IThree years ago, I had my vitamin D levels checked. The result: 14 ng/ml. The lower reference value is 30, and the optimal range is 50 to 70. My doctor said dryly: "You're in a range where 80 percent of your age group is. Nobody notices it. But your body notices it every day."

Vitamin D is not a vitamin in the classic sense. It is a hormone that almost every cell in the body needs – from bones to muscles to the brain. In the summer, the skin produces it itself as soon as enough sunlight hits it. In winter, this doesn't work in Northern Europe – the sun is too low, the UVB radiation doesn't get through.

What Vitamin D does for your golf

A low vitamin D level impairs neuromuscular control. Specifically, this means reaction times become longer, depth perception becomes less accurate, and balance stability—crucial for putting—suffers measurably.

Studies show that seniors with suboptimal vitamin D levels are twice as likely to fall as well-nourished control groups. On the golf course, often on uneven terrain, this is a direct risk factor. And one that can be measured and easily corrected.

80% of people over 60 in Germany have vitamin D levels below 30 ng/ml—the threshold at which adverse effects on muscles and bones begin.

Why Outdoor Sports Alone Aren't Enough

Even those who regularly spend time outdoors build up practically no reserves from October to April. In Hamburg, Berlin, or Munich, the sun is so low during this time that the UVB radiation is absorbed by the atmosphere before it reaches the skin. Summer reserves, if stored well, last about three months – until the end of January. After that, you are in deficit without supplements.

When it comes to Vitamin D, correction is trivial, but diagnosis is crucial. Without a blood test, you don't know where you stand — and all assumptions lead you astray.

— Endocrine Society, Practice Guideline 2024

Three measures are practically indispensable for every senior golfer in Northern Europe. They are inexpensive, easy to implement, and show measurable results within eight to twelve weeks.

Blood test at the general practitioner

The test costs around 30 Euros and is rarely covered by insurance. It clarifies whether you are in the deficient, deficit, or target range. Without this information, any supplementation is guesswork.

1,000 to 2,000 IU daily

With a proven deficiency, 1,000 to 2,000 International Units daily is the standard. Higher doses should only be taken under medical supervision. You can take a break in the summer; taking it in the winter is advisable from October onwards.

Also magnesium and K2

Vitamin D only works properly when magnesium and vitamin K2 are also available. A tablet with a combination of active ingredients costs about five euros per month – and makes the difference.

What Vitamin D is not

Vitamin D is not a miracle pill. It won't make you faster, longer, or better if you just take it on top. But when deficient, it prevents your body from functioning normally. Those within the target range gain no additional benefit from more. More is even dangerous — toxicity symptoms begin above 100 ng/ml.