Why Dietitians Stock Frozen Wild Blueberries Over Fresh

When you think about what typically is a “healthy fruit,” you will likely conjure up the image of a freshly picked blueberry. It’s probably glistening in the sun on an organic farm and bursting with vitamins and antioxidants. But we have some bad news: that is totally wrong. And it’s not to say that fresh blueberries are “unhealthy” in any way. But, if you want to optimize the full potential of the superfood that is a blueberry then you need to head over to the frozen food section of your nearest grocery store.

Surprise! Frozen blueberries are usually healthier than fresh, and freezing actually concentrates the antioxidants. But the truth is, you can’t buy just any frozen blueberries. 

The actual food-science research on frozen versus fresh blueberries is genuinely interesting. So below is what the peer-reviewed literature says, where the viral version overstates, and why frozen wild blueberries are probably still the smarter buy for most weeks of the year.

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Here’s the takeaway

It’s not that freezing blueberries adds anything to the blueberries themselves. What it does is it lets them retain one of their super healthy nutrients, something called anthocyanin antioxidants. So it’s like you’re eating them just right as they came off the vine. Or branch (I’m not sure if blueberries grow on a vine or a branch, or bush. I’ll look that up.) But regardless, freezing blueberries are also cheaper, they last longer and they have a higher nutritional density. It’s kind of win-win-win for frozen over fresh.

What the studies actually found

The most-cited peer-reviewed study is from a 2004 study by three guys with some incredible names: Lohachoompol, Srzednicki, and Craske, published in the Journal of Biomedicine and Biotechnology. What they did was measure the anthocyanin content in three different versions of blueberries: fresh, frozen, and cabinet-dried. They wanted to put to the test the value of freezing.

Here’s what they found:

• Fresh blueberries: 7.2 ± 0.5 mg of total anthocyanins per gram of dry matter
• Frozen blueberries (3 months of storage): No significant decrease from the fresh baseline
• Dried blueberries: 4.3 mg/g (untreated) and 3.7 mg/g (pretreated) — a 41 to 49 percent loss

What they saw was that the frozen blueberries held onto their anthocyanin content over the course of three months. And the results were pretty clear. Freezing helps retain anthocyanin. The older your blueberries are, the less nutrient dense they are.

A separate study from South Dakota State University reached a similar conclusion: freezing as a storage method maintains anthocyanin concentration across months, while fresh blueberries lose meaningful content over the same window of refrigerated storage.

Why frozen wins the long-storage comparison

This is the second most important factor in this whole story. When we’re measuring frozen vs fresh, we’re never really sure what “fresh” means. The frozen blueberries are harvested at their peak ripeness and then quickly frozen. Meaning, the anthocyanin content is captured at its highest point and…frozen…there (sorry for the pun). Which essentially stops them from degrading. 

But the blueberries you see in the grocery store weren’t picked that morning. Most likely they have been traveling for the last week, so they’ve already started to degrade. And then they also sit in many people’s fridges for quite a few more days…and continue to lose their nutrient density.

Meanwhile you can let the bag of frozen blueberries sit in your freezer for months and they will still have all the peak ripeness like they had when the day they were picked.

This is the mechanism that drives the “frozen is healthier than fresh” claim. It is true when you compare a 3-month-old frozen sample to a 1-week-old refrigerated fresh sample. It is much less true when you compare flash-frozen to a blueberry you picked off a bush this morning.

The bioavailability boost no one mentions

And there’s yet another benefit to frozen blueberries. This gets a little technical, but when you freeze any plant it forms ice crystal in the water inside it. And water expands when it freezes. So when it the crystals form inside the blueberry, it breaks the plant’s cell walls. When that blueberry thaws all that anthocyanin is way more accessible for your body. So not only is there more of it, you can actually absorb it better too. And we’re all trying to get more antioxidants these days.

So according to a 2014 South Dakota State University study covered by ScienceDaily, this cell-wall rupture appears to increase the bioavailability of anthocyanins during digestion. Your gut can extract and absorb more of the compounds because they are no longer trapped behind intact plant-cell walls. The total anthocyanin content does not change. But the share your body actually uses goes up.

Why wild blueberries beat the cultivated kind

When buying frozen blueberries you need to make sure you get the wild version. Why? I’m glad you asked. You know those giant blueberries you see in the store? The ones that looked nothing like the blueberries you used to get as a kid? Those are bred for shipping and beauty. The truth is those blueberries have half the antioxidants that wild blueberries have. The ones you want are the lowbush blueberries that are usually found in Maine, Eastern Canada (Nova Scotia etc) and parts of Northern Europe.

The ones in the grocery store may look nice, but they are kind of empty inside when it comes to nutrients. Think of it sort of like a supermodel vs a librarian.

The reason is mostly about size. Wild blueberries are smaller, so the antioxidant-rich skin makes up a larger fraction of each berry. Specifically, the skin is where the anthocyanins concentrate. More skin-to-flesh ratio means more anthocyanins per gram of blueberry.

How to actually use frozen blueberries

Here are some super easy and tasty ways to use frozen blueberries:

• Don’t bother thawing. The best way to use frozen blueberries are in smoothies. Just toss them into the blender while they’re still frozen and they’ll help keep it cold. And they’re so small that if you toss them into something hot (like oatmeal) they will thaw pretty quickly on their own. 
• If you bother thawing, save the juice. There are tons of nutrients in the thawed blueberry juice. The dark liquid is actually concentrated anthocyanin. Make sure you include it in whatever you’re using them in.
• Pair with protein and fat. Plain Greek yogurt + frozen wild blueberries + a tablespoon of ground flax delivers about 6 grams of fiber, 18 grams of protein, and a serious dose of anthocyanins. This is the most popular breakfast that dietitians recommend because it packs so many great things in one simple, nearly perfect meal.
• Heat kills their benefits. Heating anthocyanins above 158°F (70°C) will start to degrade them. There’s no issue in smoothies. But if you want to make blueberry jam (which requires boiling), you’re not going to get any antioxidants. 

When fresh blueberries still win

Let’s not kid ourselves, there are ways where fresh blueberries are the better options. And it’s not like fresh blueberries offer no benefit! They offer a lot. It’s just not as much as frozen.

• During your local peak season (July to early September in the U.S.). If you have access to freshly picked blueberries from a blueberry farm or farmer’s market where you can literally eat them the same day, that’s the best of both worlds. 
• When you want it to look pretty. Thawed frozen blueberries look like a horror movie. Just dark colors bleeding out everywhere. Fresh hold their shape way better.
• Baking where you want intact berries. If you’re making blueberry muffins and you want to bite into big, meaty blueberries, then fresh is the way to go. 
• The handful of blueberries snack. The bigger the better here.

Asked and answered

Are organic frozen blueberries worth the price premium?
Sadly, yes they are. Because blueberries seems to always show up on the Environmental Working Group’s “Dirty Dozen” list for foods with pesticide residue. Another reason to go wild? Wild blueberries are usually harvested from low-spray forests and usually have fewer pesticides.

Do frozen blueberries have added sugar?
No, not at all. Having said that, if you are buying a package of blueberries and there is anything other than “blueberries” on the ingredient package, then you are buying something else. Blueberries don’t need to be sweetened! Make sure you’re just getting straight fruit with nothing added.

Are blueberry concentrate or powder products as good as the berries?
Usually no. Whole frozen blueberries give you the glorious fiber as well as the antioxidants. And concentrates usually have to be pasteurized at high heat, which kills the anthocyanin content (which is one of the main reasons you’re eating them in the first place.)

What about other frozen berries — do strawberries and raspberries work the same way?
For the most part yes. Strawberries hold up especially well because fresh ones are usually picked at lower ripeness (which means lower anthocyanin content) but frozen strawberries are picked at peak ripeness (more anthocyanin content) 

How long do frozen blueberries actually keep?
The Lohachoompol study tracked them for three months without finding much anthocyanin loss. So the truth is we don’t really know. But you’re probably good for six months and maybe even 12. But if you’re eating them on a consistent basis, that bag won’t last that long in your freezer.

The takeaway

Frozen wild (it has to be wild!) blueberries are the closest thing you can get to the best blueberries (the ones with the most nutrient density) at the time when they are most nutrient dense. And they will stay that way in your freezer for three months. It’s that simple. We’re not saying only eat frozen all the time. But if you’re making things like smoothies or pancakes or anything else where you don’t really see the full berry, these are the best option. 

Not to mention frozen blueberries are cheaper as well as longer lasting. They should be a staple in your freezer at all times. And the next time you’re having some yogurt, toss a half cup of frozen blueberries into it. If you eat them consistently they will cost you about $4 a week. Not too bad!

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Joseph Misulonas

Joseph has been writing and editing for a wide variety of publications over the last decade. He loves covering news in the health and wellness space and has written extensively about all aspects of wellness for a wide range of publications.