Vitamin D is an elusive nutrient for many in the modern world, just like omega-3s, which is why so many health professionals encourage increased intake. But as research continues at a frenetic pace, the focus has evolved to put more emphasis on one’s vitamin D blood level. In other words, because of the complex factors at play when it comes to sun exposure, intake, and metabolism—as well as gender, genetics, lifestyle, to name a few—it cannot be predicted with certainty what someone’s vitamin D level is just based on how much they take.

This is the same premise behind Omega-3 Index testing. While dosage is an important guideline for people, knowing what their level is first will go a long way toward pinpointing a more precise
intake pattern.

Where Vitamin D Comes From
To get to an optimal vitamin D level, you first need to know where to find it. 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). 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, egg yolks, and fortified foods. Finally, supplements are a potent source of vitamin D and raise blood levels effectively.

What is the Optimal Level of Vitamin D?
The reference range of 30-100 ng/mL refers to the range of blood vitamin D levels considered healthful and normal. The desirable range of 30-50 ng/mL 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 is predictive of a lot of good health outcomes (see list below), so we consider it a therapeutic threshold.

• Lower risk of overall mortality: People with a blood level of 30 ng/mL and above had a lower risk of mortality (Garland et al. 2014).
• Lower risk of cardiovascular disease (CVD) and cancer mortality: Lowest risk for death from all-causes, cancer, and CVD in individuals with a vitamin D blood level of at least 30 ng/mL (Michaelsson et al. 2010).
• Lower risk for respiratory tract infections: Those with vitamin D blood levels at or above 30 ng/mL had the lowest risk of upper respiratory tract infections (Ginde et al. 2009).
• Lower risk of hip fractures and falls: Older individuals who achieved a vitamin D blood level of at least 30 ng/mL had a reduced risk of hip fractures (Bischoff-Ferrari et al 2009).
• Lower risk of preterm birth: Pregnant women with levels of at least 30 ng/mL were at the lowest risk of preterm birth, as well as babies born with low birth weight and small for gestational age (Miliku et al. 2016).

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 may impart more health benefits than a level of 30 ng/mL, 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, one needs at least 1,000-2,000 IU/day, and the upper limit is currently set at 4,000 IU/day.

These are our recommendations, but we always advise people to consult with their doctor before making any dietary changes, especially if it includes taking high doses of a vitamin D supplement.

No Consensus on ‘Optimal’ Vitamin D Level … Yet
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 “insufficiency” vs. “desirable” blood levels (Holick MF. 2017) and what endpoint is being considered (e.g., bone health vs. infection risk). The Institute of Medicine (IOM) guidelines use bone health outcomes (e.g., rickets in kids and osteoporosis/hip fracture risk in adults) to set their levels for “sufficiency,” which are the primary health outcomes related to a deficiency in vitamin D. Thus, according to the IOM, a serum level of >20 ng/mL is considered sufficient and <12.5 ng/mL is deficient.

The Endocrine Society also bases its recommendations for screening and supplementation primarily on bone health outcomes, but does acknowledge the evidence for other endpoints as important to consider as more research comes out. Its recommendations include values from 21-29 ng/mL as “insufficient” (as compared to the IOM), thus >30 ng/mL is the “sufficient” or “desirable” range.

From OmegaQuant’s perspective, optimal vitamin D levels are considered more from a “whole health” perspective rather than just specific to bone health, thus the higher “optimal” target of at least 30 ng/mL.

What About Vitamin D Dosage?
It depends! At OmegaQuant we recommend aiming for a vitamin D blood level >30 ng/mL, 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 IOM recommends taking no more than 4,000 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 vitamin D through sun exposure and not need any supplemental vitamin D.

Immune Support Helps Shine New Light on Vitamin D
Vitamin D has been shown to be protective against contracting upper respiratory tract infections, especially when people with very low vitamin D blood levels (<12 ng/mL) take supplements to increase their levels. There have been several publications on the relationship between SARS-CoV-2 severity and vitamin D blood levels, with higher levels resulting in less severe disease. However, low vitamin D blood levels are typical in the elderly and obese populations, which are major risk factors for having a severe case of SAR-CoV-2, which is difficult to disentangle.

Still, there is mechanistic evidence that vitamin D plays several roles in the immune response to infectious diseases. There is little risk and potentially large health benefits to maintaining an optimal vitamin D blood level as a part of an overall healthy lifestyle, especially during this COVID winter.

Advances in Vitamin D Testing
Typical vitamin D testing requires a blood draw, but technology has paved the way for a simpler approach, allowing people to test their own levels, at home, safely, and without a doctor’s prescription. Requiring only a few drops of blood, a vitamin D blood spot test will provide an accurate picture of someone’s level over a period of three to four months. Once they know their level, they can take the appropriate steps to reach optimal status.

At OmegaQuant we measure the plasma total 25-hydroxyvitamin D concentration (i.e., sum of D2 and D3) from a dried blood spot using the gold-standard LC/MS method of analysis. The value we provide is directly comparable to a total 25-hydroxyvitamin D plasma level measured from a blood draw.

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About the Author: Kristina Harris Jackson, PhD, RD, is the research director for OmegaQuant, Sioux Falls, SD. She has conducted numerous studies on fatty acid testing and its impact on health outcomes, with a particular focus on omega-3s in maternal health. To that end, she helped create the Prenatal DHA test (launched in 2019) and the Mother’s Milk DHA test. Her latest focus is OmegaQuant’s Vitamin D test (launched in 2020). She can be reached at kristina@omegaquant.com.