Vitamin D in the Israeli Winter: Sunshine Is Not Enough for Everyone

Israeli sunshine sounds like a guarantee. In practice, an air-conditioned office, long sleeves, sunscreen, and bowel disease that impairs absorption leave quite a few people with low vitamin D levels. Even in October. Even in Eilat.

Vitamin D is not a trend. It is a test. And the important question is not which supplement to buy, but whether there is a deficiency at all.

Why sunshine is not enough

The skin produces vitamin D when exposed to a particular type of radiation, which is weaker in winter and in the morning and evening. Someone who leaves home at seven, goes into an office, and returns at six encounters the sun mainly through a window. Glass blocks most of this radiation.

There are other variables too: darker skin produces less vitamin D with the same exposure. Older age reduces production. Clothing that covers most of the body changes the picture. Sunscreen, which is very important for other reasons, also reduces production. None of these factors means you should give up sun protection. They mean that sunshine alone is not a plan.

Who should ask about testing

People with persistent fatigue. Those living with bowel disease, particularly when it affects the small intestine or after surgery. People who rarely leave home. Those with darker skin. People taking certain medications long-term, such as steroids, that affect bone. And those whose diet contains almost no fortified sources.

This list is not a diagnosis. It is a reason to request a test, not to buy the biggest bottle.

One test, and interpreting it properly

A vitamin D test is a simple blood test. Interpreting it, however, is not always simple: reference ranges vary between laboratories, and the decision about whether to supplement and at what dose also depends on age, health, and medications. Do not translate a number into a supplement on your own using an online chart. Take the result to your doctor and ask when to repeat the test.

Excess is not a bonus

Vitamin D accumulates in the body. Taking high doses for a long time without monitoring can lead to harmful excess, including through increased blood calcium levels. “Vitamin” does not mean “the more, the better.” Without a laboratory result, there is no direction.

Sunshine as a plan

Brief skin exposure, at times and for durations recognized by your doctor or local guidance, is part of the picture. But a sunburn is not a dose, and a tan is not treatment. If you take medications that increase sensitivity to light, ask before increasing exposure. And sunshine, however pleasant, does not treat bowel inflammation.

Food

Oily fish, egg yolks, and fortified products provide vitamin D, but in relatively modest amounts when it comes to correcting a significant deficiency. They are part of a routine, not an infusion. Someone who does not eat fish has not “failed.” They simply need another source if their level is low, as recommended.

Infants, children, and adults

Some age groups have established, consistent vitamin D recommendations, such as infants in their first year, under Ministry of Health guidance. For older adults who go outside less and whose skin produces less, the question arises more often. For children and teenagers with bowel disease, testing is part of their care team's monitoring. At every age, the principle is the same: a number first, a decision afterward.

Bowel disease: not just D

With inflammatory bowel disease, vitamin D testing often comes alongside other tests because absorption of more than one vitamin is affected. Iron, B12, folic acid. Persistent fatigue can involve any one of them, or several together. We wrote about iron and fatigue that another salad will not resolve iniron and bowel disease.

Monitoring and timing

After starting a supplement, repeat the test at the scheduled time. Do not increase the dose because winter continues, or stop because summer has arrived. Keep the product name and dose for your next conversation.

If you take several medications and supplements, also ask about timing. Some supplements are better absorbed with a meal containing a little fat, and some interact with other medications. We explained how to organize a day of pills without wasting it inbowel medications and food.

This is general news information and is not a substitute for personal advice from a doctor or dietitian.