Fish and Soyabean: A great combination for improved human healthBy Adewolu Morenike A.

Introduction

One of the serious problems facing developing countries today is how to match food production levels, particularly proteinous foods, with increasing demand by a growing population. The magnitude of this problem is shown in the prevalence of kwashiorkor and other diseases associated with protein deficiencies. In Nigeria, the average protein intake is low; it is estimated as 45.4g per day. This is below the Food and Agriculture Organisation (FAO)\World Health Organisation (WHO) recommendation of 70g per day with half coming from plant sources and the remaining half from animal protein sources. This article highlights the importance of fish and soyabean protein as crucial diets for Nigerians.

Fish as the healthiest animal protein source  

Fish, when compared to beef, chicken, and milk protein has a higher tendency to support health in terms of digestibility, biological value, protein efficiency ratio and amino acid profile. Fish is the most easily digestible of all the dietary animal proteins because of the presence of lower connective tissue. Human beings can utilize up to 85% (WHO). In addition, the cost of fish production when compared to other livestock is cheaper. Fish is more available and readily affordable than other animal protein sources.

Nutritional benefits of eating fish

Nutritionally, fish can be classified into three major categories:

Oily Fish – These fish contain significant amount of oil (about 30%) in their body tissues, belly cavities and guts. Examples are mackerel, salmon, sardines and catfish

Lean Fish – These are the white fish with lower amount of fat content. Examples are soles, cod fish (panla) and tilapias

Shell Fish – These are fish that are covered with shell. Examples are crabs, oysters, lobsters and prawns\shrimps

Fish is an important source of high-quality and digestible protein that contains all the essential amino acids.

It contains water soluble vitamins like vitamin B complex, vitamin B12, B6, B2, folic acid, biotin and very little quantity of vitamin C. It is also rich in fat soluble vitamins, A, D, E and K. Fish also contains important micronutrients (minerals) such as calcium, iron, selenium, zinc, lead and copper. These minerals may be beneficial or toxic to man, depending on the level of exposure. Fish, especially marine fish, are a dietary source of iodine. It is an important source of polyunsaturated fatty acids. Basically, the most important nutrients needed for human body are found in fish. Several factors may affect the nutrient composition of fish, these include the age or size, sex, environment, season of the year, amount of food available and physical activities.

Some fish species stop feeding before spawning and draw on their protein and fats reserves, thus affecting their nutrient content. Also, fish, when overcrowded, may not have enough food intake thereby affecting the nutrient composition. It is important to mention that nutrient content varies within an individual fish. For example, fat may not always be distributed uniformly throughout the flesh of a particular fish. In Pacific salmon, there may be twice as much fat in the muscle around the head as in the muscles of the tail.

In the lean fish of cod family, the fat content of the muscle is generally low, below 1%. Majority of the fat content is in the liver, which is not normally eaten, and may contain greater quantities of oil soluble vitamins A and D. In contrast, these two vitamins may be present in the flesh of other fish, e.g eels. The nutrient content of fish, if carefully processed, are not affected by preservation, provided storage is not very prolonged.

Eating fish may lower the risk of heart attacks and strokes because of the presence of omega-3 fatty acids. The high amount of polyunsaturated fatty acids in oily fish is valuable in decreasing the serum cholesterol. Fish, as a good source of vitamin D and calcium, can improve bone health and

growth. Omega-3 fatty acids in fish are beneficial to improving visions and eyes health.

Eating of oily fish may improve quality of sleep due to the high concentration of vitamin D. Fish as a high packed nutrient, when eaten, may boost our immune system, especially during this period of COVID-19 pandemic. Fish oil is supportive in lowering blood pressure due to its high concentration of omega-3 fatty acids. Omega-3 fatty acids help in the breakdown of triglycerides and fatty acids in the liver, thereby lowering the risk of fatty liver disease. It helps blood flow to the brain and improves its performance during mental tasks. The fat and the pituitary gland in the fish head are rich in Vitamin A, which can fight free radicals and reduce oxidative stress. Higher consumption of fish can reduce the inflammation of joint in rheumatoid arthritis, prevent depression and may reduce the risks of autoimmune diseases. Research has shown that children who consume fish regularly have lower risk of asthma, improved memory and reduced risks of contracting diseases. It is recommended to eat two to three servings of fish per week to enjoy all the benefits.

Soyabean as the healthiest plant protein source

In line with the FAO/WHO recommendations that half of the estimated protein needed by man may come from plant sources, the plant protein source may come from soyabean, which is affordable and contains essential nutrients. Soyabeans are unique from other legumes because they have a concentrated source of isoflavones and have weak estrogenic. They have higher amount of protein and fats than other legumes. They are relatively low in carbohydrate. Nutritionally, soyabean is one of the best sources of high-quality plant protein, containing about 40-56 per cent of the dry weight. The fat content is approximately 18 per cent of the dry weight, mainly polyunsaturated and monounsaturated fatty acids and zero cholesterol.

The predominant type of fat in soyabeans is linoleic acid, which accounts for about 50 per cent of the total fat. Soyabeans are low in carbohydrates, hence very low on the glycemic index (GI), which is a measure of how foods affect the rise in blood sugar after a meal. Soyabeans contain a moderate amount of soluble and insoluble fibre. It is a good source of several vitamins and minerals, including vitamin K1, the B-vitamins, folate, copper, manganese, potassium, phosphorus, and thiamine. They are a rich source of various bioactive plant compounds, including isoflavones, saponins, and phytic acid. Generally, composition, protein quality and nutritive value of soybeans depend on numerous factors, including seed variety, environmental conditions during growing, harvesting and storage of the beans.

Health Benefits of Soyabeans                                       

Soyabeans have a number of health benefits. It may reduce the risk of cancer. The isoflavones and lunasin in soyabean may be responsible for the potential prevention of cancer. Exposure to isoflavones early in life may be protective against breast cancer later in life. The high levels of antioxidants in soyabean may prevent the onset of several cancers; it may help to kill several cancer cells and remove free radicals from the body. Research studies indicate that isoflavones, found in soyabeans, may alleviate menopausal symptoms. A number of studies suggest that consumption of soyabeans can help lower the cholesterol in the body by 4-6 per cent.

The high amount of fiber in soyabeans may help to lower the cholesterol from other foods. It plays a vital role in the digestive system. People suffering from constipation are advised to consume fibre-rich foods to help them excrete regularly. Soyabean also contains oligosaccharides, a carbohydrate that is known to stimulate the growth of healthy gut bacteria, acting as a prebiotic. Soyabeans help in healthy weight management. Its high protein content allows for the development of leaner muscle it helps in regulating insulin levels thereby curbing obesity. Soyabeans may lower high blood pressure because of its high protein, high potassium and low carbohydrate content, a mixture that helps to bring down blood pressure.

Fish and Soyabeans combination

The combination of fish and soyabeans makes it a complete protein, containing all the essential amino acids and other important nutrients needed in the human body. Dietary habits of consuming soyabeans and fish have a lot of health benefits, as this combo can lower the risk of diabetes, heart diseases, stroke, cancer and other diseases affecting millions of Nigerians. This combo is cheap and readily available. Nigerians, especially the pregnant women, children and the elderly, can survive and live healthily on it. This superfood is recommended to all.

Adewolu Morenike is a professor at the Lagos State University and specialises in Fish Nutrition.