The Importance of Vitamin D

In my practice treating infections, chronic illness, COVID, and weight-related conditions, the topic of vitamin D deficiency comes up often. Vitamin D plays over 200 roles in the body and is essential for immunity, energy metabolism, cellular growth, and more. More than half of our human cells have receptors for vitamin D, highlighting its importance in overall health.

Understanding Vitamin D Levels

In 2010, the Institute of Medicine (now the National Academy of Medicine) defined vitamin D deficiency, insufficiency, and sufficiency based on serum 25-hydroxyvitamin D [25 (OH)D] levels:

• Deficient: < 12 ng/ml
• Insufficient: 12-20 ng/ml
• Sufficient: 20-30 ng/ml

However, these values were based on bone health, not immunity or chronic illness. In 2011, the Endocrine Society recommended levels above 30 ng/ml, but emerging research suggests that levels between 50-90 ng/ml are necessary for functional health and 80+ ng/ml for optimal health.

Factors Influencing Vitamin D

Your vitamin D levels are influenced by:

• Geography: Latitude, season, time of day
• Biology: Genetics, skin pigmentation, age
• Metabolism: Vitamin D3 is processed in the liver into its active form (calcitriol), which has a longer half-life in the body

Since vitamin D3 has a short half-life (1-2 days), but its metabolized form lasts 2-3 weeks, testing the 25-OH hydroxy vitamin D is the best way to assess your levels. Click here to order your test.

Supplementing Vitamin D

If you’re deficient, it can take months to achieve optimal levels with 5,000 IU daily. However, prescription-strength 50,000 IU vitamin D is highly absorbable, low-cost (~$3 for a 3-month supply), and often covered by insurance.

• Vitamin D3 vs. D2: Vitamin D3 is 30% more bioavailable than D2.
• Combining Supplements: If taking >8,000 IU/day, add:
• Vitamin K2 (100 mcg/day or 800 mcg/week)
• Magnesium (250-500 mg/day)

Both vitamin K2 and vitamin D have anti-cancer properties. Click here to request a prescription-strength vitamin D supplement. 

Vitamin D and Weight

Weight Loss

Studies suggest vitamin D can help with weight loss by:

1. Regulating appetite: Vitamin D receptors in the hypothalamus reduce food intake.
2. Reducing fat storage: Vitamin D promotes apoptosis (cell death) in fat cells.
3. Improving metabolism: Clinical trials show vitamin D supplementation supports weight loss better than a placebo.

Weight Gain

Conversely, low vitamin D levels contribute to weight gain by:

• Disrupting glucose regulation
• Promoting fat accumulation
• Interfering with insulin signaling in muscles

My Perspective on Vitamin D Testing

Given the obesity epidemic and rising cases of long COVID and frequent infections, I find it concerning that the Endocrine Society (July 2024) recommended against routine vitamin D testing for the general population. Their rationale is that only specific groups—such as older adults, pregnant individuals, and children—need supplementation without testing.

However, I believe most people are not in optimal health. Of those I test, only 10-15% have levels at or above 70 ng/ml.

What About Your Vitamin D Levels?

I am offering vitamin D testing at no extra cost during your next visit. I can submit this through insurance, or you can use Ulta Labs, which offers discounted testing through Quest Labs. Lab costs are:

• With a visit (provider order): $24.12
• Without a visit (self-order): $49.95

Click here to schedule your visit and test your vitamin D levels.  

If your levels are low, treatment may be as simple as adjusting your daily dose. If prescription vitamin D is needed, you can request it here.

For a full supplementation guide, check out the IMA Health Protocol here.

Sincerely,
Anna Yoder, DNP, APRN, ANP/GNP-BC

References:

1. Sisley SR, Arble DM, Chambers AP, et al. Hypothalamic Vitamin D Improves Glucose Homeostasis and Reduces Weight. Diabetes. 2016;65(9):2732-41. doi:10.2337/db16-0309.
2. Sergeev IN. Vitamin D Status and Vitamin D-Dependent Apoptosis in Obesity. Nutrients. 2020;12(5):E1392. doi:10.3390/nu12051392.
3. Lotfi-Dizaji L, Mahboob S, Aliashrafi S, et al. Effect of Vitamin D Supplementation Along With Weight Loss Diet. Clinical Endocrinology. 2019;90(1):94-101. doi:10.1111/cen.13861.
4. Xenos K, Papasavva M, Raptis A, et al. Vitamin D Supplementation and Genetic Polymorphisms Impact on Weight Loss Diet Outcomes. Frontiers in Medicine. 2022;9:811326. doi:10.3389/fmed.2022.811326.
5. Abboud M, Liu X, Fayet-Moore F, et al. Effects of Vitamin D Status and Supplements on Anthropometric and Biochemical Indices. Nutrients. 2019;11(12):E3032. doi:10.3390/nu11123032.
6. Benetti E, Mastrocola R, Chiazza F, et al. Effects of Vitamin D on Insulin Resistance and Myosteatosis. PloS One. 2018;13(1):e0189707. doi:10.1371/journal.pone.0189707.
7. Bouillon R, Carmeliet G, Lieben L, et al. Vitamin D and Energy Homeostasis: Of Mice and Men.
8. Independent Medical Alliance (IMA). Retrieved March 20, 2025, from: IMA Health Protocol.