I’m lucky to live in warm climates with year-round access to fresh produce, but not everyone can pop over to their local farmer’s market or co-op whenever they want and grab the ingredients for a big-ass salad. Farm-to-table cuisine is great, the Primal ideal even, but the reality is that cooking with fresh, local ingredients requires access and time to shop and prepare food that not everyone enjoys, not always. Many people rely on preserved food for much or all of the year to meet their meat and produce needs, “preserved” meaning frozen, canned, dried, or fermented.
Whenever the topic of canned food comes up, I inevitably get questions about whether canned vegetables are nutritious, safe, or even Primal. (And I inevitably get comments about how we don’t need vegetables at all, which I discuss in my Definitive Guide to the carnivore diet.) Sure, Grok wouldn’t have eaten canned vegetables. But modern humans spend almost every minute of every day engaging with technology our ancestors couldn’t have imagined, from highly engineered mattresses topped with cooling pads to regulate our sleep temperature to air fryers to whatever device you’re reading this post on right now.
So I’m not too concerned about drawing some Primal line in the sand at food canning. The other questions are important, though. How does canned food stack up to fresh or frozen?
Are Canned Vegetables as Nutritious As Fresh or Frozen?
It depends on which vegetable and which nutrient you look at, but in general, canning tends to reduce nutrient content compared to fresh or frozen vegetables. But that’s not true across the board. Sometimes, specific nutrients are actually higher in canned offerings.12
Furthermore—and this is a crucial point—nutrient losses due to canning often even out by the time the food makes it to your plate. Canning exposes food to high heat, so much of that nutrient loss is essentially due to the “cooking” that canned food undergoes. Most frozen vegetables only withstand a quick blanching before being flash frozen. Thus, if you compare fresh, frozen, and canned vegetables immediately after harvesting and processing, canned generally looks the worst, nutrient-wise. However, research shows that canned vegetables maintain their nutrient levels as they sit on the shelves, whereas the nutrients in frozen and fresh vegetables tend to degrade, bringing them more on par with canned. Once you factor in storing and then cooking fresh and frozen vegetables, you find that the initial disparities are much less pronounced as you’re forking it into your mouth.3
Clearly, the best choice is fresh vegetables consumed as close to harvesting as possible. The reality, though, is the produce at your supermarket may be many weeks out from when it was picked, making it less “fresh” than you might imagine. There’s also the whole issue of seasonal and regional availability to consider.
Overall, in terms of building a nutrient-dense diet, in most circumstances, canned vegetables are going to be just as good or nearly as good as grocery store or frozen vegetables.
BPA Concerns in Canned Foods
Nutrient content isn’t the only consideration when weighing canned versus fresh or frozen vegetables. There’s also the can itself. I have historically avoided canned vegetables in the store due to concerns over BPA in the can linings. (Home-canning in jars is different, of course. I’m all for home canning.) BPA is a known endocrine disruptor linked to immune system dysfunction, cancer, reproductive issues, and more. Since scientists and health watchdog groups have sounded the alarm about BPA in the past decade, industry reports suggest that almost all American manufacturers have moved away from BPA-lined cans.4
While that seems like a positive step, the BPA lining was there for a reason: to prevent corrosion and help preserve the food inside. Manufacturers replaced it, by necessity, with other types of materials that are supposed to be safer—“supposed to” being the operative words here. However, at this point, it’s hard to pinpoint exactly what materials are being used by which manufacturers and, more importantly, how they are being tested for safety. Thus, I can’t say with any certainty that these new linings are better.
How Long Do Canned Foods Last?
Food waste is a massive global problem that is both economically and environmentally costly. One way we can reduce food waste is by learning what the expiration dates on our pantry items really mean. According to the USDA, “best by” dates aren’t about food safety but food quality.5 After those dates, the flavor and texture may start to take a hit, but canned foods are still perfectly edible.
There’s certainly no reason to throw canned food away simply because it is a week, a month, or even longer past its best by date. Canned foods stay good for up to five years in your cupboard, though you’ll want to use more acidic items like canned tomatoes within a year or so. Home-canned foods should be used within a year, ideally.
Just use common sense (and your nose). If a can looks damaged—rusted, bulging, or badly dented—it’s not worth taking a chance. Likewise if the food inside has a strange odor. Texture changes, slight discoloration, and crystallization are not signs that the food is spoiled.
For the most part, I continue to opt for fresh, frozen, or shelved food in glass packaging when available. The notable exception is canned fish. The convenience of a canned sardine or anchovy, and the benefits of the omega-3s they deliver, means they still have a standing place in my cupboard.
Some items are hard to find outside a can, though. Cooked beans don’t come frozen (another argument for skipping legumes?), and while they’re easy and affordable to prepare from dried, that requires preplanning. If beans are a staple in your home, consider preparing big batches and freezing them in individual portions. Tetra Paks are becoming more common for things like stewed tomatoes and soups, but there are questions about their sustainability. They are technically recyclable, but many recycling facilities don’t have the proper machinery, so they end up in a landfill. And glass can be more expensive, which matters especially when the cost of groceries is on the rise.
If you’re going to choose canned foods for reasons of convenience or availability, still look for “BPA-free” on the label. Don’t leave canned tomatoes sitting on the shelf for months at a time. It gives the acidity more time to erode the lining. Buy them close to when you are ready to use them. Same goes for canned fruit. If you are laying up food for emergency preparedness, look at dehydrating as an option.
Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.