Food & Wine If it's a Saturday in the spring, I'm probably hitting the local farmer's markets...
I love buying fresh produce when it's in season. I'll even exchange what I grow in my garden – like blackberries, raspberries, peaches, rhubarb, tomatoes, and herbs – for anything I don't grow.
Everyone knows they should eat their vegetables. In fact, in my recent article on the "Dirty Dozen," I recommended eating as many fruits and veggies as possible. That's easy advice. But there are also plenty of nitty-gritty details that you should consider.
Two questions stood out from the e-mails I received from you recently...
- What are the differences between fresh and frozen vegetables (like when a favorite veggie isn't in season)?
- And what are the best cooking methods for veggies?
Both of these are excellent questions for times when you can't always get fresh produce.
But be careful what you read out there... Many of the articles on frozen vegetable nutrition were conducted by or paid for by frozen food companies. Don't fall for them.
If you're new to Retirement Millionaire Daily, we follow the money. We don't like to report on studies with conflicts of interest. And the truth on frozen veggies is likely more complicated than you think...
Manufacturers freeze vegetables shortly after the harvest. The idea is to "lock in" nutrients before the veggies start to decay. However, packers blanch vegetables before freezing. Blanching is a way of heat-treating the vegetables to remove bacteria and other nasty bugs.
Here's the thing... that kind of heat reduces levels of some water-soluble vitamins. According to Gene Lester, program leader for food quality at the Department of Agriculture (USDA), the blanching lowers levels of vitamin C. But B vitamins and carotenoids are still preserved.
Blanching also destroys enzymes in the vegetables. The most notable is myrosinase in broccoli. This enzyme helps make something called sulforaphane... a molecule that helps protect you from cancer.
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The freezing process destroys another molecule... folate.
Folate is a molecule that helps protect our DNA from damage, meaning it's a great way to fight cancer. You can find it in vegetables like broccoli, Brussels sprouts, and cauliflower.
However, folate is also unstable, meaning that any exposure to heat can cause foods to lose much of their folate activity. One small study out of Poland's University of Warmia and Mazury in Olsztyn found that folate levels changed based on the freezing process.
The researchers measured folate levels in frozen and fresh forms of green beans, yellow beans, peas, cauliflower, broccoli, and spinach. They found that the more fragmented (think pre-chopped) the vegetable, the lower the folate level. Also, smaller veggies (the peas) had much lower levels.
As for time, longer periods of frozen storage had an effect in some of the vegetables. Cauliflower had the largest drop, losing 95% of its folate in just three months. However, green beans and yellow beans didn't see a drop in folate until nine months of storage. So, the common belief is that eating folate-rich veggies raw is best for getting this nutrient.
Now, there's also the question of cooking. Namely, does cooking veggies drain out all the nutrients? And if not, which methods are best?
The general rule is that boiling or steaming tends to be better than higher-heat cooking like frying or roasting.
I love throwing vegetables on the grill. But when you grill them, coat them in olive oil and keep them away from high heat.
The real question of content also depends largely on the type of nutrient. Unfortunately, the answer here isn't black and white...
As we mentioned earlier, vitamin C breaks down in heat. So foods high in vitamin C are better raw. That includes red peppers and broccoli, too.
Similarly, a study from the British Journal of Nutrition found that folks who ate strictly raw vegetables had much higher levels of vitamin A and beta-carotene.
However, cooking also helps release some nutrients by breaking down cell walls in the plants. For example, lycopene becomes more available for us to absorb when you cook tomatoes.
Spinach, too, is better for us when cooked. That's because spinach contains something called oxalic acid. This acid prevents us from absorbing much of the calcium that spinach contains. However, cooking spinach lowers the oxalic acid levels and allows for better calcium absorption.
In short, eat your broccoli, cauliflower, and red peppers raw, cook your tomatoes and spinach (I just had some of the best creamed spinach in my life at the Stansberry Editor's Conference we just hosted in Kiawah Island), and don't be afraid to use some frozen foods to supplement your veggie intake (and focus more on uncut, larger veggies). Eat them raw in salads or cooked as you prefer (a mix of both is best).
I like to shop by season and get what's local and fresh. That way I know they haven't had time to decay in shipping. That's one reason I love local farmers' markets. You can find a breakdown of fruits and veggies by season right here.
What We're Reading...
- Something different: This tiny new species of crab is climbing to new heights...
Here's to our health, wealth, and a great retirement,
Dr. David Eifrig and the Retirement Millionaire Daily Research Team
March 30, 2017