Any diet that decreases food variability has the potential to increase the risk of nutrient deficiencies — if it is not well planned. With a GFCF diet, nearly all dairy, many grains, and grain-based products (wheat, barley, and rye) will be eliminated. The removal of dairy and gluten-containing foods can subsequently decrease the intake of vitamins and minerals these products contain naturally and are typically fortified with. Namely calcium, fiber, and the B vitamins.
While it may seem simple for an adult to just get wheat or dairy associated nutrients from other foods, nutrient intake issues can be tricky in developing children, who typically don’t make their own eating decisions, and especially children with specific health conditions. One study found that boys with ASD[1] had lower bone mineral density and vitamin D intake from food as well as measured in serum. With the elimination of dairy, particular attention is needed to ensure adequate intakes of calcium and vitamin D are being consumed to maintain bone health.