Cod Liver Oil Benefits: What Grandpa Got Right

Every grandpa had one trick that the family laughed at. Ours was a spoonful of cod liver oil before breakfast, served with a wink and the words "trust me, kiddo." It turns out the old fella was onto something. He just never had the footnotes.

So here's what cod liver oil actually is, what the nutrients in it do in the body, and where the line sits between sensible habit and snake oil. No miracle cures. Just grandpa wisdom, with sources.

Quick heads-up: Grandpa Finn's doesn't sell cod liver oil. This guide is general education about cod liver oil and its nutrients, not a claim about any Grandpa Finn's product. Our range is Omega-3 Fish Oil (EPA and DHA), a Daily Multivitamin and the Daily Stack with both.

What is cod liver oil?

Cod liver oil is oil taken from the livers of cod. That small detail matters. Regular fish oil is usually pressed from the flesh of oily fish such as anchovies, sardines or mackerel. The liver is where a fish stores fat-soluble vitamins, so cod liver oil carries three things in one spoonful:

Omega-3 fatty acids, mainly EPA and DHA
Vitamin A, in its preformed (retinol) form
Vitamin D

The US National Institutes of Health Office of Dietary Supplements (NIH ODS) lists cod liver oil alongside fish oil, krill oil and algal oil as one of the main types of omega-3 supplement. It also names fish liver oils among the best natural sources of vitamin D.

The nutrients in cod liver oil and what they do

Omega-3s (EPA and DHA)

Omega-3s are building blocks of the membranes around every cell in your body. According to the NIH ODS, DHA levels are especially high in the brain and the retina of the eye. Omega-3s also have roles in the heart, blood vessels, lungs, immune system and hormone system.*

Your body can turn a little of the plant omega-3 ALA into EPA and DHA, but only a small amount. The NIH says getting EPA and DHA from food (and supplements, if you take them) is the only practical way to raise your levels. Harvard's Nutrition Source makes the same point: EPA and DHA are best obtained directly.

In plain grandpa terms, omega-3s support normal heart function and normal brain function as part of a healthy diet.*

Vitamin A

The NIH ODS explains that vitamin A is important for normal vision, the immune system, reproduction, and growth and development. It also helps your heart, lungs and other organs work properly.*

Preformed vitamin A has a catch: too much can be harmful, and high intakes during pregnancy can harm a developing baby. We cover that in its own section below, because it's important.

Vitamin D

Vitamin D helps your body absorb calcium, one of the main building blocks of bone. The NIH ODS notes your muscles need vitamin D to move, your nerves need it to carry messages, and your immune system needs it too. So vitamin D supports normal bones, muscle function and immune system function.*

Very few foods contain much vitamin D naturally, which is one reason cod liver oil earned its place in so many old kitchen cupboards, particularly in places with long, grey winters.

Cod liver oil benefits, summed up honestly

Here's what the nutrients in cod liver oil are generally known to do, in the careful language the science supports. This is general nutrition education, not a claim about any Grandpa Finn's product:

Supports normal heart health (EPA and DHA)*
Supports normal brain function and eye health (DHA)*
Supports normal immune system function (vitamins A and D)*
Helps maintain normal bones and muscle function (vitamin D)*
Supports normal vision (vitamin A)*

What it isn't: a cure, a treatment or a shield against any disease. The NIH is clear that researchers are still studying how omega-3 supplements affect health. Many of the benefits seen in people who eat fish may come from the fish itself and the wider diet. Harvard also notes that eating fatty fish has a stronger track record than supplements alone. That's why grandpa never skipped his Friday fish dinner either.

Food first, then fill the gaps

Both the NIH and Harvard recommend getting most of your nutrients from food. Harvard suggests eating fish or other seafood 1–2 times a week, particularly fatty fish such as salmon, sardines, mackerel and herring. A supplement makes sense as a top-up when your diet doesn't hit the mark: if you don't like fish, eat it rarely, or live somewhere the winter sun is weak.

Is cod liver oil safe? The bits that matter

Vitamin A adds up

Cod liver oil contains preformed vitamin A, and so do some multivitamins, liver and liver pâté. The NIH sets the adult upper limit for preformed vitamin A at 3,000 mcg a day from all sources combined. If you take a multivitamin as well, add up the labels before you double up.

Pregnancy

The NIH ODS warns that too much preformed vitamin A during pregnancy can cause birth defects. If you're pregnant, might be, or are breastfeeding, don't start cod liver oil without your doctor's say-so.

Blood thinners and other medicines

The NIH notes that high doses of omega-3s may cause bleeding problems when taken with warfarin or other anticoagulants. If you take any regular medication, check with your doctor or pharmacist first.

Mild side effects

The usual suspects are a fishy aftertaste, burps, heartburn or an upset stomach. These are mostly mild, and taking your oil with food often helps (see our guide on how to take cod liver oil).

Frequently asked questions

What is cod liver oil good for?

It supplies omega-3s (EPA and DHA), vitamin A and vitamin D. These nutrients support normal heart, brain, eye, immune, bone and muscle function as part of a balanced diet.*

Is cod liver oil the same as fish oil?

No. Cod liver oil comes from the liver and contains vitamins A and D. Fish oil usually comes from the flesh of oily fish and is mostly just omega-3s. Grandpa Finn's makes an Omega-3 Fish Oil, not a cod liver oil. See cod liver oil vs fish oil.

Can I take cod liver oil every day?

Many people do, at the dose on the label. Don't go above the label dose, and count vitamin A and D from any other supplements you take.

Can children take cod liver oil?

Children have lower upper limits for vitamins A and D. Use only a product made for their age group, and check with your doctor first.

Does cod liver oil cure anything?

No. It's a dietary supplement, not a medicine. It isn't intended to diagnose, treat, cure or prevent any disease.

Grandpa's verdict

Grandpa's spoonful wasn't magic. It was simply a reliable way to top up a few nutrients many of us run short on. Eat your fish, get some sensible sunshine, and if you want a top-up, pick one that's easy to stick with.

Want a top-up? Grandpa Finn's makes an Omega-3 Fish Oil and a Daily Multivitamin, or grab both together as the Daily Stack. Shop the range.

Sources

NIH Office of Dietary Supplements, Omega-3 Fatty Acids – Consumer Fact Sheet
NIH Office of Dietary Supplements, Vitamin A and Carotenoids – Consumer Fact Sheet
NIH Office of Dietary Supplements, Vitamin D – Consumer Fact Sheet
Harvard T.H. Chan School of Public Health, The Nutrition Source, Omega-3 Fatty Acids: An Essential Contribution

Grandpa's fine print: This article is general information only, not medical advice. Supplements don't replace a varied, balanced diet. Talk to your doctor or pharmacist before starting any supplement, especially if you're pregnant, planning a pregnancy or breastfeeding, taking blood thinners (anticoagulants such as warfarin) or other medicines, have a health condition, or are buying for a child. Always read the label and use only as directed.

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.