In recent years, we have been observing a growing interest in supplementing food with extracts or other components derived from biomass of microalgae. The composition and properties of microalgae and macroalgae (seaweed) make them not only a supplementing component  to restore deficiency of the selected, biologically active ingredients in the diet but, also, essential factors to impact functional and pro-health features of the product. In the research study, it was attempted to design functional breadstuffs containing extracts from  Arthrospira platensis and Ascophyllum nodosum algae. Some selected bioactive components in the algae were analysed and their  bioavailability was estimated using an in vitro technique. Based on the results of the HPLC determination and, next, of the simulation of  digestion in the human gastrointestinal tract, it was showed that enriching rye breadstuffs with algae caused the content of vitamin B2 to  increase 2 to 3 times; in the case of one of the bread variants, this increase provided nearly 30 % of the recommended daily intake of  riboflavin and it caused the content of thiamine to rise 50 to 145 % compared to the content of that vitamin in the bakery products without  algal additives at a comparable level of the in vitro bioavailability of the control sample (60 %). In the breadstuffs designed, a significant  increase, ranging from 17 to 30 %, was also reported in the content of the selected phenolic acids, mostly of the gallate and vanillinate, at a different level of the in vitro bioavailability of the polyphenols in total. The results of the analyses presented as well as the positive  (unpublished) data obtained by using sensory tests bring promising prospects for the introducing of functional breadstuffs with algae  additives into the bakery products market.