As with all nutrients, our bodies need vitamin D from the environment (through food or sunlight in this case) to function properly. Vitamin D has a particularly important role in bone health by helping with calcium absorption. This is a very clear relationship as its classic deficiency symptoms are diseases of “soft bones” – rickets in children and osteoporosis and fractures in adults (Bilke DD, 2014). However, with the discovery of vitamin D receptors in virtually every type of cell in the body (Pludowski et al. 2018), we have found that vitamin D affects many other parts of the body, like the immune system (Ginde 2009) and the cardiovascular system (Michaelsson et al. 2010). This combination of health benefits may be why several studies have found that those with higher vitamin D blood levels live better for longer (Garland et al. 2014). So, we need vitamin D to build and keep our bones strong, but also to help the rest of our body work like it should.
Vitamin D3 is the primary raw material to make active and usable vitamin D. It is produced when the body is exposed to sunlight (ultraviolet B radiation sunlight). Our bodies are amazingly efficient when it comes to producing vitamin D3; brief sunlight exposure of the arms and face will enable our body to produce 200 international units (IU) of vitamin D3. The precise amount of vitamin D3 produced will vary depending on factors such as skin type, geographical location, season, and time of the day. Vitamin D can also come from our diet but there are very few foods in nature that contain it. The best sources of Vitamin D in nature are fatty fish like salmon, tuna, mackerel, as well as cheese, mushrooms, apples, egg yolks, sardines and fortified foods. Finally, supplements are a potent source of Vitamin D and raise blood levels effectively.
It depends! At OmegaQuant we recommend aiming for a Vitamin D blood level >30 ng/mL or >75 nmol/L, but that can be achieved in several ways. Some people may be able to reach this level through exposure to the sun, while some may achieve it through a high-fish diet and fortified foods, and others may take a supplement. Still, most will need a combination of two or three of these. If you go the supplement route, the US Institute of Medicine recommends taking no more than 4000 IU per day on average, but, beyond that, how much supplemental vitamin D you should take depends on your blood level.
The best way to know what you need to do to maintain a desirable blood level of vitamin D is to test regularly and change your habits accordingly. There is a seasonal variability in blood levels depending on your latitude, so your levels could drop during the darkest part of the year and you might want to supplement during that time. On the other hand, during the summer you might get enough through vitamin D through sun exposure and not need any supplemental vitamin D.
There is not yet an agreed upon “optimal” Vitamin D level in the scientific community. This mostly comes from a disagreement on “deficiency” (Taylor C, et al. 2018) vs “optimal” blood levels (Holick MF. 2017) and what endpoint is being considered, i.e. bone health vs. infection risk. At OmegaQuant, we recommend aiming for a level of at least 30 ng/mL or 75 nmol/L. The evidence for the 30 ng/mL or 75 nmol/L cut off is demonstrated by Garland et al. 2014 where the hazard ratio for mortality plateaus around 30 ng/mL or 75 nmol/L, by Michaelsson et al. 2010 where the lowest risk for death from all-causes, cancer and cardiovascular disease is at 30 ng/mL or 75 nmol/L, by Ginde et al. 2009 where those with levels >30 ng/mL or >75 nmol/L have the lowest risk of upper respiratory tract infections, and by Miliku et al. 2016 where pregnant women with levels >30 ng/mL or >75 nmol/L were at the lowest risk of preterm birth, as well as babies born with low birth weight and small for gestational age. This seems like an excellent target level for several different populations and health states.
You may notice that none of these outcomes are related to bone health (rickets in kids and osteoporosis/hip fracture risk in adults), the primary health outcome related to a deficiency in Vitamin D. For this endpoint, according to the Institute of Medicine, a serum level of >20 ng/mL or >50 nmol/L is considered sufficient and <12.5 ng/mL or <31.25 nmol/L is deficient. From OmegaQuant’s perspective, optimal vitamin D levels are considered more from a “whole health” perspective rather than specific to bone health, thus the higher target of at least 30 ng/mL or 75 nmol/L.
You can take a Vitamin D test at any time. This test is a long-term stable view of your Vitamin D intake and will not be affected by any short-term dietary or supplementary changes. A test will simply tell you if your diet is delivering enough Vitamin D to maintain an optimal level.
Yes! Even those who live in sunnier climates and/or take Vitamin D still might be falling short, because there are so many individual factors that can affect your blood level. The only way to truly know if your diet or environment is delivering what you need is to take a test.
The “blood” level of vitamin D that we present is equal to the concentration of total vitamin D level in plasma or serum. It is measured from a dried blood spot using an LC/MS method, which is a gold standard technique. We have validated our method of measuring plasma vitamin D levels from a dried blood spot against levels in liquid plasma.
The reference range is provided simply to give an idea of how these values compare to a large number of others taken from a relatively healthy population. The reference range of 20-80 ng/mL or 50-200 nmol/L refers to the range of blood vitamin D levels from a normal population. When we at OmegaQuant have more of our own vitamin D data, we will create our own reference range encompassing the values from 99% of individuals that we test. Currently, we are utilizing the reference range from another dried blood spot testing lab.
The desirable range of 30-50 ng/mL 75-125 nmol/L is a “goldilocks” range where we believe most of the health benefit has been realized (as compared to having low levels) and there doesn’t seem to be much extra benefit in having higher levels. Many research studies show that >30 ng/mL or >75 nmol/L is predictive of a lot of good health outcomes (see list below), so we consider it a therapeutic threshold.
The other important thing to consider is what it takes to have very high vitamin D blood levels. For example, a vitamin D blood level of 70 ng/mL or 175 nmol/L may impart more health benefits than a level of 30 ng/mL or 75 nmol/L, but the supplemental dosage required to reach those levels could be very high. On average, for someone with low levels to reach 30 ng/mL or 75 nmol/L, one needs at least 1000-2000 IU/day, and the upper limit is currently set at 4000 IU/day.
These are our recommendations, but we always advise you to consult with your doctor before making any dietary changes, especially if it includes taking high doses of a vitamin D supplement. Many other organizations have their own targets and rationales (Institute of Medicine, Endocrine Society), and you are free to use our Vitamin D test to track your progress towards their recommended target ranges if you wish.
