Not long ago, Dr. Peter Osborne, author of No Grain, No Pain, gave a fascinating talk on vitamin D. Here are some key insights from that discussion:

• You can live in a sunny climate and still be vitamin D deficient. One major cause? Being overly hygienic—specifically, too many showers.
• Food isn’t a great source of vitamin D. Liver and mushrooms are among the best, but overall, food provides very little. Even fortified products contain the inactive form (D2), which offers minimal hormonal benefit. As Osborne puts it, taking low doses of D2 is like “trying to spit on a forest fire.”
• Most vitamin D is made from sun exposure. A form of cholesterol on your skin converts to vitamin D when UV light hits it. But here’s the kicker:
  That vitamin D takes about 16 hours to absorb into your bloodstream—and it still needs to be processed by your liver and kidneys to become active.
• Daily showers with soap can wash away your vitamin D. Even with adequate sun, you’re literally sending it down the drain. That’s why frequent showering—especially with full-body soaping—is a common reason for deficiency.
• The overuse of hygiene can backfire. The germ theory made us afraid of dirt, but balance is key. You don’t need to wash your hands a dozen times a day or shower twice daily. Excessive cleanliness can contribute to autoimmune conditions.
• Vitamin D helps regulate your immune system. It tells immune cells to “calm down” when they’re overreacting—without it, you end up with a biological house party where all the furniture gets wrecked.
• You need 20–30 minutes of direct sunlight daily—without sunscreen. Any SPF over 8 blocks vitamin D. Most makeup contains at least SPF 15, which means women who wear makeup regularly may be blocking their primary source of vitamin D—especially in winter when only the face is exposed.
• Sun phobia is real. Many still believe sun exposure causes cancer. That’s not entirely true. Sunburn can increase the risk of cancer, but sensible sun exposure is beneficial. Saying “avoid the sun because it causes cancer” is like saying “don’t drink water because you might drown.”
• Vitamin D is actually a prohormone, not a vitamin. It plays a vital role in many bodily functions—particularly in supporting muscle strength and growth. Deficiency can lead to weakness and muscle loss, which in turn affects your metabolism.

Take-Home Message

Shower every other day, or if you must shower daily, use soap only on the “stinky” parts—let the oils on your skin (and the vitamin D they carry) absorb, especially in sun-exposed areas. Shower in the morning before sun exposure—not at night—to give your body time to absorb vitamin D while you sleep.