Tuna with mayo is a genuinely nutritious meal for most people, thanks to tuna’s high protein content and heart-healthy omega-3 fats. The catch is that standard mayonnaise adds a significant dose of calories and omega-6-heavy soybean oil that can dilute those benefits if you’re heavy-handed with it. A typical sandwich-sized serving of tuna salad made with two or three tablespoons of regular mayo can easily pack over 400 calories, with much of that coming from fat rather than the protein and micronutrients you opened the can for. The good news is that small adjustments to how you prepare it can shift the balance substantially.
Why Tuna Itself Is Worth Eating
Canned tuna is one of the most affordable and shelf-stable sources of lean protein available. A standard can delivers roughly 20 to 25 grams of protein with very little saturated fat, along with meaningful amounts of selenium, niacin, vitamin B12, and vitamin D. But the nutrient that gets the most attention is the omega-3 fatty acids EPA and DHA, which are concentrated in fatty fish and are difficult to get in sufficient amounts from other common foods.
The cardiovascular evidence behind omega-3s is strong. Consuming fish or fish oil containing these fats has been shown to reduce the risk of coronary heart disease, lower triglycerides and blood pressure, decrease inflammatory markers, improve blood vessel function, and reduce the risk of dangerous heart rhythm disturbances.1PubMed. Omega-3 fatty acids and the cardiometabolic syndrome A review in Nature Reviews Cardiology noted that individuals without existing heart disease should aim for at least 250 to 500 milligrams of long-chain omega-3s daily, and that eating fish is arguably better than taking supplements because whole fish also delivers vitamin D, selenium, and antioxidants that capsules lack.2Nature Reviews Cardiology. Omega-3 fatty acids: cardiovascular benefits, sources and sustainability A three-ounce serving of canned light tuna provides somewhere around 200 to 250 milligrams of EPA and DHA combined, so eating it a few times a week gets you comfortably into that range.
What Mayonnaise Actually Does to the Equation
Mayonnaise is, at its core, an emulsion of oil, egg yolk, and acid (usually vinegar or lemon juice). A tablespoon of regular mayo contains about 90 to 100 calories and 10 grams of fat. Most commercial mayonnaise in the United States is made with soybean oil, which is high in omega-6 fatty acids. Omega-6 fats are not inherently harmful and are in fact essential, but the modern Western diet already overloads on them relative to omega-3s. Adding several tablespoons of soybean-oil-based mayo to your tuna shifts the overall fat profile of the meal toward omega-6 dominance, which partly works against the omega-3 benefit you’re eating tuna for in the first place.
That said, the type of oil in mayo matters more than most people realize. A randomized trial comparing soybean-oil-based mayonnaise to palm-olein-based mayonnaise found that the soybean version led to lower total cholesterol and lower LDL cholesterol, though it also slightly lowered HDL cholesterol, with the overall LDL-to-HDL ratio staying unchanged between the two. Blood sugar and markers of oxidative stress also didn’t differ between the two types.3PubMed Central. Comparing effects of soybean oil- and palm olein-based mayonnaise consumption on the plasma lipid and lipoprotein profiles in human subjects: a double-blind randomized controlled trial with cross-over design In other words, soybean-oil mayo isn’t metabolically catastrophic in moderate amounts. The problem is portion size: most people don’t measure, and tuna salad has a way of absorbing mayo until it’s more condiment than fish.
Calories add up fast. Two tablespoons of regular mayo contribute about 180 to 200 calories and 20 grams of fat to your bowl. Three tablespoons, which is common in restaurant-style tuna salad, pushes past 270 calories from mayo alone. At that point, the mayo is contributing more calories than the tuna itself. If you’re watching your weight or trying to keep a meal lean, this is where the math starts working against you.
Better Swaps That Actually Work
The goal with any mayo alternative isn’t just to reduce calories. It’s to preserve the creaminess and moisture that makes tuna salad appealing while improving or at least not worsening the fat profile. Here are approaches that deliver on both counts:
- Greek yogurt: Plain nonfat or low-fat Greek yogurt provides a tangy, creamy base with a fraction of the calories and a bonus of extra protein. Mixing half mayo and half Greek yogurt is an easy first step if you’re not ready to go all-in. The texture is slightly thinner, so letting the salad chill for 20 minutes helps it set.
- Mashed avocado: Avocado contributes monounsaturated fat, which is widely considered the most heart-friendly fat category. It adds richness without the processed-oil concern. A quarter of a ripe avocado mashed into a can of tuna gives you a creamy consistency with about 60 calories and 5 grams of mostly monounsaturated fat.
- Olive oil and lemon: A drizzle of extra virgin olive oil with fresh lemon juice and a pinch of salt makes something closer to a Mediterranean-style tuna preparation. You lose the emulsified creaminess, but the flavor is brighter and the fat quality is excellent.
- Hummus: A couple tablespoons of hummus mixed into drained tuna provides creaminess, fiber, and a mild savory depth. The calorie count is similar to a reduced portion of mayo, but the fiber and plant protein are a meaningful upgrade.
- Cottage cheese: Blended or whipped cottage cheese has become a popular substitute in high-protein cooking. It’s nearly flavorless once mixed with tuna and seasonings, and it adds substantial protein while keeping fat very low.
Light or reduced-fat mayo is also fine. It cuts calories roughly in half compared to regular mayo, typically by substituting water and starch for some of the oil. It won’t win any culinary awards, but for a quick lunch it keeps things familiar without the caloric hit.
Choosing the Right Tuna for Mercury
Mercury is the one health concern with canned tuna that genuinely warrants attention, especially if you eat it frequently. Mercury accumulates in fish as they age and grow, so larger, longer-lived tuna species carry more of it. The practical distinction for shoppers comes down to white versus light tuna. White canned tuna is almost always albacore, a larger species that averages about 0.41 parts per million of total mercury. Light or chunk light tuna is typically skipjack, a smaller species that averages about 0.12 parts per million, roughly a third of the albacore level.4PubMed. Mercury in canned tuna: white versus light and temporal variation
For most adults, eating two to three servings of light tuna per week falls well within guidelines from the FDA and EPA. If you prefer albacore, limiting yourself to one serving per week is a reasonable precaution. Pregnant and breastfeeding women, as well as young children, should lean toward light tuna and keep portions conservative. The advice isn’t to avoid tuna altogether but to pick the lower-mercury option and not make it your only protein source day after day.
Microplastics in Canned Tuna
Mercury isn’t the only contaminant worth knowing about. Research over the past few years has found microplastics in canned tuna at levels that have caught the attention of food safety researchers. One study analyzing commercial canned tuna found a substantial presence of microplastics: roughly 690 particles per 100 grams in tuna packed in water and about 440 per 100 grams in tuna packed in oil. Most of the particles were tiny, with about 90 percent falling in the 1 to 50 micrometer size range, and the most common plastic types identified were PET, polystyrene, and nylon.5PubMed. Presence of microplastics in commercial canned tuna That study noted the canning process itself, including the ingredients and inputs, likely contributes to the contamination.
A separate study looking at various canned seafood products found microplastics in every sample tested, with canned tuna in olive oil among the most contaminated, averaging about 5 particles per can. Fibers were the most common shape, and polyester was the dominant polymer type.6PubMed. Uncovering microplastics contamination in canned seafood A broader systematic review of microplastic contamination across tuna species found high concentrations in tuna from certain ocean regions, with the Bay of Bengal and Persian Gulf showing particularly elevated levels in the fish themselves before any canning occurs.7PubMed Central. A Systematic Review of Microplastic Contamination in Tuna Species: General Pathways into the Food Chain with Ecotoxicological and Human Health Perspectives
The honest answer is that scientists are still working out what these exposure levels mean for human health. The particles are extremely small, and we don’t yet have long-term data on what chronic low-level ingestion does to the body. This isn’t unique to tuna; microplastics have been found in bottled water, table salt, honey, and many other foods. Avoiding canned tuna specifically to reduce microplastic intake would be missing the forest for the trees. But it’s worth being aware of as the research matures, particularly if you eat canned seafood daily.
The Emulsifier Question in Commercial Mayo
Here’s something most people don’t think about when debating whether to add mayo to their tuna: the additives in commercial mayonnaise may matter beyond their calorie contribution. Store-bought mayo often contains emulsifiers and stabilizers such as modified food starch, xanthan gum, or other gum-based thickeners to maintain texture and extend shelf life. These ingredients are present in small amounts per serving, but emerging research on dietary emulsifiers and gut health raises questions worth tracking.
Several studies suggest that commonly used dietary emulsifiers, including carboxymethylcellulose and polysorbate 80 (found more often in low-fat and processed dressings than in standard mayo), can shift the composition of gut bacteria toward a more inflammatory pattern associated with metabolic syndrome and intestinal inflammatory disease.8PubMed Central. Food Emulsifiers and Metabolic Syndrome: The Role of the Gut Microbiota Lab research testing a range of common emulsifiers directly on human gut microbiota found that many, though not all, altered the microbial community in ways expected to promote intestinal inflammation.9PubMed Central. Direct impact of commonly used dietary emulsifiers on human gut microbiota A broader review of ultra-processed foods in general, which share many of the same synthetic additives found in commercial condiments, linked their consumption to decreased microbial diversity, lower levels of beneficial gut bacteria, and increases in pro-inflammatory microorganisms associated with chronic conditions including metabolic syndrome and type 2 diabetes.10PubMed Central. The Detrimental Impact of Ultra-Processed Foods on the Human Gut Microbiome and Gut Barrier
This doesn’t mean a tablespoon of Hellmann’s is going to wreck your gut. The doses used in lab studies are often higher or more concentrated than what you’d encounter in a sandwich. But it’s one more reason why making your own mayo from olive oil and egg yolks, or choosing a simpler ingredient list when shopping, could be worthwhile if tuna salad is a regular part of your diet rather than an occasional lunch.
How to Drain and Store Tuna Safely
One underappreciated aspect of tuna salad safety is histamine, a compound that builds up in tuna flesh when bacteria break down the amino acid histidine. Tuna is naturally high in histidine, which makes it one of the most common fish involved in scombroid poisoning, a type of food poisoning that mimics an allergic reaction with flushing, headache, and sometimes hives.
Temperature control is everything. Research tracking histamine formation in tuna steaks found that at refrigerator temperature (about 4°C or 39°F), histamine levels rose modestly from about 13 mg/kg on day one to around 68 mg/kg by day six. But at 12°C (about 54°F), which is what a warm fridge or a countertop in a mild room might reach, histamine skyrocketed from about 24 mg/kg on day one to over 2,700 mg/kg by day six, well past the danger threshold.11PubMed Central. Development of Histamine in Fresh and Canned Tuna Steaks Stored under Different Experimental Temperature Conditions The FDA considers histamine levels above 50 mg/kg a potential hazard in fish.
For canned tuna, the canning process itself keeps histamine in check while the can is sealed. The risk begins once you open it, mix it with mayo, and store the salad. Tuna salad left in an insulated lunch bag without an ice pack, or sitting on a buffet table, can develop histamine levels that make people sick within hours. The fix is straightforward: keep prepared tuna salad refrigerated at or below 40°F and consume it within three to four days. Don’t leave it at room temperature for more than two hours, or one hour if the ambient temperature is above 90°F.
When Tuna With Mayo Doesn’t Fit
For a few groups, the standard tuna-and-mayo combination deserves extra thought. People with egg allergies obviously need to avoid traditional mayo entirely, but many commercial “vegan” mayonnaises substitute aquafaba or other plant-based emulsifiers and work fine in tuna salad. People on low-sodium diets should check the can: a single serving of canned tuna in water can contain 200 to 300 milligrams of sodium before you add anything, and mayo contributes another 70 to 100 milligrams per tablespoon. Rinsing canned tuna under water for 20 to 30 seconds can reduce sodium content meaningfully.
People with histamine intolerance, a condition where the body has trouble breaking down histamine from food, may react to canned tuna regardless of how it’s prepared. Canned fish tends to be higher in histamine than fresh because of the time between catch and processing. For these individuals, switching to freshly caught and quickly frozen tuna steaks, or choosing a different protein entirely, makes a bigger difference than any mayo swap.
For anyone managing their weight, the simplest intervention is measuring. A kitchen scale or even a basic tablespoon measure can turn a 500-calorie tuna salad into a 300-calorie one without changing the recipe at all. Most people who switch from free-pouring mayo to actually measuring two level tablespoons are surprised by how much less they need. Adding volume with diced celery, red onion, pickles, or capers makes the salad feel generous without extra fat, which is why those ingredients show up in nearly every classic recipe to begin with.