A paper published in 2022, analyzing OAT test data from 316 individuals with chronic fatigue syndrome (CFS), found that a functional B12 deficiency, caused by a vitamin B2 (riboflavin) deficiency, could be a big contributor to the disease state. 

“Analysis of OAT data from the cohort of 316 individuals diagnosed with CFS revealed that every individual within the cohort had a reduced efficiency to gain energy from fats, carbohydrates and protein, due to a functional deficiency in vitamin B2.”

Vitamin B2 deficiency can seemingly cause a functional B12 deficiency, where the markers of B12 status appear normal, but its cellular utilization is impaired. The supplementation of vitamin B2, as well as creatine and CoQ10 (the synthesis of which is reduced in functional B12 deficiency), could be helpful for some individuals with CFS. The foods most abundant in vitamin B2 are organ meats (liver, kidneys), dairy, and hard-boiled eggs. 

Important note: Many nutrients and hormones are involved in turning fats, carbs and proteins into energy, and many toxins (incl. mould toxins and heavy metals) can interfere with these processes. A B2 deficiency or a functional B12 deficiency could be just one of the possible “root causes” behind CFS. Deficiencies of iron, vitamin B1, folate, magnesium, vitamin D, and selenium have all been linked to the pathology of CFS, as has impaired thyroid function, either due to impaired conversion of T4 to T3 by the liver or poor cellular T3 uptake. The bottom line is that a nutrient-dense diet (containing shellfish, dairy, some organ meats, ripe fruit, and well-cooked vegetables) should be foundational to treating CFS.