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Blueberries: Heart Healthy or Myth

Kaitlin Gibler

10/10/08

 

            Growing up, many of us were often told to make sure we ate our fruit because it is good for us.  Well what exactly is it that makes fruit, particularly blueberries, so healthy?  There have been recent crazes in finding nutritious foods that have the ability to prevent and cure diseases, but are they really able to do what health food companies are claiming?  Lately, there have been many claims that blueberries are heart healthy and full of antioxidants that can prevent cardiovascular disease.  Many websites explain these perceived benefits of blueberries and how their antioxidants can prevent heart disease.  However, are blueberries really able to prevent heart disease, or is this just another way to entice the consumer to buy more of their product?   

 

Heart Disease and Free Radicals

 

Heart disease is caused by damage to arterial cells as a result of free radicals (http://www.healingdaily.com/conditions/free-radicals.htm).  These so-called free radicals are unstable oxygen molecules that can cause oxidative stress that hardens or breaks down the lipids within our cell walls, as well as damage our DNA and enzymes.  The free radicals come from a poor diet, being exposed to chemicals, smoke, alcohol, and other substances, as well as from metabolic processes in our body that break down compounds for use in the body (http://www.trueblueberry.com/blueberry/antioxidants.asp).   With the hardening of the cell walls from oxidative stress, the cell is unable to carry out its proper function and is not receiving the proper nutrients it needs, thereby resulting in heart disease (http://www.healingdaily.com/conditions/free-radicals.htm).  This is where the antioxidants are believed to come in and prevent the free radical damage.

 

Antioxidants and their Ability to Fight Free Radicals

 

According to numerous health foods and wild blueberry websites, antioxidants that come from our diet have the ability to neutralize the free radicals and make them harmless by donating electrons in order to prevent cell damage (http://www.wildblueberries.com/health_benefits/antioxidants.php).  By neutralizing the free radicals, they are not able to cause oxidative stress on our cell walls, which is the cause of heart disease.  It is difficult to prevent free radicals with drugs because they tend to increase the number of free radicals in the body.  Consequently, antioxidants from our diet appear to be one of the ways to prevent this damage that is causing many diseases, especially heart disease (http://www.healingdaily.com/conditions/free-radicals.htm).

 

Claims about Blueberries and their Antioxidant Potency        

 

(http://www.wildblueberries.com/health_benefits/antioxidants.php)   

 

 

As a result of the abilities of antioxidants, people are now looking for foods that contain antioxidants that are able to prevent disease.  Blueberries (Vaccinium angustifolium) are thought to contain the highest antioxidant capacity compared to other fruits according to tests that show its high Oxygen Radical Absorbance Capacity (ORAC) (http://www.wildblueberries.com/health_benefits/antioxidants.php).  Blueberries contain many antioxidants and nutrients including: flavonoids, such as anthocyanins, phenolics, Vitamin C and E, as well as a possible newly identified compound.  Because of all these nutrients, many people are claiming that blueberries are rich in health benefits and have the ability to prevent cardiovascular disease (http://198.173.241.4/health.htm).  They are claiming that the nutrients in blueberries are able to strengthen blood vessels, which will promote heart health and anti-aging (http://www.trueblueberry.com/blueberry/antiaging.asp). 

 

The rich blue pigment of the blueberries contains the antioxidants.  Therefore, the darker the blue color of the blueberries, the more antioxidant potency they contain.  The pigment is made up of phytonutrients, known as anthocyanins, which contain polyphenols that are potent antioxidants.  The anthocyanins are believed to stabilize the collagen matrix in the capillaries that is caused from free radical damage in heart disease.  Consequently, these antioxidants seem to be one aspect of what makes blueberries so healthy and beneficial.  (http://www.whfoods.com/genpage.php?tname=foodspice&dbid=8)

 

            Additionally, the USDA has claimed to identify a compound known as pterostilebene that they believe has the potential to fight heart disease because it lowers cholesterol.  It is similar in function to the antioxidants in the skin of blueberries that they believe have the ability to lower the unfavorable LDL cholesterol.  Some websites claim that more research needs to take place, but that this could be as effective as drugs in preventing heart disease without side effects (http://www.healthylivingnyc.com/article/95). 

 

The Origin of these Claims

 

            Many of the claims about the potency of blueberries are originating from Agriculture and Food Companies, especially companies that sell blueberries.  Because of the multitude of their healthy claims about blueberries, it can make one wonder about their motives for promoting the apparent benefits of blueberries.  For instance, are they using these claims as a way to attract consumers into buying their blueberries with claims that may or may not be 100% accurate?  Although some of the claims appear to be valid, not all of the websites included references to studies that have taken place to support their claims.  Some of the companies did cite research journals that supported their claims, but can the scientific data support these claims about antioxidant potency in blueberries?   

 

Scientific Data

 

            Many studies have been done to look into the antioxidant potency of blueberries, as well as their potential benefits on the heart.  There are many claims that are on the Internet concerning blueberries which need to be tested to see if they are accurate statements or mere claims to get consumers to buy their product.

 

Phenol Antioxidant Quantity and Quality in Foods: Fruits

 

            Because many websites state that blueberries have the highest antioxidant activity, they have also claimed that they protect against cardiovascular disease.  This claim was tested by a study conducted by Vinson, Su, Zubik, and Bose (2001).  Their goal was to assess the quantity and quality of phenol antioxidants in various fruits.  For the study, they prepared, extracted and hydrolyzed the fruit extracts.  They subsequently measured the phenol concentration with HPLC and determined the quality of phenols using the concentration needed to inhibit oxidation 50% (IC).  A low number suggests a higher antioxidant capacity, which would be beneficial.  When looking at the overall quantity/ quality index, the researchers used PAOXI to determine the berry with the best index. (Vinson et al. 2001) 

With this measure, berries were found to be the best source of polyphenol antioxidants, which could make them better at reducing risk for cardiovascular disease.  By having high quality and quantity antioxidants, they have a stronger ability to “enrich lower density lipoproteins”, which protects them from oxidation.  (p. 5319).  By protecting the lipoproteins from oxidation, the blueberries have potential to reduce the risk of cardiovascular disease.  Similarly, it appears there are potential benefits of flavonoids in protecting against heart disease, which is another component of blueberries.  By using ORAC, they were able to determine that blueberries do have the highest antioxidant activity among fruits.  As or their protection against cardiovascular disease, their data seems to suggest that the potential is there, but no conclusive evidence.  (Vinson et al. 2001)

 

Anthocyanins and Heart Health

 

            Similarly, many websites have claimed that the anthocyanins concentration in blueberries may be responsible for their antioxidant potency and consequently heart healthy aspects.  Data that was published by Geuseppe Mazza (2007) describes anthocyanins, a type of flavonoid, and their potential ability to reduce the risk of coronary heart disease.  Anthocyanins affect lipoproteins, platelets, and blood vessels, as well as protect LDL against oxidation.  Combining these features with anthocyanin’s affect on vasodilation capacity, it seems they could positively affect one’s risk for heart disease. (Mazza 2007) 

 

Oxygen Radical Absorbing Capacity of Phenolics

 

            Another nutrient in blueberries that needs to be examined is their phenolics.  In a published study, Zheng and Wang (2003) studied the phenolic compounds in certain berries and their ability to absorb oxygen radicals.  The purpose of the study was to quantify the antioxidant capacity of the phenolic compounds in the berries, including blueberries.  Also, they wanted to examine the structures and activities of flavonoids and phenolic acids compared to their Oxygen Radical Absorption Capacity (ORAC).  For their experiment, they used the ORAC test as well as high performance liquid chromatography (HPLC) to separate the two compounds.  Although blueberries did not have the largest percent of antioxidants, they had high antioxidant activities and a large percentage of phenolic compounds and cholorgenic acid, an important antioxidant.  Therefore, they concluded that blueberry’s high, varied antioxidant activity could be linked to the various phenolic compounds.  Because the phenolic compounds have been known to inhibit LDL, bad cholesterol, and oxidation, blueberries may have the potential to reduce the incidence of cardiovascular disease. (Zheng and Wang, 2003)

 

Wild Blueberry Consumption Affects

 

       Overall, the universal claim of websites about blueberries is their potency in preventing oxidative stress, which they claim then leads to a decrease in the risk for cardiovascular disease.  In a study conducted by Kalea et al. (2006), the consumption of wild blueberries and its effect on the aorta was investigated in rats.  By looking for effects on the aorta, researchers looked at the Glycosaminoglycans (GAGs) that were found in the different rat aortas.  GAGs are a structural element of the aorta that are important for blood coagulation, lipoprotein metabolism, and regulation of cellular proliferation.  As a result of these functions and interactions with enzymes and cytokines, they are known to have a role in degenerative diseases. (Kalea et al. 2006)

            For this experiment, 10 rats were used in two groups, a control group and a blueberry diet group.  The two groups were fed the same diet, with the blueberry group also eating blueberries in their meal.  They were on this diet for 13 weeks.  After every meal, they were not allowed to eat for 12-14 hours and thoracic aortic tissue samples were taken from each rat to assess the GAGs.  The researchers were looking for hylauronan (HA), heparin sulfate (HS) and galactosaminoglycans (GalAGs). (Kalea et al. 2006)

            The results demonstrated that the rats in the blueberry group had a higher concentration of GAGs, especially GalAGs.  From previous research, it is known that oxidative stress from free radicals in rats causes a decrease in the concentration of GAGs that can be found in their aorta, heart tissue, and liver.  As seen in this study, an increase in dietary blueberries causes an increase in GAG and GalAG levels in rats.  This also appeared to cause a decrease in vascular constriction in response to particular receptors.  Because a lack of fruits and vegetables causes oxidative stress, this type of diet tends to decreases GAG concentrations and increases one’s risk for heart disease.  Consequently, it appears that blueberries can reduce the oxidative stress by increasing the GAG levels, which could potentially decrease the risk for heart disease.  Although this seems like a logical explanation, more research needs to be done to develop a deeper understanding.  (Kalea et al. 2006).    

 

 

The Verdict

           

By looking into scientific research on the topic of blueberries and cardiovascular disease, it seems to be common knowledge that blueberries are one of the leaders in antioxidant capacity among other fruits and vegetables. Similarly, many studies cite that the phenolic compounds are able to inhibit LDL and liposome oxidation, which could be beneficial to cardiovascular disease.  There also seems to be a common consensus among research that antioxidants have the ability to reduce oxidative stress caused from free radicals.  However, it appears that the overall belief is that further research still needs to take place to see how they affect cardiovascular disease in humans.  There are multiple mechanisms explained that could cause blueberries to reduce the risk of cardiovascular disease.  Many of the studies presented possess aspects that could provide logical explanations and demonstrate the potential for blueberries to prevent heart disease.  However, there is not conclusive data yet and there will not be until more in vivo studies take place. 

Blueberries are definitely a healthy food and should be a part of many people’s diets.  The richer the color of the berry, the more anthocyanins and antioxidant potency is in the berry.  So when you were growing up and were told to eat your fruit because it was good for you, they were right.  However, just because blueberries are seen to have many health benefits, not all of the claims about the potential for blueberries to prevent heart disease are supported by scientific evidence.  There is great potential and all of the data seems to point in that direction.  However, there is no concrete data that shows that blueberries definitely prevent heart disease.  Until that can be done, continue to eat your blueberries, but do not expect a definite reduction in the risk for heart disease.   

 

References

 

Healingdaily.com. (2006). Free Radicals and your health. Retrieved October 6,

2008, from http://www.healingdaily.com/conditions/free-radicals.htm

 

Kalea, A.Z., Lamari, F.N., Theocharis, A.D., Cordopatis, P.,

Schuschke, D.A., Karamanos, N.K., & Klimis-Zacas, D.J. (2006).  Wild blueberry (Vaccinium angustifolium) consumption affects the composition and structure of glycosaminoglycans in Sprague-Dawley rat aorta. Journal of Nutritional Biochemistry, 17, 109-116.

 

Mazza, Giuseppe (2007). Anthocyanins and heart health. Ann 1st Super Sanita,

43, 369-374.

 

Michael, L.  Compound in Blueberries May Prevent Heart Disease and Type 2 Diabetes. Healthy Living NYC. Retrieved October 6, 2008, from

http://www.whfoods.com/genpage.php?tname=foodspice&dbid=8

 

TrueBlue. (2008). Health Benefits of Blueberries. Retrieved October 6, 2008, from http://www.trueblueberry.com/blueberry/antioxidants.asp

 

US Highbush Blueberry Council, (2002). Blueberry Health Benefits. Retrieved

October 6, 2008, from http://198.173.241.4/health.htm

 

Vinson, J.A., Su, X., Zubik, L., & Bose, P. (2001). Phenol Antioxidant Quantity

and Quality in Foods: Fruits. Journal of Agriculture and Food Chemistry, 49, 5315-5321.

 

Wild Blueberries: Nature’s Antioxidant Superfruit. Health Benefits. Retrieved

October 5, 2008, from http://www.wildblueberries.com/health_benefits/antioxidants.php

 

The World’s Healthiest Foods. Blueberries. Retrieved October 5, 2008, from http://www.whfoods.com/genpage.php?tname=foodspice&dbid=8

 

Zheng, W., & Wang, S. Y. (2003). Oxygen Radical Absorbing

Capacity of Phenolics in Blueberries, Cranberries, Chokeberries, and Lingonberries. Journal of Agriculture and Food Chemistry, 51, 502-509.

 

 

 

 

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