Recent research shows that vitamin D has beneficial effects on almost every organ and system in the body. But to obtain these health benefits you must have a plentiful supply of vitamin D. That comes from taking an effective vitamin D dosage. So how much do you deserve?

A small amount of vitamin D will prevent a child from getting rickets (a bone and joint disease). Somewhat more might prevent an adult from getting osteomalacia (soft bones). Even more might help prevent diabetes, auto-immune disease, or bone fractures in the elderly. More still might help a person to avoid heart-disease, or cancer.

That's one reason why various authorities recommend different vitamin D dosages, and why the official Adequate Intake level is a paltry 200 International Units (for people up to age 50). You see, 200 IU per day is just enough to stop a child from getting rickets.

So why not just take a really big vitamin D dose every day? Well, you could do that for a while. Your body stores of vitamin D would build up, and eventually you would reach the optimum range and reap the maximum health benefit. And even after that, you would just continue building a growing, healthy vitamin D reserve.

But if you carried on long enough with a vitamin D dose that was quite excessive, you might reach the limit of your capacity to safely store vitamin D. Then if you took more still, the excess would become toxic to you and make you ill.

So it makes sense to get it right, and the best way to do that is to look at vitamin D blood levels.

In warmer climates, blood levels of the storage form of vitamin D (25-hydroxy-vitamin-D) are generally around 50-70 ng/ml (equivalent to 125-175 nm/L) for healthy people who spend plenty of time in the sun. Because the sun shines frequently for most of the year in those climes, these people are able to maintain healthy vitamin D levels throughout the year, on sunlight exposure alone.

So it comes as no surprise that researchers, looking into how vitamin D influences our health, have found that the greatest protection from disease occurs when vitamin D blood levels are in that same range: 50-70 ng/ml.

Now if that's the level that maximizes vitamin D's many health benefits, then surely that is the level you deserve!

Can you get there with a vitamin D dose of 200 IU daily? No. Not unless you spend time outdoors in the sun, almost every day. But without sunlight, most people need more than 20 times that amount!

That is why there are so many vitamin D-deficient people everywhere, most especially in places that don't enjoy frequent, strong sunshine for most of the year. You could be one of them.

Raising your blood level into that optimum range takes more vitamin D than you might think - your body squirrels it away, into muscle and fat cells. When those cells are well-stocked, your vitamin D blood level will also be high.

But when a person is vitamin D-deficient, most of the vitamin D they take in gets routed into those storage cells (saved for a rainy day, literally!) There is only a brief and small effect on the level of vitamin D in the blood.

Eventually (probably after two or three months of effective vitamin D dosing) that person's blood level will reach the optimum range. Then they will only need to take in as much vitamin D as their body actually uses. For an 80 kilogram (176 pound) adult in good health, that is about 5000 IU daily from all sources (including sunlight).

But we are all different, so it is best to calculate your own personalized vitamin D dosage, taking sunlight and body mass into account. Then you will get the vitamin D dosage, and benefits, you deserve.