifestyle, possibly year round irrespective of where you live.
Can I get my Vitamin D from my diet?
Yes, but not in significant amounts. There are only a few naturally occurring food sources of vitamin D. These include fatty fish, fish liver oil, and egg yolk. Cod liver oil is the densest nutrient source available at a reasonable cost.
Some foods are fortified with vitamin D, with vitamin D2 and D3. Cow’s milk is widely fortified as are other processed foods. Vitamin D fortification in developed countries was undertaken as an inexpensive and effective way to prevent “Rickets” which is a serious disorder of bone development mainly found in children, especially those who are desperately poor.
See our article: Dietary Sources of Vitamin D.
What is the Difference Between Vitamin D2 and Vitamin D3?
Vitamin D3 (cholecalciferol) is a natural by-product of animal origin that is created from exposure to the sun, while vitamin D2 (ergocalciferol) is a synthetic by-product of plant origin.
Even though there are similarities between Vitamin D2 and D3, vitamin D3 is more readily absorbed and utilized by the human body. There is no reason to supplement with Vitamin D2 (2) although unfortunately it is still used to fortify food. In Canada milk is fortified with vitamin D3, and while optional, nearly all milk sold in the U.S. is also fortified with vitamin D3.
How do I Know What my Vitamin D Levels Are?
Fortunately, there is a relatively simple blood test that measures serum concentration of 25 hydroxyvitamin D, the active form of vitamin D in the liver. This test is the best way to determine someone’s vitamin D levels and reflects the total amount of vitamin D from food, supplements and sun exposure.
How Much Vitamin D do I Need to Take?
There is no clear consensus as to the required amount. To start with, each body is unique and processes vitamin D differently. To further complicate matters, away from the equator UVB levels in sunlight are too weak, for 4-6 months of the year, to make any significant amount of vitamin D naturally.
The “official answer” comes from the US Institute of Medicine (IOM) which was asked by the Canadian and US governments to assess the current data on health outcomes associated with calcium and vitamin D, as well as updating the nutrient reference values, known as Dietary Reference Intakes (DRIs).(3)
In 2010 the IOM produced a report with recommendations largely aimed at bone health which calls for 600 IU of vitamin D daily for all ages up to age 70 and 800 IU after age 71. This assumes a limited amount of sun exposure. The report declared a safe upper limit of 4,000 IU daily for those above 9 years of age and a safe upper limit of 1,000 to 3,000 IU per day for children depending on age.(3) These recommendation are generally accepted, with some authorities recommending slightly higher levels. The Vitamin D council–a nonprofit research group– recommends 5,000 IU daily
How Much Vitamin D Should I Have in my Body?
The answer to this question is controversial because research concludes that the official recommended levels are far too low. According to the IOM, vitamin D level of 50 nmol/l (20 ng/ml) is sufficient for 97.5 percent of the population and the maximum level ought not to exceed 125 nmol/L (50 ng/mL).(3)
This recommendation is at odds with the research. In 2009 two double blind studies concluded that 50 nmol/l (20 ng/ml) was insufficient for fracture or fall reduction. (4) (5) In addition, a very large population based analysis found that bone density increased with higher levels far beyond 50 nmol/l (20 ng/ml) in younger and older adults.(6)
The ideal blood level of vitamin D that The Vitamin D Council recommends is 125 nmol/i (50 ng/ml).(7)
According to the The National Center for Biotechnology Information (NCBI) the desirable blood level of Vitamin D is between 90-120 nmol/l (36-48 ng/ml). (8)
A study in 2010 by Dr. William Grant estimated that if Canadians raised their vitamin D blood levels to105 nmol/L (42 ng/mg) it would prevent 37,000 deaths and save $14B in associated healthcare costs.(9)
Can I Take Too Much Vitamin D?
Vitamins are classified as either fat soluble (vitamins A, D, E and K) or water soluble (vitamins B and C). Fat soluble vitamins, once they have been stored in tissues in the body, tend to remain there.
Although fairly rare, you can take too much vitamin D. Excessive amounts of this vitamin will pull too much calcium into the bloodstream, ultimately leading to a disease called hypercalcemia, which can cause calcium deposits in the joints, and calcification of the arteries. Other symptoms of hypercalcemia include muscle weakness, joint pain, confusion, loss of appetite, constipation, abnormal heart rhythm, and even kidney stones.
On the bright side, it would appear that it is nearly impossible to get too much vitamin D from sunlight. This makes sense because the form of vitamin D that we get from the sun is “inactive,” and is stored in the skin and liver until the body activates it, based on its needs. Therefore the body activates only as much it needs, which means that the levels of vitamin D from sun exposure should be the optimal levels, more on that later.
Nearly all vitamin D overdoses come from supplements or foods, and even those overdoses are extremely rare. Recent studies suggest that healthy adults can tolerate more than 10,000 IU of vitamin D per day.(10)
Vitamin D Co-Factors?
Even more good news: it would appear that vitamin D overdose is even less likely so long as its partners (co-factors) vitamin A and vitamin K2 are present in the body in sufficient quantities. It is now believed by some experts that vitamin D toxicity, when it does occur, may in fact be due to a lack of vitamin A and vitamin K2. Interestingly, the inverse seems to hold true as well for vitamin A; its toxicity may come from taking high levels of vitamin A without adequate vitamin D and vitamin K2. (11)
We believe that much can be learned from nature. When we consume vitamin D in the active form, from foods, it is most commonly found in liver (fish and mammals), where it occurs in combination with vitamin A. Where vitamin A creates compounds in the body that break down bone (osteoclasts), vitamin D creates compounds that reform bones (osteoblasts). Together they maintain the health and density of the skeletal structure.
When there is too much calcium in the blood, it is up to vitamin K2 to move it back into the skeletal structure. From this we can see that we need to look at vitamin D supplementation as part of a triumvirate that includes vitamins A and K2. By ensuring that we have adequate amounts of vitamins A and K2, it is far more likely that we can safely take higher doses of vitamin D.
Dr. Kate Rheaume-Bleue, a naturopathic physician, in her book, titled: Vitamin K2 and the Calcium Paradox: How a Little Known Vitamin Could Save Your Life, stated:
“We don’t see symptoms of vitamin D toxicity very often. But when we do, those symptoms are inappropriate calcification. That’s the symptom of vitamin D toxicity. And it is actually a lack of vitamin K2 that can cause that”.
Are Doses of Vitamin D Over 5,000 IU Safe?
There is no consensus due to the lack of credible large randomized controlled trials. Thankfully, there is currently underway a significant study at Brigham and Women’s Hospital, an affiliate of Harvard Medical School, in Boston, Massachusetts. This study, appropriately named VITAL, is an ongoing research study of 25,874 men and women across the U.S. investigating whether taking daily dietary supplements of vitamin D3 (2000 IU) or omega-3 fatty acids (Omacor® fish oil, 1 gram) reduces the risk for developing cancer, heart disease, and stroke in people who do not have a prior history of these illnesses. The results are expected in late 2017.(12)
Vitamin D is very widely researched. As of March 19, 2016, the total number of publications on the topic listed at PubMed.com was 66,891. This total compares to vitamin C at 55,646 and Vitamin E at 38,651.(13)
So even though there is a lack of large randomized studies, there is no shortage of papers and smaller studies to guide us.
For the moment the IOM remains the leading authority with regard to vitamin D recommendations.
How Controversial are the IOM’s Recommendations?
In 2015 researchers from the University of Edmonton published a paper which aimed to prove that the IOM made a calculation error in defining the vitamin D intake needed to reach and maintain 50 nmol/l (20 ng/mL). It is their contention that if the IOM had calculated it correctly, the RDA would have been ten times greater than what the IOM recommends.(14)
This conclusion was corroborated by Researchers from the University of California at San Diego and Creighton University in Omaha who claimed that their data confirmed the Institute of Medicine’s miscalculation as noted by the Canadian investigators. In a press release dated March 17, the American researchers stated that their work showed the current recommended daily intakes for vitamin D are only about one-tenth those needed to cut incidence of diseases related to vitamin D deficiency.(15)
What Does Evolutionary Anthropology Teach Us?
It is generally accepted that humans evolved in the horn of Africa, close to the Equator over 30,000 years ago. Their days were spent out in the full sun, with little or no clothing. Their skin pigment evolved and protected them from sun burns and allowed the production of vitamin D through the skin. Living and working indoors, without sunshine exposure, is a relatively recent development.
In evolutionary terms it makes sense that people with darker pigmentation living in equatorial areas would have, as a general rule, optimal serum vitamin D levels.
A very interesting 2012 study found that Massai pastoralists and Hadzabe hunter-gatherers have high serum vitamin D concentrations. The investigators measured serum 25(OH)D in 35 Massai and 25 Hadzabe and found that mean serum 25(OH)D levels were 47.7 ng/mL for the Massai, and 43.7 ng/mL for the Hadzabe. Even though the sample size was relatively small, it is significant that none of the participants was found to be vitamin D deficient. (study#16)
To get an idea of optimal vitamin D levels we can also look at studies that deal with outdoor workers to see what their levels are. As discussed earlier, vitamin D from the sun is stored in the skin and liver until the body activates it, based on its daily needs. Therefore the body activates only as much it needs, which means that levels from sun exposure should be the optimal levels.
Outdoor workers in the tropics typically have high vitamin D levels ranging from 120 to 200 nmol/L (48 to 80 ng/ml).(17) By contrast, Statistics Canada reports that the average Canadian only has a vitamin D level of 68 nmol/L (27 ng/ml).(18)
Benefits of Higher Vitamin D Levels
Here is a summary of the health benefits that Dr. Holick, PhD., M.D., Boston University School of Medicine, believes could be achieved by raising the public’s vitamin D levels to 125 nmol/L:
- Rickets, reduced by 100%
- Osteomalacia, reduced by 100%
- Cancers, all combined, reduced by 75%
- Breast Cancer, reduced by 50%
- Ovarian Cancer, reduced by 25%
- Colon Cancer, reduced by 67%
- Non-Hodgkins, reduced by 30%
- Kidney Cancer, reduced by 67%
- Endometrial Cancer, reduced by 35%
- Type 1 Diabetes, reduced by 80%
- Type 2 Diabetes, reduced by 50%
- Fractures, all combined, reduced by 50%
- Falls, women reduced by 72%
- Multiple Sclerosis, reduced by 50%
- Heart Attack, men, reduced by 50%
- Peripheral Vascular Disease, reduced by 80%
- Preeclampsia reduced by 50%
- Caesarean Section, reduced by 75%
Nearly every cell in the body uses vitamin D, and its health benefits range from reducing heart disease to boosting the immune system. It could be argued that the most important thing people can do to improve their overall health is to make sure they are getting enough of this vitamin to reach and maintain their optimal level. To that end, having a blood test is the only way to really know if you are getting enough vitamin D or not. Seasonal monitoring is also a good idea. For example, outdoor workers in low sunlight winter regions probably synthesize plenty in the summer, but not during the dark days of winter. Supplementation should be guided by how much Vitamin D people require and make use of over time because it varies as we age, change jobs, and move from place to place.