How about seafood?

Few foods have confused patients as much as seafood.   Seafood is any form of sea life regarded as food by humans in different parts of the world that includes fish, squids, octopus and shellfish such as prawns, oysters, crabs, squids, and even seaweeds.  We shall collectively call  all of these varieties as “seafood or fish’ - and they can be from the sea or from freshwater.  

 Many patients worry that eating seafood while undergoing cancer treatment or recovering from cancer can be harmful.   Even though the health benefits associated with eating fish and shellfish continue to expand, fears of seafood continue and oftentimes overshadow the good associated with eating more seafood.  

 Seafood can actually be very good for you.   Seafood is  the main source of nutrition for those living in the coastal areas and globally they provide more protein than cattle, sheep, or poultry. Fish is a valuable component of the human diet because it is easily digestible and contains high-quality protein that our bodies cannot make themselves and must be obtained through our food.

 Nutrients in seafood

 Seafood is nutrient rich food.  It is a good source of protein, vitamins (including A, B and D) and a good selection of minerals (phosphorus, iron, calcium, magnesium, and selenium), trace minerals (iodine, selenium, chromium, zinc and iodine in marine species).   Fatty seafood has the highest level of marine omega 3 fatty acids and vitamin D.   In short, consumption of seafood can have positive benefits on your cardiovascular, neurologic, immune, behavioral and mental health. 

 Let's look at the nutrient content of some of the commonly eaten seafood

 Squid — a good source of protein, Omega-3 fat, B vitamins and minerals (copper, zinc, and iodine).

 Oyster — a good source of protein, Omega-3 fat, vitamins (A, C and B12), and minerals (zinc and iodine, iron, phosphorus)

 Mussels — good source of protein, omega 3 fat, .vitamins (A and B) and  minerals (selenium, iron, iodine and zinc.)

 Prawn — good source of protein, high in Vitamin B (B12, B6, niacin) they also  contain minerals (zinc, selenium, copper, magnesium and phosphorus) and some omega 3 fatty acids  They are also high in cholesterol.  Most crustaceans are high in   cholesterol - bear in mind cholesterol is necessary in order to produce sex hormones and to process Vitamin D in the body. 

 Lobster—contains iodine, selenium,  and B vitamins.

 Crabs — a good source of protein, Vitamin C, B vitamins such as Riboflavin, Niacin, B12 and minerals (Iron, Magnesium, sodium and Phosphorus, Zinc, Copper, chromium and Selenium.  It is also high in cholesterol.

 Japanese people enjoy one of the longest average life spans in the world with far lower rates of obesity and chronic  disease and part of that success is due to their high consumption of seafood.  Japanese love their seafood.  It is rolled in rice as sushi, served raw as sashimi, simmered in a pot, grilled or deep-fried as tempura.  There are  many more creative ways to prepare and consume seafood and the Japanese serve these in most homes almost every day.

What are the health risks associated with seafood?

 Although eating fish is a healthy option that may not always be the case today.  Like other sources of nutrition, seafood is subjected to the same deterioration in quality and may become harmful due to the way it is farmed,   environmental contaminations, bacterial contamination and additions of preservatives and additives.  Therefore, when it comes to deciding on whether to consume the seafood,  the most important considerations are:


 1.  Source of your seafood— how much exposure to environmental contaminants?

 Generally the sources of seafood are:

   Ö from the wild, 

   Ö from fish farms, and

   Ö from individuals who catch fish for recreation or to supplement their household food supply.

 It is important to know where your fish comes from – farmed fish are more likely to be contaminated by mercury, antibiotic and pesticides.  Fish farms are the aquatic version of a concentrated animal feeding operation (CAFO) and just like land-based cattle and chicken farms, diseases and   infections are potential issues due to crowding in a small space.  

 In addition, farmed fish are often of inferior quality due to the increased amount of grain in their diet (often genetically modified corn and soy feed).  Therefore, eat the ‘wild’ ones whenever possible.

 Do note that not all farmed fish are raised irresponsibly — check with the breeder to ensure that you get good quality fish or prawns.

 Fish or shellfish harvested from lakes, rivers, streams, beaches, bays or harbors that are contaminated byenvironmental pollutants (from factories, household wastes, industries etc.) increase chances of  poisoning and contamination. 

How about mercury contamination?

Fish do take in methylmercury (a form of mercury), and nearly all fish have traces of it.   The potentially toxic effect of mercury appears to be abolished by the selenium that fish contain. That selenium protects against the toxicity of heavy metals has been known for 40 years, although how it works has only recently been described.    Selenium, a potent antioxidant, is incorporated into proteins capable of binding heavy metals 1.

 Other points to remember:

 --- smaller fish are less likely to accumulate pollutants when compared to larger ones.

 --- Oysters, prawns, crabs, clams and scallops are notorious for picking up pollutants

 2.   Exposure to harmful bacteria

 Like other perishable foods, another health risk from eating seafood is exposure to harmful bacteria.  However this can be prevented through proper handling, storing, and cooking.  Those   seafood products that are consumed raw or partially cooked represent the highest risk.   If you are undergoing chemotherapy*, you are advised not to consumed any raw or partially cooked seafood.  (*Your immune system is compromised by the chemo drugs)

 3.     Do you have an allergy to any of the seafood?

 If you have an allergy to any of the seafood, you should be careful not to eat it.  In addition, if you are allergic to say crab, you may also be allergic to other types of shellfish, including lobster and prawns. 

 4.    Do you have problems with your thyroid functions?

 Your thyroid gland is one of the largest endocrine or hormone-secreting glands in your body     located just beneath the Adam's apple.  It utilizes iodine from the food to form thyroid hormones that   control your cellular energy (example T3 and T4  hormones tell the cells how much energy is needed). Thyroid disease occurs when the thyroid gland starts to produce too little (hypothyroidism) or too much (hyperthyroidism) of these hormones.

 In any form of thyroid disease it is important to make sure that the intake of iodine is kept within normal range.   Iodine is an essential trace element found naturally in high concentrations in very few foods especially seafood and marine plants (seaweeds eg. Kelp and Dulse).  Among the seafood, the highest ranking are crabs, lobster, oysters and other forms of shellfish.

 For someone with hyper active thyroid disease it is advised not to consume food that has high iodine  content.  Please consult your doctor on this issue.



Remember, what can and cannot be eaten or why we eat  are influenced by many factors such as cultural, emotional, religious, economic conditions, and more.    In some culture, some food are considered as pests and are too ‘dirty’ to be consumed whereas the same food is considered an elite food elsewhere.  Do you know that snails (escargot) are eaten as a delicacy in Spain and France?  Like most mollusks, escargot is high in protein it is estimated to contain 15% protein, 2.4% fat and about 80% water.  

When it comes to food, your selection guidelines should always be:  Whether there are possible presence of toxins, degree of processing and the nutrients it contain. 



  1. Kosta L, Byrne A, Zelenko V. Correlation between selenium and mercury in man following exposure to inorganic mercury. Nature 1975;254:238-239.








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