The authors investigated in a group of 44 adult vegans the iron and haemoglobin levels, values of calcium, zinc, total proteins, glutathione, the fatty acid plasma profile, product of lipid peroxidati- on and antioxidant vitamins. The values were compared with a group eating a mixed diet (omni- vores, n = 42). In vegans the following results were recorded in 57 % hyposideraemia (vs. 5 % in omnivores), 39 % anaemia (vs. 2 %), 52 % hypocalcaemia (vs. 9 %), 11% hypozincaemia (vs. 0 %) and 16 % hypoproteinaemia (vs. 0 %). Iron, calcium, zinc, protein are risks of an alternative diet. The lower quality of plant proteins was manifested in a significantly lower glutathione blood level in vegans. The higher value of the index of fatty acid peroxidability did not imply a greater lipid peroxidation in vegans – significantly lower values of conjugated fatty acid dienes were found. This is due to the adequate protection by essential antioxidants – levels of vitamins E, C and beta-carotene are significantly higher in vegans. These are overthreshold values of a reduced risk of free radical diseases. Despite a higher supply of linoleic acid and alpha-linolenic acid for the formation of n-6 and n-3 fatty acids with C 20 and more , the only possibility in vegans (food source is lacking), this group on an alternative diet had an insignificantly lower content of arachidonic acid (n-6) and a significantly reduced content of n-3 acids. Iron deficiency in vegans reduces the activity of d6 desaturase and this caused lower polyunsaturated fatty acid levels. The results provide evidence of the risk of an alternative diet of the vegan type in adults.

        Key words: vegans – omnivores – iron – calcium – zinc – protein – fatty acids – antioxidant vitamins