Information on the retention of vitamin D in food following household cooking is scarce. So far the retention of its metabolites vitamin D3, vitamin D2, and 25-hydroxyvitamin D3 has shown that the type of food and the cooking method are the essential determinants, and there is no significant difference between the metabolites. We investigated the retention of vitamin D3 and vitamin D2 in sunflower oil, vitamin D3 in rainbow trout, and vitamin D2 in button mushrooms. The investigated cooking methods were boiling at different pH, steam cooking, microwave cooking, pan-frying, and oven baking. There was no difference between the retention of vitamin D3 and vitamin D2 added to sunflower oil, which ranged from 70 to 99%. In rainbow trout, the retention of vitamin D3 at 85-114% was not significantly different from 100%, except for panfrying at 85%. However, the retention of vitamin D2 in mushrooms at 62-88% was significantly different from 100% (p ≤ 0.05).

Further research on vitamin K is necessary as growing evidence of vitamin K's importance in human health beyond blood coagulation and bone health is emerging. We present a cost-effective LC-ESI-MS/MS method for quantification of phylloquinone (PK), and menaquinones (MK) 4-10 in food using deuterium labelled (d7) compounds (d7-PK, d7-MK-4, d7-MK-7 and d7-MK-9) as internal standards. The validation of the method included assessment of matrix effect, limit of quantification (LOQ), precision, and trueness. The LC-ESI-MS/MS method runtime is 9 min. The method was compared to a validated LC-FLD method (CEN 14148), for quantification of vitamin K in broccoli, cheese, natto, liver, and microalgae. LOQs of the LC-ESI-MS/MS method were ≤4 µg/100 g food. The intra- and inter-assay precision was <15% for PK, MK-4, MK-7 and MK-9; <20% for MK-5, MK-8, and MK-10, and ≤25% for MK-6. No significant differences between the quantified content by the LC-ESI-MS/MS and LC-FLD methods were observed.