Squash, summer

The delicate flavor, soft shell and creamy white flesh of summer squash is a perfect addition to any summer meal. While especially plentiful in the U.S. marketplace during the summer months, summer squash is actually available through the year. Summer squashes, members of the Cucurbitaceae family and relatives of both the melon and the cucumber, come in many different varieties. While each variety may have a distinct shape, color, size and flavor, all varieties share some common characteristics. Regardless of variety, all parts of summer squash are edible, including the flesh, seeds and skin. Some varieties of squash also produce edible flowers. Unlike winter squash, summer squash are more fragile and cannot be stored for long periods of time unless frozen. For Native Americans, squashes were considered as one of the "three sisters" along with corn (maize) and beans. What's New and Beneficial about Summer Squash Although summer squash has long been recognized as an important food source of carotenoids, only recently have research studies documented just how fantastic summer squash can be when it comes to these key antioxidants. For some groups of study participants, summer squash turns out to be the primary food source of alpha-carotene and beta-carotene in the entire diet! For lutein, zeaxanthin, and beta-cryptoxanthin (three other health-supportive carotenoids) summer squash also comes out among the top three food sources in several studies. When we think about food and antioxidants, what first comes to mind might be fresh fruit and vitamin C, or bright orange carrots and beta-carotene. Yet several recent studies have underscored the unique contribution made by summer squash to our antioxidant requirements. While not as rich in some of the more widely-publicized antioxidants like beta-carotene, summer squash is a very strong source of other key antioxidant nutrients, including the carotenoids lutein and zeaxanthin. Since the skin of this food is particularly antioxidant-rich, it's worth leaving the skin intact and purchasing organic summer squash to help avoid potential unwanted contaminants. If you usually microwave or boil your summer squash, you'll be interested to know this: steaming is much better than either of these two methods in terms of nutrient retention. New evidence shows that summer squash can retain a large amount of its antioxidant activity after steaming. Using zucchini as their summer squash, researchers found that steaming was a better way to preserve zucchini's antioxidant activity than boiling or microwaving. Interestingly, even previously frozen zucchini held on to its antioxidant activity fairly well after steaming. These findings are great news for anyone enjoys steamed vegetables and who sometimes needs to freeze surplus vegetables for later use. We tend to think about squashes, both summer and winter, as starchy vegetables. This thinking is correct, since about 85-90% of the total calories in squashes (as a group) come from carbohydrate, and about half of this carbohydrate is starch-like in composition and composed of polysaccharides. But we also tend to think about polysaccharides as stagnant storage forms for starch that cannot do much for us in terms of unique health benefits. Here our thinking is way off target! Recent research has shown that the polysaccharides in summer squash include an unusual amount of pectin—a specially structured polysaccharide that often include special chains of D-galacturonic acid called homogalacturonan. It's this unique polysaccharide composition in summer squash that is being linked in repeated animal studies to protection against diabetes and better regulation of insulin. We expect to see future studies on humans confirming these same types of benefits from consumption of summer squash.

This chart graphically details the %DV that a serving of Squash, summer provides for each of the nutrients of which it is a good, very good, or excellent source according to our Food Rating System. Additional information about the amount of these nutrients provided by Squash, summer can be found in the Food Rating System Chart. A link that takes you to the In-Depth Nutritional Profile for Squash, summer, featuring information over 80 nutrients, can be found under the Food Rating System Chart.

• Health Benefits
• Description
• History
• How to Select and Store
• Tips for Preparing and Cooking
• How to Enjoy
• Individual Concerns
• Nutritional Profile
• References

Health Benefits

As a general rule, summer squash has not been as thoroughly studied from a health benefit standpoint as many of the other World's Healthiest Foods. Much of the research evidence specific to summer squash and its health benefits comes from animal versus human studies, and these research studies often look at squash as an overall food group rather than examining specific benefits from summer (versus winter) squash. However, in spite of these research limitations, there are still well-documented health benefits that are offered to us by summer squash!

Antioxidant Benefits

No category of health benefits from summer squash is better researched than the category of antioxidant benefits. As an excellent source of manganese and a very good source of vitamin C. summer squash provides us with a great combination of conventional antioxidant nutrients. But it also contains an unusual amount of other antioxidant nutrients, including the carotenoids lutein and zeaxanthin. These antioxidants are especially helpful in antioxidant protection of the eye, including protection against age-related macular degeneration and cataracts. While we often think first about carrots as providing us with antioxidant-related eye health benefits, we also need to start including summer squash in our list of antioxidant-rich foods that can provide us with health benefits in this area.

If properly handled and prepared, summer squash also provides us with special antioxidant advantages in terms of its antioxidant stability. Recent research has confirmed strong retention of antioxidant activity in summer squash after steaming. Research has also confirmed excellent retention of antioxidant activity in summer squash after freezing. These findings mean that the antioxidant benefits of summer squash are available to us under a wide variety of circumstances. We have the option of enjoying raw summer squash, briefly steamed summer squash, and previously frozen summer squash while still coming away with well-documented antioxidant health benefits.

To obtain full antioxidant benefits from summer squash, we need to eat not only the flesh, but also the skin and the seeds. Many valuable antioxidant nutrients are found in those portions of the food, and studies document their importance in the overall antioxidant activity of summer squash. Purchasing organic summer squash is your best way to lower risk of potentially unwanted contaminants (like pesticides) on the skin of this vegetable. While purchasing organic, it's still worthwhile to use a natural bristle brush and gently cleanse the skin of the summer squash under cold running water.

Blood Sugar Benefits

The list of nutrients in summer squash related to healthy blood sugar regulation is a long one. Metabolism of sugar in the body requires ample presence of many B-complex vitamins, and most of these B-complex vitamins are found in valuable amounts in summer squash. Included here are the B-vitamins folate, B6, B1, B2, B3, and choline. Also important in blood sugar metabolism are the minerals zinc and magnesium, as well as omega-3 fatty acids, and all of these nutrients are provided by summer squash.

A mainstay of dietary protection from type 2 diabetes—as well as a key step in food support of diabetes problems—is optimal intake of fiber. Summer squash not only provides a very good amount of dietary fiber at 2.5 grams per cup, but it also provides polysaccharide fibers like pectin that have special benefits for blood sugar regulation. The pectin polysaccharides in summer squash often include chains of D-galacturonic acid called homogalacturonan. An increasing number of animal studies now show that these components in summer squash help keep insulin metabolism and blood sugar levels in balance, and protect against the onset of type 2 diabetes.

Anti-Inflammatory Benefits

While lacking extensive research documentation, there are several other areas of health benefits from summer squash that are definitely worth noting and that may eventually have strong scientific back-up. The first of these areas involves inflammation-related conditions. The presence of omega-3 fats in the seeds of summer squash, the presence of anti-inflammatory carotenoids like lutein, zeaxanthin and beta-carotene, and the presence of anti-inflammatory polysaccharides like homogalacturonan make this vegetable a natural choice for protection against unwanted inflammation. Several preliminary animal studies show potential anti-inflammatory protection from summer squash for the cardiovascular system and also for the GI tract. (Two special areas of digestive tract interest involve anti-inflammatory protection against gastric ulcer and duodenal ulcer.) Insofar as chronic, unwanted inflammation is also a risk factor for development of type 2 diabetes, the anti-inflammatory benefits of summer squash may play an important role in its protection against type 2 diabetes as well.

Antimicrobial Protection

The seeds of summer squash and oils extracted from its seeds have a long history of use in botanical and folk medicine in two areas. The first area involves the anti-microbial properties of summer squash seeds, and especially their anti-parasitic properties. Interestingly, dried summer squash seeds are still used in some parts of the world for treatment of intestinal tapeworms or other intestinal parasites. We have not seen peer-reviewed studies focusing on the antimicrobial benefits of summer squash seeds, but from our perspective, these benefits are unlikely to come from a food approach to summer squash that includes this vegetable in modest amounts as part of a healthy, whole foods diet. Far more likely these benefits will come from a medicinal approach to summer squash that involves consumption of its dried seeds in non-food amounts or extract of oils from those seeds.

Prostate Health Support

The second area of folk medicine use involves non-cancerous enlargement of the prostate gland known as benign prostatic hyperplasia, or BPH. Seeds of summer squash (and oils from those seeds) have traditionally been used to help lower frequency of urination that is commonly experienced in men diagnosed with BPH. Like the area of anti-microbial benefits, we have not seen peer-reviewed studies focusing on summer squash seeds and their potential benefits in lessening frequency of urination in BPH. But from our perspective, these benefits are also unlikely to come from a food approach to summer squash that includes this vegetable in modest amounts as part of a healthy, whole foods diet. Far more likely these benefits will come from a medicinal approach to summer squash that involves consumption of its dried seeds in non-food amounts or from seed oil extracts.

Anti-Cancer Benefits

The combination of antioxidant and anti-inflammatory nutrients in summer squash is a very logical nutrient combination for providing anti-cancer benefits. The development of many cancer types depends on chronic, unwanted oxidative stress that can occur along with poor intake of antioxidant nutrients, and chronic, unwanted inflammation that can occur along with lack of anti-inflammatory nutrients. While we eventually expect to see well-documented anti-cancer benefits from summer squash in large-scale human studies, the anti-cancer research on summer squash is still in a preliminary stage.

Description

Summer squashes belong to the Cucurbitaceae family of plants and are relatives of winter squashes (including pumpkins), melons (including watermelon), and even cucumbers. But summer squashes are typically much more delicate than their fellow Cucurbitaceae, and are more often eaten fresh and shortly after harvest. The list presented below will give you more details about the Cucurbitaceae food family and shows how exactly how summer squashes fit in.

• Cucurbita Genus
  • winter squashes
  • summer squashes
• Cucumis Genus
  • cucumbers
  • casaba melons
  • Crenshaw melons
  • honeydew melons
  • muskmelon
• Citrullus Genus
  • watermelons
  • bitter apple

In the United States, you'll generally find three types of summer squash:

• Zucchini, whose skin can be yellow in color but is much more often found in grocery stores showcasing its dark green skin. (The dark green skin of zucchini may also be naturally striped or speckled.) Zucchini is one of the summer squash types that grow on flowering plants with edible flowers. Black beauty, cocozelle, golden, courgette, and dark green are some of the popular varieties of zucchini.
• Crookneck and straightneck squashes, usually yellow in color. While sometimes available with light green skins, bright yellow crookneck and straightneck squashes are the varieties that we most commonly associate with summer squash. (We've become especially accustomed to seeing small, bulb-shaped, bright yellow crookneck squashes in the United States.) Crookneck and straightneck summer squashes can be very similar in appearance, since crookneck varieties may have a very minimally curved neck that is almost swan-like in appearance. Golden summer, yellow crookneck, and early straightneck are some popular varieties of crookneck and straightneck squashes. Cushaw squashes are special varieties of crookneck squashes that are much larger than other crooknecks, even though they are easily recognized by their similar bulb-like shape. Cushaws take about twice as long to grow as other crooknecks, and are often used in baking (for example, in pies).
• Scallop squashes, also called pattypan squashes. These summer squashes are typically saucer-shaped and come in a wide variety of colors from very pale yellow to golden yellow to medium green. Scallop squashes sometimes have a slightly sweeter flesh than other summer squashes. Popular varieties include green tint scallop, scallop early white bush, scallop yellow bush, and sunburst. In some countries, you'll also hear the words "scallopini" or "button squash" used to describe the scallop squashes.

For readers interested in the scientific classification of these amazing summer squashes, we've provided a list below that shows basic types of summer and winter squashes and their botanical genus and species:

Cucurbita Genus and Species of Foods (including Summer Squash varieties)

• Cucurbita pepo (variety melopepo)
  • zucchini (summer variety)
  • yellow crookneck squash (summer variety)
  • scallop squash (summer variety)
• Cucurbita pepo (variety pepo)
  • acorn squash (winter variety)
  • delicata squash (winter variety)
  • spaghetti squash (winter variety)
• Cucurbita maxima
  • buttercup squash (winter variety)
  • Hubbard squash (winter variety)
  • banana squash (winter variety)
  • Boston Marrow squash (winter variety)
  • Turkish turban (winter variety)
• Cucurbita moschata
  • butternut squash (winter variety)
  • winter crookneck squash
• Cucurbita argyosperma*
  • cushaw squash (summer variety)

*This genus/species can also be referred to as Cucurbita mixta.

History

Amazingly, scientists have found squash seeds (from the genus-species Cucurbita pepo, which includes summer squash) preserved in Mexican caves for more than 10,000 years! It was that long ago when domestication of summer squash originated in Mexico and Central America. Cultivation of squashes (including summer squash) quickly became popular in North, Central, and South America, and Native Americans often referred to squashes as one of the "three sisters" alongside of corn (maize) and beans. Squashes were one of the North American foods that Columbus brought back to Spain from North America, and Portuguese and Spanish explorers introduced squashes to many parts of the world.

Commercial production of squash (including summer squash) now takes place on a worldwide basis, and the largest producers of squash including the United States, China, India, and Russia. The Pacific Islands region—including Papua New Guinea, Tonga, French Polynesia, Fiji, Hawaii, and New Zealand—is also an important area for squash production. Total global production of squash measures more than 5 billion metric tons, with over 500,000 acres planted. Florida, California, Georgia and New York are the top squash-growing states in the U.S., producing more than 650 million pounds of squash. The U.S. is also the world's largest importer of squash, importing nearly 300,000 metric tons per year. (Ninety-five percent of U.S. imported squash comes from Mexico.)

How to Select and Store

When purchasing summer squash, look for ones that are heavy for their size and have shiny, unblemished rinds. Additionally, the rinds should not be very hard since this indicates that the squash are over-mature and will have hard seeds and stringy flesh. Purchase summer squash that are of average size since those that are overly large may be fibrous, while those that are overly small may be inferior in flavor.

Summer squash is very fragile and should be handled with care as small punctures will lead to decay. It should be stored unwashed in an air-tight container in the refrigerator, where it will keep for about seven days.

While it can be frozen, this will make the flesh much softer. We don't recommend freezing as a routine storage method. Yet, it is a great process to turn to if you have amounts larger than you will be able to consume (for example, if you grow summer squash in your garden and have a bounty of it). The fact is that the freezing of summer squash can be an excellent storage process in terms of nourishment. A recent research study has shown excellent retention of the antioxidant activity in frozen summer squash.

Begin by slicing your summer squash and steaming for three minutes. Steaming is prefereable to the more traditional boiling method as it minimizes water contact and therefore minimizes nutrient loss. Remove squash from steamer and let cool thoroughly before placing in freezer bags and storing in the freezer.

Tips for Preparing and Cooking

Tips for Preparing Summer Squash

Wash summer squash under cool running water and then cut off both ends. You can then proceed to cut it into the desired size and shape for the particular recipe.

The Healthiest Way of Cooking Summer Squash

Of all of the cooking methods we tried when cooking summer squash, our favorite is Healthy Saute. We think that it provides the greatest flavor and is also a method that allows for concentrated nutrient retention.

To Healthy Saute summer squash, heat 3 TBS of broth (vegetable or chicken) or water in a stainless steel skillet. Once bubbles begin to form add sliced squash, cover, and Healthy Saute for 3 minutes (1-1/2 minutes on one side, and then 1-1/2 minutes on the other side) on medium heat. Transfer to a bowl and toss with our Mediterranean Dressing. (See our 3-Minute Healthy Sauteed Summer Squash recipe for details on how to prepare this dish.)

How to Enjoy

A Few Quick Serving Ideas

• Sprinkle grated zucchini or other summer squash on top of salads and sandwiches.
• Enjoy an easy to make ratatouille by healthy sautéing summer squash, onions, bell peppers, eggplant and tomatoes and then simmering the mixture in tomato sauce. Season to taste.
• Serve raw summer squash with your favorite dips.

WHFoods Recipes That Feature Summer Squash

• Any Time Frittata
• Italian Tofu Frittata
• Zesty Mexican Soup
• Southwestern Cod Saute
• Primavera Verde
• 5-Minute Healthy Sauteed Summer Squash
• Calabacitas (Mexican-flavored vegetable side dish)
• Steamed Vegetable Medley
• Tahini and Crudites Appetizer

Individual Concerns

Summer squash is among a small number of foods that contain measurable amounts of oxalates, naturally-occurring substances found in plants, animals, and human beings. When oxalates become too concentrated in body fluids, they can crystallize and cause health problems. For this reason, individuals with already existing and untreated kidney or gallbladder problems may want to avoid eating summer squash. Laboratory studies have shown that oxalates may also interfere with absorption of calcium from the body. Yet, in every peer-reviewed research study we've seen, the ability of oxalates to lower calcium absorption is relatively small and definitely does not outweigh the ability of oxalate-containing foods to contribute calcium to the meal plan. If your digestive tract is healthy, and you do a good job of chewing and relaxing while you enjoy your meals, you will get significant benefits—including absorption of calcium—from calcium-rich foods plant foods that also contain oxalic acid. Ordinarily, a healthcare practitioner. For more on this subject, please see "Can you tell me what oxalates are and in which foods they can be found?"

Nutritional Profile

While not often considered as a premiere food source of antioxidants, summer squash can provide you with unique amounts of antioxidant nutrients, including the carotenoids lutein and zeaxanthin. While summer squash contains very little overall fat (only 1/2 gram per cup), the fat in summer squash (mostly stored in its edible seeds) is unique in composition and includes omega-3s (in the form of alpha-linolenic acid), monounsaturates (in the form of oleic acid), and also medium chain fats (in the form of lauric and myristic acids). Summer squash is an excellent source of copper and manganese. It is a very good source of vitamin C, magnesium, dietary fiber, phosphorus, potassium, folate, vitamin B6, and vitamin K. Additionally, it is a good source of vitamin B1, zinc, omega-3 fatty acids, niacin, vitamin B2, pantothenic acid, calcium, iron, choline, and protein.

For an in-depth nutritional profile click here: Summer squash.

In-Depth Nutritional Profile

In addition to the nutrients highlighted in our ratings chart, an in-depth nutritional profile for Squash, summer is also available. This profile includes information on a full array of nutrients, including carbohydrates, sugar, soluble and insoluble fiber, sodium, vitamins, minerals, fatty acids, amino acids and more.

Introduction to Food Rating System Chart

In order to better help you identify foods that feature a high concentration of nutrients for the calories they contain, we created a Food Rating System. This system allows us to highlight the foods that are especially rich in particular nutrients. The following chart shows the nutrients for which this food is either an excellent, very good, or good source (below the chart you will find a table that explains these qualifications). If a nutrient is not listed in the chart, it does not necessarily mean that the food doesn't contain it. It simply means that the nutrient is not provided in a sufficient amount or concentration to meet our rating criteria. (To view this food's in-depth nutritional profile that includes values for dozens of nutrients - not just the ones rated as excellent, very good, or good - please use the link below the chart.) To read this chart accurately, you'll need to glance up in the top left corner where you will find the name of the food and the serving size we used to calculate the food's nutrient composition. This serving size will tell you how much of the food you need to eat to obtain the amount of nutrients found in the chart. Now, returning to the chart itself, you can look next to the nutrient name in order to find the nutrient amount it offers, the percent Daily Value (DV%) that this amount represents, the nutrient density that we calculated for this food and nutrient, and the rating we established in our rating system. For most of our nutrient ratings, we adopted the government standards for food labeling that are found in the U.S. Food and Drug Administration's "Reference Values for Nutrition Labeling." Read more background information and details of our rating system.

In-Depth Nutritional Profile for Squash, summer

References

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• Sarkar S and Buha D. Effect of ripe fruit pulp extract of Cucurbita pepo Linn. in aspirin induced gastric and duodenal ulcer in rats. Indian J Exp Biol. 2008 Sep;46(9):639-45. 2008.
• Smith BD. The initial domestication of cucurbita pepo in the Americas 10,000 years ago. Science. Washington: May 9, 1997. Vol. 276, Iss. 5314; p. 932-934. 1997.
• Wang DC, Pan HY, Deng XM et al. Cucurbitane and hexanorcucurbitane glycosides from the fruits of Cucurbita pepo cv dayangua. J Asian Nat Prod Res. 2007 Sep-Dec;9(6-8):525-9. 2007.
• Xia T and Wang Q. D-chiro-inositol found in Cucurbita ficifolia (Cucurbitaceae) fruit extracts plays the hypoglycaemic role in streptozocin-diabetic rats. J Pharm Pharmacol. 2006 Nov;58(11):1527-32. 2006.
• Younis YM, Ghirmay S, and al-Shihry SS. African Cucurbita pepo L.: properties of seed and variability in fatty acid composition of seed oil. Phytochemistry. 2000 May;54(1):71-5. 2000.

• Much grattidtude to George Mateljan,and the George Mateljan Foundation for www.whfoods.com