I’m fortunate to live in warm climates with year-round access to fresh produce, but not everyone can go to their local farmer’s market or co-op whenever they want and grab the ingredients for a big salad. Farm-to-table cooking 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 likes, not always. Many people rely on canned foods for much or all of the year to meet their meat and produce needs, where “canned” means frozen, canned, dried, or fermented.
Whenever the topic of canned food comes up, I am inevitably asked if canned vegetables are nutritious, safe, or even original. (And I inevitably get comments about how we don’t need veggies at all, which I discuss in my Definitive Guide to the Carnivore Diet.) Sure, Grok wouldn’t have eaten canned veggies. But modern humans spend nearly every minute of their day dabbling in technologies our ancestors never could have imagined, from high-tech mattresses with cooling pads to regulate our sleeping temperature, to air fryers, to the device you’re reading this post on .
So I’m not too concerned about drawing a primal line in the sand when canning food. But the other questions are important. How does canned food stack up to fresh or frozen?
Are canned vegetables as nutritious as fresh or frozen?
It depends on what veggies and what nutrients you’re looking at, but in general, canning reduces the nutrient content compared to fresh or frozen veggies. But that’s not true across the board. Sometimes certain nutrients are actually higher in canned offerings.
Additionally – and this is a key point – nutrient losses due to canning often even out by the time the food makes it onto your plate. Canning involves subjecting foods to high heat, so much of this nutrient loss is largely due to the “cooking” that canned food undergoes. Most frozen vegetables only survive a short blanch before being snap frozen. So when you compare fresh, frozen, and canned vegetables immediately after harvesting and processing, canned vegetables generally look the worst in terms of nutrients. However, research shows that canned vegetables retain their nutritional content while they sit on the shelves, while the nutrients in frozen and fresh vegetables tend to break down, making them more on par with canned vegetables. Once you factor in the storage and subsequent cooking of fresh and frozen vegetables, you’ll find that the initial differences are much less pronounced once you put them in your mouth.
The best choice, of course, is fresh vegetables, consumed as close to harvest as possible. However, the reality is that the produce in your supermarket can be many weeks past being harvested, making it less “fresh” than you might think. Then there is the whole question of seasonal and regional availability.
All in all, canned vegetables are, in most cases, as good or nearly as good as store-bought or frozen vegetables when it comes to building a nutrient-dense diet.
BPA concerns in canned food
Nutritional content isn’t the only consideration when weighing canned vegetables versus fresh or frozen vegetables. There’s also the can itself. I’ve avoided canned veggies at the store in the past due to concerns about BPA in the can liners. (Home canning in jars is different, of course. I’m all for home canning.) BPA is a well-known endocrine disruptor that’s been linked to immune system dysfunction, cancer, reproductive problems, and more. Since scientists and health watch groups have been sounding the alarm about BPA for the past decade, industry reports suggest that almost all American manufacturers have moved away from BPA-lined cans.
While that seems like a positive move, the BPA liner was there for a reason: to prevent corrosion and to preserve the food inside. Manufacturers have inevitably replaced it with other types of materials that are said to be safer – “should” are the operative words here. At this point, however, it’s difficult to pinpoint exactly which materials are used by which manufacturers and, more importantly, how they are tested for safety. So I can’t say for sure that these new pads are better.
How long do canned goods last?
Food waste is a massive global problem that is both economically and environmentally costly. One way to reduce food waste is to learn what the expiration dates on our pantry items really mean. According to the USDA, “best before dates” aren’t about food safety, they’re about food quality. After these dates, the flavor and texture may diminish, but canned foods are still perfectly edible.
There’s certainly no reason to throw away canned food just because it’s a week, a month or more past its sell-by date. Canned foods stay in your cupboard for up to five years, although within a year you should be moving to more acidic foods like canned tomatoes. Self-preserves should ideally be used up within a year.
Just use your common sense (and your nose). If a can looks damaged—rusted, dented, or badly dented—it’s not worth risking. Likewise if the food inside has a strange smell. Textural 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 where available. The notable exception is canned fish. The convenience of a canned sardine or anchovy and the benefits of the omega-3s they provide means they still have a permanent place in my cupboard.
However, some items are difficult to find outside of a can. Cooked beans don’t come frozen (another argument in favor of skipping legumes?), and while they’re easy and affordable to make from dried beans, doing so requires advance planning. If beans are a staple in your household, consider preparing large batches and freezing them in individual servings. Tetra Paks are being used more and more for things like stewed tomatoes and soups, but there are questions about their sustainability. They’re technically recyclable, but many recycling facilities don’t have the right machinery, so they end up in a landfill. And glass can be more expensive, which is especially important when food prices are rising.
If you choose canned food for convenience or availability reasons, still look for “BPA-free” on the label. Don’t leave canned tomatoes on the shelf for months. It gives the acid more time to erode the lining. Buy them nearby when you’re ready to use them. The same applies to canned fruit. If you’re saving food for emergency preparedness, consider dehydration as an option.
That pretty much covers it. Anything I missed?
About the author
Mark Sisson is the founder of Mark’s Daily Apple, godfather of the primal food and lifestyle movement, and New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, in which he explains how he combines the keto diet with a primal lifestyle for optimal health and longevity. Mark is also the author of numerous other books, including The Primal Blueprint, which in 2009 is credited with accelerating the growth of the Primal/Paleo movement and maintaining optimal wellness, Mark founded Primal Kitchen, a real food company that sells Primal/ Paleo, Keto, and Whole30-friendly kitchen clips.
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