Vitamin D

What it does:

Bone Health:
Vitamin D plays a critical role in calcium absorption, which is essential for building and maintaining strong bones and teeth. Inadequate levels can lead to conditions like rickets in children and osteomalacia or osteoporosis in adults.

Immune System Support:
Vitamin D is a key regulator of immune function. It helps modulate both innate and adaptive immune responses and has been shown to support the body’s defense against respiratory infections and inflammation.

Mood and Mental Health:
Low levels of vitamin D are linked to mood disorders such as depression and seasonal affective disorder (SAD). Vitamin D is involved in brain function and may help regulate mood.

Muscle Function:
Vitamin D is important for muscle strength and function, which helps prevent falls and injuries, particularly in older adults.

Cardiovascular and Metabolic Health:
Emerging evidence suggests vitamin D may support healthy blood pressure levels, cardiovascular function, and insulin sensitivity, which could reduce the risk of metabolic disorders.

Food sources:

Fatty Fish: Salmon, mackerel, sardines, and tuna are some of the richest dietary sources.

Cod Liver Oil: A traditional but highly concentrated source of both vitamins D and A.

Egg Yolks: Contain small amounts of vitamin D, especially from pasture-raised chickens.

Mushrooms: Some varieties (like maitake or UV-exposed portobello) naturally produce vitamin D2.

Fortified Foods: Many dairy products, plant-based milks, cereals, and orange juices are fortified with vitamin D.

Supplementation:

Due to limited natural food sources and reduced sun exposure (especially in winter or higher latitudes), vitamin D supplementation is often recommended.

Form: Look for supplements containing vitamin D3 (cholecalciferol), which is more effective at raising blood levels than D2.

Absorption: As a fat-soluble vitamin, it’s best taken with food containing fat.

Personalised Needs: People with darker skin, older adults, and those with certain medical conditions may require higher intake levels. Blood testing can help determine individual needs.

Safety:

RDA (Recommended Dietary Allowance):

600 IU/day for adults up to 70
800 IU/day for adults over 70

Commonly Recommended Dose for Maintenance:

1,000–2,000 IU/day, particularly for those with low sun exposure or known deficiency.

Upper Limit:

4,000 IU/day is considered the tolerable upper intake level for adults. Higher doses may be prescribed under medical supervision.

Consulting a healthcare provider before starting any new supplementation regimen is recommended, especially for disease prevention.

Signs of Deficiency:

Fatigue
Bone or back pain
Frequent infections
Depression
Muscle weakness

Toxicity Warning:

Too much vitamin D from supplements can lead to hypercalcemia (excess calcium in the blood), causing nausea, kidney problems, or confusion. Always consult a healthcare provider before taking high doses.

Always consult a healthcare professional, especially when seeking optimal levels for disease prevention.

Learn more about Vitamin D:

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Disclaimer: The information in this article is for educational purposes only and is not intended as medical advice. For diagnosis and treatment of medical conditions, please consult a healthcare professional.

References:

USANA Health Sciences. “Vitamin D.” Accessed April 2025.

USANA Health Sciences. “MagneCal D.” Accessed April 2025.

USANA Health Sciences. “HealthPak.” Accessed April 2025.

Harvard T.H. Chan School of Public Health. “Vitamin D.” Accessed April 2025.

NIH Office of Dietary Supplements. “Vitamin D Fact Sheet for Consumers.” Accessed April 2025.

Mayo Clinic. “Vitamin D: Benefits, Sources, Deficiency, and Dosage.” Accessed April 2025. Healthline. “The Benefits of Vitamin D and How to Get Enough.” Accessed April 2025