A lot of credence is given to the importance of eating raw, living plants as a way to promote health and wellness. That’s a good idea. But what about frozen vegetables?
Do they carry the same benefits as the fresh produce you buy at the superstore? Are they any better? Worse?
Lindsay Nixon wrote about the benefits of fresh vs. frozen vegetables at Happy Herbivore. She’s a more concise writer than I am, so if you want a shorter treatment of the topic with less science jargon, I’d suggest reading her instead. But here’s my take.
The specific details depend on the plant being bought, but in general, yes, frozen vegetables are a good substitute for fresh ones, and sometimes even better.
Health Benefits of Frozen Vegetables
By and large, frozen vegetables have the same health benefits as fresh ones, particularly if the fresh vegetables you’re buying are transported a long way before they reach the supermarket. The transportation process itself and prolonged exposure to the air, different environmental elements, and warm temperature cause a lot of fragile nutrients to lose their potency by the time you buy them at the store, and many of these benefits are maintained when food is frozen.
Typically the frozen vegetables you buy at the store are frozen within hours after being picked, sometimes minutes, and this is all well and good. Most vitamins stay intact upon being frozen. This is true both for “water loving vitamins” like vitamins B and C, and “fat loving” vitamins like vitamin A.
A telling example comes from an article published in the journal Food Chemistry in 1998. It compared the vitamin C content in spinach, broccoli, carrots, green beans, and peas that had been frozen for one year with the vitamin C content found in the same vegetables bought in the supermarket. In every case the vitamin C content in the frozen vegetables was comparable to those found in the supermarket, and in the case of spinach, it was considerably higher. Similar results have been found for other vitamins.
The same cannot be said for the presence of more delicate micro-nutrients like phenolic compounds and antioxidant molecules. These compounds are more sensitive to temperature, and degrade very easily. A study published in the Journal of Agricultural and Food Chemistry in 2003 compared the phenolic and ORAC values of 6 different types of vegetables after being frozen, and found that 4 of the six veggies had significantly lower values after being frozen. Even more, there was significant variation in the amount of nutrient reduction. In some cases the ORAC values varied by as much as 4.5 fold. This makes sense. Because many of these compounds are fragile small differences in processing techniques can produce large variations in their level of degradation.
So it’s important to note tha while frozen vegetables retain many of the nutritious properties of fresh vegetables, freezing them will significantly reduce their phenolic and ORAC values.
(And in case you didn’t know, ORAC stands for Oxygen Radical Absorbance Capacity, and is a measure of how strong an antioxidant something is. The higher the score the better).
Buying Fresh + Buying Local = Good Health.
It’s not always a good idea to buy local, for no other reason that buying local forecloses the opportunity to eat some of the most nutritious foods mother nature has to offer. I grew up in Ohio, and if I insisted on buying local, yummy and nutritious foods like pomegranates, peaches, pineapples, and guava would have been an impossibility. It makes no sense to blunt the benefits of comparative advantage.
However, when a produce *is* naturally grown in your area, it’s usually a good idea to buy local if you can. Really fresh produce (like the kind that’s picked off the vine) will have an abundance of the fragile, delicate, and wholly nutritious compounds that are vital to your health and hard to get elsewhere. It’ll also taste delicious. In Ohio, this would mean things like corn, apples, and some forms of squash or tomatoes. But for produce that’s grown fresh somewhere else, it’s just as well and often better to buy frozen instead of fresh produce.
Favell, D.J. “A Comparison of the Vitamin C Content of Fresh and Frozen Vegetables.” Food Chemistry. May, 1998, pgs 59-64. http://www.sciencedirect.com/science/article/pii/S0308814697001659
Ninfali, Paolini, et. al. “Polyphenols and Antioxidant Capacity of Vegetables Under Fresh and Frozen Conditions.” Journal of Agriculture and Food Chemistry. March, 2003, pgs 2222-2226. http://pubs.acs.org/doi/abs/10.1021/jf020936m