What vitamin should I take for strong bones?

For strong bones, vitamin D is the most important thing - without it, calcium simply won't be absorbed, no matter how much you get from food. That's the critical part. Second is calcium itself, but everyone knows the sources: dairy products, fish with bones, leafy greens. But people often overlook vitamin D, especially if they live somewhere with short daylight hours or spend a lot of time indoors.

Vitamin D is produced in your skin when exposed to sunlight, so it's enough to just spend 15 - 20 minutes a day in the sun, and that solves the problem in many cases. If that's not possible or you live somewhere with little sun, vitamin D is found in fatty fish (herring, mackerel), egg yolks, and butter. But honestly, the amounts aren't very high - you usually have to supplement.

About supplements: doctors often recommend them, especially for people over 50 and those who don't get much sun exposure. Go with vitamin D3 supplements; they're inexpensive. Just get a blood test first to check your vitamin D levels - you might be fine already, and supplements might not be necessary.