What is the recommended dosage for Vitamin D?

General: 600-800 IU/day (RDA); Ibd Support: 1,000-4,000 IU/day (target serum 25(OH)D >30 ng/mL); Deficiency Correction: 50,000 IU/week for 8 weeks, then 1,000-4,000 IU/day maintenance

What are the side effects of Vitamin D?

Potential side effects include: Hypercalcemia at very high doses (nausea, vomiting, weakness, confusion), Kidney stones with excessive long-term supplementation, Constipation, Metallic taste.

What is vitamin D and how does it work for gut health?

Vitamin D is a fat-soluble vitamin and hormone that plays a significant role in intestinal health beyond its well-known function in calcium absorption. It helps maintain the integrity of tight junctions between intestinal epithelial cells, modulates gut immune responses, and influences the composition of the gut microbiome. Research suggests that vitamin D deficiency is associated with increased risk of inflammatory bowel disease and other GI conditions.

What is the recommended dosage of vitamin D for gut health?

The standard recommendation is 600-800 IU per day, but many researchers suggest 1,000-4,000 IU daily for optimal levels, especially in individuals with deficiency. Studies in IBD patients have used 1,000-5,000 IU per day. Blood levels of 25(OH)D between 30-50 ng/mL are generally considered optimal. Testing vitamin D levels before supplementing can help determine the appropriate dose.

Are there side effects or interactions with vitamin D?

Vitamin D is safe at recommended doses but can cause toxicity at excessive levels (typically above 10,000 IU per day over extended periods), leading to hypercalcemia, kidney stones, and nausea. Vitamin D may interact with thiazide diuretics, corticosteroids, and certain weight loss medications that reduce fat absorption. Individuals with granulomatous diseases (sarcoidosis) may be more susceptible to vitamin D-induced hypercalcemia.

Vitamin D

vitamin

Also known as: Cholecalciferol, Vitamin D3, Ergocalciferol, Calciferol

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About

Vitamin D plays an important role in intestinal health by binding to VDR receptors on intestinal epithelial cells, which may help enhance tight junction protein expression and support the mucosal immune response. Deficiency is common in IBD patients (up to 60%) and correlates with disease activity. Research suggests vitamin D supplementation may help reduce relapse risk in both ulcerative colitis and Crohn's disease, and support overall intestinal barrier integrity.

How It Works

Binds VDR receptors on intestinal epithelial cells enhancing tight junction protein expression (claudin-2, -12, -15); modulates mucosal immune response via regulatory T cell differentiation; induces cathelicidin antimicrobial peptide production in intestinal macrophages; deficiency associated with IBD relapse and increased intestinal permeability.

Evidence For Conditions

Condition	Grade	Studies	Participants
Inflammatory Bowel Disease (IBD) — General	B	10	1500	View →
Irritable Bowel Syndrome (IBS)	C	3	400	View →

Side Effects

Hypercalcemia at very high doses (nausea, vomiting, weakness, confusion)
Kidney stones with excessive long-term supplementation
Constipation
Metallic taste

Drug & Supplement Interactions

Thiazide diuretics (may increase risk of hypercalcemia)
Corticosteroids (reduce vitamin D absorption and metabolism)
Orlistat and cholestyramine (reduce fat-soluble vitamin absorption)
Statins (vitamin D may affect statin metabolism)

Always inform your healthcare provider about all supplements you take.

Related Ingredients

Vitamin A

Quick Facts

Dosage: General: 600-800 IU/day (RDA); Ibd_Support: 1,000-4,000 IU/day (target serum 25(OH)D >30 ng/mL); Deficiency_Correction: 50,000 IU/week for 8 weeks, then 1,000-4,000 IU/day maintenance
Forms: capsule softgel liquid drops tablet gummy
Natural Sources: Sunlight (UV-B exposure), Fatty fish (salmon, mackerel, sardines), Egg yolks, Fortified milk and dairy, Mushrooms (UV-exposed)
Upper Limit: 4,000 IU/day (100 mcg); higher doses under medical supervision only
Best Time: With a meal containing fat for better absorption

Evidence Summary

Inflammatory Bowel Disease (IBD) — General B

Irritable Bowel Syndrome (IBS) C

FDA Disclaimer: These statements have not been evaluated by the Food and Drug Administration. The products and information on this website are not intended to diagnose, treat, cure, or prevent any disease. The evidence grades presented are based on our analysis of published peer-reviewed research and do not constitute medical advice. Always consult your healthcare provider before starting any supplement regimen.