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Taurine is the most abundant non-proteinogenic sulphur amino acid in humans, and its level decreases dramatically with aging. In humans, the highest levels of taurine are present in retina, leukocytes, heart, skeletal muscles and brain. Taurine is necessary to ensure proper homeostasis and recent research in animals (for example mice and monkeys) have shown that it significantly increases life expectancy and improves health. At the cellular level, taurine is involved in a number of processes such as osmoregulation, modulation of calcium levels and stabilization of cell membranes. Moreover, it has an inhibitory effect on the central nervous system and has antioxidant, anti-apoptotic and anti-inflammatory activity. The development of neurodegenerative diseases is associated with improper functioning of mitochondria, oxidative stress, development of inflammation, excessive activation of ionotropic and metabotropic glutamate receptors and neuronal apoptosis. In vitro and in vivo studies have shown that taurine inhibits the above-mentioned pathological processes and has neuroprotective properties. The antioxidant effect of taurine results from neutralizing hypochlorous acid, a strong oxidant that is produced by neutrophils at the site of the inflammation. Taurine chloramine (Tau-Cl) produced in this reaction reduces oxidative stress and inhibits the production of pro-inflammatory cytokines (e.g. TNF-α, IL-1β, IL-6), nitric oxide (NO) and prostaglandin E2. Moreover, this compound stimulates the expression of antioxidant enzymes (e.g. peroxiredoxin 1, thioredoxin-1, hemooxygenase-1, glutathione peroxidase, catalase). Within the nervous tissue, the anti-inflammatory and antioxidant effect of taurine is related to reduced expression of IL-1α, IL-1β, TNF-α, IFN-γ, IL-6 and GM-CSF, and increase in the activity of antioxidant enzymes (peroxidase-, reductase- and S- glutathione transferase, superoxide dismutase) and glutathione concentration. Taurine is necessary for the proper functioning of mitochondria. Its deficiency blocks the synthesis of taurine-modified leucine tRNA (τm5U-tRNALeu), which results in inhibition of the synthesis of NADH-ubiquinone oxidoreductase, improper functioning of complex I of the respiratory chain and increase in oxidative stress. Endoplasmic reticulum (ER) stress is a hallmark of neurodegenerative diseases and can lead to neuronal apoptosis. Taurine deficiency increases the accumulation of misfolded cellular proteins and induces ER stress. Taurine supplementation reduces neuronal ER stress by inhibiting ATF6- and IRE-1-dependent signalling pathways. Moreover, taurine inhibits apoptosis of neuronal cells by increasing the expression of Bcl-2, decreasing the expression of p53, CHOP and Bax and reducing the activity of caspase-3. In the central nervous system, taurine also serves as an inhibitory neurotransmitter due to binding with γ-aminobutyric acid and glycine receptors (GABAA and GlyR, respectively). Such interactions causes an increased influx of chloride ions into neurons, hyperpolarization of the cell membrane and, consequently, inhibition of glutamatergic neurotransmission and excitotoxicity induced by glutamic acid. The neuroprotective activity of taurine is due to its pleiotropic effects related to the inhibition of apoptosis, oxidative stress, ER stress, and also to its anti-inflammatory activity and inhibition of neuronal excitability.

Polyunsaturated fatty acids, which include acids from the omega-3 and omega-6 groups, play an important role in the human body. The omega-3 family of acids includes α-linolenic acid (ALA), docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). The main sources of α-linolenic acid in the diet are vegetable oils (the largest amounts are found in flax seed oil and chia oil), nuts, while docosahexaenoic and eicosapentaenoic acids are fish and marine algae. Omega-3 fatty acids (especially DHA) are crucial for proper prenatal brain development, as well as children's behavioral and intellectual development. This extremely important function of DHA is due to the stimulation of cellular processes important for proper neuronal development and function. High concentrations of DHA are found in the phospholipids of the retina, the membranes of brain-building cells, and are essential for normal vision as well as neuronal development. The neurotrophic and neuroprotective effects attributed to DHA may be related to the activity of DHA's metabolite N-docosahexaenoyl ethanolamine (synaptamide). Synaptamide (SA) is synthesized in the brain, retina, adipocytes or macrophages and is a more potent stimulator of synaptogenesis compared to DHA. The fetal demand for DHA is significantly increased during the third trimester of pregnancy. An important determinant of normal fetal blood levels of DHA is the mother's diet. In published studies, supplementation with omega-3 fatty acids has been shown to reduce the risk of pre-eclampsia and preterm labor. Pregnant women should consume adequate amounts of omega-3 fatty acids by providing them with their diet (e.g., vegetable oils, marine fish) and/or in the form of supplements (fish oil or preparations containing docosahexaenoic acid derived from marine algae. Higher intake of DHA-rich marine fish has been correlated with a lower incidence of postpartum depression in mothers. The aim of the article is to describe the biosynthesis, food sources and the recommended daily intake of DHA, with particular emphasis on pregnant women. In addition, the effects of DHA and synaptamide in the neurogenesis and their role in the proper functioning of the brain are discussed.