By Dogs Naturally Magazine in Nutrition And Diet
Are fish oils and their omega-3 fats a good addition to your dog’s diet?
The primary benefit of fish oil supplementation is its ability to balance out the more inflammatory yet still necessary omega-6 fats. Typically, a dog who is fed a grain-free diet, preferably with raw, grass-fed meats, shouldn’t need much in the way of supplementation. But if your dog’s diet contains a lion’s share of omega-6 fats, most commonly as a result of a heavy grain content and plant-based oils, then he might need fish oil to balance his diet. But it’s a good idea to change the diet and get those inflammatory grains and vegetable oils out of your dog before considering adding fish oil to his diet.
But that begs the question,
How Can You Tell If Your Dog Needs More Omega-3?
Omega-6 fats aren’t your dog’s enemy. Because both omega-3 and omega-6 fats control important hormones in the body, they’re both important. And if your dog eats too much or too little of either one, then those hormones and his immune system will be out of balance.
But what is the right balance?
A much talked about animal experiment suggested that the ideal ratio of omega-6 to omega-3 fatty acids is 4 to 1, but this experiment injected rats with fatty acids rather than feeding them the oils. (Yehuda S, Carasso RL. Modulation of learning, pain thresholds, and thermoregulation in the rat by preparations of free purified alpha-linolenic and linoleic acids: determination of the optimal omega 3-to-omega 6 ratio. Proc Natl Acad Sci U S A. Nov 1 1993;90(21):10345-10349.)
A more realistic experiment that fed rats a mix of various vegetable oils, just like modern diets, showed that a ratio of 9 to 1 was just as healthy as lower ratios. (Bourre JM, Dumont O, Pascal G, Durand G. Dietary alpha-linolenic acid at 1.3 g/kg maintains maximal docosahexaenoic acid concentration in brain, heart and liver of adult rats. J Nutr. Jul 1993;123(7):1313-1319.)
Dogs who are fed a species appropriate, raw diet of grass-fed meats would enjoy about a 3 to 1 ratio of omega-6 to omega-3. This is a nice place to be. However, cattle who are raised on grains suffer the same fate as dogs and their ratio can exceed 20 to 1.But the amount of omega-3 fats in grain-fed cattle varies quite a bit. The longer they’re fed grains, the lower the omega-3 content will be. Feedlot cattle have the lowest amounts of omega-3 fats.
There are other factors apart from diet that might make you consider supplementing your dog’s diet with fish oil. Puppies have a higher need for essential fatty acids of all kinds, as do pregnant and lactating dogs, and those recovering from injury or chronic disease. During these times, foods such as liver and egg yolks from grass-fed animals, as well as small amounts of cod liver oil might be enough supplementation for a already dog eating a high quality diet.
Some dogs may still need more omega-3 oils in their diet. Symptoms of omega-3 deficiency include:
- fatigues easily
- dry coat
- dry/flaky/itchy skin
- brittle nails
- joint pain
If you feel your dog isn’t getting enough omega-3 from his diet, or his life and environment mean that he needs more omega-3 fats, then you could consider giving him fish oil. But before you do, it’s important to first understand the potential pitfalls of this $1 billion dollar a year industry. Because like all nutritional supplements that make miraculous claims, there can sometimes be more misinformation than miracle involved.
The Dark Underbelly Of Fish Oil
There are some of downsides of this popular supplement and some reasons why you really want to research the company you’ll place your trust in. Not all fish oils are created equally and you’ll want to find the few companies who swim against the stream and offer a safe and nutrient-dense fish oil.
But let’s first decide whether you want to give your dog fish oil – or if a healthy serving or two of fish would do the trick instead. Here are some little known facts about fish oil you’ll want to know before you decide.
The Science Is Fishy
To start with, most of the science behind omega-3 fats (and most notably its derivatives, EPA and DHA) in the diet, is short-term. This is problematic because most pet owners feed their dogs fish oil for life. So more research needs to be done on long term supplementation.
To date, the DART-2 trial is the only fish oil study lasting more than four years. It showed some disturbing results, with an increase in heart disease and sudden death in the people taking the fish oil. (Ness AR, Ashfield-Watt PA, Whiting JM, Smith GD, Hughes J and Burr ML: The long-term effect of dietary advice on the diet of men with angina: the diet and angina randomized trial. J Hum Nutr Diet. 17: 117-9, 2004.)
In addition, a review published in the online journal BMJ examined data from 38 studies and found that eating two to four servings of fish a week reduced stroke risk in humans by 6 percent compared to eating one serving or less, and having five servings a week reduced the risk by 12 percent.
But the results of the randomized trials that used fish oil supplements showed no significant effect on risk. So maybe giving your dog fish is a better idea than giving him fish oil.
What’s interesting about this study is that it also shows there is inherent danger in the reductionist thinking in nutritional research. The surprising ineffectiveness of the processed, isolated oil, compared to the whole food source, is similar to that found in studies on vitamins and cancer.
The now famous Beta Carotene and Retinol Efficacy Trial (CARET) studied the combination of beta carotene and vitamin A in the prevention of lung cancer among high-risk men and women. They terminated the study after just four years of treatment and told the participants to stop taking their vitamins; the results showed 28% more lung cancers and 17% more deaths among the participants taking beta carotene and vitamin A.
These results were similar to those published earlier from the Alpha-Tocopherol, Beta-Carotene (ATBC) Lung Cancer Prevention Trial carried out in Finland. In the ATBC study, more than 29,000 middle-aged male smokers were randomly assigned either 50 mg of alpha tocopherol, 20 mg of beta carotene, both, or a placebo daily for five to eight years.The trial failed to detect any significant protective effect for lung cancer for either of the vitamins. In fact, the study showed 18% more lung cancers and 8% more deaths in the group taking the beta carotene!
So scientists are beginning to learn that food derivatives may not always provide the same expected results as whole food sources. That brings us to our next point.
Vitamin E Deficiency
When it comes to fish oil, more is not better. In fact, too much fish oil and omega-3 can lead to a vitamin E deficiency. Some fish oils will contain vitamin E to compensate for this, but as we learned from the studies on beta carotene, vitamin A and alpha-tocopherol, synthetic vitamins don’t always act predictably in the body, especially when given over long periods of time.
It’s also important to consider that the saturated and monounsaturated fats are likely much more important to the body than the PUFAs or polyunsaturated fats because they’re by far the largest component of most mammals’ fatty tissues. In fact, only about 4% of your dog’s calories should be PUFAs – so a few ounces of fresh fatty fish per week could be all your dog needs. Giving massive amounts of fish oil will certainly deplete your dog’s vitamin E reserves much faster than smaller doses. Additionally, a diet high in carbohydrates can also deplete vitamin E stores, so once again, a high quality diet is an important first step.
Oxidative Damage
One other reason why giving your dog fresh fish might be a better option than fish oil is that omega-3 (and omega-6) fatty acids are extremely vulnerable to oxidative damage.
When fat particles oxidize, they break down into smaller compounds, like malondialdehyde (MDA), that are dangerous because they damage proteins, DNA, and other important cellular structures. A study by Mata et al demonstrated that oxidative damage increases as intake of omega-3 fat increases.
This isn’t surprising if you understand the chemical composition of fats. PUFAs, including omega-3 and omega-6, are highly vulnerable to oxidative damage because they’re the only fatty acids that have two or more double bonds, and it’s the carbon that lies between the double bonds that’s vulnerable to oxidation.
Saturated and monounsaturated fats don’t increase oxidative damage by a significant amount: saturated fats have no double bonds, which means they’re well protected against oxidation. Monounsaturated fats are slightly more vulnerable, since they have one double bond, but not nearly as much as PUFAs which have several double bonds.
A randomized, double blind, placebo-controlled trial showed that 6 grams per day of fish oil increased lipid peroxides and MDA in healthy men, regardless of whether they were supplemented with vitamin E. And consumption of fresh, non-oxidized DHA and EPA has been shown to increase markers of oxidative stress in rats.
About Toxins
Although the fats stored in fish are nicely loaded with omega-3s, fat is also where toxins are stored. And our oceans are becoming more and more polluted by the minute.
Heavy metals such as arsenic, cadmium, lead and mercury are a byproduct of our industrial lifestyle. They aren’t easily broken down, and end up in the environment at low levels, especially in fish. And fish oil.
The adverse effects from heavy metals can include cognitive impairments, nervous system dysfunction, blindness, lack of coordination, deafness, development of certain cancers, irreversible liver and kidney damage and even death.
Along with heavy metals, there are also other toxic compounds that accumulate in fish. Polychlorinated biphenyls (PCBs) can cause skin problems, muscle spasms, bronchitis and nervous system disorders. Dioxins and furans have been linked to a number of adverse health effects including skin, liver and immune system problems, endocrine and reproductive disruptions and the development of certain cancers. This is especially a concern for young dogs. However, PCBs and dioxins are also found in meat, dairy and vegetables.
If you decide to feed fish instead of fish oil, then it’s important to determine which fish contain the least amount of toxins and also which fish are sustainable. In general, fish that are lower on the food chain like sardines and anchovies naturally have a lower concentration of contaminants. For this reason, it may be wise to look for a product made from these fish.
High doses of fish oils taken every day may raise the percentage of toxins significantly. So fish oil manufacturers use a process called molecular distillation to remove the toxins from the oil. But whole fish contains an important ingredient that fish oil doesn’t: selenium.
Of course, mercury is a concern when it comes to feeding fish. However, selenium has an affinity for mercury and binds with it, forming a new substance, making it difficult for the mercury to enter the brain. In fact, selenium can prevent oxidative brain damage associated with mercury toxicity.
Most fish that is consumed in North America contains significantly more selenium than mercury (with the exception of many fish at the top of the food chain, such as shark, marlin, king mackerel, swordfish, etc.).
So if you feed your dog fish instead of fish oil, mercury may be less of a concern. If you choose to feed fish oil, then providing your dog with a whole food source of selenium might be a good idea, for the reason below.
Integrative practitioner Chris Kresser warns that although almost any fish oil manufacturer will tell you their product is free of the above toxins, independent lab analyses may say otherwise. So it’s essential to ask for a Certificate of Analysis (COA) from the manufacturer before you buy their product. A COA is an analysis performed by an independent lab to measure the ingredients of a product and confirm whether it lives up to the claims made by the manufacturer.
Make sure that the independent lab they use is in fact independent and is preferably accredited, sponsored by a government agency, or has a solid reputation in the field.
Bio-Availability
The ability to absorb the beneficial components of fish oil is based on the molecular shape of the fatty acids. The more natural and less chemically altered the structure, the better the bioavailability.
This is true for any nutrient, of course, and this is why it’s always preferable for your dog to derive his nutrients from food or food-based sources whenever possible. Each additional step in processing from the natural state of a food to an extract or isolate increases the risk of damaging the nutrient, or changing its chemical form so that it’s more difficult to absorb or affects the body in a different way.
When comparing the bioavailability of fish to fish oil, there are a few components to consider.
Nutrient Content
Fish oil contains mostly EPA and DHA, although fish liver oils will also contain vitamin D. On the other hand, whole fish contains not just EPA and DHA, but vitamin D, selenium, protein, cofactors and a more complete fatty acid profile than fish oil.
Potency
This is where fish oil may have an advantage over fish. Fish oil contains much higher concentrations of DHA and EPA. However, 6 ounces of wild salmon contains 883 mg of EPA and 1,111 mg of DHA.
The EPA and DHA requirements for dogs are largely unknown, but the National Research Council has established a safe upper limit (although it has yet to establish one for cats). The data suggest that a dose between 20 to 55 mg combined EPA and DHA per pound of body weight is safe for dogs. So 6 ounces of fish per week might be all a thirty pound dog would need.
Absorption
The levels of EPA and DHA in fish oil don’t mean much if they aren’t absorbed by the body. Several studies indicate that fish oil supplementation might not be as effective as consuming fish. The reason may be that other fats found in the fish are required to absorb the EPA and DHA properly.
In one study comparing the effects of fish and fish oil, researchers found that levels of DHA after 6 weeks of salmon consumption were nine times higher than after fish oil use.
The authors hypothesized that the configuration of fatty acids in whole fish is familiar to the body and thus easier to absorb. Another study confirmed this by demonstrating that fish oil is absorbed much better in the presence of a high fat meal. They found that the content of omega-3 fatty acids in the body tissues rose dramatically when the fish oil was taken along with 12 g of olive oil.
So it appears that EPA, and especially DHA, is much better absorbed from fish than fish oil. The effect may be as great as nine-fold. This means that our dogs would need nine times less DHA from fish to obtain the same amount of DHA from fish oil.
However, giving your dog fish oil capsules with a high-fat meal can greatly improve their absorption to the point where they may be on par with whole fish. Unfortunately the scientific literature is mixed on this.
All Fish Oils Are Not Created Equally
There are three forms of fish oil currently available on the market:
- Natural triglyercide oil. This is what you get when you “squeeze” the whole fish and extract the natural oil from it. It’s the closest to eating fish oil in its natural form, and is highly bioavailable. The drawback of this form is that, because it’s not concentrated, it usually has low levels of EPA and DHA. And because it isn’t purified, it can have high levels of contaminants such as heavy metals, PCBs, and dioxins.
- Ethyl ester oil. Occurs when natural triglyceride oil is concentrated and molecularly distilled to remove impurities. The ester form is still in a semi-natural state because it is the result of a process that naturally occurs in the body. The advantage to this form is that it can double or triple the levels of EPA and DHA.
- Synthetic triglyceride oil. This form occurs when natural triglycerides are converted to ethyl esters for concentration (as above), but then re-converted into synthetic triglycerides. The original position of the triglyceride’s carbon bonds change and the molecule’s overall structure is altered, which impacts the bioavailability of the oil.
Studies on the absorption of the various types of fish oil suggest that, unsurprisingly, the natural triglyceride form is absorbed better than the ethyl ester form, which in turn is absorbed better than the synthetic triglyceride form. (Beckermann B, Beneke M, Seitz I. (1990). Comparative bioavailability of eicosapentaenoic acid and docosahexaenoic acid from triglycerides, free fatty acids and ethyl esters in volunteers. Arzneimittelforschung; 40(6):700-704.)
The ethyl ester oils are also much less stable and are more likely to produce harmful oxidation byproducts than the natural triglyceride oils. (Song JH, Inoue Y, Miyazawa T. (1997). Oxidative stability of docosahexaenoic acid-containing oils in the form of phospholipids, triacylglycerols, and ethyl esters. Biosci Biotechnol Biochem. 61(12):2085-8)
Unfortunately, the vast majority of fish oils on the market are ethyl ester oils. You can determine how your dog’s fish oil is produced by contacting the company or by trying this simple test at home:
Place a few ml of your fish oil in a styrofoam cup and put it on a plate (you might need this). Leave the cup for 10 minutes, then check for leakage. Due to their chemical composition, ethyl ester fish oils will eat right through the cup after 10 minutes time. Natural triglyceride fish oils will only show minor leakage and only after 2 to 3 hours in the cup.
The Bottom Line
When it comes to deciding whether your dog would be better off eating fish or fish oil – or if they are required at all – it really depends on several complex factors.
In general, if your dog is eating a healthy raw diet composed mainly of grass-fed animals, free of grains and vegetable oils, then the occasional meal of fish might be all he needs. However, if he suffers from chronic disease, stress, injury, or is growing (or if you have a pregnant dam), then fish oil supplementation might be a good idea. Whether it’s required in the long term may or may not be the case – it really would depend on your dog’s condition.
For dogs eating a processed, grain-based diet, then a combination of fish and a high quality fish oil might ensure he gets the benefits of whole fish, plus the extra EPA and DHA.
If you do decide to give your dog fish oil, then it’s important that you do the following:
- Ask for a Certificate of Analysis (COA) from the manufacturer before you buy their product.
- Supplement with vitamin E, preferably from a whole food source. Supplementing grain-based diets with fish oil isn’t a good long term solution as both will deplete vitamin E in the your dog.
- Make sure your dog gets plenty of healthy fats to increase the absorption of the fish oil
- Choose a high quality fish oil in the natural triglyceride form. Not only is this better absorbed, but there will be less oxidative damage.
- Consider using both fresh whole fish and fish oil to give your dog a full array of healthy fats.