Low Vitamin D? Depression, Fatigue, & Inflammation Are Signs
- Annaelle Lamers PA-C
- Jul 27
- 3 min read
How common is low vitamin D?
Around 42% of U.S. adults are below conventional sufficiency levels. This is something I often test in my patients here in Naples Florida. Despite the sunny climate, I find that about 80% of my patients have sub-optimal levels.
Low vitamin D may be the unseen cause behind many health issues — but by supporting pathways with the right foods and nutrients, you can restore vitality and resilience.
Symptoms of low Vitamin D
Chronic fatigue & low energy
Depression, mood swings, anxiety
Persistent inflammation or joint/muscle pain
Frequent colds or slowed immune recovery
Muscle weakness or cramps
Bone pain, hair loss, slow wound healing
Gut issues, poor metabolism, weight gain
What Does Vitamin D Support?
Vitamin D is involved in much more than bone health. It supports:
Immune regulation: Modulates both innate and adaptive immunity, helping reduce infections and autoimmune risks (1)
Cardiovascular function: Helps regulate blood pressure and endothelial health, reducing risk for heart disease (2)
Muscle function and fall prevention: Maintains strength and protects against frailty in older adults .
Brain health: Supports neurotransmitter production and plays a role in neuro-protection (3)
Gut integrity and metabolic health: Supports intestinal barrier, insulin regulation, and metabolic balance. (4)
Improve Cancer Outcomes: influences cellular proliferation and apoptosis. Evidence shows improved mortality. (5) + (8)
Mood & Depression: Improves mood and associated with lower risk of depression, self-harm and suicidaility. (6)
"It is estimated that there is a 30 to 50% reduction in risk for developing colorectal, breast, and prostate cancer by either increasing vitamin D intake to least 1000 IU/d vitamin D or increasing sun exposure to raise blood levels of 25(OH)D >30 ng/ml." (8)
Supportive Nutrients: How Vitamin D Works with Magnesium, Vitamin K, Omegas & Calcium
Vitamin D metabolism begins when UVB light or diet provides cholecalciferol, which is first hydroxylated in the liver to 25(OH)D, then further hydroxylated in the kidneys (or immune cells) to active calcitriol. This activation depends heavily on magnesium, which acts as a cofactor for both hydroxylase enzymes—without enough Mg, vitamin D can’t reach its functional form. (7)
Once activated, calcitriol binds to the vitamin D receptor (VDR) in multiple tissues—including intestines, bones, immune cells, heart, and brain—to regulate gene expression. Vitamin K plays a vital role by carboxylating osteocalcin and matrix Gla-protein, which directs calcium into bone and prevents soft-tissue calcification.
Because vitamin D is fat-soluble, healthy fats and omegas improve its intestinal absorption and carry it efficiently to tissues, while also providing anti-inflammatory benefits. Finally, calcium relies on vitamin D to upregulate transport proteins in the gut and bone, maximizing mineralization and skeletal strength.
Whole Food Sources of Vitamin D
Fatty fish (e.g., salmon, mackerel, sardines)
Egg yolks from pastured raised hens.
Beef Liver Can be cooked or supplement form.
Supplementation, Sunlight, & Nutrition: A Practical Approach
Aim for 10-15 minutes of sunlight daily as well as incorporating food sources of Vitamin D.
Consider supplementing with 2,500–5,000 IU of
vitamin D₃ daily to reach functional levels (60–90 ng/mL) - Check with your doctor before starting any new supplements.
I often recommend vitamin D blends with Vitamin K2 to help support absorption and calcium regulation.
Always take with a meal containing healthy fats to further aid absorption.
Include dietary calcium from dairy, leafy greens, or bone broth.
Retest 25‑OH D levels every 3–6 months to track progress.
Vitamin D is can have a positive impact on health and mood. If you are struggling with depression, joint pains, gut issues, muscle aches, weight gain, fatigue, or frequent infections/illness - consider getting your Vitamin D levels checked.
Ready to uncover if vitamin D is the missing piece? Harmony Health Clinic in Naples, FL offers functional testing and personalized support—book your wellness assessment today!
Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult a licensed healthcare professional.
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