Is Local More Nutritious? It Depends
This article from the Harvard School of Public Health is no longer available online, but I think it’s very thorough and a great discussion of how our food loses nutrients along the production line so I kept a copy of it saved:
Local food advocates and confirmed “locavores” are quick to claim that local food is more nutritious. But is it really? While this seems like a simple straightforward question, it is anything but! The answer, like many having to do with food and nutrition, is a definite, “It depends.”
By the time fruits and vegetables reach your kitchen counter – whether from a stall at a local farmers market, or the supermarket produce department – several factors determine their nutritional quality: the specific variety chosen, the growing methods used, ripeness when harvested, post harvest handling, storage, extent and type of processing, and distance transported. The vitamin and mineral content of fruits and vegetables depends on decisions and practices all along the food system – from seed to table – whether or not that system is local or global. But before concluding there is no nutritional justification for eating locally, let’s take a closer look at this system.
Variety.
Most varieties of fruits and vegetables found in supermarkets today were chosen first and foremost for yield (how many pounds, pecks, bushels, etc. are harvested per acre), growth rate, and ability to withstand long-distance transport. Unfortunately, these traits which benefit national and international produce distribution often come at a cost: nutritional quality. Fruit and vegetable varieties differ in appearance and taste, as well as their vitamin, mineral, and phytochemical content. Farmers producing for a local and direct market (farmers’ market, community supported agriculture (CSA) members, or a local restaurant or grocer, for example), are more likely to prioritize taste and nutritional quality over durability when making varietal decisions.
How Crops are Grown
Production methods that improve the health of the soil – such as the use of cover crops and composted manure for fertilizers – tend to yield crops with higher nutritional content. The roots of crops grown organically or in some Integrated Pest Management systems are healthier and grow deeper allowing them to more efficiently take up nutrients. Composted manures and other organic fertilizers release nutrients more slowly and over longer periods than synthetic chemical alternatives, which also enhances nutrient uptake by the plants.
Post-harvest handling
Maintaining nutritional quality after fruits and vegetables are harvested requires careful handling. This means, chilling (to remove the “field heat”) immediately, preventing bruising, and maintaining specific temperature, and humidity during storage and distribution. Careful handling preserves plant integrity and quality and careless handling chemically alters plant structure, often diminishing nutritional quality. Further, nutrients differ in how they are affected by various farming and post-harvest practices. Bruising from handling is one of the most common problems. Mechanical harvesting methods like those used in mass production have the potential to be most damaging and can result in accelerated nutrient losses. Bulk handling involving forklifts or trucks after picking significantly contributes to crop injury particularly with apples. Delicate items like berries and tomatoes are also easily affected. In tomatoes, there has even been evidence of abnormal ripening following impact bruising.
Ripeness.
When produce is ready for harvest varies from one fruit and vegetable to another and depends on whether it is “climacteric” not. Climacteric fruits – such as apples, nectarines, melons, apricots, peaches, and tomatoes – are capable of generating the ripening hormone ethylene, after being detached from the mother plant. Non-climacteric crops – for example, peppers and citrus – reach commercial maturity on the plant only. Being somewhat autonomous, from the ripening point of view, climacteric fruits will change in taste, aroma, color and texture as they reach and pass a transitory respiratory peak related to ethylene production. Climacteric produce such as tomatoes reach full red color even when harvested green while non-climacteric vegetables, such as bell peppers, will not. As a general rule, the more mature the product, the shorter its post-harvest life. So, if destined for distant markets, climacteric fruits are often harvested as early as possible, after reaching their physiological maturity, in order to withstand mechanical harvesting and long-distance transport without damage.
While full color may be achieved after harvest, nutritional quality may not. Total vitamin C content of red peppers, tomatoes, apricots, peaches and papayas has been shown to be higher when these crops are picked ripe from the plant which, in the case of tomatoes, is attributable to increased sun exposure while attached to the mother plant. While the vitamin C content of tomatoes, for example, will increase to some degree after picking, it will not reach levels found in those allowed to vine ripen. Because tomatoes make up nearly a quarter of total US vegetable consumption, following production and harvest practices that maximize their nutritional content is particularly important to public health of Americans.
Processing and Packaging
Fruits and vegetables are increasingly found on supermarket shelves pre-cut in open containers or in various types of packaging. These items are considered “fresh cut” or “lightly or minimally processed products” and have increased in sales in the US in billions of dollars since the mid-1990s. These products are highly perishable, as they have already experienced stress and are left without intact skin for protection and prevention of nutrient loss. Minimal processing – cutting, slicing, chopping, peeling, etc. – while tremendously useful from a food service standpoint, causes injuries to the plant tissues and initiates enzymatic changes, such as ethylene production, respiration, accumulation of secondary metabolites and water loss from tissues. This increases susceptibility to microbial spoilage, which not only compromises food safety, but alters chemical make-up and promotes loss of nutrients. The effect of processing on antioxidants and phytonutrients vary. To preserve moisture and humidity as well as protect fresh-cut products, films and coatings are used. Packaging can help preserve some nutrients in fresh-cut products, particularly if done at the right time and under appropriate conditions, mainly because it delays ripening and deterioration. Other techniques such as irradiation, chemical preservation (dips in ascorbic acid, calcium chloride, and/or citric acid), modification of pH, and reduction of water activity (with sugars/salts) are also used to control deterioration of processed products.
Storage
Due to continued respiration and enzymatic activity, minimally processed fruits and vegetables suffer changes in nutritional value and sensory quality including loss of texture, appearance and flavor during storage, especially if factors such as temperature, atmosphere, relative humidity and sanitation are not well regulated. Fresh-cut produce must be maintained at lower temperatures than whole fruits and vegetables, as they tend to have higher respiration rates, which increase as temperature rises. Temperature maintenance is considered most deficient factor in post-harvest handling of minimally processed foods, which is why contained, modified atmospheres are important.
Transportation
The advent of refrigerated trucks and rail cars has made it possible to eat fresh California or Mexico produce in the Northeast. But even when temperature and humidity are optimal from harvest to supermarket, there is some nutrient loss during days-long trip. If temperature control is faulty, losses accelerate. Bruising damage, with subsequent decrease in nutrition quality, is likely when transported at high speeds on bumpy roads. The longer the trip, the more potential for damage.
The Bottom Line
While all of the factors affecting nutritional quality of fruits and vegetables – crop variety, production method, post-harvest handling, storage, and processing and packaging– apply equally to produce that is produced locally or on farms across the country, relying on local sources for your produce needs has some distinct advantages. First, even when the highest post-harvest handling standards are met, foods grown far away that spend significant time on the road, and therefore have more time to loss nutrients before reaching the marketplace.
Second, farmers growing for a local (and especially a direct) market favor taste, nutrition and diversity over shipability when choosing varieties. Greater crop diversity from the farmer means greater nutritional diversity for the eater. Third, in direct and local marketing strategies, produce is usually sold within 24 hours after harvest, at its peak freshness and ripeness, making consuming them a more attractive prospect. Fourth, during this short time and distance, produce is likely handled by fewer people, decreasing potential for damage, and typically not harvested with industrial machinery. Minimizing transportation and processing can ensure maximum freshness and flavor, and nutrient retention. This may seem like an overly simplistic explanation of why local fruits and vegetables are more healthful than those from our conventional long haul agricultural system. In the Northeast {remember this is an article originally written by Harvard students, but also true for the midwest} diets based on foods available locally can be nutritionally adequate year-round. Concerns over nutritional adequacy usually arise because people are unaware of what is available. Fortunately, {myself and additional resources found at our local farmers markets} can provide you with information regarding delicious seasonal items, and how to prepare and store them.
NEXT – Nutrition Notes
Nutrition Notes
During grad school in Central WI – the 2nd largest producer of organic produce, I took a course on sustainable food systems. Throughout this course, I thought about food and nutrients in a very different way. My summary:
There’s a balance we must find between cost, availability, quality and ethics. At the beginning of my nutrition education, nutrients seemed like the primary focus. But nutrients are a small part of this very big picture of health and lifestyle. In my dietitian role, I suppose the goal should be “ultimate nutrition”, but as a human, mother, wife, friend, citizen; my goal is to help my clients improve their quality of life. Often, we can use nutrition to do this, but sometimes an unhealthy obsession with nutrition will ruin your quality of life.
What is a CSA?
Is a CSA worthwhile? Cost: At one point, a study was conducted comparing and contrasting different ways to purchase produce. For organic produce, an organic CSA was the most cost effective purchasing method. Now that many CSA’s have moved to a model where the customer chooses what goes into their basket, this whole study will have to be redone, but the old fashion farms are still out there. You can still get great deals on boxes of organic produce that you pay in advance for (making it unrealistic for many customers, but vital for the farmers). And you can still find old fashion farms that will allow you to work on the farm in exchange for your produce boxes.
Nutrition: there are things we know, but don’t have adequate research for, and things we know. We know that produce starts to lose its nutrition the second it’s plucked from it’s mother plant - some varieties faster than others. We know that produce grown in healthy soil has a better nutrition profile. We know that pesticides used on produce can have harmful effects on the farmers that are most exposed to them, and the wildlife they come in contact with. We know that when we sign up for a CSA, we have access to the farmer and their farm so we can know how long ago our produce was picked, what the quality of their soil is, and what chemicals are and aren’t used on our produce.
We don’t have sufficient proof that pesticides are harmful to humans via consumption of produce. And we DON’T know for sure that people who get their produce from CSA’s are healthier than people who don’t when considering lifestyle factors such as income, stress, environmental polution, etc.
Joining a CSA is not step one to eating healthier. People join a CSA to support their local producers, to reduce reliance on big box stores like Walmart, and to be more connected with what grows in their local environment. It requires some processing (freezing/dehydrating) and cooking-from-scratch skills that many people don’t have. For some it’s step 4 on their path to healthier eating, and for some it’s step 10. When the timing is right, I think you’ll find it worthwhile.
NEXT – Meal Ideas
Meal Ideas
In an ideal world, we’d all know enough about cooking methods and flavor combinations that we’d never need recipes. Searching for recipes is time consuming, and buying recipe ingredients is more expensive than cooking with what you have on hand, but we all have to start somewhere.
When I need a recipe, I like to look here: EatingWell.com
One of the benefits to cooking off-book is that it gives you an opportunity to sub things in and out. If you’re a CSA member, or you get produce from your local farmers market regularly, you likely come across things like kohlrabi, various turnips and radishes, plus their green tops, garlic scapes, and rutabaga. These things are so nutritious, and so affordable! But it took me years to figure out how to make meals that I actually enjoyed with them. I’ve included some ideas below.
My Go-To’s: Quick & Healthy
Tika Masala
I made this from scratch one time and it was delicious, but it requires you keep many spices on hand, so I never made it again. Then I discovered the pre-made sauces! You can add chicken, chick peas, frozen mixed veggies, and serve with rice and/or naan bread. I’ve made this with carrots, cubed radishes and asparagus (satay) to use up things in my CSA box and it was wonderful
Stir-Fry
I used to make my own sauce, but then I moved into a smaller kitchen, had another small child, and now I use the sauce from Trader Joes. There are so many variations to this American-mom version of stir fry: pretty much any protein, any combo of 3 veggies (don’t get to nuts on variety of veggies, I try to use 3 different colors), and then serve with rice, rice noodles or frozen prepared dumplings.
Roast
My insta pot or slow cooker meal. I either use a venison roast or a whole chicken but you could use beef or pork roast too. Flavor with your favorite herbs, plenty of salt or seasoning salt mix, onion, garlic. My mom always uses a packet of French onion soup mix. And throw in potatoes, carrots, and green beans. If you’re family is full of brave eaters you can mix up the veggies: kale, chard, cabbage? And serve with delicious bread from a local bakery
Fish Tacos
If I don’t make my tacos fish tacos, we don’t tend to eat enough fish. Fish also makes these tacos easier and quicker to make since it doesn’t take long to thaw or cook. I like to make these with plenty of lime juice and cilantro. I keep a homemade chipotle mayo on hand most of the time (it’s good on many things) and it comes in handy here. They’re good with guacamole and shredded cabbage which you can turn into a slaw if you have the energy. If it’s radish season and you end up pickling a bunch, throw these on too!
Chili
Mine is heavy on the beans. I don’t use a recipe, but always include 1lb ground venison, onion, chopped tomatoes (either one’s I’ve frozen from last summer’s bounty or canned), green pepper, zucchini, cumin, chili powder, oregano, salt, pepper, and lots of beans. Serve with corn bread, cheese and plain yogurt.
Additional Notes
Salmon burgers or black bean burgers with a side salad.
I love Costco’s salmon burgers. I’m sure there are other good ones out there.
Meals can get simpler than this: tomato soup and grilled cheese, fried eggs and toast, tuna salad sandwich, etc. However, for my family, these meals have not proved to be satisfying enough (physically or mentally) and everyone is searching for snacks an hour later. Watch out for this pitfall.
*Modifying recipes to use local produce is something most folks can figure out on their own, but often our unique health conditions require us to seek out food sources of iron, zinc, potassium and magnesium. If you need help modifying recipes and meals in a nutrient specific way, feel free to reach out: homegrownnutritionllc@gmail.com.