The Mediterranean diet encourages the consumption of fish around twice a week for most people. It’s a food that’s high in protein and is packed full of healthy vitamins and minerals.
However, if you want to choose the best fish when on the Mediterranean diet, you’ll generally want to choose one that is low in mercury and high in the types of omega-3 we don’t consume enough of.
This article will look into the levels of mercury and omega-3 fats for common fish species eaten and give a ranking based on these.
Note that there is different advice for women who are pregnant or breastfeeding, and children and babies, who should aim to minimize mercury and may need to reduce their consumption of particular types of fish.
How to Choose the Healthiest Fish
Even though the vitamin and mineral makeup will change depending on the fish, the most important aspect is the omega-3 fatty acids.
This is because they can be found in high quantities in particular types of fish and are difficult to find in other foods.
They can be found in other foods such as walnuts, seaweed, flaxseeds, and chia seeds, but not in the quantities and the type that is recommended. This is why most health bodies will recommend you eat fatty fish.
The criteria for the best fish in this article are:
- Low in mercury
- High in omega-3 fatty acids
We’ll rank the fish on these criteria and then give a ranking after.
Types of Fish
Different types of fish and shellfish provide different nutrients. This will help give you some idea of the types of fish you should be eating.
These types of fish are high in omega-3 fats. They include:
Fresh and canned tuna do not count as oily fish.
These are low-fat fish, meaning they are not as high in omega-3 fats. However, they are still a lean meat source that makes a great alternative to red or processed meats, which are higher in saturated fats.
- Sea Bass
These are low in fat and are a great source of certain minerals like zinc, selenium, iodine and copper. They do contain some omega-3 fats, but not as much as oily fish.
How Much Mercury in Fish is Acceptable?
The U.S. Environmental Protection Agency recommended avoiding fish with more than 0.5 parts per million (PPM) of mercury.
The fish species and mercury levels of them are given below:
Species Mean Mercury Concentration (PPM)
Salmon (Canned) 0.014
Salmon (Fresh/frozen) 0.022
Mackerel Atlantic (N.atlantic) 0.05
Haddock (Atlantic) 0.055
Croaker Atlantic (Atlantic) 0.069
Trout (Freshwater) 0.071
Mackerel Chub (Pacific) 0.088
Lobster (Spiny) 0.093
Lobster (Northern / American) 0.107
Perch Ocean 0.121
Tuna (Canned, Light) 0.126
Tilefish (Atlantic) 0.144
Tuna (Fresh/Frozen, Skipjack) 0.144
Perch (Freshwater) 0.15
Lobster (Species Unknown) 0.166
Bass (Saltwater, Black, Striped, Rockfish)  0.167
Mahi Mahi 0.178
Mackerel Spanish (S. Atlantic) 0.182
Weakfish (Sea Trout) 0.235
Croaker White (Pacific) 0.287
Tuna (Canned, Albacore) 0.35
Bass Chilean 0.354
Tuna (Fresh/frozen, Yellowfin) 0.354
Tuna (Fresh/frozen, Albacore) 0.358
Tuna (Fresh/frozen, All) 0.386
Tuna (Fresh/frozen, Species Unknown) 0.41
Grouper (All Species) 0.448
Mackerel Spanish (Gulf Of Mexico) 0.454
Orange Roughy 0.571
Tuna (Fresh/frozen, Bigeye) 0.689
Mackerel King 0.73
Tilefish (Gulf Of Mexico) 1.123
Fish above this threshold include:
- King Mackerel
Tuna has always been considered a low mercury fish, but particular types are actually quite high.
The Environmental Protection Agency recommended highest dose someone should consume is 0.1 microgram/kg body weight per day.
Explaining the Different Types of Omega 3 Fats
There are 3 different types of omega-3 fats:
- Alpha-linolenic acid (ALA)
- Eicosapentaenoic acid (EPA)
- Docosahexaenoic acid (DHA)
These omega-3s cannot be produced by the body and must be consumed from the diet. ALA is found in many foods such as flaxseeds and soybeans and as such, many people in the US consume sufficient ALA (ref).
However, many of us don’t consume enough EPA and DHA and these contribute a very small amount to daily omega-3 intake (40mg in children and 90 mg in adults) (ref)
Fatty fish are one of the only food groups containing EPA and DHA and they are by far the biggest source, hence the omega-3 ratings will include these, not ALA (since you can get ALA from plenty of other foods).
Side note: ALA can be converted into EPA and then DHA, but this conversion rate is very poor, at roughly 15%. Therefore, getting EPA and DHA from foods or supplements is the only practical way to increase these fatty acids.
The figures below are taken from the NIH (National Institutes for Health) and we’ve sumed the DHA and EPA for a total:
|DHA||EPA||Total DHA + EPA|
|Salmon, Atlantic, farmed cooked, 3 ounces||1.24||0.59||1.83|
|Herring, Atlantic, cooked, 3 ounces*||0.94||0.77||1.71|
|Salmon, Atlantic, wild, cooked, 3 ounces||1.22||0.35||1.57|
|Sardines, canned in tomato sauce, drained, 3 ounces*||0.74||0.45||1.19|
|Mackerel, Atlantic, cooked, 3 ounces*||0.59||0.43||1.02|
|Salmon, pink, canned, drained, 3 ounces*||0.63||0.28||0.91|
|Trout, rainbow, wild, cooked, 3 ounces||0.44||0.4||0.84|
|Sea bass, cooked, 3 ounces*||0.47||0.18||0.65|
|Oysters, eastern, wild, cooked, 3 ounces||0.23||0.3||0.53|
|Shrimp, cooked, 3 ounces*||0.12||0.12||0.24|
|Tuna, light, canned in water, drained, 3 ounces*||0.17||0.02||0.19|
|Lobster, cooked, 3 ounces*||0.07||0.1||0.17|
|Scallops, cooked, 3 ounces*||0.09||0.06||0.15|
|Cod, Pacific, cooked, 3 ounces*||0.1||0.04||0.14|
|Tilapia, cooked, 3 ounces*||0.11||0.11|
|Tuna, yellowfin, cooked 3 ounces*||0.09||0.01||0.1|
* USDA database does not specify whether fish are farmed or wild-caught.
Ranking the Best Fish for the Mediterranean Diet
From the data above, the criteria you should generally looking for when deciding the best fish is:
- It is low in mercury (less than 50 PPM of mercury)
- Highest in omega-3 fats (specifically DHA and EPA, the fats we can’t consume in high quantities elsewhere).
Based on this, the ranking would be:
To Sum Up
If you’re looking from a purely health perspective, salmon was the best fish for the Mediterranean diet.
It has the highest amount of EPA and DHA omega-3 fatty acids per serving whilst being one of the lowest in mercury.
However, there are many different types of fatty fish and all offer significant health benefits, so you shouldn’t fret over which is healthier.
Consider what you like and try to eat fatty fish at least once a week.