Fish is good for health, but contaminated fish is dangerous, particularly for pregnant women

Compared with eggs and organ meats, fish have the richest source of dietary Docahexaenoic acid (DHA), a a major component of fish oil. DHA is a vital component of phospholipids of human cellular membranes, especially those in the brain and retina. It is necessary for optimal neural development and visual acuity. DHA is the most abundant omega-3 fatty acid in human breast milk 

By Syed Akbar
Fish is an excellent source of nutrients for the growth of brain, but health experts warn that pregnant women 
should double check from where they had obtained the fish. This is because fish from polluted rivers and other water bodies will not only damage the health of pregnant women but also affect the growth of brain cells of the foetus they carry in their womb.
With incidence of foetal deaths and infant mortality on the higher side in India, scientists warn that it is important to know where the fish comes from and whether there is any contamination associated with those waters, particularly mercury or lead. The presence of metal contaminants and industrial pollutants in fish overshadows the beneficial effect it gives to carrying mothers and the unborn child in the womb.
If the source of fish is a good water body, then consumption of fish will improve the intelligence of the child. Fish is the best source of omega-3 fatty acids. Mercury, lead or heavy metals present in fish grown in polluted waters can harm the baby’s brain or nervous system.
Compared with eggs and organ meats, fish have the richest source of dietary Docahexaenoic acid (DHA), a a major component of fish oil. DHA is a vital component of phospholipids of human cellular membranes, especially those in the brain and retina. It is necessary for optimal neural development and visual acuity. DHA is the most abundant omega-3 fatty acid in human breast milk.
"DHA is taken up by the brain in preference to other fatty acids and is incorporated into the phospholipids of the cell membranes of brain cells and the retina. DHA-containing phospholipids in the cell membranes of the neurons appear to be necessary for neurite elongation and formation of synapses. These phospholipids are believed to be vital for cell signalling. It is the prominent structural fatty acid in the grey matter of the brain and retinal tissues of humans, as well as other animals," says Dr Kamini A Rao, representative to the Asia Oceania Federation of Obstetrics and Gynaecology.
According to US Environment Protection of Agency, though fish is an important part of a healthy diet, some fish caught in polluted lakes, rivers, estuaries and even oceans may contain chemicals that could pose health risks if they are eaten in large amounts. "Fish taken from polluted waters might be hazardous to your health. Eating fish containing chemical pollutants may cause birth defects, liver damage, cancer, and other serious health problems," the EPA warns.
Fish may be exposed to chemical pollutants in water and in the food they eat. They may take up some of the 
pollutants into their bodies. The pollutants are found in the skin, fat, internal organs, and sometimes muscle tissue of the fish, an EPA report points out.
Though fish has the capacity to excrete pollutants, most of the persistent contaminants are stored in the soft, fatty tissue and gradually build up, or bioaccumulate. The EPA is of the view that persistent contaminant concentrations in older, larger lake fish may be more than a million times higher per unit weight than concentrations in the surrounding lake water. The process by which a contaminant increases in concentration as it rises in the food chain is called biomagnification. And pregnant women is at high risk thanks to this biomagnification.
The Central Pollution Control Board, New Delhi, has identified several river stretches where the existing water quality is "below the water quality required by their designated best use criteria". The CPCB refers to these stretches as polluted river stretches and they include the major rivers Ganga, Brahmaputra, Narmada, Yamuna, Godavari, Krishna and Cauveri. While identifying these stretches, the CPCB took dissolved oxygen, biochemical oxygen demand and total Coliform as the critical pollutants. It has identified as many as 13 heavily polluted and 26 medium polluted river stretches.
Pregnant women living in these areas should be careful about the fish they eat. They should verify whether the fish is caught from these polluted or highly polluted river stretches.
The negative side apart, fish, if caught from good waters, contributes to the fast growth of the brain in infants. As the development of brain is the fastest during foetal life and the first two years after birth, the requirement of DHA is the maximum during pregnancy and nursing. "Moreover, there is evidence of DHA supplementation improving gestational age and reducing chances of pre-term delivery. A mother transfers all of the DHA needed for development to her baby for foetal brain, eye, and central nervous development. The content of DHA in a mother’s diet will determine the amount of DHA passed on to the developing baby," says Dr Kamini.
She said research had shown that children of mothers who take a DHA supplement during pregnancy have a 
higher IQ than others. Similarly, a child’s vision is also positively affected through the intake of DHA while 
nursing. The Vitamineral factor Adequate levels of all vitamins and minerals are important in pregnancy. Minerals required by the body are iron, calcium, magnesium, phosphorus, zinc, sodium, potassium and iodine. Since it is difficult to get adequate quantity of all essential vitamins, minerals during pregnancy and breast feeding, a good nutritional supplement would help to obtain optimal levels of vitamins, minerals and other antioxidants.
Moreover, since 70 per cent of the baby’s brain growth takes place in the womb, the importance of taking a 
balanced nutritious diet with supplements of brain-friendly nutrients during pregnancy plays all the more 
important role.
However, far from being a time for overindulgence, pregnancy is a time to eat sensibly and healthily. It is a myth that a pregnant woman should eat for two. In fact, she should eat for one plus one very small being. Most women only need to consume an extra 300 calories per day.