playing with peas and carrots on dinner plate

Are Frozen Vegetables Healthy or Bad For You?

[toc]In the age of COVID-19, fresh produce is no longer something you can reliably depend on. There are supply chain interruptions, as well as the concern “Do I really I want to eat this fresh tomato after a dozen other shoppers squeezed it? Suddenly, your freezer may seem like the preferred option!

As a kid, frozen peas and carrots may have been one of the foods you pushed around on your dinner plate.

Now as an adult, there’s a good chance you actually like peas and carrots. Coming from a Birds Eye microwaved pouch is not your preferred form, but you eat them anyway because you think they’re more nutritious than some other foods you could be having (yet you still consider them 2nd place to fresh).

But based on science, are the kid’s actions more justified than the adult’s? Or is it the opposite, where the freezer variety is better for you?

Fresh vs. frozen vs. canned foods

Are frozen vegetables better than canned? Most of the time, yes. Not all canned food is unhealthy, but often times it is due to these two reasons.

1. Added salt

This issue mainly applies to veggies since salt is usually not added to canned fruit like peaches, pears, pineapple, and oranges. With fruit, they often add corn syrup or another form of sugar and those versions should be avoided.

The American Heart Association recommends eating no more than 1,500 mg of sodium per day (1).

That does not mean 1,500 mg of added sodium, but total sodium – including what is naturally contained in foods. Do we need sodium to survive? Absolutely. But the truth is there is already ample amounts in everything we eat – raw vegetables, grains, and especially prepared meats and cheeses – so the salt shaker is not necessary to get our required sodium. Everything you eat already has sodium.

Trader Joes canned corn nutrition facts
Even if its a plain can of veggies, most have added salt. Plus, a BPA lining is more likely than not.

If you have high blood pressure or it runs in your family, reducing intake is ideal. Unfortunately most canned foods – including plain veggies like canned corn or beans – contain high amounts of added salt.

Even if you don’t have hypertension, when buying canned vegetables, we believe you should go with the versions that have no salt added.

The bad news is that it’s nearly impossible to find something as simple as canned corn which has no salt + organic + BPA-free can. And that brings us to the second thing to look out for…

2. Most cans still use BPA

You would think by now this stuff would have been phased out, right? But year after year, we see little improvement.

A study published last year looked at nearly 200 different canned vegetables, fruits, soups, chili beans, and other foods to determine who was still using it. Guess what? 67% of food cans still use BPA (2).

We’re not just talking dollar store brands either. True, they were among the worst offenders, however the study paints a broad stroke of guilt across the entire industry:

BPA lining on canned food

  • 100% of Campbell’s Soup canned products still had BPA in them
  • 100% of Target brand cans
  • 88% of Walmart private label cans like Great Value and Sam’s Choice
  • 83% for Dollar Tree’s and Family Dollar’s own generic brands
  • 71% of Del Monte cans
  • 62% for private label and generics overall In addition to the dollar stores, this included store brands from Kroger, Albertsons, Trader Joe’s, Walmart, Target, Meijer, Publix, Gordon Food Service, and Loblaws.
  • 50% of Green Giant, Progresso, and other General Mills brands (excluding Annies, which they now own).
  • Only a couple cans from each were tested, but they came back positive; Thai Kitchen, which sells canned coconut milk (owned by McCormick), Nestle Carnation, Goya, Ocean Spray, Vilore, Thai Agri, and Empire.

Which brands of canned food don’t use BPA linings?

Eden Foods was the first and pioneered the whole movement beginning in 1999. Other major companies on the list who now use BPA free cans are Amy’s Kitchen, Annie’s, ConAgra Foods (which includes Hunt’s, Rotel, Chef Boyardee, Bertolli, Healthy Choice, plus others), and brands owned by Hain Celestial Group (Health Valley, Walnut Acres, Earth’s Best baby foods, and others).
BPA-free can brands
How much more do BPA-free cans cost to produce? That’s the most pathetic part. Even 5 years ago, it was only an additional 2.2 cents per can (3). Since then those costs have likely came down even further as their demand as grown. All the manufacturers who continue to use BPA cans to save literally a penny should be slapped in the face.

Setting aside the added salt and BPA concerns, are canned vegetables less nutritious than frozen? The heat-treatment (pasteurization) of the cans during manufacturing does destroy some vitamin content. Being that they are water-soluble, vitamin C and B vitamins will also further deteriorate over time.

Are frozen peas raw? What about frozen carrots, black-eyed peas, beans, and other common veggies? Unfortunately they are not raw. Almost always, they are pre-cooked or blanched to destroy bacteria and parasites. So just like canned, they likely have had some vitamin content destroyed by heat processing.

For that reason, the nutritional value of from the can and from the freezer will be almost the same, at least according to the selected criteria listed on the nutrition facts label. But as you’ll see in a moment, that label only tells you part of the story.

Is frozen fruit a raw food? Yes, almost always. Unlike veggies, blanching is extremely rare for berries, melons, and pretty much every other type you can think of. For non-organic, there might be irradiation to kill off bacteria, especially when it’s imported from outside the country.

Antioxidants in fresh vs. frozen

Vitamin C may be the most well known antioxidant, but it’s only one of many. In fact, there are over 6,000 types of plant flavonoids that have been identified so far and that’s only one class of antioxidants! Many are exponentially more potent. For example, astaxanthin is up to 600,000% more potent than vitamin C when tested in vitro.

The best way for evaluating the total antioxidant capacity of a food is with an ORAC test. Here’s a look at how some of those test results come back for fresh vs. frozen vs. canned vegetables.

ORAC Values Compared
Fresh Frozen Canned
Spinach 1,513 1,687 n/a
Sweet Corn 728 522 413
Artichokes 6,552 n/a 4,760
Broccoli 1,510 496 n/a
Green Peas 260 600 120
Cauliflower 870 620 n/a
Green String Beans 799 n/a 290

Source: ORAC values database

These tests results prove that frozen fruits and veggies are healthier than fresh, in some circumstances. That’s right, even with the blanching or boiling which is done before they are undergo freezing, they are still left with more antioxidants than their fresh counterparts. This is true with spinach and green peas (reflected above) as well as many others.

ORAC test results for canned aren’t as widely available. There’s not much incentive to conduct expensive testing for canned products since they are generally purchased for price versus taste or nutrition. That being said, tests have suggested that with some veggies – primarily those containing fat soluble vitamins and phytonutrients – their antioxidant value is comparable to frozen. Those containing primarily water soluble flavonoids – like peas, spinach, and many green leafy veggies – will experience more profound deterioration versus freezer-stored and fresh.

How is this possible?

Most people are perplexed when they hear that fresh vegetables are not better than frozen, at least with many varieties. It goes against what we have been taught, that fresh is always best.

It is true that freshest is best, but what you get at the grocery store is far from that. Here’s why…

1. Harvested before ripeness

unripe tomatoes
At best, this is what your tomatoes look like when they are harvested.

Sure, those bright red organic beefsteak tomatoes sitting there at Whole Foods may look ripe. Given their $4.99/pound price tag, you certainly would expect that! But guess what? They were likely still green when picked (at least partly green). They didn’t turn that vivid ripe red until days later, after maybe traveling 2,000 miles by truck from Mexico to Ohio or New York where you bought them.

The problem with this is that after they are picked, the nutrients in plants begin deteriorating. Even if their appearance continues to ripen, their nutrients do not. In order to reach peak vitamin content, fruits and veggies need to mature on the plant, not in the back of a truck.

Tomatoes, green bell peppers, avocados, and a lot of other produce is picked long before being ripe. Are they still healthy for you? Of course! But they have much less vitamin content than they otherwise would.

There are a few exceptions to this rule. For example, red rice has higher antioxidant content before it’s mature. Likewise for most sprouted foods.

Contrast that to frozen or canned peas, which are typically harvested at full ripeness and processed immediately. That’s one reason why even after their pasteurization or blanching, the frozen may still be more nutritious for you versus fresh peas. But that’s not the only reason…

2. Light, heat, and oxygen

If the orange or apple was still hanging on a tree, these things obviously would not be a problem. Once they’re plucked, these all become factors which accelerate the destruction of vitamins and nutrients.

  • Light – This destroys many polyphenols, which is why it’s best to store your produce in a dark place.
  • Heat – We all know high heat is bad, but even refrigerated and room temperatures still allow for rapid deterioration. Freezing almost entirely stops that.
  • Oxygen – Why does an apple turn brown within 20 minutes of cutting it? Oxidation. That’s what’s going on with your produce. Fruits with thicker skins like apples do a relatively good job protecting themselves, which is why they have a longer shelf-life than say, berries. Likewise for pumpkins, squash, and gourds.

3. Freezing locks in the nutrients

blocks of frozen spinachWhat causes nutrient loss in vegetables? Respiration. That’s the process they use to stay alive after they are removed from their source of life (the stem, plant, or tree). Since the veggie is no longer being supplied nutrients, they begin breaking down carbohydrates to their constituent parts in order to create energy and keep their cells alive. From that process, oxygen is used and carbon dioxide is released.

This process of respiration “burns” through the compounds containing the antioxidant and vitamin nutrients. It’s also why the taste and sweetness will change.

Respiration Rate Plant Type
Very Low Dried nuts and fruits
Low Potatoes, sweet potatoes, apples, grapes, onion, garlic
Moderate Lettuce, tomatoes, cabbage, peppers, carrots, pears, peaches, plums, nectarines, apricots, figs
High Green beans, artichokes, green onions, brussels sprouts, flowers
Extremely High Sweet corn, broccoli, asparagus, green peas, mushrooms

Source: Wilson, L. G., M. D. Boyette, E. A. Estes. 1999. Post-harvest handling and cooling of fresh fruit, vegetables, and flowers for small farms.

When you freeze produce, the respiration process stops (or close to it). Food with higher respiration rates may be healthier for you if you buy them frozen, at least when they’re out of season and are being shipped in.

How much nutrients are lost over time? Take a look at these examples from a 2013 study conducted by the University of Chester in England (4).

decrease over time of lutein in vegetables

Above is a look at the antioxidant lutein and how much is in frozen broccoli, carrots and brussel sprouts versus those which are fresh and refrigerated. As you see, just 3 days later a significant amount of nutritional value is lost. 3 days isn’t much time, considering that it probably takes that much time to reach your supermarket, or longer!

The most stunning in the study was cauliflower…

fresh vs. frozen cauliflower nutrition

Look at that! After just 3 days, there are no detectable anthocynanins, which is one its most important antioxidants. Being that fresh cauliflower only has a moderate ORAC value to begin with, it means this is one of the healthiest frozen vegetables. Based on that chart, you might conclude you should always buy frozen vs. fresh cauliflower due to the latter having significantly less nutrition. But there is one major exception and that is its vitamin C content…

vitamin C content in cauliflower

Looking at just the vitamin C content, even 3 days after refrigeration, the fresh has almost 400% more than what you get from the freezer. This is not really surprising, because frozen cauliflower is not raw, it’s been blanched or boiled to kill bacteria. Vitamin C is easily destroyed by heat.

However in green beans and sweet corn, the frozen versions have more vitamin C. This may seem bizarre but it has a lot to do with how high the vitamin C level is in fresh cauliflower to begin with; nearly 20x more than corn and 8x more than green beans.

Conclusion? For everything except C, frozen cauliflower is probably healthiest. But being how important C is – an essential nutrient for humans – it means you should not ignore the fresh, either.

Cauliflower is an extreme example of how a fresh veggie can be less healthy for you (for mostly everything other than vitamin C). On the other end of the spectrum we have sweet corn, which is an outlier because the amount of anthocyanins it has actually goes up slightly after harvesting.

corn is healthier 3 days after harvest

As you see not only is fresh corn healthier than frozen, but its anthocynanins continue to develop for the first 3 days.

Canned sweet corn is still nutritious (as seen in the earlier table) but ultimately, this is one where it absolutely makes sense to buy the fresher raw form if its in season. You now have yet another good reason to hit up those summer corn stands on the side of the road in the Midwest and elsewhere.

A lot of us at Superfoodly actually prefer buying frozen berries. This example with red raspberries demonstrates why…

decrease of nutrients in raspberries

Given their high water content and composition, many fruits like berries are particularly susceptible to deterioration. As you see above, fresh raspberries have less anthocyanins than frozen after 3 days… almost 1/3 less! Unless you can get them in-season from local sources, we recommend buying from the freezer aisle. Not only will it save you money, but you will get more antioxidants.

When it comes to vitamin C amounts in frozen fruit, the results can vary greatly, even among similar types. With blueberries, the frozen always have higher C. With raspberries, the fresh do have more but the difference by day 3 is almost non-existent.

vitamin C levels in raspberries over time

When it comes to total polyphenol content, frozen blueberries always have more. However with raspberries, day 3 is more than day 1 and frozen. So there are outliers, but also some general overall trends…

Does COID-19 survive freezing temperatures?

Yes. Whether it’s the COVID-19 coronavirus or any other type of virus, like influenza or HIV, these and all others survive being frozen and thawed. Unlike bacteria, which are cells that usually get ripped apart upon freezing, viruses are not cells. Their structure remains fully intact. In fact, researchers store virus samples in the freezer for preservation. Based on what has been seen with other viruses, COVID-19 most likely can survive decades or even centuries in a freezer.

As such, if you are concerned about potential viral contamination of your frozen food, you should cook it thoroughly before eating. Since canned vegetables are essentially boiled during the canning process, they theoretically should be virus-free.

The verdict

We’ve only discussed with you a handful of examples. Based on all the research, the key takeaways are:

Eating frozen fruit is as good as fresh, if not healthier, especially with soft fruits like berries. Some types of antioxidants will be higher in one form over the other, but overall the total polphenol content in fruit a few days post-harvest will often times be less nutritious versus frozen. So those who say they are bad for you are dead wrong.

Vegetables follow a similar pattern, but to a lesser extent. While its true that fresh broccoli, carrots, and brussel sprouts deteriorate quickly, others such as corn are actually healthier 3 days after harvesting. Lettuces and many that are water-rich won’t hold up to freezing (and definitely not canning) which leaves you will little choice but to eat them fresh.

Frozen will almost always be better than canned, but not always by a wide margin. So if geographic your location or budget require you to buy canned veggies, that’s perfectly fine as long as you choose those with no added salt and BPA-free cans. Fruit is a bit trickier, since not as many varieties are sold in cans.

The exception to all of the above are truly fresh veggies and fruits. You can’t beat what was just picked from your garden or that which is purchased from a legit and trustworthy seller at a local farmer’s market. But if they’re out of season and purchased at the grocery store, there’s no telling how long ago they were picked. When you can get truly fresh produce within a day or two of being picked, that remains to be the preferred choice but its advantage over frozen is not nearly what most people perceive it to be.