Even though Indonesia is on the equator, studies show 50–80% of Indonesian adults are vitamin D deficient. The main reasons: indoor work, covered clothing, sunscreen, and a low-sun-exposure lifestyle.
What vitamin D does: calcium absorption, bone strength, immune function, mood regulation, muscle function.
Test: serum 25-hydroxy vitamin D. Results: <20 ng/mL = deficiency; 20–29 = insufficiency; 30–100 = normal; >100 = excess.
How to raise it: 10–15 min morning sun (arms + legs, no sunscreen), 3–4× a week. Food: fatty fish (salmon, sardines, tuna), egg yolks, mushrooms, fortified milk/yogurt. Supplement 1000–4000 IU/day per doctor advice if deficient.
Screening recommended: seniors, pregnant/breastfeeding women, children with chronic fatigue, osteoporosis patients.