Vitamins2 min readLabel reading
How much vitamin D do you get in Bangkok?
One of the sunniest cities on earth, and the answer is still less than you think. Where the sunlight goes, and what the numbers on the label mean.
The sun is outside the building
Bangkok gets more usable UVB in a year than most of Europe sees in five. That fact does very little for the person who leaves a condo at 7am, sits under office lighting until 6pm, and crosses two skywalks in between.
Skin makes vitamin D from UVB specifically, and UVB is the part of sunlight that ordinary window glass blocks almost entirely. A desk by a bright window is a pleasant place to work and contributes essentially nothing. Air-conditioned transit, long sleeves against the sun and sunscreen are all sensible in this climate, and all of them subtract from the same total.
None of that makes a supplement compulsory, but a tropical address does not settle the question either.
IU, micrograms, and the label arithmetic
Vitamin D is stated two ways, and both appear on shelves here. The conversion is fixed: 40 IU is 1 microgram, so 1,000 IU is 25 mcg and 5,000 IU is 125 mcg. A bottle marked “50 mcg” is a 2,000 IU bottle.
Two more numbers decide what you are buying: the amount per softgel and the serving size in softgels. A panel reading 5,000 IU per serving, at two softgels a serving, is a 2,500 IU softgel.
- D3 (cholecalciferol)
- The form in most supplements; usually from lanolin, sometimes from lichen for a vegan label.
- D2 (ergocalciferol)
- Plant-derived, and the form used in some fortified foods. Treated as less potent per IU in most reference material.
- In oil
- Vitamin D is fat-soluble, so it comes in an oil base or is taken with a meal that has fat in it.
What the reference intakes say
The commonly published adult reference intake is 600 IU a day, rising to 800 IU past 70, with 4,000 IU generally given as the upper level for regular intake. Those are population figures for healthy adults, not a prescription for one person, and they assume food is contributing as well.
Higher short courses exist, and they are a matter for a clinician. If you are pregnant, taking medication that interacts with fat-soluble vitamins, or asking because of a symptom rather than a habit, a blood test is the way to find out.
What the article names, on our shelves
Matched on the form printed in each product’s own title.
This is about labels, not about you: nothing here is a diagnosis or a dose. Reference intakes quoted are population figures. If you take medication, are pregnant or breastfeeding, or are asking because of a symptom, ask a pharmacist or a doctor first.
