The Benefits of Vitamin D: From Bones to Eyes, Roles You May Not Know

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The Benefits of Vitamin D: From Bones to Eyes, Roles You May Not Know

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VDO Knowledge

The Benefits of Vitamin D: From Bones to Eyes, Roles You May Not Know

Dr. Non Rerkthanom, Specialist in Integrative and Anti-Aging Medicine

Vitamin D is an essential nutrient that affects many systems in the body. It is not limited to bones and teeth, but is also connected to immunity, muscle function, brain health, and reducing the risk of chronic diseases such as diabetes, heart disease, and certain cancers. Recent evidence also shows that vitamin D levels are linked to the risk of developing cataracts.

What is Vitamin D?

Vitamin D is a fat-soluble vitamin that the body can synthesize when the skin is exposed to sunlight, produced from cholesterol. It can also be obtained from foods such as bone-in animal products, salmon, egg yolks, and vitamin D-fortified milk.

Main Functions of Vitamin D

Helps absorb calcium and phosphorus, strengthening bones.
Enhances immune system function.
Reduces inflammation in the body.
Regulates cell growth and activity.

How to Measure Vitamin D Levels

Testing is done via a blood test to measure 25-hydroxyvitamin D [25(OH)D], the most accurate indicator of vitamin D status.

Vitamin D Level Guidelines (approximate):

< 20 ng/mL → Deficient
20–29 ng/mL → Insufficient
30–50 ng/mL → Adequate
100 ng/mL → Risk of toxicity

Who Should Test Their Vitamin D Levels?

People who work indoors, such as office workers.
Older adults.
Those with osteoporosis or frequent bone fractures.
Patients with liver disease, kidney disease, or chronic conditions affecting absorption.
People with obesity or those taking certain medications regularly.

Vitamin D and Cataract Risk: New Evidence

Recent reports suggest that vitamin D benefits not only bones but also eye health. A study from the UK Biobank (published in the British Journal of Ophthalmology, August 2025) examined over 440,000 people with an average follow-up of nearly 11 years and found:

Individuals with severe vitamin D deficiency (<10 ng/mL) had increased cataract risk:
- Cross-sectional: 12% higher risk
- Longitudinal: 11% higher risk
Under 50 years old → 27% higher risk
Age 60 and older → 9% higher risk

This research suggests that vitamin D may play an important role in eye health, especially in younger adults. Supplementation early in life may help prevent cataracts in the future.

Benefits of Testing Vitamin D Levels

Determine whether your body is receiving enough vitamin D.
Guide lifestyle adjustments such as sun exposure and dietary choices.
Help set appropriate supplementation dosage—not too little, not too much.
Prevent long-term health issues such as osteoporosis, weakened immunity, and potentially cataracts.

Measuring vitamin D levels is not a small matter. Vitamin D is a “key” factor connected to bone health, immunity, chronic diseases, and even vision. New research reinforces that maintaining sufficient vitamin D from a young age is an investment in long-term health.

Reference: British Journal of Ophthalmology, August 18, 2025

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Medical Article

The Benefits of Vitamin D: From Bones to Eyes, Roles You May Not Know

Medical Article

VDO Knowledge

The Benefits of Vitamin D: From Bones to Eyes, Roles You May Not Know