When Should You Not Eat Mackerel? Key Health and Safety Considerations

Mackerel is widely favored for its nutritional profile, especially for its rich omega-3 fatty acids, but there are specific situations where it should be avoided or consumed with caution. Recognizing the potential health risks, such as high mercury content, spoilage, and allergic reactions, is crucial for safe consumption. This guide provides a detailed overview of when you should not eat mackerel.

Quick Summary

It is not advisable to eat mackerel when pregnant, if a species is high in mercury, or if the fish is improperly stored and develops toxic histamine. Exercise caution with allergies and high sodium canned varieties. It is vital to recognize spoilage signs to prevent foodborne illness.

Key Points

• Avoid High-Mercury Varieties: Do not eat king mackerel, especially for pregnant women and children, due to high mercury levels.

• Prevent Scombroid Poisoning: Skip mackerel that has been improperly refrigerated, as spoilage can cause a heat-stable histamine toxin.

• Prioritize Freshness: Never consume mackerel that exhibits signs of spoilage, such as a sour smell, dull skin, or sunken eyes.

• Limit for Vulnerable Groups: Pregnant or nursing individuals should limit their intake of oily fish like Atlantic mackerel to no more than two portions a week.

• Beware of Allergies: Individuals with a fish allergy should avoid mackerel entirely, as cross-contamination is a risk.

• Monitor Sodium Intake: If on a low-sodium diet, be mindful of the added salt content in many canned mackerel products.

Avoiding Mercury Contamination

Mercury is a naturally occurring element that can build up in fish as methylmercury, a potent neurotoxin. The level of mercury varies significantly among different species of mackerel, primarily based on their size and position in the food chain. Larger, predatory fish tend to have higher concentrations of mercury.

King Mackerel: The Primary Concern

King mackerel is the species most associated with high mercury levels, and the U.S. Food and Drug Administration (FDA) explicitly advises certain groups to avoid it.

• High Risk Group: Pregnant women, women who may become pregnant, nursing mothers, and young children should completely avoid eating king mackerel.
• Mercury Buildup: Mercury from fish can accumulate in the bloodstream and can take over a year to clear, making it dangerous for those planning a family.

Safer Alternatives: Atlantic and Pacific Mackerel

In contrast, smaller species like Atlantic and Pacific mackerel have significantly lower mercury levels. These can be a healthy part of a balanced diet, even for pregnant women, in moderation. The FDA considers Atlantic mackerel a "best choice" due to its low mercury content.

The Threat of Scombroid (Histamine) Poisoning

Another critical reason to avoid mackerel is the risk of scombroid poisoning, a foodborne illness caused by high levels of histamine. This occurs when mackerel and other scombroid fish are improperly stored or refrigerated after being caught.

How Spoilage Leads to Histamine

• Naturally occurring bacteria on the fish convert the amino acid histidine into histamine.
• This process can happen quickly if the fish is not chilled immediately and kept at proper temperatures (below 5°C).
• Unlike other bacteria that are killed by cooking, the histamine toxin is heat-stable and remains potent even if the fish is grilled, smoked, or canned.

Recognizing the Symptoms

Symptoms can appear rapidly, often within minutes to an hour after consumption, mimicking an allergic reaction. They can include:

• Flushing of the face and upper body
• Burning or tingling sensation in the mouth
• Hives, rash, or itching
• Headache, dizziness, and heart palpitations
• Severe cases may include blurred vision or respiratory distress

How to Tell if Mackerel is Spoiled

Preventing scombroid poisoning starts with selecting fresh fish and handling it correctly. While some contaminated fish may look, smell, and taste normal, these signs of spoilage should prompt you to discard it immediately.

Visual and Olfactory Cues of Spoilage:

• Eyes: Sunken, cloudy, or discolored eyes
• Skin: Dull, washed-out appearance with a loss of its natural sheen
• Gills: Dark red or brown, potentially with a dark, slimy mucus
• Odor: A sour, oily, or sweaty smell. A faint hint of ammonia may also be present.
• Flesh: A soft, flabby texture that doesn't spring back when pressed

Comparison of Mackerel Species

Feature	King Mackerel	Atlantic Mackerel	Spanish Mackerel
Mercury Level	High (Avoid for sensitive groups)	Low (Best Choice)	Moderate (Limit for sensitive groups)
Size	Large (up to 100 lbs)	Small to Medium	Small to Medium
Lifespan	Long-lived	Short-lived	Intermediate
FDA Recommendation	Avoid	Best Choice (low mercury)	Good Choice (limited intake)
Reason for Concern	Bioaccumulation of mercury due to long life and size.	Very few concerns for most populations.	Some mercury present, but lower than king mackerel.

Additional Circumstances for Avoiding Mackerel

Fish Allergies

Individuals with a known fish allergy should avoid all types of mackerel. Fish allergies can cause severe reactions, including anaphylaxis. Cross-contamination can also occur, so individuals with fish allergies should be vigilant about avoiding all seafood unless certain it is prepared in a fish-free environment.

Canned Mackerel with High Sodium

While convenient, canned mackerel often contains high levels of added sodium. This can be problematic for individuals managing hypertension or following a sodium-restricted diet. Always check the nutrition label and opt for low-sodium options where available.

Conclusion: Prioritizing Safety and Freshness

Mackerel offers significant nutritional benefits, especially its rich content of omega-3 fatty acids, but it is not without its risks. Knowing when you should not eat mackerel is essential for protecting your health. The primary concerns revolve around mercury contamination in larger species like king mackerel, and the rapid spoilage that can lead to histamine poisoning in all species. By opting for low-mercury varieties like Atlantic mackerel, prioritizing absolute freshness, and being aware of personal health conditions like fish allergies, you can safely enjoy this oily fish. Always remember to store and handle mackerel correctly to prevent the formation of dangerous toxins. For official guidance on fish consumption, refer to resources like the FDA's advice about eating fish.

Mackerel Safety Checklist

Mercury Levels: Choose low-mercury varieties like Atlantic mackerel and avoid high-mercury king mackerel. Freshness: Only eat fresh fish that smells clean, has firm flesh, and bright eyes to prevent histamine poisoning. Storage: Refrigerate or freeze mackerel immediately after purchase to prevent bacterial growth and histamine formation. Preparation: Cook mackerel thoroughly; cooking does not remove histamine once it has formed. Allergies: If you have a fish allergy, avoid mackerel entirely due to the risk of allergic reactions. Canned Options: Choose low-sodium canned mackerel if you are managing blood pressure or salt intake.

When to Reconsider Your Mackerel Meal

• Pregnancy and Young Children: When the risk of mercury is a concern, especially with king mackerel.
• Poor Handling: If there's any suspicion that the fish has been improperly handled or refrigerated.
• Known Allergies: If you have a documented allergy to fish, as reactions can be severe.
• High Blood Pressure: If you rely on canned mackerel and need to control your sodium intake.

Signs of Spoilage to Look For

• Eyes are sunken and cloudy.
• Skin appears dull and has lost its vivid, brilliant color.
• Gills are dark red or brown instead of a bright pinkish-red.
• A sour, oily, or ammonia-like odor is present.
• The fish feels slimy or tacky to the touch.
• The flesh is soft or flabby and doesn’t spring back when pressed.

Frequently Asked Questions

Is mackerel generally high in mercury?

Mercury levels vary significantly by species. Smaller Atlantic mackerel are relatively low in mercury and safe to consume a couple of times a week. Larger king mackerel, however, have high levels and should be avoided by pregnant women and children.

What is scombroid poisoning and how does it relate to mackerel?

Scombroid poisoning is a foodborne illness caused by high histamine levels in fish that has been improperly handled or stored. Mackerel is one of the fish species most often implicated in scombroid poisoning, as it has high levels of histidine that can be converted to histamine by bacteria.

Can cooking spoiled mackerel make it safe?

No, cooking spoiled mackerel does not make it safe. The histamine toxin responsible for scombroid poisoning is heat-stable and is not destroyed by cooking, freezing, or smoking.

How can I check if fresh mackerel is still good to eat?

Check for bright, non-sunken eyes, shiny and vivid skin, and firm flesh that bounces back when pressed. The fish should have a clean, mild ocean smell, not a sour or ammoniated odor.

Are pregnant women advised to avoid all mackerel?

No, but they should avoid high-mercury species like king mackerel entirely. For low-mercury options like Atlantic mackerel, pregnant women should limit their consumption to no more than two portions per week.

Why should people with fish allergies avoid mackerel?

Individuals with fish allergies should avoid all fish, including mackerel, because most species share similar proteins that can trigger a reaction. There is also a risk of cross-contamination in places like fish markets.

What are the health risks of eating canned mackerel?

Canned mackerel can have high levels of sodium, which is a concern for individuals with high blood pressure. However, low-sodium varieties are often available. Canned mackerel retains its omega-3 benefits but consumers should be mindful of the salt content.