Obstacles to Vitamin D Sufficiency- Why It Can Be Hard to Achieve

It happens more often than I would expect in clinical practice: a patient is faithfully taking their vitamin D, yet still not achieving the individual vitamin D levels set for their health goals. In reality, vitamin D sufficiency isn’t always so easy to reach. The reason why our patients often fall short of optimal vitamin D levels is that they are confronted with a variety of factors that interfere with vitamin D absorption.

This article will address those factors that stop our patients from meeting targeted vitamin D goals and provide an easy solution to enhance the absorption of a nutrient critical to cardiovascular, neurocognitive, cellular, bone, and immune health.^1-3

Symptoms of Low Vitamin D

Vitamin D insufficiency and deficiency aren’t always obvious, at least not at first. Here are some symptoms I see in clinical practice and in the research that correlate with low vitamin D levels. ^4-6

• Bone pain
• Changes in mood, such as depression and irritability
• Fatigue
• Frequent fractures
• Getting sick often (a sign of a weakened immune system)
• Muscle weakness, cramps, or aches
• Sleep problems

Underrecognized Causes of Vitamin D Insufficiency and Deficiency

Digestive and Gastrointestinal Causes

These affect how vitamin D (a fat-soluble vitamin) is released from food and absorbed in the intestines: ⁷

• Celiac disease – damage to intestinal villi reduces nutrient uptake.
• Crohn’s disease – inflammation can affect absorption in the small intestine.
• Ulcerative colitis – can reduce fat absorption during flares.
• Short bowel syndrome – less surface area for absorption after surgery.
• Pancreatic insufficiency (e.g., cystic fibrosis, chronic pancreatitis) – poor fat digestion means vitamin D can’t be freed from food.
• Bile duct obstruction or cholestatic liver disease – bile salts are essential for emulsifying fat; without them, vitamin D uptake is reduced.

Dietary and Lifestyle Factors⁷

• Low dietary fat intake – vitamin D needs fat for absorption.
• Strict vegan diet without supplementation – vitamin D2 from plants is less efficiently converted to active D.
• Low sun exposure – no synthesis in skin.
• Dark skin pigmentation – melanin reduces UVB-driven vitamin D synthesis.

Increased Needs or Losses⁷

• Obesity – vitamin D is sequestered in fat tissue, making it less available in circulation.
• Pregnancy or lactation – increased demand.
• Aging – skin is less efficient at synthesizing vitamin D.

Medications and Supplements That Cause Low Vitamin D

Several medications can block the absorption of vitamin D or lower levels via other mechanisms. Some dietary supplements can have the same effect. This table lists the primary offenders:^7-9

An Easy Way To Improve Vitamin D Absorption

VESIsorb® technology, is an ideal way to ensure that patients are absorbing an optimal amount of vitamin D3, even in the face of a host of factors that interfere with vitamin D absorption. VESIsorb® delivery system offers enhanced absorption by promoting the ability for vitamin D to dissolve readily in an aqueous environment. VESIsorb® eliminates the need for taking vitamin D3 with a fatty meal. VESIsorb® provides a self-assembling colloidal system that forms evenly dispersed fluid droplets upon contact with water in the GI tract. These droplets have a mean diameter of less than 100 nanometers, allowing the bioactive to cross the water layer of the GI tract for absorption.¹⁰

References:

1. Dawson-Hughes B, Harris SS, Krall EA, Dallal GE. Effect of calcium and vitamin D supplementation on bone density in men and women 65 years of age or older. N Engl J Med. 1997;337(10):670-676.
2. Garland CF, Garland FC, Gorham ED, et al. The role of vitamin D in cancer prevention. Am J Public Health. 2006;96(2):252-261.
3. Giovannucci E, Liu Y, Hollis BW, Rimm EB. 25-hydroxyvitamin D and risk of myocardial infarction in men: a prospective study. Arch Intern Med. 2008;168(11):1174-1180.
4. Abukhalil AD, Falana H, Hamayel R, et al. Vitamin D Deficiency Association with Comorbid Diseases in Palestine: “A Cross-Sectional Observation Study”. Int J Gen Med. 2022;15:8033-8042.
5. Al Zarooni AAR, Nagelkerke N, Al Marzouqi FI, Al Darmaki SH. Risk factors for vitamin D deficiency in Abu Dhabi Emirati population. PLoS One. 2022;17(2):e0264064.
6. Sabião TDS, Menezes-Júnior LAA, Batista AP, et al. Exploring the interaction between vitamin D pathway gene polymorphisms, vitamin D status, and depression: A population-based study. Nutrition. 2025;137:112802.
7. Vitamin D Deficiency. Cleveland Clinic. https://my.clevelandclinic.org/health/diseases/15050-vitamin-d-vitamin-d-deficiency. Published 2022. Accessed August 13, 2025.
8. Gröber U, Kisters K. Influence of drugs on vitamin D and calcium metabolism. Dermatoendocrinol. 2012;4(2):158-166.
9. Jung JW. Drug-Induced Vitamin Deficiency. Ann Clin Nutr Metab. 2022;14(1).
10. Knaub K, Sartorius T, Dharsono T, Wacker R, Wilhelm M, Schön C. A Novel Self-Emulsifying Drug Delivery System (SEDDS) Based on VESIsorb(®) Formulation Technology Improving the Oral Bioavailability of Cannabidiol in Healthy Subjects. Molecules. 2019;24(16).