The Benefits & Side Effects of Omega-3 -6 and -9 Fish Oils

Omega-3, omega-6 and omega-9 fatty acids are essential components for keeping your body healthy. Each fat plays a role in helping to lower your risk of chronic degenerative diseases. You can get fish oil from your diet or from supplements. It’s important to know the functions of each type of fatty acids and the amounts required in order to make sure you're getting the right balance of omega fats.

Get the healthy benefits from the omega fatty acids from food or from fish oil supplements. (Image: Elena_Danileiko/iStock/GettyImages)

What Is Omega-3?

Omega-3 is an essential fatty acid. It cannot be made or stored in your body — you must get adequate amounts from food or fish oil supplements. Omega-3 is found in both marine and plant-based foods and is important for the functions of your heart, lungs, blood vessels and immune system.

There are many types of omega-3 fatty acids. The three most common are:

Eicosapentaenoic acid (EPA):
The main function of EPA is to reduce inflammation and maintain your circulatory and cardiac health. As an essential fatty acid, EPA helps your brain by maintaining blood flow and influencing hormones. It is also beneficial to your immune system.

Docosahexaenoic acid (DHA):
Making up 8 percent of the weight of your brain, DHA levels are especially high in your retina. An essential polyunsaturated fat, DHA is beneficial for maintaining your mood, controlling your behavior, mental performance, cognitive function, memory and learning ability. DHA is found in fish and seafood and is usually a component of fish oil supplements.

Alpha-linolenic acid (ALA):
Your body uses ALA for energy. It can be converted into EPA and DHA, but only in limited amounts. ALA is an essential omega-3 fat found primarily in plant oils. Dietary Guidelines recommends a daily intake for adults between 1.1 and 1.6 grams of linolenic acid, depending on age and gender.

Sources of Omega-3

USDA advises getting adequate omega-3 fatty acids by eating more fish to replace some meat and poultry in your diet. The American Heart Association recommends you eat at least two 3.5-ounce servings of fish per week. Getting your omega-3s from food is preferable but, if you can’t consume enough omega-3 rich foods or you have coronary artery disease, you may want to consider fish oil supplements.

According to the University of Rochester, some of the best fish sources of omega-3, with the quantity per 3-ounce serving, are:

  • Salmon: 1.1 to 1.9 grams
  • Flounder or sole: 0.48 gram
  • Pollock: 0.45 gram
  • Scallops: 0.18 to 0.34 grams
  • Shrimp: 0.29 gram
  • Crab: 0.27 to 0.4 gram
  • Clams: 0.25 gram
  • Canned tuna: 0.17 to 0.24 gram
  • Catfish: 0.22 to 0.3 gram
  • Cod: 0.15 to 0.24 gram

Plant sources, including flaxseeds and walnuts, can also help supply your omega-3 requirements, which is useful if you are vegetarian. However, plants contain the ALA type of omega-3, which doesn't efficiently convert into the active forms EPA and DHA. Fortified foods are also a good source of omega-3s.

Omega-3 and Fish Oil Side Effects

If you have too low a level of omega-3 fatty acid in your body, you may need to take a fish oil supplement, especially if you experience the deficiency symptoms of skin irritation, including:

  • Rough, scaly skin
  • Swollen, red, itchy rash

However, NIH warns that consuming more than 3 grams a day of EPA and DHA combined has the potential to cause bleeding, which can be dangerous if you are taking warfarin or anticoagulant medication. Taking more than 2 grams of omega-3 daily from fish oil supplements can affect your immune system as well. Although evidence isn't conclusive, taking high doses of omega-3 fish oil supplements can stimulate glucose production, which may lead to increased blood sugar, which could be of concern if you have diabetes. Other side effects from fish oil include:

  • An unpleasant taste
  • Heartburn
  • Bad breath
  • Nausea and stomach pain
  • Headache
  • Diarrhea
  • Smelly sweat

What Is Omega-6?

Omega-6 is also an essential polyunsaturated fatty acid, primarily used to produce energy in your body. It helps with the health of your bones, stimulates hair growth, regulates metabolism and maintains your reproductive system.

Linoleic acid is the most common omega-6 fatty acid. It is important to the formation of cell membranes, especially in your skin. Linoleic acid also produces prostaglandins, which are hormone-like lipids that help your blood clot, induce inflammation and control muscle contraction.

Sources of Omega-6 Fatty Acids

Your diet likely contains far more omega-6 fatty acids than your body needs, primarily due to the use of processed seed and vegetable oils. Having an overabundance of omega-6 fatty acids can actually do harm by promoting inflammation instead of decreasing it.

Soybean oil is the largest source of omega-6 fatty acids. Because it’s so readily available in foods you commonly eat, it is not included in fish oil supplements. In fact, it is recommended that you try to reduce your intake of omega-6s to balance the optimal ratio of omega-3 to omega-6.

To help limit your omega-6 fatty acid intake, choose from foods that are relatively low in omega-6’s linoleic acid:

  • Olive oil
  • Butter
  • Coconut oil
  • Lard
  • Palm oil

Foods that are highest in omega-6 content should be limited. These include:

  • Sunflower oil
  • Corn oil
  • Soybean oil
  • Cottonseed oil

Omega-6 Side Effects

Omega-6 or linoleic acid deficiency is uncommon. But it has been reported in infants who are fed skim milk, in people with chronic fat malabsorption and in individuals receiving nutrition intravenously. A low linoleic acid level may result in:

  • Poor growth and development in infants
  • Scaly dermatitis
  • Impaired immune response

What Is Omega-9?

Omega-9 fatty acid is a monounsaturated fat found primarily in vegetable sources, especially olive oil. Unlike omega-3 and omega-6 fatty acids, omega-9s are not considered essential and can be made and used in your body. As a result, there is no need to supplement omega-9 fatty acid.

Oleic acid is the primary omega-9 fatty acid. It has benefits for your heart and brain and can help to lower cholesterol, reduce insulin resistance and boost the immune system.

The American Journal of Clinical Nutrition published results of a study in 2013 that showed that the oleic acid in omega-9 has a significant effect on mood and behavior. When dietary saturated fat was replaced with oleic acid, a reduction in feelings of anger and hostility, as well as an increase in cellular energy, were noted in two cohort studies.

Omega-9 fatty acids are found mostly in vegetable oils and nuts, including:

  • Olives and olive oil
  • Avocados and avocado oil
  • Almonds and almond oil
  • Pecans
  • Cashews
  • Hazelnuts
  • Rapeseed
  • Mustard seed
  • Macadamia nuts

Balancing Omega Fatty Acids

Although omega-3 and omega-6 fatty acids are important fats in your diet and have many health benefits, it’s essential that they be taken in the right balance to be the most effective.

Over the course of time, the human diet has evolved away from a diet equally balanced with omega-6 and omega-3 fatty acids. Now the typical American eats far more omega-6s than omega-3s — by about a ratio of 16-to-1, on average — due to dietary changes and refinement of food over the last 100 years or so.

Although omega-6s are important for lowering LDL cholesterol, high amounts or high ratios of omega-6s to omega-3s can increase inflammation. This may contribute to heart disease, cancer, asthma, rheumatoid arthritis and other chronic health problems, according to GB HealthWatch.

One study supporting this theory assessed the effect that the ratio of omega-6 to omega-3 has on weight gain and obesity. Researchers noted that an unbalanced omega-6 to -3 ratio may contribute to the increased prevalence of arteriosclerosis, obesity and diabetes, while eating diets richer in omega-3 has been associated with low incidence of these diseases.

The results of the study, published in Nutrients in 2016, found that high omega-6 levels led to an increase in insulin resistance and weight gain, whereas omega-3 prevented overweight and obesity. The conclusion was that a balance of omega-6 to omega-3 in a 1-1 to 2-1 ratio was recommended in the management of obesity.

What About Fish Oil Supplements?

If you don’t eat much fish or seafood, taking an omega-3 fish oil supplement may help to effectively balance the omega-3 to -6 ratio. Omega-3 fish oil liquid is commonly found in supplements in the form of fish oil capsules or soft gel forms. They are available in both natural and processed forms and vary in content and how they are processed and absorbed.

In natural fish oils, omega-3 fatty acids, including EPA and DHA in the form of triglycerides, come from the tissue of oily fish. The common sources are from salmon, sardines and cod liver. Omega-3 accounts for about 30 percent of the oil; the remainder consists of other fatty acids that help with absorption. Natural fish oil also contains vitamins A and D and sometimes K2.

Processed fish oils are the most common type on the market. When fish oil is processed to concentrate or purify it, ethyl ester is produced. If the ethyl esters are converted back into triglycerides, the result is termed reformed triglycerides, which are better absorbed. Concentrating the oil increases EPA and DHA levels to a point of 50 to 90 percent for maximum fish oil benefits.

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