Nutrition - fish in the diet?

Friday 04 May 2018

Should I eat or avoid fish?  is a question I am so often asked. There are a few concerns that people can have. Firstly there is a concern because of all the articles and reports on the levels of contamination in fish as well as people being aware of how scarce some species are becoming. Lets have a look at this now:

The concerns about fish
Many of the books and web articles that are available that give recommendations on diet and cancer lean very much towards a diet that is rich in vegetable forms of protein like beans, peas and lentils and away from the animal products like red meat, poultry, dairy foods and fish.

The reasons would take up a whole new blog, basically it is due to the adulteration that meat undergoes in the rearing and breeding processes and the fact that all animal foods contain levels of insulin growth factor which I am going to blog about next week.  

Leaving these out of the diet is all very ideal in theory but in practice may not suit some peoples digestive system and for those used to a high meat diet can be a step too far and as we know that to eat a diet that is difficult to maintain and one which creates too much stress can be very counterproductive to all of our good intentions .

So to fish, It seems to be an ideal easily digestible high protein food to include. Fish can be very beneficial because it contains all of the essential amino acids associated with a good quality protein, oily fish contains good levels of essential fatty acid omega 3, calcium (when bones are eaten as in sardines and tinned salmon)and vitamins A and D. It is always available, very versatile and easy to prepare especially for those who have no incentive to cook or prepare more complicated dishes. A simple piece of poached salmon or sardines on toast could not be easier.

If we look a little deeper at the omega 3 content. Omega 3 is called essential because we cannot make it ourselves so it is important that we get it from our diet.

The foods that contain omega 3 are very limited and it is very easy to become deficient. It is found in walnuts, seeds (especially pumpkin and flaxseeds) oily fish (sardines, salmon, mackerel, tuna, trout, shark and sword fish) and egg yolk from chickens fed an omega 3 rich diet. It is interesting to note that because omega 3 is unstable some food manufacturers remove it from their products so that the food will last longer and not spoil!!!!

Omega 3 fatty acids are involved in many vital biochemical processes in the body. Including the integrity of the cell membranes, essential for good cell communication and more. I covered this in some detail in my blog on fats . It is composed of many fatty acids namely Alpha linolenic acid (ALA) , docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA). You may be familiar with the abbreviations especially if you buy fish oil supplements.

Some studies have found that Omega 3 supress the formation and growth of some types of cancer, probably by binding to cell membranes to protect healthy cells and inhibit cancer cells, (as shown when tested on mice). However there are also a few studies that I came across with more conflicting results which are not convinced of omega 3 for these benefits. Despite this, a big area of interest is the ability of omega 3 to reduce cellular inflammation. In research it has been show to stop the production of some Prostaglandins,  substances that can encourage cancer and poor cell division and that omega 3 can protect against the spread of solid tumour cells that are related to hormone production particularly breast cancer.

Some people also believe that it inhibits the growth of colon, pancreatic and prostate cancers. Again evidence is mixed depending on what you choose to read and most studies focus are positive and of course we cannot miss the very real benefits about its ability in reducing heart disease and high levels of triglycerides, which are still an important consideration whether you have cancer or not.

Joanna Budwig  famously advocated high levels of 0mega 3 as she claimed it would fight cancer. She developed the Budwig blend (here is the link to my blog on the budwig diet for you to read). She was concerned about the loss of iron and oxygen in the blood of cancer patients and showed that after treating patients with her blend the oxygen capacity increased and tumour sized decreased.

A clinical study published in the journal Cancer concluded that omega 3 seemed to prolong the survival of cancer patients who were also malnourished. Although again the claim has been challenged by some experts who drew different conclusions seeing no substantial evidence of a link.

When we talk about the benefits of fish as a source of the essential omega 3 it leads to some worry and confusion because of the high level of contamination that is reported to be in fish. Mercury is one that raises concern.  Mercury enters the atmosphere by combustion of waste and coal. The element then enters the ocean from the atmosphere where it is converted to methyl mercury by microorganisms and then taken up by marine life and concentrated in fish As methyl mercury is not fat soluble, unlike dioxins it does not reside in fatty tissue. Methly mercury has been shown strongly neurotoxic.

Levels are increased in fish that eat other fish known as food predators (tuna, shark and swordfish). Fish that are not predatory such as sardines, salmon and shrimp have very low levels by contrast. Some Tuna and salmon also contain other chemicals such as dioxin and PCB’s( polychlorinated biphenyls) which could potentially increase the risk of cancer .

An analysis of the potential harmful effects of these contaminants in fish versus the benefits of eating fish has concluded that the levels of PCB’s and dioxins in some  fish are low and potential carcinogens and other possible negative effects are outweighed by the potential benefits of fish intake. Some studies show that farmed raised fish carry more toxins that wild fish.

Basically It is recommended to eat wild as opposed to farmed fish with the exception of Tilapia which is a fresh water fish well suited to farming with low concentrations of contaminants. Wild Alaskan salmon (pink, coho, sockeye, chum and king varieties) seem to be the best choice but is expensive to buy. Rainbow trout which again is a fresh water fish. Sardines the world’s most underrated fish are top of the list for suitability to eat as they are free of mercury and PCB’s and one of the best sources of omega 3.

The American cancer society and the world health cancer research fund recommends including fish as a regular part of a balanced diet to replace red meat. Eating it steamed, baked or poached rather than deep fried In batter or with rich sauces.

So it appears that eating fish is good for us and although there are some negative factors concerning the contaminants found in fish if we choose wisely avoiding the predator type fish and keeping to the smaller wild types we get the green light.

Easy ways to include fish are; Canned in water or brine and rinsed before eating ;in a sandwich or on toast; Poached in water ideal for pieces of salmon;  as a parcel wrapped in foil with a little vegetable stock perhaps some sliced mushroom, onion and or tomato and baked which suits all types of fish; Cold with a salad or hot with steamed or stir fried vegetables; In a kedgeree. Drained canned fish is so convenient and ideal in the store cupboard for days when something quick and simple is the order of the day.

The good fish guide Marine conservation society

Blog originally written by Caroline January 2013

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