Vitamin D on GAPS: Sunlight, Foods and Seasonal Guidance

The GAPS book places sunlight first in its vitamin D discussion, then considers food and cod liver oil when sunlight is limited. Dr. Natasha Campbell-McBride treats the nutrient as part of the food-and-lifestyle pattern, rather than an isolated bottle.^[1]

That makes this a seasonal question as well as a supplement question. What the skin produces, what food provides and what a supplement contains are related, but they are not interchangeable measurements.

Where Vitamin D Comes From

Vitamin D production begins in the skin when ultraviolet B light acts on 7-dehydrocholesterol, a cholesterol precursor. Vitamin D from skin, food or supplements then undergoes conversion in the body. The GAPS book describes this more simply as vitamin D made from cholesterol through sunlight.^[1][2]

The food examples in the chapter include oily fish, eggs, butter, liver and cod liver oil. Use the foods in forms allowed for your phase. The GAPS food list and the Full GAPS meal guide help put those examples into actual meals.

The Book’s Seasonal Pattern

Campbell-McBride recommends time outdoors and emphasizes oily fish and cod liver oil during the colder, darker season. She says the majority of people do not need cod liver oil in summer when sunlight is doing its work, while also stressing individual nutritional needs.^[1]

This is the author’s seasonal framework, not a fixed calendar date at which every household should stop or start the same amount. Season, location and actual exposure are different from simply being in the month of July or January.

Her official FAQ rejects tanning beds as a substitute for natural sunlight. It recommends outdoor time even in winter and discusses food and cod liver oil when sunlight is limited.^[3]

Read the Sunlight Advice in Its Full Context

The book argues strongly against avoiding sunlight and connects skin health with food and environmental exposures. For the actual GAPS sun-exposure discussion, including gradual exposure and avoiding burning, use our sunlight guide rather than turning a vitamin D paragraph into an exposure schedule.^[1][3]

Vitamin D production and skin protection are distinct questions. Producing vitamin D does not mean that burning is desirable or that unlimited ultraviolet exposure is harmless.^[2]

Why the Chapter Discusses Deficiency

The book connects vitamin D with bone mineralization and a much wider range of functions. Its list discusses blood-sugar control, heart health, mental illness, autoimmune conditions, obesity, osteoarthritis, muscle and neuromuscular function, blood pressure, cancer, pain, immunity and hyperparathyroidism, as well as rickets and osteomalacia.^[1]

These are subjects in the author’s deficiency discussion. A symptom on that list does not establish vitamin D deficiency, and the list is not a promise that one supplement prevents or treats every condition named. Its practical role here is to explain why the chapter considers vitamin D alongside the rest of nourishment.

Vitamins A and D Are Partners

Campbell-McBride describes A and D as partners and argues that an imbalance between them matters. She criticizes adding synthetic vitamin A to processed foods without considering vitamin D, and explains her preference for cod liver oil supplying both together.^[1]

The book’s ratio discussion is not a reason to calculate a personalized dose from a single blood result. It also says cod liver oil is only part of the picture: food supplies vitamin A and some vitamin D, while sunlight supplies more vitamin D. The vitamin A guide covers food forms and digestion.

Keep Sources, Tests and Amounts Separate

A common blood marker of vitamin D status is serum 25-hydroxyvitamin D, written 25(OH)D. That is different from the amount of vitamin D listed in a serving of oil. A label amount, a blood concentration and time spent outdoors are three different records.^[2]

The GAPS chapter favors natural food sources and warns about excessive synthetic supplementation. Skin production is regulated and is not the usual route to vitamin D toxicity. Excessive supplemental vitamin D can cause toxicity, so a “natural” label is not a reason to disregard the amount in a concentrated product.^[1][2]

Use the cod liver oil guide for its product and amount distinctions. The supplement overview retains the introduction sequence and epilepsy exception instead of treating the seasonal advice as permission to skip those conditions.

Make the Seasonal Notes Practical

Record the foods and product actually used, the serving size and any planned change. If a test is part of your care, keep its date, units and result together. You can then discuss what changed without confusing a teaspoon with a blood value.

The Supplement Introduction Tracker is listed in my WFLI Shop.

For the wider starting plan, return to food first and supplement timing. The vitamin D chapter belongs within that plan.

References

1. Campbell-McBride, N. Gut and Physiology Syndrome (2020), “Vitamin D,” “Vitamins A and D are partners!” and “How much cod liver oil should we supplement?”.
2. NIH Office of Dietary Supplements, Vitamin D: Health Professional Fact Sheet, synthesis, 25(OH)D and toxicity.
3. Campbell-McBride, N. GAPS FAQs, sunlight, tanning-bed and gradual sun-exposure answers.