GARDENING FOR TOP NUTRITION
Better nutrition is a major goal of many people who grow their own food. But actually, when it comes to the choice of vegetables to plant we probably choose, more than we realize, from taste and cultural preferences. Within these preferences, and a little bit of thought and planning, we can get a lot more good out of our garden space.
We don’t need to turn our world of gardening and eating totally upside down, but it is good to know and use less of those vegetables that might fill the stomach without packing much of a nutritional punch. We can limit the crops that are moderate in vitamins and minerals—like cucumbers, summer squash and iceberg lettuce—and emphasize those crops that are especially high on these nutrients. Vegetables like carrots, spinach, tomatoes and broccoli usually come to mind here, but there are many others that we are often not aware of. Since more is being discovered every day about phyto-nutrients and the antioxidant content of various foods, this article is not meant to be dogmatic in evaluating crops based on a few factors, but only to highlight some major points.
One of the best ways to boost the nutrition from your garden is to grow more greens, and to select the type of greens that have the most nutrition. Many people grow spinach because it can be harvested early and is easy to grow. However, collards, kale, turnips and mustard may be better choices, since they contain much lower levels of oxalic acid than spinach, Swiss chard and beet greens. I still grow some spinach and Swiss chard in the spring, but try to grow other greens, since oxalic acid ties up iron and calcium. For those who like the tender texture of spinach, try orach or its wild relative, lambsquarters. It is even more nutrition-packed than the traditional greens just mentioned, and grows well during the late spring and summer, when spinach goes to seed. Amaranth is another summer green that tops the charts of nutritional values. However, since it is high in oxalates its use should be limited.
For those with more adventuresome tastes, dandelion (wild or domestic) heads the list for beta-carotene and iron. One has to develop a taste for dandelion greens, but they are often the first fresh greens in the spring. A steaming hot sweet-sour sauce poured over the fresh dandelion greens makes a perfect complement to its strong flavor. Arugula is very high in calcium and beta-carotene. I like it in my salad mix; just a few leaves give it an exotic flavor that I have never tired of.
You may be turning up your nose at all this talk of greens, but once one realizes the nutritional gold mine they are, the next step is to find creative ways to slip them into the diet. Dishes like spinach (amaranth or orach) lasagna or quiche, greens waffles or burgers along with mixed salads are ways to pack in more nutrition without upsetting our cultural tastes too much.
Most people know that broccoli is good for you, but are not aware that broccoli leaves are actually more nutritious than the buds, being similar to kale or collards. Instead of leaving the leaves in the garden, they can be harvested individually or at the same time as the head by cutting the stem down low, leaving only 3-4 leaves at the base. This will cause a few, but larger, side shoots to regrow.
Varieties of vegetable can also play an important role in nutritional yield. When we talk of fresh salads, choosing varieties of lettuce that are dark green and loose leaf or loose head will give the best vitamin content. Romaine lettuce has 6 times the vitamin C and 10 times the beta-carotene of iceberg lettuce. However, arugula has about 4 times the vitamin C and 3 times the beta-carotene of Romaine. Most of the non-lettuce salad greens are higher in nutrients than lettuce and can add variety to the texture and taste of a salad. I love to go out into the garden and fill my bowl with a sampling of mache, cress, spinach, mizuna, sorrel, orach, red Russian kale, purslane, pac choi and arugula in addition to the lettuce. When they appear on the table I feel as if I am sitting down to a feast of delicious vitamins, minerals, antioxidants and phyto-chemicals.
Butternut squash is my favorite winter squash, not only because of its superior taste, texture and keeping qualities, but also because its orange flesh has twice as much beta-carotene as most other varieties. The lowest amount is probably found in spaghetti squash, which has only a trace. Varieties make a similar difference, nutritionally, with sweet potatoes. Centennial and All Gold have 18 mg carotene per 100g, compared to Georgia Red and Puerto Rico which contain only 6 mg carotene per 100g. In general, a deeper shade of orange in the flesh indicates a greater carotene content and vitamin A activity.
Because I like green beans I tend to grow quite a few, even though they have only moderate amounts of vitamins and minerals. A better choice, nutritionally, are vegetable soy beans, also called soy limas or edamame. Harvested when the beans have grown to full size but are still green and tender, they have a delectable nutty flavor when cooked. We cook them in the pods and then pop them out of the pods, often directly into the mouth. They have more protein and yield more than lime beans, especially in northern areas.
If you are looking for a way to fit another vegetable into your available garden space, soy limas can be planted at the last cultivation between the rows of early sweet corn, when the corn is 1-2 ft. tall.
Nutrient content can also be affected by the harvesting time. Bell peppers allowed to ripen until they are red contain over 10 times the beta-carotene and 1 ½ times the vitamin C of green bell peppers.
Whether the crop is peppers, green beans or greens, vitamin C increases in the crop when there is lots of sunshine. Tomatoes ripened in full sun have up to 40% more vitamin C than those grown in the shade – even the shade of their own leaves. This principle also applies to tomatoes that finish ripening off the vine. Those ripened in the windowsill will have more vitamin C than those ripened in the dark.
Of course, once the produce is picked it is very important to use it as quickly as possible. This is especially true for salads and other greens, peas, sweet corn, etc. If the veggies are not eaten right away they should be refrigerated or processed quickly by blanching and freezing or canning. I believe in the old adage about having the pot already boiling when you go out to pick the sweet corn.
Organic methods and in-depth soil testing are yet another way to ensure the nutritional quality of the food coming from our gardens. The readily available nutrients in chemical fertilizers tend to overfeed the plants with the major elements, which block the uptake of other essential nutrients. This is especially true of nitrogen, which blocks micronutrients like copper. On the other hand a soil that has been built up with compost and other organic fertilizers is rich in humus, the end product of decomposition of organic matter. This humus feeds the plants cafeteria style, so that they enjoy more balanced nutrition. In-depth soil testing also plays an important role in assessing the need for adding specific nutrients that general organic methods may not adequately supply. Some soils are extremely low in certain nutrients because of mismanagement or basic deficiencies in the parent material of the soil.
When testing soils in various countries around the world I have observed that often in addition to the need for major elements, the soils are very deficient in calcium, magnesium, sulfur, copper, boron, zinc, to mention some. Not only do these mineral deficiencies show up to one extent or another in the plants , but they also affect the vitamin content of the food. In one study the vitamin C content of Brussels sprouts was increased by correcting a manganese deficiency in the soil. I like to take an in-depth soil audit once every 3 years and correct any imbalances that show up in order to enjoy the best possible nutrition from my gardening efforts.
There is much talk today of the need for vitamin and mineral supplements due to the fact that our soils are depleted or our food is not fresh. I was reminded of this when some multilevel supplement marketers knocked on our door some time ago and made their presentation. When we told them that a large share of our food was carefully grown in our own garden I was surprised to see them packing their case because they felt that we did not especially need their products ! There may be a place for some supplements in very special situations, but the attentive gardener can find those expensive vitamins, minerals and nutriceuticals packaged in the most bio-available forms—as the Creator intended—right in his own backyard, complete with all factors perhaps as yet undiscovered .
The following can be put in a box and added to or subtracted from as you have room:
A cup of cooked collard greens contains as much calcium as a cup of cow’s milk. One small stalk of cooked broccoli contains 40% more vitamin C than a 6-ounce glass of orange juice. A quarter of a muskmelon provides more vitamin C than half a grapefruit. A 2 ½ ounce pepper has 12% more vitamin C than a 7 ¼ ounce orange. And only 4 Brussels sprouts have more vitamin C than the same orange.
Comparing Salad Greens 3 ½ ounces raw (2 cups)
Type Calories Beta Carotene (mg) Vitamin C (mg) Calcium (mg) Iron (mg)
Arugula 23 4 91 309 1
Belgian endive 15 trace 0 18 1
Bibb 13 0.6 8 35 2
Boston 13 0.6 8 35 2
Chicory (curly endive) 23 2 24 100 1
Escarole 17 1 7 52 1
Iceberg 13 0.2 4 19 1
Looseleaf 18 1 18 68 1
Mache 21 4 38 38 2
Romaine 16 2 24 68 1
Spinach 22 4 28 99 3
Watercress 11 3 43 120 <1
From USDA Handbook 8
Some Garden Sources of major nutrients
For vitamin A: carrots, collards, leafy greens, orange-fleshed squash, sweet potatoes
For thiamine (vitamin B1): asparagus, beans, broccoli, cowpeas, dark green leafy vegetables, okra, onions, peas, pecans, potatoes, soybeans, sunflower seeds, sweet potatoes
For riboflavin (vitamin B2): asparagus, almonds, avocados, broccoli, Brussels sprouts, collards, leafy greens, lima beans, mushrooms, okra, sweet corn, winter squash
For niacin (vitamin B3): asparagus, amaranth, avocadoes, broccoli, Brussels sprouts, mushrooms, muskmelons, peaches, peanuts, peas, potatoes, sunflower seeds, tomatoes
For vitamin C: amaranth, broccoli, Brussels sprouts, cabbage, citrus fruits, collards, kale, kohlrabi, muskmelons, sweet peppers, strawberries
For potassium: amaranth, avocadoes, beans, New Zealand spinach, potatoes, soybeans, squash, watermelons
For phosphorus: beans, cowpeas, lentils, nuts, soybeans, sunflower seeds
For calcium: almonds, amaranth, broccoli, collards, leafy greens, okra
For protein: almonds, beans, Brussels sprouts, cowpeas, leafy greens, lentils, peanuts, soybeans, sunflower seeds
For iron: beans, leafy greens, lentils, butterhead lettuce, soybeans, sunflower seeds, watermelon
Used with permission and adapted from: Gardening for Maximum Nutrition, by Jerry Minnich
Comparing Vitamin and Mineral Contents of Greens (½ cup cooked)
Type Protein (g) Calcium (mg) Iron (mg) Vitamin C (mg) Vitamin A (I.U.)
Amaranth 1.4 137 1.5 27 1,828
Beet Greens 1.3 72 1.4 11 3,700
Chard 1.6 64 1.6 14 4,725
Collards 3.3 168 0.8 49 7,410
Dandelion 2.1 147 1.9 19 12,290
Kale 2.5 103 0.9 51 4,565
Lambsquarters 2.8 232 0.6 33 8,730
Mustard 1.6 97 1.3 34 4,060
Spinach 2.7 84 2.0 25 7,290
Turnip Greens 1.6 126 0.8 34 4,135
by Stephen Meyer
Source: USDA, Agriculture Handbook No. 456, Nutritive Value of American Foods in Common Units
Amaranth and Lambsquarters values from USDA Nutrient Database for Standard Reference, Release 15 (August 2002)