It looks like you are referring to this product: https://shop.kingarthurbaking.com/items/gluten-free-bread-flour Their site says: "Made with gluten-free wheat starch to give baked goods incredible taste and texture, it’s ideal for classic yeasted recipes like artisan boules, bagels, cinnamon rolls, and burger buns", and it is true that Codex quality wheat starch is gluten-free, and does make better baked goods. However, it also contains very low levels of gluten (under 20ppm), and some celiacs do react to this level, so if you are super sensitive it's best to avoid it. They also make this very similar product, which doesn't include any wheat ingredient, and is certified gluten-free:...

Our Functional Medicine doctor has always ordered the Spectracell Test for Micronutrient Deficiencies.  It tests the intracellular levels of the nutrients, not blood levels.  When high dose, targeted supplementation did not resolve the deficiencies after retesting at 6 months and then a year, he ordered genetic tests.  I have a genetic inability to process Vitamin D, B12 and antioxidants, so I am on high doses of those for life.  The rest of the initial deficiencies resolved within 6 months to a year and a good multi vitamin is sufficient to address those.  My husband has historically had high homocysteine levels and his low folate, B 12 and B6  levels are because of his MTHFR gene...