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How You Select, Grow, Harvest, Store and Cook Your Food

Fruits and vegetables that are dark in color often have the highest amount of nutrition.

By Leah Smith

Food is supposed to do more than simply satisfy your hunger; it is supposed to provide your body with the nutrients it needs to function. Good food does this, but as most people in this country continue to be overfed and undernourished, and as we find that the chronic diseases that bedevil society have their origins in poor health and nutrition, it seems that good food is getting harder to come by. However, there are many steps that can be taken to improve the nutritional content of the produce you grow to feed your family. These steps occur not just at one point in your “food chain.” From plot to pot, here are some ways to provide a nutritional boost to your plate.


Building Healthy Soils

Nutritious foods begin with healthy soils for a couple of reasons. Many antioxidants that humans want to consume are produced by plants if they are growing in nurturing conditions. If a plant is struggling to survive, it is using its energy to provide for its basic needs and will not be producing the anthocyanin, lycopene, lutein, and numerous other protective phytonutrients that benefit both the plant itself and us. People also require minerals for health; these need to be in the soil in order to be taken up by plants and thus be made available to humans as well.

So what makes a healthy soil? Soil microbes play a critical part. They are a biological component that works with the physical components of soil to create the overall picture of healthy soil.

Carbon in its many stages of composition (and decomposition) is also essential. It is the building block of plant life and also of soil biology. Dan Kittredge of the Bionutrient Food Association (an organization whose objective is to increase the quality of food) advocates not only providing soils with minerals, microbiology and carbon sources, but also aiding them in maintaining the necessary levels of air and water.

Providing and maintaining each of these soil components becomes so interrelated that it can be hard to separate one from the other — humic substances increase a soil’s water holding capacity, which encourages plants to grow well, which causes them to send exudates into the soil, which causes the soil microbes to proliferate, which also increases the soil’s water holding capacity and mineral levels, and on and on.

Plants are an integral part of the picture. Remember that various plants should be continually growing in your soil, whether cash crops or cover crops.

Selecting Healthy Plants

Now it’s time to plant. Let’s start with some basic information. Cucumbers, summer squash and zucchini, green beans and fresh peas have little nutrition. They have some nutrition; all fresh produce at least has some vitamin C because it is fresh. But especially when matched against a number of other fruits and vegetables that are simply loaded with nutrition, they have none by comparison.

On the other hand, garlic, red cabbage, red pepper, kale and beets have loads of nutrition. So an initial thought might be to adjust your planting selections with the intention of altering your menu. This might sound like no guarantee that you will eat any healthier if you simply don’t eat these “strange and foreign vegetables” in the end.

On the other hand, if children are more apt to try eating different vegetables when they are involved in the cooking of them, maybe parents would be equally willing if they grew them. But if you love cucumbers, don’t remove them from you diet or garden. Rather, be mindful about how you consume them. Instead of making cucumber salad with three cups of cucumber, maybe you can start to eat more green salads with a “healthy” topping of cucumber instead.

It is not always a question of produce selection. In many cases, increased nutrition can be achieved (more painlessly) by variety selection. For example, purple carrots not only have more beta carotene than orange carrots, but they also have high amounts of alpha carotene and anthocyanins. The Purple Peruvian potato has anthocyanins of its own as well, and because of this it is much more nutritious than white-fleshed and white-skinned potatoes. This is one of the trends in food nutrition: the deeper and darker the color of a vegetable (or fruit), the more nutrition it will have, and the purples, reds and greens (the darker the better in each case) are superior to yellows and whites. So select sweet corn that is blue, red or at least a deep yellow in color. Grow those tomatoes that are deep red, purple or even described as black or brown. And pick the purple carrots and potatoes.

A second rule for increased nutrition is that the smaller in size a fruit or vegetable is, the more nutritious. A currant or cherry tomato has more nutrition than a beefsteak-style, large tomato. A pearl onion has more nutrition than one of those one-pounders.

The reason size matters is that nutritional components (the antioxidant-type) are concentrated in the skin and outer layers of produce, so the more skin you eat the better. To approach this another way, for a set volume of food like tomatoes, you need to increase the crop surface area (skin) you are going to eat; 2 cups of diced tomato from large tomatoes is going to include much less skin than if you made your 2 cups from sliced cherry tomatoes.This is somewhat related to the third principle, which is that the more open a crop is, the more nutrition it should have due to exposure to the sun, which stimulates the production of phytochemicals. Phytochemicals means nutrition for you. Selecting for exposure to the sun should lead you to looseleaf heads or leaf lettuce as opposed to tight heads of lettuce, and looseleaf radicchio instead of a firm head of radicchio.

Certain varieties of many kinds of crops are also genetically disposed to being more nutritious than other varieties. The Ovation strawberry has two times more antioxidants than most other strawberry varieties. Packman is a broccoli that is extra nutritious, as is Jersey Knight asparagus. Reading variety descriptions can help to identify these powerhouses.

Additionally, Dan Kittredge recommends selecting any variety that specifically mentions being valued for its flavor. Flavor comes from nutrition, so any time flavor is mentioned, the variety intrinsically has a greater potential to produce nutritious food. It is important to note that the nutrition a plant is described as having is its genetic potential. If a growing plant is showing signs of nutrient deficiency, the potential of the crop is now limited, and it will not be able to be as nutritious as it could have been because it is not getting all the nutrition it needs to grow.

A Healthy Culture

Cultural techniques also impact the nutritional levels of plants. Many practices here overlap with maintaining healthy soils.

Plants (and soils) need water and air, so maintaining moisture levels in the soil is important, of course. This may take the form of planting into raised rows or beds so that moisture drains properly from the root zone. It could include mulching the soil (or planting a cover crop) to hold in moisture and to protect the soil surface from weathering.

Note that too much water is as much of a problem as too little. It forces air out of the soil, and produce from plants that have been receiving more than the ideal amount of water do not have as intense of a flavor; the taste is “watered down,” and good flavor goes a long way toward encouraging willing consumption. Good cultural practices also means not working the soil when it is too wet, which will lead to the destruction of soil pores used by both air and water.

As mentioned above, sunlight touching plant surfaces stimulates the plant into producing protective compounds that add to their nutritional content for humans. This is why an apple on a sunny portion of a tree will be more nutritious than one grown in a shady portion. So while apples and pears, peppers and tomatoes may need some protection from the sun via their plant’s leaves, growing underneath too dense a canopy would mean too little sunlight and therefore a loss of nutrition. Likewise, it is possible for a crop to spend too much time underneath a shade cloth and to reduce its nutritional performance in this manner.

Before we get to post-harvest handling, a word on harvesting itself. Not only are many fruits and vegetables at the peak of flavor when they are at the peak of ripeness, but this is also when they are at the peak of nutrition. Some crops, such as tomatoes, apples and peaches, give you a little leeway and continue to ripen after harvesting. However, berries, cherries and grapes do not ripen after harvest. So if you are harvesting for immediate family use, allow your foods to be as ripe as possible.

Actually, while on the subject of ripeness, make sure that if you grow winter squash you learn how to test for their ripeness accurately so that you only harvest them when they are fully ripe. Though the difference may not be as stark as with ripe and not-fully-ripe strawberries, for example, a fully mature butternut squash is more flavorful and also more nutritious than one that was harvested too early.

At this point, you may be asking yourself about green versus colored bell peppers. A green bell pepper is immature (there are some peppers whose immature color is a white or purple, but shades of green are most prevalent). Does that mean that once it has ripened and is fully mature (typically red, orange or yellow) that it, too, is more nutritious? Yes, it most certainly does. In fact, the red bell pepper is one of the most antioxidant-rich vegetables there is; the green pepper is nowhere in the running.

Post-Harvest Handling

Anyone who raises produce for sale is familiar with this concept. The way you harvest and handle your crops has a huge impact on their appearance and, therefore, sell-ability.

But harvesting impacts nutrient levels at the same time. A harvested crop is not a dead crop. It is alive and “breathing,” or respiring. This means it is consuming carbon dioxide (and nutrients) and producing oxygen. This process is slowed by lower temperatures. That’s why cooling off crops as quickly as possible is so important for nutrient retention.

Harvest early in the morning so that your crops have been naturally cooled by the night air. Do not let harvested crops sit in the sun. You must get your produce into the cooler as quickly as possible.

But before that there is washing to consider. If you have picked a cool crop and it really isn’t that dirty, just get it right into the fridge. If it is dirty, clean it and drain it thoroughly, as excess moisture creates the perfect environment for decay; just don’t forget about it and leave it out too long.

An important wrinkle to remember is that if you are harvesting a crop that isn’t already cool, let it soak in water for a time, whether it is dirty or not; view it not as a cleaning step but rather as a cooling-off step, as the water will bring down its temperature much more quickly than simply refrigerating it will.

Ideal post-harvest handling means more than just rapid cooling; other steps can be taken, especially when the harvest is for personal consumption and not for sale. Remove the tops from root crop like carrots and beets. Leaving them on during storage increases respiration and nutrient lost. In some cases, just using the produce as soon as possible (no storage at all) is the best step to prevent the loss of nutrition. Spinach that has been stored for one week will have lost half of its antioxidants, and lettuce should not be stored for extended periods either. However, proper post-harvest handling and storage in closed plastic bags with pinprick-size holes to allow for respiration will help to maintain their quality for as long as possible.

Preparing ‘Health Food’

We are now at the final link in the chain, and it is time to prepare your produce to eat.

Fast Food: Different elements come into play for nutrient retention when we talk about food preparation. The first is how quickly produce is used after harvesting. For some crops this is a critically important issue, and for others not so much. Remember the respiration rates we talked about earlier? This is where they become very important.

As you might expect, some crops have high respiration rates and some have low ones. A low rate means that the crop can be harvested and held; it is a good storage crop that will not have used up all of its nutrients before you consume it. Cabbages, beets and carrots are these sort of vegetables; even cauliflower can be stored for roughly a week with negligible nutrient loss.

Vegetables that have a high respiration rate use up their stores of nutrients promptly and are best eaten very fresh. Broccoli and Brussels sprouts, two vegetables with some of the highest antioxidant levels, are very prone to loosing nutrition and sweetness in storage due to respiration. Asparagus is much the same.

Skin Is In (and More): Strange as it may seem, how food is prepared can influence its ultimate nutrition as well — not the cooking method, but the preparation itself.

As discussed above, vegetables and fruits have their greatest nutrition in and below their skin or peel. This holds true for foods you would never think of peeling or can’t peel (celery and strawberries, for example), and also, more importantly, ones that often are peeled. This list is long and includes apples, carrots, cucumbers, peaches, pears, potatoes, etc. So whenever possible you should leave the skin on your foods.

The effects can be dramatic. Potatoes have 50 percent of their antioxidant content in their skin. Another instance of the importance of preparation relates to garlic. Garlic is by far the most effective cancer-fighting component to your diet, thanks chiefly to its allicin content. However, whether or not you reap its substantial benefits depends entirely on how you prepare it for cooking — it is strictly a question of time.

Freezing is a food preservation method that is often a preparation step on the road to a finished dish, and it has nutritional specifics of its own. Some foods loose so much nutrition when they are frozen that this method of preservation should be avoided. Broccoli, carrots, cauliflower and Brussels sprouts are good examples. On the other hand, blueberries and raspberries possess almost as much nutrition when frozen as when fresh. You can conserve more nutrition when you freeze items as quickly as possible (both in terms of how quickly you freeze after harvesting and how quickly the food itself is actually frozen).

In Hot Water: And lastly, how you ultimately cook (or don’t cook) your food is your final opportunity to get the most nutrition out of it. Not only do you need to avoid nutrient loss, but if you play your cards right you will be able to increase nutrient availability as well.

Some foods, such as arugula and kale, are most nutritious when eaten raw. Many foods, however, benefit from light cooking, such as sautéing, because the heat makes its nutrients more bioavailable (it converts it to a form more accessible to the body). This group includes asparagus, beets, carrots and tomatoes. Many foods also benefit from being cooked with a fat, since fat-soluble vitamins (A, D, E, K) are more bioavailable in its presence. Boiling is consistently the worst way to prepare vegetables in terms of nutrient loss, and is especially harmful to arugula, beets, broccoli, carrots and cauliflower.

Now that you have all of this information, it is time to get active and creative. Trade a low-nutrition tomato variety for a high-nutrition one. Make favorite recipes “potato-skin friendly.” Look for cooking options that will allow you to swap high-nutrition food in. For example, if you want onion on your sandwich, you would benefit greatly from using red or yellow (cooking) onions that are much, much more nutritious than sweet white onions; but you must sauté or caramelize them first to remove their assertive heat (this is doubly beneficial, as cooking will itself increase the content of the antioxidant quercetin in the onions).

Knowledge is power — in this case, the power to improve the nutrition in your food.

Leah Smith works on her family’s organic farm in mid-Michigan, Nodding Thistle. She is a home and market gardener, avid reader and writer, and editor of the Michigan Organic Food and Farm Alliance (MOFFA) quarterly newsletter. She has learned a great deal of information about plant variety selection and food preparation for increased nutrition from the work of Jo Robinson and her book Eating on the Wild Side: The Missing Link to Optimum Health.