compare their 25-hydroxy vitamin D levels, for one thing. One of the twins could still have a genetic variation or SNP that is different, and if for example that happens to affect the Vitamin D receptor and the efficiency of utilizing Vitamin D synthesis for innate immunity, well there you go.
compare their 25-hydroxy vitamin D levels, for one thing. One of the twins could still have a genetic variation or SNP that is different, and if for example that happens to affect the Vitamin D receptor and the efficiency of utilizing Vitamin D synthesis for innate immunity, well there you go.
Do they both work outside in the same amounts?