Home » Health and Nutrition » Vegetarian Nutrients of Concern #6: Fish Oil

Vegetarian Nutrients of Concern #6: Fish Oil

Jennifer Hanes MS, RDN, LD

As we continue on with our discussion on nutrients that vegetarians should pay attention to, we finish with Omega 3 fatty acids, particularly those often referred to as fish oils. 

There’s a lot of conversation around fish oil and its health benefits, and it’s obviously not a nutrient vegetarians come by easily.

A brief overview of the Types of Fats

Dietary fats (chemically known as fatty acids) are a huge group of compounds. However, there are a few categories of fats that we will pay attention to.   

Categorizing fats helps us determine basic functions, health roles, and more without having to remember all of the different names.

They are composed of a long chain of carbon atoms with a specific structure (COOH) at one end and hydrogen molecules along the carbons.  

All fats supply the body with energy and storage, and they form the foundations for some hormones as well as chemicals known as eicosanoids that participate in cell signaling.

Because of this, fats play a role in our cardiovascular, pulmonary, immune, and endocrine systems.

Saturated and Unsaturated fats

A fat is saturated when, chemically, every carbon atom in the chain has 2 hydrogen atoms.

Unsaturated fats have 1 or more double bonds between carbons, which takes away a hydrogen atom. Anyone having flashbacks to high school chemistry yet?

Side note: the unsaturated fat pictured is a cis fat. A trans fat is rotated around the double bond.

Saturated fats generally come from animal sources, though coconut and palm oils are also highly saturated. 

In a vegetarian diet, saturated fats come mostly from dairy, coconut oil and milk, and palm oil (often found in premade baked goods and mixes).

Unsaturated fats come primarily from plant sources (olives, avocados, nuts, and seeds) and fish.

While we tend to refer to foods as having either unsaturated or saturated fats, in reality, almost all fat-containing foods contain a blend of both saturated and unsaturated fats.  What we are referring to are the dominant types of fat in those foods.

We need to move away from the idea that saturated fats are “toxic” and unsaturated fats are “good,” we should strive to increase our unsaturated fat intake and lower our saturated fat intake.

In general, saturated fats are solid at room temperature, and unsaturated fats are liquid. 

Fats behave in our bodies in a similar manner, meaning that our cell walls and other fat-containing structures are more flexible when they contain higher percentages of unsaturated fat.

This flexibility is important as it allows those structures, such as your blood vessels, to respond to their circumstances, such as better tolerating an increase in blood pressure.

In addition to eating foods that have unsaturated fats, we should also aim to cook more frequently with unsaturated cooking fats such as olive, avocado, flaxseed, and sesame oils, among others.

(side note: don’t stress about social media “nutrition experts” fearmongering seed oils).

Monounsaturated and Polyunsaturated fats

The next group of fats are subcategories of unsaturated fats and is quite easy to distinguish chemically from each other. 

Monounsaturated fats have 1 double bond between carbons, and polyunsaturated fats contain more than one double bond.

Monounsaturated fats help reduce your LDL (“bad”) cholesterol and may help increase your HDL (“good”) cholesterol [though studies are mixed]. They are found in avocados, olives, peanuts, almonds, pecans, pumpkin seeds, and sesame seeds. 

Cooking oils high in monounsaturated fat include olive, canola, peanut, safflower, and sesame oils.

Polyunsaturated fats also reduce LDL cholesterol. They are also more likely to contribute to overall cell health and play a role in normal blood clotting. They are found in oily fish, walnuts, flaxseeds, sunflower seeds, tofu, and soybeans.

Cooking oils high in polyunsaturated fat include canola, corn, soybean, and sunflower oils.

So what does this mean to you?  Honestly, not a whole lot. I never ask my clients to consider mono and polyunsaturated fats separately. It’s too much to focus on, and there’s not enough difference in the health outcomes between the two to stress out about.  

The only “exceptions” to this are the fats in fish oil: EPA and DHA.

Omega 3 and Omega 6 Fats

 Both omega-3 and omega-6 fats are polyunsaturated fats.  Starting with structure again, the term omega (in regard to fatty acids) indicates where the first double bond occurs, counted from the tail end.  

Despite some social media claims that omega 6 fats are bad, we actually need both omega 3 and omega 6 fats in our diet.  Health outcomes do become worse when we have a heavy emphasis on omega-6 fats compared to omega-3 fats.

There are also omega-9 fats, which are usually monounsaturated and not too important to today’s conversation.

Omega-6 fats have to come from our diet because we cannot produce them ourselves. We get omega-6 fats from cooking oils, nuts, and seeds. Research indicates that omega-6 fats can reduce our risk of heart attack and stroke.

Omega-3 fats also have to come from our diet. Alpha-linolenic acid (ALA), the most common dietary omega-3 fat, is present in flaxseeds, chia seeds, walnuts, canola oil, soy/tofu, and very small amounts in beans.

ALA has been found to protect the brain, reduce anxiety and depression, reduce the risk of heart attack and stroke, and improve health outcomes in those who have already suffered a heart attack or stroke.

Your body can convert to the fats found in fish oil (EPA and DHA), but not very efficiently. 

A healthy ratio of omega-6 to omega-3 fatty acids is between 1-to-1 and 4-to-1. However, a typical Western diet may consume a ratio of between 15-to-1 and almost 17-to-1.

What Is Fish Oil?

Basically, when we talk about fish oil, we are really talking about 2 different polyunsaturated, omega-3 fatty acids: Docosahexaenoic Acid (DHA) and Eicosapentaenoic Acid (EPA).

These fats are considered non-essential because, technically, our bodies can make both of them from the above-mentioned ALA.  

While ALA is heart-healthy and anti-inflammatory, additional benefits come from EPA and DHA.


Omega-3s (including ALA) are a part of all of your cell membranes. 

EPA prevents excessive blood clotting, reduces triglyceride levels, and can reduce pain and swelling. EPA can also reduce symptoms of depression and anxiety alone and also improve response to the medications used to manage them.

DHA plays a structural role in your eyes, skin, and brain. It can also reduce LDL and triglyceride levels and may slow cognitive decline in patients at risk for Alzheimer’s or other neurodegenerative disorders.

Intake of EPA and DHA (aka fish oil) are linked to:

Improved symptoms of depression and anxiety

Better management and outcomes in bipolar disorder and schizophrenia

Greater brain development in utero and early life

Reduced risk of Alzheimer’s disease and other causes of dementia

Improved risk factors for heart disease (lower “bad” cholesterol and triglycerides, higher “good” cholesterol.

Lower rates of chronic inflammation

Reduced risk of auto-immune diseases

Prevention of some cancers

Improves Mental Health

Supplemental doses of fish oil have been shown to improve symptoms of depression, anxiety, bipolar disorder, and schizophrenia.  

EPA seems to be more important to the improvement of mood disorders, but DHA is not harmful. In fact, while EPA may be better at reducing overall symptoms of depression and anxiety, DHA appears to reduce suicidal thoughts specifically.

Brain development

thisFetal and infant brain development is greatly enhanced by adequate intake of EPA and DHA by the mother. 

Some studies show benefits, particularly in school behavior, when fish oil consumption increases in older children. However, results on the impact of fish oil supplementation on behavior are mixed.

Most prenatal vitamins and infant formulas now contain at least DHA, but usually DHA and EPA for this reason.

Reduces Chronic Inflammation

Fats play a role in the messenger and receptor molecules and pathways.  While saturated fats and high levels of omega-6 fats can increase the number of inflammatory pathways, omega-3 fats increase the number of anti-inflammatory pathways.

Notably, fish oil reduces serum levels of interleukin-1 (IL-1).

Many chronic health conditions, including diabetes, heart disease, some cancers, major depression, and many autoimmune conditions, involve high levels of IL-1.


Studies show that fish oil can protect against the onset or the progression of Parkinson’s, Alzheimer’s, and Huntington’s disease, as well as mild cognitive impairment.

Suggested mechanisms include reducing inflammation, improving the gut microbiome, reducing oxidative stress, and improving the structure of neuronal cells.

Lowers risk of Heart disease

thosStudies are mixed, but for the most part, studies on fish oil and heart disease are very positive. A 2018 study showed a reduced rate of heart attacks of up to 77%, depending on the population.  Black Americans showed the most improvement.

This study also found a reduced mortality rate among those who experienced a cardiac event.

Possible reasons for mixed outcomes in studies are:

  • Varying doses – trials range from <1 g to 4 g of fish oil.
  • Concurrent medication use – studies vary on whether or not participants were also taking medications to manage their heart disease risk, such as cholesterol or blood pressure medications.
  • Fish oil intake prior to study – if a participant already has an adequate intake of fish oil, we would expect less of a change with supplementation than for someone who never had any.
  • Type of oil used – some studies use a blend of EPA/DHA similar to most readily found supplements. However, other studies used only EPA or only DHA in their supplementation.
  • Population studied – If the study required participants to have a personal or family history of heart disease, then we could expect interventions to be more noticeable than someone without that history.

Reduces Risk of Autoimmune Conditions

 Arthritis, Crohn’s disease, ulcerative colitis, and lupus are all associated with elevated IL-1.  

When you consume adequate amounts of fish oil, it reduces IL-1, thereby helping to prevent the expression of these autoimmune conditions.

It’s important to note that fish oil, or any other dietary measure, cannot reverse the systemic, chronic, and severe inflammation observed in individuals with autoimmune conditions.

Those with autoimmune diseases should be careful to take all medications recommended by their healthcare team.

Prevents some Cancers

Once more, studies yield mixed results for similar reasons as mentioned before, as well as the wider array of cancer types compared to heart disease.

Breast, colorectal, and prostate cancer, in particular, seem to respond to fish oil supplementation in observational studies.

Skin, esophageal, ovarian, endometrial, and pancreatic cancer have not shown any improvement in risk or outcome with increased fish oil intake.

Additionally, we don’t have a clear mechanism for how fish oil would prevent any type of cancer, though some postulate that it’s related to the reduction of chronic, systemic inflammation.

There’s so much more research left to do here!

Daily Recommended Intake of Fish Oil

There is no set standard for intake for DHA and EPA, the “fish” oils, mostly because they are non-essential nutrients. The minimum recommended intake for all Omega-3 fats is between 1.3 to 1.6 g per day, so it’s pretty low, actually. 

For those who choose to eat fish, 2 servings of fatty fish per week is an “adequate” intake of fish oil.  Some improved health outcomes are seen when supplements are taken at a combined 300 mg per day. 

However, most studies that show positive results are giving supplemental doses of 1-4 g per day.


Fish is the main source of dietary EPA and DHA.  The amount of fish oil in the fish depends on a range of factors including, but not limited to, their diet, water temperature, and sourcing (farmed vs wild-caught).

Your omnivorous friends and family should look for cold-water fish such as tuna, salmon, mackerel, and sardines. Bass, tilapia, and cod have less, and shellfish have even less.

Challenges for Vegetarians in EPA and DHA

Unfortunately for us, there isn’t really any veg*n source of EPA and DHA from our diets. This doesn’t necessarily cause a deficiency disease, so to speak. Remember that only ALA is an essential omega-3 fat, and that comes from plant sources.

But wouldn’t it be nice to reap some of those benefits listed above?

Luckily, as research shows more benefits of fish oil, certain egg and dairy products are now fortified with DHA. 

Despite its colloquial name of fish oil, fish don’t actually produce DHA and EPA. Instead, they get it from their food: microalgae and phytoplankton.

Nowadays, we have algal-based supplements for “fish” oil.  I often recommend these products for vegetarians and vegans alike. Just make sure they contain both EPA and DHA.

If you’re grabbing some DHA-fortified milk, make sure to check the label. Some brands source their DHA from fish, and others from algae.

Symptoms of Fish oil Deficiency

Symptoms of fat (any fat) deficiency include rough, scaly skin and dermatitis. Unfortunately, at this time, we do not have a set laboratory value in which low levels of EPA and DHA begin to result in poor visual, neural, or immune system function.

All that being said, a true fat deficiency is almost non-existent in the United States. Furthermore, inadequate intake of DHA and EPA does not cause any overt symptoms or show on routine blood work.

Although studies repeatedly link high intakes of fish oil to better health outcomes, low intake does not appear to directly correlate with poor health!

Symptoms of Fish oil Toxicity

There is no known toxicity of EPA and DHA.  Very high-fat diets can cause NAFLD; a fatty liver that can lead to liver cirrhosis/liver failure if untreated.

Very high doses of fish oil supplementation (>2 grams per day) can lead to stomach upset and headache, which resolves when you stop taking the supplement.

Tips for Optimizing Omega-3 Intake on a Vegetarian Diet

  • Incorporate chia seeds, hemp seeds, ground flaxseeds, and walnuts into snacks
    • sprinkle on top of yogurt or oatmeal
    • incorporate into smoothies
    • use as the crunch element for salads
    • add to homemade breads and desserts
  • Use ALA-rich oils for cooking and salad dressings
    • flaxseed, hemp, soybean, and canola
  • Use algal oil supplements for DHA and EPA

Should I take a supplement?

It really depends on you and your individual risk factors.

Despite EPA’s ability to improve your cholesterol, high doses of DHA may do the opposite and actually raise your LDL “bad cholesterol.”

ALA, the precursor to DHA and EPA, has its own set of health benefits beyond just its ability to inefficiently convert to the “fish oils” EPA and DHA.  This is a fat that is readily available in our food supply.

In general, vegetarians show much lower levels of EPA and DHA than meat-eaters, but this has not shown a clinical impact on health outcomes. In fact, vegetarians tend to have lower rates of chronic conditions such as heart disease and diabetes.

If you have high cholesterol that won’t budge, medication-resistant mental health disorders, or a strong family history of auto-immune disorders, it may be worth it to you to try.

And studies show that algae oil supplements are as effective as fish oil-based supplements.

Those who take Coumadin or other anticoagulant medications or are alcohol-dependent should not take fish oil supplements without informing their doctor.

What supplementation won’t do

 As always, supplementation won’t overcome a poor diet. It is always better to get our nutrition from food.  A pill won’t correct a food pattern primarily made of veggie burgers and fries, vegetarian fast food, refined grains, and a lot of sugar.

Any concern for omnivores?

It’s easier for them, but if they don’t like fish or only eat it fried, they may not be getting enough either.

To Learn More:

Are You an Unhealthy Vegetarian?

Other nutrients in this series include B12, Protein, Calcium, Iron, and Zinc.

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