Vitamin D
Daily vitamin D — the one supplement most people actually need
Vitamin D is the one supplement where nearly every serious scientist agrees: most people in northern latitudes are under-supplied, especially in winter. From October to April, the sun is too low here for your skin to produce meaningful vitamin D. And yet most adults take nothing. Daily vitamin D as a habit is one of the simplest and most effective micro-habits there is — and it costs pennies a day.
Why this habit matters
Vitamin D isn't just 'a bone vitamin.' It's involved in immune function, muscle strength, mood regulation, sleep quality. Research shows deficiency correlates with higher infection susceptibility, depressive mood, and fatigue. Typical February levels in northern countries sit at half the recommended value — many people live for years in chronic under-supply without seeing the link to winter fatigue, low mood, and frequent colds. A daily dose of 1000 to 2000 IU covers most adults. Get your level tested once at a doctor (or via a direct lab) and you know exactly where you stand. One of the rare cases where the data is genuinely clear.
Three tricks that actually help
Anchor the pill to your breakfast. Vitamin D is fat-soluble — it absorbs better with a meal containing some fat. Breakfast with avocado, eggs, or a tablespoon of olive oil in your yogurt is ideal. If you don't eat in the morning: take it with the first meal of the day. Put the bottle next to your dishes so you see it. The visibility is the cue. Out of sight, you'll forget.
Get your level measured once. At the doctor or via a private lab, costs around 20 to 40 dollars depending on the provider. Then you know if 1000 IU is enough or if you need 2000 or 4000. Generic dosing works for most, but knowing your number is a small investment for years of clarity. Test in February, the lowest point — if you're good there, you're good year-round.
Forgot a day? Doesn't matter. Vitamin D is fat-soluble and gets stored in the body. Whoever forgets for a few days has no measurable effect. Don't double-dose, just resume tomorrow. Some people take a higher dose once a week instead of daily — also works. What matters is consistency across months, not every single day. Be pragmatic, stick with it.
How to start tomorrow
Today or tomorrow: buy vitamin D 1000 IU (or 2000 IU) at the pharmacy or drugstore, costs between 5 and 15 dollars for months of supply. Pills or drops, both fine. Put the bottle right next to your coffee machine or breakfast plate. Tomorrow morning: one pill with the first meal. The day after: same thing. Every day. Test your level in two to three months to see if the dose fits. Tiny habit, big lever — especially in the winter months.
Related habits
Part of the Starter Challenge.