Eye On Reversing A Troubling Trend: Vitamin D Deficiency

Vitamin D was first discovered in the early 1900s as a possible panacea for Rickets, a childhood bone disease that compromises calcium and phosphorus absorption and results in soft and weak bones. Within a decade of its discovery, fortification of foods with vitamin D (like cereals, orange juice, and milk products) essentially eradicated rickets from the scene, and it became rare in the United States.

Fast forward one hundred years: While rickets is exceedingly uncommon, since 2000 it has been on the rise.

An article in Mayo Clinic Proceedings discusses the rise of rickets cases in the US and around the world, claiming that it has dramatically increased since 2000.” The article states: “the annual incidence of rickets in Canada is estimated at 9-12 cases per 100,000 children, and in the United States, we found even greater incidence rates (24, 38, and 95 per 100,000) in Caucasian, Asian, and black children, respectively. (Mayo Clinic Proceedings)

This was a stunning headline to read, given we have viewed Ricketts as a disease eradicated with the injustices of the industrial revolution.

Even if all cases of nutritional rickets in this study were in children younger than three years old and also attributable to other factors besides low vitamin D levels, like calcium-deficient diets, the recent resurgence of rickets has placed vitamin D deficiency back in the spotlight of modern science. And, it calls into question ‘what is happening with our modern lifestyles to set us on this backfoot?”

Vitamin D plays a fundamental role in maintaining bone health and immunosignaling (among other key physiologic processes), and vitamin D deficiency is common in the US and around the globe. It is commonly held across primary care clinicians that >80% of their population will be vitamin D deficient.

Vitamin D remains a controversial conversation piece within the medical community, and experts continue to debate several questions surrounding this essential vitamin: How much vitamin D does a person need for bone health? Do higher levels of vitamin D offer additional health benefits? Is supplementation a good idea for everyone?

Below, we survey the scene surrounding vitamin D and attempt to sort out the latest research and recommendations.

How Common is Vitamin D Deficiency?

It’s a big problem in the United States too. According to the CDC’s Second Nutrition Report, which offers a snap shot of the US population’s nutrition status, “a substantial percentage of adult Americans have inadequate vitamin D levels – with estimates ranging from 35% to 70%” depending on factors like age, gender, race, ethnicity, and health status. (Centers for Disease Control and Prevention)

The Role of Vitamin D and the Consequences of Inadequate Intake

Vitamin D’s best-known role is to keep bones healthy by increasing the absorption of calcium and phosphorus in the intestines. Chronic or severe vitamin D deficiency can cause a decline in calcium and phosphorus absorption, which can lead to hypocalcemia (low calcium) and hyperparathyroidism (overactive parathyroid glands).

This is how the process works:

When vitamin D levels are low, calcium levels can also be low; when calcium levels are low, the parathyroid glands work overtime to release a hormone (PTH) that stimulates the release of calcium from bones, which can cause accelerated bone demineralization (bones break down faster than they can rebuild).

This low-vitamin D/low-calcium/high-PTH state can contribute to a constellation of health conditions, including osteomalacia (soft bones), osteopenia (reduced bone density), and osteoporosis (significant bone loss). Osteomalacia and osteoporosis, especially, lead to brittle and porous bones that are unstable and more prone to fracture.

Vitamin D deficiency can also cause muscle weakness, myalgia (muscle pain), arthralgia (joint pain), muscle fatigue, and fasciculations (muscle twitching).

Additionally, studies have shown an association between vitamin D deficiency and cancer, type 2 diabetes, cardiovascular disease, autoimmune disorders, and depression.

Vitamin D also plays a crucial role in modulating the immune system and influencing inflammatory processes. This happens through several mechanisms.

• Firstly, vitamin D suppresses the production of pro-inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interleukin-1β. These signaling molecules promote inflammation in the body.
• Secondly, and conversely, vitamin D promotes the production of anti-inflammatory cytokines, like interleukin-10 (IL-10). A balance of pro-inflammatory and anti-inflammatory cytokines is essential for maintaining immune homeostasis.
• Thirdly, vitamin D influences the function of certain immune cells, including T cells and B cells. It can inhibit the differentiation and activation of pro-inflammatory T helper 1 (Th1) cells and T helper 17 (Th17) cells while promoting the development of regulatory T cells (Tregs), which suppress excessive immune responses. In this way, vitamin D helps maintain a balance between these pro-inflammatory T cells and immuno-suppressive T cells.
• Additionally, vitamin D suppresses the differentiation of B cells into plasma cells, which are responsible for producing antibodies. Influencing B cell activation, inhibiting plasma cell generation, and reducing the overall production of antibodies is important, especially in the development of autoimmune diseases, where autoantibodies play a role.

Taken together, vitamin D’s critical role in bone health, its influence on the immune system and inflammatory response, and its association with other health conditions explains why there is so much interest in vitamin D and such a hotly contested debate over the right approach to take when it comes to supplementation.

Where Does Vitamin D Come From? | How Do We Get Vitamin D? | Factors that Influence Vitamin D Levels

The best source of vitamin D is the sun, but most people aren’t exposed to enough sunlight to provide sufficient vitamin D. How much sunlight is needed? Some experts suggest that approximately 5-30 minutes of sun exposure between 10 AM and 4 PM daily to the face, arms, hands, and legs without sunscreen leads to sufficient vitamin D synthesis. (National Institutes of Health)

Getting up to thirty minutes of sunlight on 40% of exposed skin every day isn’t achievable for many people. There are other complicating factors too: Older people and people with darker skin tones don’t absorb ultraviolet light well, and many people live in geographic regions (Northeast, Midwest) without consistent sunlight throughout the year.

Diet is another way to get vitamin D, but it’s only found in a small number of foods – like fatty fish, beef liver, egg yolks, and cod liver oil. Several more popular food items are fortified with vitamin D (think cereals, milk products, and orange juice), but for most people, it’s impractical to get enough vitamin D from food sources alone.

Certain medical conditions (like Celiac and Crohn’s disease), gastric bypass surgery, obesity, lack of physical activity, and some medications can also impact vitamin D absorption and conversion.

Enter vitamin D supplementation and the ongoing debate over its usage and utility.

The Controversy Over Vitamin D and the Confusion Surrounding Recommendations

Once vitamin D is produced in the skin through sunlight exposure or obtained from food/supplements, it enters the bloodstream and is converted to its active form (25-hydroxyvitamin D) by the liver. Healthcare providers use serum 25-hydroxyvitamin D as a proxy for a person’s vitamin D status.

While there is general consensus that very low levels of vitamin D pose health risks and that most people could benefit from supplementation (considering the majority of the US population has either vitamin D deficiency or insufficiency), experts disagree about two primary questions:

• What levels of 25-hydroxyvitamin D does the body need for health and disease prevention?
• What dosage of vitamin D supplementation is safe and effective?

How Much is Enough?

Generally, most experts align on what is considered vitamin D deficiency: Levels of 25-hydroxyvitamin D below 20 ng/ml (nanograms per milliliter). The medical community also tends to agree that 25-hydroxyvitamin D levels between 20 and 30 ng/ml represents vitamin D insufficiency.

Put another way: We need at least 30 ng/ml of vitamin D for bone health and other possible wellness benefits.

How Much is Too Much?

Although the maximum safe upper level of 25-hydroxyvitamin D is not well-established, levels above 100 ng/ml may pose a risk of toxicity and levels above 150 ng/ml is considered toxic.

The Recommendations

Most scientists agree that current recommended dietary allowances (RDAs) may be sufficient for bone health, but not for broader health benefits. The current RDAs for vitamin D are 600 IU per day for adults 19-70 and 800 IU per day for adults over 70.

The biggest disagreement among vitamin D experts is about how high above 30 ng/ml someone should aim for in order to reap the preventive and protective benefits of this essential vitamin; to reduce the risk of bone issues and chronic diseases, such as heart disease, certain cancers, and autoimmune conditions.

Recently, the Journal of Endocrinology updated to its 2011 guidelines for vitamin D. In the article, the Endocrine Society essentially reiterates its previous recommendation regarding vitamin D levels and supplementation and suggests a target range of 30-60 ng/ml. The society adds this note as well: Vitamin D levels above 30 ng/ml are rarely associated with increased benefit for skeletal health in adults.

It defines vitamin D deficiency as 25-hydroxyvitamin D levels below 20 ng/ml, vitamin D insufficiency as levels between 20 and 30 ng/ml, and vitamin D sufficiency as levels between 30-100 ng/ml. (Endocrine Society)

The National Academy of Medicine generally consider a serum 25-hydroxyvitamin D level of 20 ng/ml or above sufficient for bone health for the majority of the population. (National Academy of Medicine)

It’s worth noting that both organizations, the Endocrine Society and the National Academy of Medicine, maintain that the broader benefits of vitamin D beyond bone health have not been well-established and, thusly, levels of 25-hydroxyvitamin D beyond 30 ng/ml don’t necessarily translate to improved health outcomes.

A systematic review and meta-analysis conducted by The Lancet Diabetes & Endocrinology “found no significant effect of vitamin D supplementation on bone mineral density, falls, or fractures in adults.” Its findings suggest that “while vitamin D is essential for bone health, supplementation alone may not be sufficient to prevent fractures or improve bone density.” (The Lancet - Diabetes and Endocrinology)

The Lancet article suggests a link between vitamin D status and other health outcomes, like diabetes, cardiovascular disease, and infectious disease, but notes that the evidence for the effectiveness of vitamin D supplementation isn’t conclusive.

A review in the New England Journal of Medicine acknowledges a possible connection between vitamin D and non-skeletal health, and suggests that 25-hydroxyvitamin D levels of 30 ng/ml or higher might be needed to provide extra-skeletal benefits. (New England Journal of Medicine)

The takeaway:

• Most medical organizations agree that 25-hydroxyvitamin D levels below 20 ng/ml is considered vitamin D deficiency and levels between 20 and 30 ng/ml is ‘borderline’ deficiency or vitamin D insufficiency.
• 100 ng/ml seems to be the cutoff for the upper limit of vitamin D.
• There are disagreements about optimal levels of vitamin D (above 30 ng/ml and below 100 ng/ml.)
• All experts agree that vitamin D plays a critical role in maintaining bone health, but not everyone believes vitamin D provides additional health benefits.

The Role of Vitamin D in Pregnancy

During pregnancy, the demand for vitamin D increases significantly to support fetal skeletal development, to improve bone health and immune function in newborns, and to reduce the risk of pregnancy complications. Adequate vitamin D levels in pregnant women are crucial for both maternal and infant wellbeing, and numerous studies have highlighted the importance of vitamin D supplementation during pregnancy.

A systematic review and meta-analysis published in JAMA Pediatrics looked at the effects of vitamin D supplementation during pregnancy on offspring growth, morbidity, and mortality and determined that “supplementation is associated with a reduced risk of SGA (small for gestational age) and improved infant growth without risk of fetal or neonatal mortality or congenital abnormality.” (JAMA Pediatrics)

Other research suggests that vitamin D supplementation during pregnancy may be associated with a lower risk of preterm birth, low birth weight, and gestational diabetes.

The National Institutes of Health examined thirty different trials (n = 7033 women) to reach its conclusion on the matter: “Supplementing pregnant women with vitamin D alone probably reduces the risk of pre-eclampsia, gestational diabetes, low birthweight and severe postpartum hemorrhage, but it may make little or no difference in the risk of having a preterm birth (< 37 weeks of gestation).” (National Institutes of Health)

Based on the best evidence available, the American College of Obstetricians and Gynecologists (ACOG) recommends that pregnant women and those breastfeeding should receive 600 IU of vitamin D daily. That said, according to ACOG supplementation with up to 4,000 IU/day of vitamin D is considered safe during pregnancy and lactation. (American College of Obstetricians and Gynecologists)

Tia’s Take on Vitamin D

Many medical decisions demand a mix of art and science; a healthy balance of evidence-based information and clinical experience and judgment. Vitamin D is no exception.

In truth, vitamin D isn’t a ‘sexy’ subject, and because the best way to get vitamin D is free to everyone (sunlight), there aren’t a lot of studies on vitamin D deficiency compared to other health conditions.

The unwritten rule of thumb when it comes to vitamin D advice is to find a provider you trust, get tested, be open and honest about your lifestyle (sun exposure, diet, physical activity), and work together to formulate a personalized plan to make sure you’re getting enough of this essential vitamin.

What is Tia’s take?

Get Tested…

It’s important for women to have a baseline for vitamin D levels, especially as they approach perimenopause (late 30s to early 40s) and bone density begins to decline.

…Early and Often

The sooner vitamin D readings deviate from the norm or bone density changes are recognized, the better and more beneficial a course-correcting regimen can be.

Strategize and Rectify

Regardless of the ongoing debate over vitamin D, if your levels hover around the American average (~ 30 ng/ml), you should consider a strategy to bring the value up.

Supplementation and Sun

Vitamin D supplementation may help, but there is no substitute for the profound effect sunlight can have. Depending on the situation (age, geographic location, perimenopause/menopause status, bone density, vitamin D levels, skin cancer risk), increasing sun exposure may be enough to move the dial in the right direction.

Pregnant Women

Supplementing with vitamin D is an important consideration for pregnant people. Thankfully, a high-quality prenatal vitamin (which is roundly recommended) contains the recommended amount of 600 IUs per day.