Yesterday, I busted a popular myth that eating vegetables raw results in better nutrition. The science shows that this assumption isn’t always true.
To recap, I discussed the science showing that cooking veggies unleashes the nutrients in carrots, mushrooms, and spinach. And today, we’ll look at two more vegetables that offer a much higher nutrient content when cooked…
A study in the International Journal of Food Science showed that simply cooking asparagus stalks raised levels of six key nutrients — including antioxidants and anti-cancer constituents — by almost 20 percent.
Another study in the Journal of Molecular Sciences found that cooking asparagus more than doubles its levels of phenolic acids. These healthy phytonutrients prevent free radical damage and inflammation, which a play role in the development of just about every chronic disease…from cancer to Type II diabetes to obesity.
To keep asparagus spears crisp while retaining their nutrients, dunk a whole bunch into a pot of boiling water. Remove as soon as they turn bright green, which is a sign that the nutrients achieved their peak levels. (This usually takes about one minute for thick stalks and up to three minutes for thicker ones.)
I also like to put asparagus stalks in a bamboo steamer over boiling water. Again, you can watch for them to turn bright green and take them off the heat. Steaming this way will also prevent nutrients from escaping into boiling water.
Some people like to immediately stick them in an ice water bath (a technique called blanching), which helps to preserve the flavor, crisp texture, and bright color.
I like to mix my asparagus with butter or olive oil and squeeze some fresh lemon juice. Sometimes I mix it up and substitute the lemon juice for vinegar. The essential fats in the dressing will also help absorb vitamins in the asparagus (as with other cooked vegetables).
Technically, tomatoes are fruits. But from a culinary standpoint, we treat them like vegetables.
Now I love sliced, raw tomatoes just as much as anyone. But heating them dramatically increases the tomatoes’ absorbable levels of the carotenoid lycopene, a powerful phytochemical associated with lower rates of cancer, especially prostate cancer and heart disease. It also gives red tomatoes their color.
According to a 2002 landmark study, cooking tomatoes boosts levels of absorbable lycopene by 35 percent. Plus, it raises the total power of the disease-fighting antioxidant by 62 percent.
These findings come as no surprise to me, as I helped discover the role of lycopene in foods and human nutrition in my research with the USDA in the mid-1980s. During that research, we also learned that student volunteers from the nearby University of Maryland had sky-high levels of lycopene thanks to their “frat-boy diet” of pizza, pasta, and tomato ketchup on burgers and fries.
It turns out these tomato-based foods provided highly concentrated doses of lycopene…
Indeed, tomatoes contain a lot of water weight (like a fruit). And removing the water by cooking the tomato concentrates the nutrients, essentially leaving you with a tomato-based nutrient supplement. A similar process happens when you cook mushrooms, as I pointed out yesterday.
Uncooked tomatoes may also contain traces of natural toxins (and likely pesticide residues if not organic) that can contribute to joint pain and gastrointestinal irritation, as is the case with uncooked mushrooms. But here again, cooking eliminates the traces of toxins and enhances the tomatoes’ nutrient content.
Of course, tomatoes belong to the Solanacea family, which includes the deadly nightshade of Europe, the source of belladonna (atropine) poison. For this reason, Europeans were reluctant to accept tomatoes, which Spanish explorers brought back to the continent from Meso-America in the 1500s. In fact, in Italy, tomatoes did not appear on menus until the early 1800s.
To unleash the power of lycopene in tomatoes, try roasting them in the oven before adding them to dishes. (Organic sun-dried tomatoes are just as good.)
Arrange sliced or quartered tomatoes in a single layer on a sheet pan. Drizzle with olive oil and vinegar and add a few dashes of garlic, herbs, salt, and pepper. Then, bake for 30 minutes at 200° F. They taste great as a side dish, tossed in a salad, or on top of a grilled chicken breast or pork filet sandwich (called bifana by the Portuguese and Azoreans in my New England fishing village of Gloucester).
As the growing season gets underway, I recommend getting at least some of your vegetables fresh by growing your own, attending your neighborhood farmers’ markets, or shopping the organic aisle at your grocery store. Whichever way you choose to get your veggies, know that sometimes it’s better not to eat them raw.
“5 vegetables that are healthier cooked,” Consumer Reports, (consumerreports.org) 9/17/17