Vitamin D
Vitamin D (calciferol) is a fat-soluble vitamin that research shows is important for our health, particularly bone health and immune function. Vitamin D can either be produced in the body starting from exposure of skin to sunlight, in particular, ultraviolet B (UVB) radiation from 290 to 315 nanometers (nm). Skin exposure to sunlight initiates a cascade of chemical reactions that result in the active form of vitamin D, called 1α, 25-dihydroxy vitamin D. Vitamin D can also be supplemented orally in the form of a pill or liquid.
(Linus Pauling Institute, 2022)
Vitamin D Levels
Vitamin D levels can be checked by medical professionals through a lab that measures serum (blood) 25-hydroxyvitamin D. The resulting number determines your vitamin D status – whether your levels are in the normal range, or whether you are deficient and in need of supplementation. However, there is debate in the medical field on the cutoff point that demarcates deficiency from normalcy.
The Institute of Medicine suggests you should not be below 20ng/mL. Other institutions, such as the Linus Pauling Institute and the United States Endocrine Society, suggest levels should not be below 30ng/mL. Higher ranges may also be beneficial for immune function according to some research, which is still up for debate.
So, what happens if your levels are below normal? After you have spoken with a medical professional who has determined your vitamin D status is deficient, they may start you on over-the-counter vitamin D supplementation. According to Dr. Adrian Gombart, Ph.D., principal investigator for the Linus Pauling Institute and professor of Biochemistry and Biophysics at Oregon State University, in his interview for the GW Integrative Medicine podcast, 2000 IU is a safe daily dose (GW Integrative Medicine, 2022). After you start supplementation for a few months, Dr. Gombart suggests rechecking levels and seeing if they are in the normal range, 30ng/mL or more. You may need to stay on supplementation to maintain vitamin D levels, but this can change depending on exposure to sunlight, nutritional intake, medications that interact with vitamin D absorption, and many other factors. Always speak with a medical professional to discuss your concerns.
Factors Impacting Vitamin D Status
There are a variety of factors that may contribute to vitamin D deficiency. According to the United States Prevention Task Force (2022), these factors include:
- Protective clothing and sunscreen: Clothing acts as a direct barrier between the exposure of sunlight to our skin, which decreases the amount of vitamin D we are naturally able to produce. Similarly, sunscreen acts as a barrier. According to research cited by the Linus Pauling Institute (2022), SPF 10 sunscreen reduces exposure to UVB radiation by 90%. This does not suggest we stop wearing sunscreen. The risk of skin cancer due to exposure to harmful types of solar radiation likely outweighs the vitamin D benefits of not wearing sunscreen.
- Season: In winter months, our skin typically has less exposure to sunlight. This is due to the increased layering of clothing due to cold temperatures and shorter days associated with the winter season.
- Latitude: Where we live also matters to natural vitamin D synthesis. If you live farther from the equator, you are at increased risk of vitamin D deficiency.
- Age: As we get older, we decrease our natural ability to synthesize vitamin D.
- Skin color: The darker your skin color is, the less able you are to synthesize vitamin D. According to the US Preventive Services Taskforce (2022), non-Hispanic black persons have 2 to 10 times greater deficiency in vitamin D than non-Hispanic white persons.
- Lifestyle: The amount of time we spend outside is also a factor in vitamin D status, with indoor lifestyles further contributing to deficiency.
The above list is non-exhaustive. Other factors that contribute to vitamin D deficiency include taking certain medications, genetics, nutritional intake of vitamin D, and breastfeeding status for children.
Most of the factors above address factors that impact synthesis of vitamin D at the skin from exposure to sunlight. Vitamin D can also be consumed in the diet. Below is a table taken from the Linus Pauling Institute on food sources rich in vitamin D.
Vitamin D and Health
According to the Linus Pauling Institute (2022), our bones are made of minerals in the form of hydroxyapatite, which is an inorganic crystal structure that composes 65% of bone material. The remaining 35% of bone tissue is composed of organic protein, mainly type 1 collagen, and makes up the remaining 35% of bone tissue (Linus Pauling Institute, 2022).
“Vitamin D is essential for the effective utilization of calcium in the body.”
Linus Pauling Institute, 2022
The mineral component includes calcium, which is important for maintaining blood calcium levels. The Linus Pauling Institute (2022) explains that blood calcium has a normal range that the body must maintain for cellular function, such as muscle contraction and nerve impulse conduction. To do this, science shows our bodies break down bone when calcium levels start to fall in the blood and build bone when calcium levels are elevated. One of the factors that regulate this process is vitamin D, which helps with the absorption of calcium by forming mineralized bone tissue (Linus Pauling Institute, 2022).
There are two major health outcomes related to vitamin D deficiency. In children, when vitamin D levels reach 12ng/mL or less, rickets may result (Linus Pauling Institute, 2022). Rickets causes the weakening of the mineralized bone tissue. This may cause malformation and bending of bone, which may impact children for life. In adults that reach this 12ng/mL level or less, osteomalacia may result (Linus Pauling Institute, 2022). Similarly, this condition causes the weakening of the bone. Instead of bending, the bone becomes brittle and causes osteoporosis, which may lead to easily broken bones. With the reduced ability to heel in older age, a broken bone may lead to disability and overall decreased quality of life.
To prevent vitamin D deficiency-related bone diseases, calcium supplementation alongside vitamin D supplementation is key. Adding calcium ensures there is a supply available to build mineralized bone tissue and prevent the weakening of bones. However, calcium should not be taken more than 500mg at a time to maximize absorption and is recommended to consume a total of 1000mg to 1200mg per day, either in the form of a supplement or a calcium-rich source of food, like dairy products (Linus Pauling Institute, 2022). Speak with your doctor to determine if supplementation is recommended for you.
While this is an over-simplification of a complex system, it provides a broad background understanding of the role of vitamin D in bone health.
Vitamin D and Other Health Conditions
Research continues to elucidate the role of vitamin D in human health. This includes indications for vitamin D supplementation, bone health, immunity, cancer, and much more. However, there appears to be no clear consensus in the scientific literature on many of these issues.
I will continue to add to this page and share updates on my weekly newsletter as I learn more about the role of vitamin D in human health. Stay tuned!
Overview of Vitamin D
Below is an overview of Vitamin D created by the Linus Pauling Institute. For more detailed information, and to read an overview of the current research behind the role of vitamin D in human health, see the links to the Linus Pauling Institute listed.
Vitamin D | Linus Pauling Institute | Oregon State University
Bone Health In Brief | Linus Pauling Institute | Oregon State University
Bone Health In Depth | Linus Pauling Institute | Oregon State University
You can also listen to the GW Integrative Medicine podcast episode “Let’s Talk Vitamin D Studies.” This 30-minute episode is a great overview of our current understanding of vitamin D.
Citations
Frame, L. and Gombart, A. (2022, October). Let’s Talk Vitamin D Studies [Audio podcast episode]. GW Integrative Medicine. Soundcloud. https://soundcloud.com/user-516347348/220818-im-pod-vitd2-01?in=user-516347348/sets/gwim
Linus Pauling Institute. (2017, December). Bone Health in Brief. Oregon State University. https://lpi.oregonstate.edu/mic/health-disease/bone-health-in-brief
Linus Pauling Institute. (2019, April 19). Bone Health in Depth. Oregon State University. https://lpi.oregonstate.edu/mic/health-disease/bone-health
Linus Pauling Institute. (2021, February 11). Vitamin D. Oregon State University. https://lpi.oregonstate.edu/mic/vitamins/vitamin-D
Disclaimer
This content is for informational and educational purposes only. It is not intended to provide medical advice or to take the place of medical advice or treatment from a personal physician. All viewers of this content are advised to consult their doctors or qualified health professionals regarding specific health questions. The publisher of this content does not take responsibility for possible health consequences of any person or persons reading or following the information in this educational content. All viewers of this content, especially those taking prescription or over-the-counter medications, should consult their physicians before beginning any nutrition, supplement, exercise or other lifestyle program.