All about fish
Both grandma and dietary recommendations advise eating fish regularly. Not only are fish a great source of macronutrients like fats and proteins, there are many essential micronutrients like vitamin D, calcium and zinc to name a few. However most of these nutrients are also available in other foods. The one essential nutrient that we rely on the most from fish are the omega-3 fatty acids DHA and EPA. Today we know that omega-3s make up a significant part of every cell but particularly the eyes, brain and nervous system.
However, the history of omega-3 fatty acids in human health is long and still unfolding. Despite scientists learning about the essential nature of some fatty acids in 1929, it wasn’t until 1982 that doctors and scientists understood that deficiency of omega-3s caused neurological symptoms. This seminal paper identified ALA as an essential omega-3 fatty acid. Subsequently, scientists discovered that two other omega-3 fatty acids were also essential, DHA and EPA. In fact, DHA is the most abundant fat in the human brain, making up approximately 40% of the fat content. Similarly, dog brains also have a very high percentage of DHA, the literature here is sparse but estimates range from 10-40% of their brain’s fat content.
For people, eating 2-3 servings of fish per week equals about 1-2 g of EPA and DHA per day. However, many doctors and scientists are now recommending 3-4 g of EPA and DHA per day. There are countless studies showing the benefit of increasing EPA and DHA consumption in canines and people. In fact the drug Vacepa is a high-purity form of EPA, and it is FDA approved as a drug to lower triglycerides and reduce risk of cardiovascular events. The dose of Vacepa is 4 g per day. Some people on our team take up to 5 g of fish oil a day.
Why flaxseed doesn’t cut it
Terrestrial plants only make ALA, and since humans and dogs also need EPA and DHA, plant sources alone are rarely enough. The reason is ALA doesn’t convert efficiently to EPA and DHA in many animals, including dogs and humans. In studies on people, the conversion of ALA to DHA is less than 4%. This means you would need to eat more than a pound of flaxseed per day to get 3-4 g of DHA -- doable, but very unpleasant.
DHA and EPA are extremely important to maintain brain function and the elasticity of cell membranes. Observational studies show that Japanese people have much longer lifespans than Americans despite higher levels of stress, hypertension and incident of smoking. One of the leading hypotheses is that it is due to a much higher levels of fish consumption. (Weight gain is not believed to be the cause, as some studies show overweight Japanese people live longer than normal weight people.)
Algae and small fish anyone?
Omega-3s in the marine food chain actually come from algae and phytoplankton. These simple life forms create their own food by absorbing sunlight the same way terrestrial plants do, except the form of omega-3 is different. The algae and phytoplankton are eaten by small fish, shrimp and zooplankton, which then get eaten by slightly larger fish, getting concentrated as it moves up the food chain.
Within food chains there is something called trophic layers, where each layer above consumes the layer below. On land there are typically fewer trophic layers. For example people are at the top of the food chain, eating plants (primary producers) and animals (primary consumers), and are only decomposed by microorganisms). In the sea there are up to seven trophic layers. As you move up each layer toxins can go up by 10-fold.
To put this simply, a mackerel may eat anchovies that have low levels of mercury. But because the toxins stay in the body, every time the mackerel eats more anchovy, they accumulate a little more mercury. Swordfish eat larger fish like mackerel, so the higher levels of mercury from mackerel get concentrated in their bodies. A swordfish may have up to 100-times the amount of mercury found in a small anchovy. Because of this we eat large predatory fish infrequently and only use small fish like anchovy or sardine in our Pup Pot Meals. Other low mercury fish include salmon, herring, haddock, cod and sole.
Are fish too salty for dogs?
A commenter on one of our videos argued that though we use “no salt added” sardines, the natural sodium levels they contain make it a harmful food for dogs. This couldn’t be further from the truth.
As we’ve written about in previous posts, the dose makes the poison. There are many documented cases of people dying from drinking too much water. So just like anything else, salt can be dangerous if consumed in excess quantities. As dogs don’t sweat like people do, they lose less electrolytes and thus have lower requirements. However, dogs still require sodium and chloride in their diets and feeding fish in moderation is definitely not harmful.
Just make sure to use "no salt added” goods to keep levels minimal. We also only use sardines canned in water as the water dilutes the salt, and less oil means less calories from fat.
What about freshwater fish?
Fresh water fish, especially those that are farmed, often have higher levels of toxins than marine fish. Tilapia, catfish, trout and carp can contain many environmental toxins. According to a study done on North American fisheries, eating one serving of fresh water fish is equivalent to drinking contaminated water for one month. Ultimately the ocean is able to dilute pollutants more than local rivers and lakes simply because of size, making fish that come from the ocean safer in general.
We rarely eat fresh water fish and never feed it to the dogs, but if you have eaten fresh water fish in the past, don’t worry. The body has an amazing capacity to regenerate and heal.
