“Fresh is best” has long been the mantra when it comes to choosing the healthiest foods. But recent studies are challenging that age-old mindset with some revealing findings.
It turns out that processing actually can boost the nutritional benefits of some foods.
case of tomatoes
Canned tomatoes were one of the first food products to highlight this phenomenon, with a study dating back to 2002 in the Journal of Agricultural Food Chemistry. The study showed that thermal (heat) processing, involved in canning tomatoes, elevated total antioxidant activity and lycopene content, enhancing the overall nutritional value, even though vitamin C was lost.
Lycopene, a carotenoid antioxidant thought to reduce the risk of certain cancers and to protect against heart disease, is also found in other red-hued foods like red bell peppers and watermelon. The heat, through cooking, helps break down the walls of the plant, releasing the nutrient. (See related story, Page 4.)
Corn and spinach
Further studies have shown that other antioxidants also respond to heat, both in cooking and thermal processing. Lutein, found in corn, spinach and kale, and known to protect the eyes from age-related macular degeneration, is one of them. A 2003 study that compared the carotenoid content – mainly lutein and zeaxanthin – of fresh, canned, and frozen corn found increased levels in canned and frozen versions, both of which were processed with heat.
Apparently, it’s not just fruits and vegetables that benefit. Boiling peanuts, which are legumes, ramped up the antioxidants to four times those of raw and roasted peanuts or peanut butter. Even roasted peanuts showed heat-related benefits via an antioxidant increase in their skins. Based on this new finding, researchers no longer throw out the skins after roasting these tasty legumes, but are testing them mixed into peanut butter to enhance its nutritional value.
Peaches get a boost
Recently, canned peaches were shown to have significantly higher levels of vitamin C, antioxidants and folate compared to fresh peaches. The canning process did decrease vitamins A and E and total carotenoids, but levels were deemed comparable to fresh peaches throughout a three-month shelf life.
What findings mean
The findings are important, but not because they disprove the concept that fresh is always best. Rather, they expand the choice of nutritious food options, especially when fresh is unavailable. Fresh, seasonal offerings, of course, are the preferred way to go, but they’re not always available or as convenient as a canned or frozen counterpart. And now you can rest easy when you choose these preserved alternatives.