Fish contains 18–20% protein, and contains eight essential amino acids including sulfur containing lysine, methionine, and cysteine (12). It provides easily digestible protein of high biological value that is important for the growth and development of the body, the maintenance and repair of worn out tissues and for the production of enzymes and hormones necessary for many of the body's processes, it's contains less fat than red meat (19).

The fat content ranges from 0.2 to 25%, especially polyunsaturated fatty acids (PUFAs), which are essential for the proper growth of children and are not associated with the occurrence of cardiovascular disease (20). Fats also contribute to the energy supply and aid in the adequate absorption of vitamins K, D, A, and E (21). Fish is a vital source of vitamins Figure 2, especially vitamins A and D of the fats, as well as thiamine, riboflavin, and niacin (vitamins B1, B2, and B3) (22). Vitamin A found in fish is more available in the body compared to plant foods and is essential for normal vision and bone growth, also, fatty fish contains more vitamin A than the lean types (22). Vitamin D, found in fish liver and oils, is essential for bone growth because, it is essential for calcium absorption and metabolism (23). Energy metabolism requires thiamin, niacin, and riboflavin (23). Fresh fish provides a small amount of vitamin C, which is essential for wound healing, maintaining the integrity of tissue, and assisting in the absorption of iron in the nervous system (22).

Phosphorus, calcium, iodine, iron, selenium, fluorine, and zinc are among the minerals found in fish and are extremely “bioavailable,” ensuring that they are readily consumed by the organism (24). Iron is critical for the formation of hemoglobin in the blood, which would be responsible for distributing oxygen across the body (24). Calcium is critical for the development and mineralization of bones, as well as the normal operation of tissues and the central nervous. It also plays a significant role in the clotting of blood (25). When young fish are consumed with their bones, the phosphorus, calcium, and fluorine consumption is greatest (25). Zinc is needed for growth performance, function of immune system and the maintenance of healthy skin (26). Iodine, found in aquatic food, is necessary for hormones that control body metabolism, growth and proper behavioral development in children (22). Fish clearly provides more to people's diets than just high-quality protein (27). As a result, fish can be a staple to every diet, avoiding starvation which, make these nutrients readily accessible to absorption by organs.

In recent decades, as people's concerns about their health have grown, so has their concern about fats (28). Fatty acids are molecules consisting of one glycerol and three fatty acids that serve as a source of energy in our body and are deposited in the meat, muscles and liver (29). When fat is ingested, lipase breaks it down into one glycerol and three fatty acids, while a few fatty oils molecules are pass through intact through the intestine (30). The ingested fat is at initial storage in the liver, the muscular or subcutaneous inner layer and then broken down as needed to provide energy (31).

Furthermore, saturated and unsaturated fatty acids are distinguished by the presence or absence of an intramolecular double bond (20, 32). Saturated fatty acids are found in animal oils and are harmful to an individual's health, while unsaturated fatty acids are found in vegetable oils and are beneficial to an individual's health (21, 33). As a result, polyunsaturated fatty acids (PUFAs), such as omega-3s, have received significant attention (12). There are several medications and able to pay foods on the market, and the number of products aimed at children has risen as well (34). However, since there is concern about indiscriminate and excessive PUFA intake, it is critical to understand the correct use of PUFAs (35). As a result, the purpose of this study is to investigate at the fundamental concepts, kinds of PUFAs, physiological mechanisms of action of PUFAs, and PUFA consumption in children.

Animal oils, like pork, and butter, are rich in saturated fatty acids. Fish oil is an unsaturated fatty acid similar to animal oil (36). Unsaturated fatty acids make up the majority of vegetable fats, although saturated fatty acids like those found in coconut and palm oils are also present (37).

The persistent stability of saturated fatty acids causes them to harden and become white at cold temperatures. It is easy to store and does not easily strip when exposed to heat or pressure (38). Saturated fatty acids are problematic because they contribute to a number of circulatory and vascular issues (39). Saturated fatty acids, that harden at low temperatures, can cause atherosclerosis, angina, and stroke by raising cholesterol levels, and they can also alter blood flow (40). Some saturated fatty acid such as myristic acid C14/0, stearic acid C18/0, monounsaturated fatty acid as palmitoleic acid C16/1, Oleic acid C18/1 (41).

Unsaturated fatty acids on the other hand do not solidify and exist in liquid form at low temperatures due to their structural instability; they strip quickly when heat or pressure is applied, and spoil quickly (42). Unsaturated fatty acids are recognized to offer a variety of health benefits (43). Unsaturated fatty acids—linolenic acid (ALA) C18/3, linoleic acid C18/2, arachidonic acid (AA) C20/4; n−6, eicosapentaenoic acid (EPA) C20/5; n−3, and docosahexaenoic acid (DHA) C22/6; n−3 are those that have a physiologically vital role for children (44). The location of the first omega double bond, the carbon atom at the end of the carbon chain (the CH3 radical) within the fatty acid molecular structure, is used to classify unsaturated fatty acids (45). The essential fatty acids ALA, linoleic acid, and AA are required for optimal growth and health, but are not produced in animals' bodies, so they are classified as essential fatty acids (46). Wild fishes have higher levels of omega-3 PUFAs than farmed fish (47). Cold-water fishes contents contain greater amounts of long chain n3 PUFAs, which aid in their adaptation to the cold temperature (47). Aquatic oil, can provide EPA, Docosapentaenoic acid (DPA), DHA, and arachidonic acid (ARA), that can be used immediately in the body for regular physiological processes (20, 48). Omega-chain fatty acids are also known as unsaturated fatty acids (49).

Omega-3 (n-3), omega-6 (n-6), and omega-9 are all good examples (n-9) (50). Fish oil (for example, Sardine (10.14 EPA; 10.66 DHA), Menhaden (13.17 EPA; 8.56 DHA), Salmon (13.20 EPA; 18.23 DHA), Cod liver (9.90 EPA; 10.97 DHA), Herring (6.27 EPA; 4.21 DHA) and Fish such as Caviar, black and red (2.74 EPA; 3.80 DHA), values are g/100 g. (51). Vegetable oils (such as perilla oil, flaxseed oil, soybean oil, and canola oil) are both high in Omega-3. ALA, EPA and DHA are the nutritionally necessary omega-3 fatty acids (52, 53).

Animals have a limited ability to synthesize EPA and DHA (long-chain fatty acids) from ALA because they cannot produce omega-3 fatty acids (short-chain fatty acids) (54, 55). Grape seed oil, soybean oil, corn oil, sunflower oil, and cottonseed oil are high in omega-6 fatty acids (56, 57). Linoleic acid, linoleic acid, and AA are all omega-6 fatty acids (58). Oleic acids belong to the class of omega-9 fatty acids, and make up more than 80% of olive oil (59). Lard, palm oil, and sesame oil also contain omega-9 fatty acids (60).

The quality and safety of food products determines the protection of public health, social stability as well as the food and nutrition security (2, 86). Fish is vulnerable to contamination by pollutants such as heavy metals that threaten their safety for human consumption. Heavy metals are classified as elements having a high atomic weight and a density of at least five times greater compared to that of water and are present in nature from the earth's crust (87–90). Despite numerous heavy metal elements present in nature, mercury (Hg), arsenic (As), cadmium (Cd), chromium (Cr), and lead (Pb) are considered the most toxic elements and threat to public health. The widespread contamination of heavy metals in aquatic environment results mainly from anthropogenic activities including agricultural, industrial (such as mining), medical, and domestic applications (87, 90). Fish accumulate heavy metals by uptake through the gills and the skin when in contact and can bioaccumulate and bio-magnify them to toxic levels for human consumption (91, 92). However, the risks associated with consuming fish depends on the levels of contamination. The Food and Agriculture Organization (FAO) has set limits within which fish contaminated with heavy metals is considered safe for consumption (Table 1). As indicated, some elements could be toxic even at low levels while others at higher levels. Invariably, the consumption of fish and fish products contaminated with heavy metals at levels beyond safe limits could have adverse effects in humans. However, children are more vulnerable due to their low body weight and behavior. For example, exposure to Pb in children could cause learning deficit, intelligence quotient (IQ) lowering, and severe damages in the brain and kidneys (93). Consuming excess Cd levels in fish products could result in kidney failure and bones softening, as well as prostate cancer in males (94, 95). Consumption of As in food products above safe level causes cardiovascular diseases, developmental anomalies, hearing defects, carcinoma, and hematologic disorders (96, 97). Hg is known to cause permanent damage to the central nervous system in children (98, 99). Effects such as heart function alteration, leukemia, kidney damage, neurocognitive defects and neuromotor disabilities have been reported in children exposed to Hg in sea food (100–102). Besides, Hg could affect children during any stage of development including maternal exposure particularly from methyl mercury (MeHg) species (87). Exposure to Cr could affect the functions of the heart, hematological parameters, kidneys, liver, and the central nervous system (103). Therefore, it is suggested that regular monitoring of heavy metals accumulation levels in aquatic environments and fish be conducted to safeguard public health (104, 105).

Fish, also being a perishable product, is vulnerable to fermentation and decomposition resulting in biogenic amines (BA) that threaten fish safety for consumption. BA refer to toxicants non-volatile amines resulting from amino acids decarboxylation (107). They are produced either by proteolytic activities of certain microorganisms or naturally during the metabolism of related precursor amino acids (108). However, in fish, histamine (HIS), cadaverine (CAD), and putrescine (PUT) are the only biogenic amines of concern when it comes to food safety and quality control (107). HIS is a monoamine produced from histidine precursor amino acid via a one-step decarboxylation reaction (108). CAD is a diamine produced from lysine and putrescine via a decarboxylation reaction (109). PUT is also a diamine but is produced either through a single-step decarboxylation from agmatine and ornithine, or indirectly after arginine hydrolysis (110). Although BA, at their physiological levels, play important roles in various cells process such as cell growth, gene expression, and tissue repair (111, 112), their ingestion at higher levels, although unlikely, could pose serious health hazards like symptoms of histamine poisoning including anaphylaxis, hypertension, nervous manifestation, and even death (113). Besides, Doeun et al. (114) reported that CAD and PUT could give way to gastric cancer during its conversion into carcinogenic N-nitroso compounds by microorganisms present in the digestive tract. Furthermore, in Europe, consumption of fish containing elevated levels of BAs was associated with widespread cases of intoxication (European Food Safety Authority EFSA (115) Therefore, it is very important that fish products are screened for BAs before administered for consumption to safeguard public health. This can be done 2-fold: maintaining high level of hygiene during fish harvesting, storage, processing and distribution to consumers, and by controlling total mesophilic (TMC) and total psychrophilic (TPsC) bacterial counts in fish products. El-Ghareeb et al. (109) observed a positive correlation between total BAs and TMC, suggesting that microorganisms play a major role in contaminating fish products with BAs.

To ensure the growth, health and development of children to their full potential, adequate nutrition during infancy and early childhood is essential. The most effective interventions to improve child health is through optimal infant and young child feeding practices (116). Poor diets will drive malnutrition in early childhood and millions of children are eating too little of what they need, and millions are eating too much of what they do not need which is the main risk factor for the global burden of diseases (117). According to Unicef (117) malnutrition, which is an umbrella term for both excess consumption of nutrients (overnutrition), inadequate consumption of nutrients (undernutrition) or micronutrient deficiency (“hidden hunger”), is primarily caused by a suboptimal diet. The burden of child undernutrition remains a global threat, with 21.3 percent of children under the age of 15 years stunted, 6.9 percent wasted and 340 million suffering from micronutrient deficiencies (3). It is reported by (118) and (119) that in addition to contributing to greater dietary diversity and boosting the micronutrient intake of women of reproductive age, the consumption of aquatic foods in the first 1,000 days of life from conception to a child's second birthday is associated with positive birth outcomes, a better nutrient composition of breastmilk, reduced stunting and a decline in the prevalence of severe acute malnutrition. It is also attested that eating fish early in life can promote positive behavioral and mental health outcomes and prevent certain allergies, such as asthma, eczema, and allergic rhinitis (41).

Aquatic foods, especially aquatic animals, have long been valued as a rich source of animal protein and thus, considered a key constituent of nutritious diets (120) but the policies on aquatic foods tend to focus primarily on production, economic efficiency, resource management, environment and climate issues whilst paying less attention to value chains and the contribution of aquatic foods to people's nutrition and health. Ahern et al. (121) recommended that aquatic foods are part of the solution to building resilient food systems and sustainable healthy diets for all, but for this to be fully achieved, they need to be available, accessible, affordable and desired. The nutritional value and health benefits of the fishes are unrecognized and undervalued. Despite a lot of benefits in the health of humans particularly the children, some people are still unaware of these benefits (122). The contribution of capture fisheries for instance to diet quality is poorly understood in most contexts, particularly where small-scale fisheries remain undocumented and overlooked in both fisheries and food system development (123, 124) hence limiting the nuanced assessment of fisheries contribution to diet quality of children under 12 years of age which is the critical age at which interventions have the greatest long-term effects for growth and health (117, 125). In contrast, Crona et al. (126) and HLPE (127) records that fish and other aquatic foods are gaining attention for their potential to efficiently provide two fundamental components of sustainable, nutritious food systems. Fish from inland fisheries are an important source of animal source foods (ASF) in monotonous diets for children in the sub-Saharan Africa and Asia (128), especially in land-locked African countries such as Malawi (129, 130) and Zambia (131). Therefore, there is a need to realize the importance of fish for human nutrition, in addition to its role in reducing poverty and hunger. This will ensure a greater impact by improving the nutritional status of children.