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The Truth About the Health Benefits of Blueberries

27/07/2011 - 11:23
Renee Despres

In recent years, media outlets have spread the word about the health benefits of blueberries, with headline after headline trumpeting claims that eating blueberries can prevent chronic disease, reduce belly fat, prevent diabetes, improve vision, memory, and balance, and more. But are blueberries worth all the hype?  What’s the truth about blueberries and your health?

Types of Blueberries

The first step in cutting through the confusion about blueberry health claims is to understand where blueberries come from and how they are grown. Three types of blueberries are grown in the United States. The blueberry’s close cousin, the biliberry, is grown widely in the United Kingdom.  

  • Highbush blueberries are the variety most often sold in stores. Bushes, which reach six to 12 feet in height, are planted in long rows. Berries are harvested by hand and machine. Hand-harvested berries are generally sold fresh in stores, while machine-harvested berries are washed and frozen.
  • Lowbush (“wild”) blueberries are not cultivated but managed.  These cold-hardy varieties are one of three berries native to North America (the others being cranberries and concord grapes). Maine and Canada are top producers of this type of berry. Unlike highbush and rabbiteye blueberry varieties, lowbush blueberries are not planted but instead spread through a system of underground runners, called rhizomes.  Wild blueberries tend to be smaller and have a more intense, sweet and tangy taste than their cultivated cousins.
  • Rabbiteye blueberries are found across the southern United States and fare well in warmer temperatures. Bushes grow 10 feet wide and 15 feet tall, producing light blue berries that ripen between late May to mid July.

Blueberries: The Research – and the Hype

An indisputable and growing body of research suggests that eating blueberries and blueberry supplements may be a  very good thing for your health. Different studies have found links between regular consumption of blueberries and reduced belly fat, improved blood sugar control, increased bone mass, prevention of heart disease, cancer, and other chronic disease, reduced blood cholesterol, reduced inflammation, improved memory, balance, and coordination in people at risk of Alzheimer’s disease, improved eyesight, prevention of urinary tract infections, and more.  

Researchers became interested in blueberries during the 1990s because of their high antioxidant content. Antioxidants are vitamins, minerals, and other substances that help to neutralize potentially damaging charged particles called free radicals. Free radicals have been linked to cancer, heart disease, Alzheimer’s disease, and other chronic health problems. Antioxidants have been linked to slower aging, prevent cancer, and improve heart health. 

Blueberries have the highest antioxidant activity of any fruit. Blueberries are rich in vitamin C, one of the most well-known antioxidant vitamins. One cup of blueberries provides nearly 25 percent of the U.S. recommended daily allowance (RDA) of vitamin C.

Blueberries also contain compounds called polyphenols – specifically, a category of polyphenols called anthocyanins. Anthocyanins, which give blueberries their rich purplish-blue pigment, are thought to provide much of blueberries’ antioxidant power. Among the polyphenols found in blueberries, resveratol  appears to be one of the most significant. Resveratol is a potential anticancer agent that has been shown to reduce the risk of heart and blood vessel disease. 

Blueberries offer a wealth of nutrition in a small package. Blueberries contain 80 calories per cup, almost all of which come from 16 grams of carbohydrates (sugars) in the berries. Blueberries contain virtually no fat and a negligible amount of protein. One cup of blueberries contains a whopping 16 grams of fiber, about 14 percent of the U.S. RDA. Blueberries are rich in vitamin K (36 percent  of the RDA per cup) and manganese (25 percent of the RDA per cup), a mineral important to healthy bones. Manganese also plays a role in helping convert proteins, fats, and carbohydrates into energy. 

The Blueberry Boom

Not surprisingly, blueberry growers’ associations jumped on research about blueberries’ health benefits, labeling the unpretentious little berries with big claims. The Wild Blueberry Association of North America has tagged wild blueberries “Nature’s Super Antioxidant Fruit,”  while the U.S. Highbush Blueberry Council has trademarked its tagline, “Little Blue Dynamos” (SM). Manufacturers started selling blueberry juice, blueberry extracts, dried blueberries, and other blueberry products.

And U.S. consumers are listening. Blueberry production in the United States and Canada – the world’s two largest producers of blueberries – rose from 91.7 million pounds in 1964 to nearly 666.7 million pounds in 2010, based on United States Department of Agriculture (USDA) data analyzed by the North American Blueberry Council. The same data show that per-person consumption of fresh blueberries in the United States and Canada rose from 13 ounces in 1994 to nearly 34 ounces in 2010. 

Does Eating Blueberries Really Make You Healthier?

While research does support all of the claims of blueberries’ potent and powerful effects on health, it’s important to put that research in context. Many of the studies cited on industry-association websites and in articles claiming their health benefits were performed in mice. For example, the USDA devoted almost half an issue to research that involved feeding blueberry products to hamsters and mice. This research is revealing many exciting possibilities – and much of the research is impeccably performed.  Still, it’s a long way from mice to men.  

Until results of these animal studies are confirmed in human trials, we won’t know exactly how much blueberries can benefit our health – and even then, the effect is likely to vary widely from person to person. Humans eat more than one food, and other factors – genetics, environment, behaviors such as smoking, body weight, and physical activity level – also affect the likelihood of a person developing a disease or condition (that’s why researchers go back to mice). It’s very difficult to account for these factors, even though most researchers use statistical methods to limit their impact.

 Human studies of food and nutrition can be problematic. Many studies involve limited numbers of people. For instance, in one study of blueberry consumption and memory, researchers asked 9 older adults – 5 men and 4 women – with mild cognitive problems to drink wild blueberry juice each day, while 7 people drank a blueberry-flavored grape juice served as a control group. The research team was led by Robert Krikorian, Associate Professor of Clinical Psychiatry at the University of Cincinnati Academic Health Center.

The blueberry group performed better on cognitive tests, leading the researchers to conclude that their study – which they noted was preliminary – might suggest that blueberry supplementation can improve memory. However, they also noted, with so few people in the study, they couldn’t draw any definite conclusions.

Nor are blueberries unique in containing high levels of beneficial phytonutrients. Other foods including berries, fruits, vegetables, and even black tea also contain generous amounts of antioxidants, including vitamins and polyphenols. Plentiful evidence exists that consumption of polyphenol-rich grapes and grape products (including wine), may also deter cardiac disease, memory loss, and aging. Blueberries are not unique in containing one key -- and well-hyped -- phytonutrient called reservatol. It’s a phyonutrient they share with grapes, cranberries, huckleberries, and other related fruits.

As one team of investigators opened their review of research about cardiovascular health and berries, all edible berries “are a good source of polyphenols, especially anthocyanins, micronutrients, and fiber.”  Blueberries are a wonderful food, but they are not the only “superfood.”

Consumers should also remember that blueberry studies are not designed to a determine what is a healthful, balanced diet but to test the specific effects of blueberries on health. This often means consuming unrealistic quantities of the blues. In most studies, participants (and mice) are asked to eat at least one cup of blueberries (or the equivalent in the form of juice, powder, or extract) per day. That’s a lot of blueberries, even for a blueberry aficionado. While juices, extracts, or dried supplements might be easier to consume, each of these forms has its own problems. Juice, especially, may add unneeded calories to the diet.

In sum, there’s enough solid evidence to say that a hundred blueberries a day might help keep the doctor away. But it’s not time to throw out your cholesterol medication or abandon other fruits and vegetables in lieu of blueberries in whatever form – fresh, frozen, juice, extract, or powder.

Should I Buy Organic Blueberries?

Every year, the Environmental Working Group (EWG) publishes its list of the “dirty dozen” fruits and vegetables on its food-focused site, www.foodnews.org. According to the EWG, these 12 foods are most likely to be contaminated with pesticides – and worth shelling out the extra money to buy organic. The EWG bases their rankings on data from the USDA Pesticide Data Program.  

The same fruits and vegetables rank high for pesticide contamination every year: apples, celery, strawberries, celery, spinach, imported nectarines, imported grapes, sweet bell peppers, and potatoes. Starting in 2008 – the first time the USDA had analyzed blueberries – the friendly little blue fruit also made the list. In 2011, EWG ranked blueberries number 10 on their “dirty dozen” list.

But a closer look at the USDA data shows that conventionally grown blueberries might not be all that bad. The USDA researchers analyzed 726 samples of blueberries and performed 166 analyses on each sample. That’s a total of 120,797 analyses. They found 46 different pesticide residues in 1,736 samples – only 1.4 percent of total samples. In three samples, pesticide residues were over the legal tolerance limit.

The appendices to the USDA report offer information about which pesticides were found on each sample. Examine these, and the picture of blueberry cultivation practices becomes less disturbing. Two fungicides – boscalid and pyraclostrobon – were found on 30 percent of blueberry samples. Eight other pesticides were found on 10 to 20 percent of samples. The remaining 37 pesticides were all found on less than 9 percent of samples, suggesting contamination occurred because of pesticide drift from nearby fields or cross contamination during storage and processing.

The bottom line: Buy organic if you prefer—and if you can afford it (it’s always a good choice to buy locally and organic if you can). But don’t miss out blueberries because you feel you must have organic. Whether you buy organic or conventionally grown berries, wash them well before eating, and enjoy their taste and potential health benefits.

How to Select and Store Blueberries

Blueberries are abundant in mid- to late-summer, when the sun warms the northern climes where they thrive. Michigan is the world’s biggest producer of highbush blueberries, while Maine produces more lowbush (“wild”) blueberries than any other region. Canada is the world’s second-largest producer of blueberries, producing about 200 million pounds per year.

Frozen and dried blueberries are available year-round, and blueberry juice is becoming more popular as a drink. Blueberry extracts and blueberry powder are sold largely as supplements.

Buy fresh berries in season at your local Farmer’s Market, farm stand, or grocers. Fresh berries should be firm and plump, with a light silvery dusting called the “bloom.” They may vary in color from a deep purple to a dark blue; red berries aren’t ripe. Beware of berries that don’t roll around in the package when you pick it up – that could indicate that berries in the middle of the carton are molded and soft and stuck together.

Pick Your Own Blueberries

If you’re lucky enough to live near a blueberry farm, you can pick your own berries straight off the bushes. Take your harvest home, enjoy some now, and freeze some for later. Visit the North American Blueberry Council website at http://www.nabcblues.org/upick.htm for a list of u-pick blueberry farms in your area.

Before storing blueberries, remove any moldy or soft berries. Do not wash berries until just before serving. Washing removes the protective bloom and allows berries to mold more quickly. Unwashed berries can be stored for up to 10 days in the refrigerator.

You can also freeze your own blueberries with minimal nutrient loss. Freezing does not appear to destroy anthocyanins, the key to blueberries’ antioxidant properties. However, freezing is likely to destroy some vitamin C and other nutrients.

To freeze blueberries, simply place the container of unwashed blueberries in a plastic freezer bag and pop it in the freezer. Then, when you’re ready to use them, wash. Once thawed, they’ll keep about three days in the refrigerator. If you prefer, you can wash the berries then freeze them. Lay the rinsed berries on a towel and allow them to dry thoroughly before freezing. Store frozen blueberries for up to six months in a freezer.

Blueberry Recipes

No one needs too many lessons in how to eat blueberries. Eat them by the handful. Toss a few onto on a bowl of cereal or oatmeal for breakfast, or mix some into muffin or scone batter. Liven up a salad with blueberries for lunch or dinner, or whip them into a smoothie for a healthful between-meal snack. For dessert, adorn some ice cream or frozen yogurt with the blue jewels, or pile them plentifully in a pie or under a cobbler crust.

Here are a few recipes to get you started using beautiful blueberries and enjoying their health benefits:

Lowfat BlueBerry Muffins

These lowfat, blueberry-filled treats go together quickly for a perfect morning wake-up call. Serve with fresh fruit and yogurt for breakfast, or bake up a batch for a tasty after-school snack for the kids.

  • 1 egg , lightly beaten
  • 3 Tablespoons orange juice
  • ½ cup plain lowfat or nonfat yogurt or buttermilk
  • ½ cup unsweetened applesauce
  • 2 tablespoons vegetable oil
  • 1 tsp vanilla
  • 1 cup unbleached white flour
  • 1 cup whole wheat pastry flour
  • ½  tsp baking soda
  • 1 ½ tsp baking powder
  • ¼ tsp salt
  • 1 cup blueberries, coated with 2 Tbsp unbleached white flour
  1. In a medium bowl, beat together egg, orange juice, yogurt or buttermilk, applesauce, oil, and vanilla.
  2. In a large bowl, stir together flours, soda, powder, and salt.Make a well in the center of the dry ingredients, then add the wet ingredients to the dry. Stir lightly with a fork until just moistened. Toss blueberries gently in  2 Tbsp unbleached white flour. Fold blueberries into batter.

Fill greased muffin cups 2/3 full and bake at 375F for 24 minutes, or until golden brown on top.

Makes 12 muffins

Nutrition Information per muffin:  calories per serving 82; 2.4 grams protein; 3 grams fat; 12 grams carbohydrates; 1 gram fiber, 111 grams sodium

Baker’s Tip: Avoid using too much baking soda in blueberry recipes. Blueberries contain a yellow pigment, which in an alkaline environment can create a green-blue color.

 

Blueberry Smoothie

This refreshing smoothie showcases blueberries at their peak. The combination of fresh and frozen berries brings out the best in flavor, while … a chilled and … drink.

  • ½ cup fresh blueberries
  • ½ cup frozen blueberries
  • 1 tsp lemon juice
  • Grated rind of ½ lemon
  •  ½ cup plain or vanilla low-fat yogurt
  • 1-2 teaspoons raw sugar (optional; omit if using vanilla yogurt)
  • ¼ tsp vanilla (optional – omit if using vanilla yogurt)
  • Dash nutmeg
  • ½ cup ice, crushed

Place all ingredients in blender. Whirl on maximum speed until smooth, about 30-40 seconds. 

Serves 2.

Nutrition Information: 95 calories per serving, 3.5 grams protein, 1.4 grams fat, 18.6 grams carbohydrate, 2 grams fiber, 42 grams sodium

Note: To make a fat-free smoothie, use nonfat yogurt. But the small amount of fat in the yogurt adds few calories and may make you feel more full until your next meal.

Blueberry Salad with Spinach and Feta

This lovely salad combines blueberries, spinach, and walnuts for a nutritional one-two-three punch. One serving provides half the RDA of vitamin A, 20 percent of the RDA for vitamin C and calcium, and an abundance of  heart-healthy omega-3s. Serve with a hearty piece of whole-wheat bread for a satisfying power lunch.

 

Dressing:

  • 1 Tbsp balsamic vinegar
  • 1 Tbsp lemon juice
  • ½  tsp sugar
  • 1 tsp chopped shallot
  • 1/4 cup olive oil

Salad:

  • 10 ounces fresh spinach
  • 1 4 oz package feta cheese
  • 1/4 cup chopped walnuts
  • 1 cup fresh or frozen blueberries
  • Freshly ground black pepper

 

  1. Place vinegar, lemon juice, sugar, salt, and shallot in a small bowl. Whisk in the olive oil until mixture becomes smooth and thick.
  2. Place spinach, feta cheese, and walnuts in a large bowl  and toss gently.
  3. Just before serving, pour on the dressing and toss again. Divide mixture onto six salad plates and sprinkle on the blueberries. Serve with freshly ground black pepper to taste

Serves 6

Nutrition information per serving: 222 calories, 5 grams protein, 16 grams fat (4 grams saturated fat), 2 grams fiber, 248 grams sodium

References

Basu A., Rhone M., Lyons T.J. (2010). Berries: emerging impact on cardiovascular health. Nutr Rev. 68(3) pp 168-77. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3068482/?tool=pubmed

Becker, H. (2001, Feb 27). Berries may protect against cancer and heart disease. United States Department of Agriculture Agricultural Research Service. Last modified Jan 03 2002. Retrieved from http://www.ars.usda.gov/is/pr/2001/010227.htm

Environmental Working Group. (2011). EWG’s 2011 Shoppers Guide to Pesticides in Produce. Available at http://www.ewg.org/foodnews/summary/

Krikorian R, Shidler MD, Nash TA, Kalt W, Vinqvist-Tymchuk MR, Shukitt-Hale B, Joseph JA. Blueberry supplementation improves memory in older adults. J Agric Food Chem. 2010 Apr 14;58(7):3996-4000.

US Highbush Blueberry Council. http://www.blueberrycouncil.org/

USDA. Economic Research Service. (2010). U.S. Blueberry Industry. United States Department of Agriculture. Economics, Statistics, and Market Information System.  http://usda.mannlib.cornell.edu/MannUsda/viewDocumentInfo.do?documentID=1765

USDA. National Agricultural Statistics Service. (2011, January). Noncitrus fruits and nuts, 2010 preliminary summary. ISSN 1948-2698.

USDA Pesticide Data Program. (Dec 2009). Pesticide Data Program: Annual Summary, Calendar Year 2008. Available at http://www.ams.usda.gov/AMSv1.0/getfile?dDocName=STELPRDC5081750

Wild Blueberry Association of North America. www.wildblueberries.com

Wood, M. (2011). “Blueberries and your health: Scientists study nutritional secrets of popular fruit.” Agricultural Research. 59,5, pp. 9-13. Available at http://www.ars.usda.gov/is/services/Introduction/May-June%202011%20AR%20Magazine.html

Nutrition information calculated at NAT Tools for Good Health. Available at http://www.myfoodrecord.com/

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