- Frozen and canned vegetables may not have the texture (and sometimes the flavour) of fresh ones, but they can be just as nutritious.
- Broccoli was the only frozen vegetable in our test that was less nutritious than fresh.
- When you buy fresh vegies, don’t keep them too long before you use them. Vegetables (especially green ones) continue to lose some of their nutrients while they’re stored in your fridge.
Fresh not always best
Next time you’re in a rush to get dinner on the table, don’t feel bad about serving frozen or even canned vegies.
- By the time you eat them, fresh vegetables can have lower levels of important nutrients, such as vitamin C, than their frozen counterparts.
- And while canned vegetables retain less vitamin C than frozen, they still contain as much dietary fibre as fresh, as well as retaining many other valuable nutrients.
We wanted to compare the vitamin levels in a range of fresh raw, fresh cooked, frozen and canned vegies to see which were more nutritious.
We chose the following vegies for testing because most people use them and you can get frozen or canned, as well as fresh:
- green beans
We tested vitamin levels of the raw and cooked produce because cooking makes vegetables more palatable for most people, but they always lose some nutrients — especially vitamin C.
We also retested the fresh vegies after storing them (uncooked) for one week in the fridge (at 4°C). They lost nutritional value in this time — especially the green vegetables (broccoli, green beans and spinach). So unless you use up your fresh veg quickly you’re better off with frozen.
For more details, see What we found.
We picked the following nutrients because some or all of the above vegetables are good sources of them. Here’s why they’re important:
Vitamin C This is the most easily destroyed nutrient in vegetables, so it’s a good marker of a vegetable’s overall freshness, as well as an important nutrient in its own right. If you don’t get enough you get scurvy — though these days that’s very rare — but it’s also an antioxidant and may be protective against heart disease and some forms of cancer. It’s one of the water-soluble vitamins (the others are the B vitamins, which include thiamin, riboflavin, niacin, folate, pyroxidine and B12).
Beta-carotene is an antioxidant and again may help to prevent heart disease and some cancers. Some of it’s lost during processing and cooking, though it’s not as easily destroyed as vitamin C. In the body, beta-carotene can be converted into vitamin A, one of the fat-soluble vitamins (the others are D, E and K).
Lycopene This is the red pigment in tomatoes; there’s now good evidence that tomatoes help prevent heart disease and prostate cancer.
The results show the levels of vitamin C and beta-carotene (and lycopene for tomatoes) per 100 g of vegetable as percentages of the recommended dietary intake (RDI) for adults (vitamin C, 45 mg; beta-carotene, 5.4 mg). As there’s no specific RDI for lycopene we used the value for beta-carotene for comparison (lycopene is regarded as a kind of first cousin to beta-carotene).
The results also show how much of the nutrients fresh vegetables can lose during cooking and over a week’s storage.
How we tested
We bought vegetables from three Coles and three Woolworths (Safeway) stores in different suburbs across Melbourne. The fresh vegetables were the best quality available from each store; the frozen and canned vegetables were top-selling brands.
- Before testing we combined each set of samples of so we’re reporting average values across both supermarket chains for fresh and across all included brands for frozen and canned vegetables.
- The fresh and frozen vegetables were steamed for 10 minutes and the canned ones heated before testing.
- Our lab then tested the vegies for the following nutrients: vitamin C, beta-carotene and lycopene (tomatoes only).
- We tested the fresh vegies both raw and cooked and then retested them a week later. The exception was corn, which we only tested cooked.