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Wild Blueberries Seen to Enhance Vascular Health
4/17/2006
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Blueberries can lower cholesterol; researchers now report that they can help keep arteries healthy… in more ways than one
by Craig Weatherby


If you like blueberries—especially wild blueberries—you’ll love the latest research news. First, let’s provide a little background.

Back in the fall of 2004, we reported the results of two studies on blueberries.

Key Points
  • A new study shows that blueberries protect key constituents of arteries from inflammation-induced damage.
  • The same research team found that blueberries help keep arteries relaxed in response to stress-related chemicals.
  • These findings build on earlier research showing that blueberries can lower cholesterol levels.
One showed that blueberries contain a compound (pterostilbene) that gives the fruit the power to lower blood levels of LDL (“bad”) cholesterol and triglycerides as effectively as the prescription drug ciprofibrate.

The other showed that wild blueberries rank number two on the USDA list of the top 20 antioxidant-rich foods, and that they outrank their cultivated cousins in terms of antioxidant capacity (Click here to read our 2004 report on blueberries, cholesterol and antioxidant power).

And late last week, researchers from the University of Maine released the results of a study in rats, which demonstrate that wild blueberries can decrease the vulnerability of heart-supplying blood vessels to oxidative stress and inflammation (Kalea AZ, 2006).

Inflammation impairs arterial health
When inflammation occurs in our blood and arteries, it promotes buildup of fatty plaque on artery walls and increases the “stickiness” of blood platelets.

The result is a vicious circle in which the build up of arterial plaque induces yet more inflammation, which attracts more cholesterol and fat to artery walls. This inflammatory cycle ultimately causes the arterial plaque to rupture, releasing clots that cause heart attacks and stroke.

Inflammation usually occurs in a healthy response to injury or infection, but chronic, low-level inflammation can result from varying combinations and proportions of infections (some originating in the gums), poor diets, stress, predisposing genetic codes, and sedentary lifestyles.

Heart-health is bound to “GAG” health
Certain sugar-bound protein compounds play key roles in the structure and key biochemical functions of connective tissues, including our skin, joints, and arteries.

These vital, sugar-bound protein compounds come in many forms, but fall into two general categories: proteoglycans (PGs) and the similar but far smaller molecules called glucosaminoglycans (GAGs).

And these compounds do much more than merely form the framework of connective tissues. Instead, PGs and GAGs interact with blood fats, blood coagulation, and the immune system, which is the body’s initiator and regulator of inflammation.

When low-level inflammation occurs chronically in the blood and arteries it initiates and then promotes chemical changes to GAGs and PGs, especially an undesirable alteration called “over-sulfation.”

The problem is that these damaged GAGs and PGs actively attract blood fats and cholesterol oxidized by free radicals: the unstable, cell-damaging molecules generated by the same chronically inflammatory vascular environment that damages GAGs and PGs.

Tellingly, in one of the early signs of arteriosclerosis, healthy arterial collagen—a key structural component of arteries—gets displaced by damaged, over-sulfated GAGs and PGs.

Research reports extending from today back to the mid-1970’s indicate that undesirable, inflammation-induced alterations to GAGs and PGs cause them to actively promote the arteriosclerosis (“hardening of the arteries”) characteristic of cardiovascular disease. If so, inflammation hurts in one more major way than researchers knew.

Here’s how the Maine team described the context that prompted their study of blueberries’ potential cardiovascular-preventive effects:

“Glycosaminoglycans (GAGs) and proteoglycans (PGs) are structural components of aortas [arteries] with great structural diversity. Their interaction with compounds such as enzymes, cytokines [inflammatory immune-system chemicals, growth factors, proteins and lipoproteins [e.g., cholesterol] and their subsequent role in degenerative diseases [specifically cardiovascular disease] has been documented.”

Accordingly, lovers of these vibrant fruits should rejoice at the new findings from Maine, since they suggest that wild blueberries can ameliorate inflammation-induced cardiovascular damage very considerably.

How wild blueberries help keep arteries healthy
Since inflammation-induced alterations to GAGs and PGs are a major factor in the development of cardiovascular disease, anything that helps protect these vital bodily constituents is a big plus.

The Maine team gave rats either a control (regular) or a blueberry-fortified version of the same diet for 13 weeks.

At the end of the experiment, the blueberry-fed rats’ arteries contained fewer damaged (over-sulfated) GAGs, and 13 percent more GAGs overall.

As the Down East scientists concluded, “Our results demonstrate for the first time that a diet rich in blueberries results in structural alterations in rat aortic tissue GAGs. These changes may… have major consequences for the [healthy] biological function of GAG molecules within the vascular environment.”

To translate the scientific jargon, diets rich in blueberries could put a real damper on burgeoning heart disease.

We should note that the blueberry research was funded by the Maine-based Wild Blueberry Association of North America.

But these encouraging findings deserve the benefit of the doubt, both because they come from academic researchers with public reputations to protect (versus a private lab-for-hire), and because they fit with everything we know about the physiological effects of the flavonoid antioxidants that blueberries contain in near-unique abundance.

New findings only add to blueberries’ arterial benefits
In 2004, the same University of Maine team reported the positive results of a another rat study, this one designed to determine the effects of dietary blueberries on arteries exposed to a chemical (phenylephrine) that causes arteries to tighten: an undesirable, stress- and inflammation-induced effect linked closely to increased risk of heart attacks (Kalea AZ, 2005).

The researchers divided rats into three separate groups, which received a standard “control” diet, a blueberry-enriched diet for 13 weeks, or a “reverse” group that that was fed the control diet for 13 weeks, and then the blueberry diet for an extra eight weeks.

They then tested the rats’ arteries using two measures of vascular health and ability to resist unhealthful pre-contraction influence of the artery-tightening chemical: 1) maximum force of contraction, and 2) blood-vessel sensitivity.

As they reported, “Our results indicate for the first time that wild blueberries incorporated into the diet affect the vascular smooth muscle contractile machinery by suppressing… [chemically induced] contraction while having no effect on membrane sensitivity of the endothelial or vascular smooth muscle cell layer.”

In other words, the blueberry-enriched diet protected rat arteries from contracting in an unhealthful way in response to stress- and inflammation-generated chemicals.

When combined with the findings of the new study from Maine, the same team’s earlier findings paint a picture in which blueberries can bring substantial cardiovascular benefits.


Sources
  • Wu X, Beecher GR, Holden JM, Haytowitz DB, Gebhardt SE, Prior RL. Lipophilic and hydrophilic antioxidant capacities of common foods in the United States. J Agric Food Chem. 2004 Jun 16;52(12):4026-37.
  • Rimando AM, Nagmani R, Feller DR, Yokoyama W. Pterostilbene, a new agonist for the peroxisome proliferator-activated receptor alpha-isoform, lowers plasma lipoproteins and cholesterol in hypercholesterolemic hamsters. J Agric Food Chem. 2005 May 4;53(9):3403-7.
  • Kalea AZ, Lamari FN, Theocharis AD, Cordopatis P, Schuschke DA, Karamanos NK, Klimis-Zacas DJ. Wild blueberry (Vaccinium angustifolium) consumption affects the composition and structure of glycosaminoglycans in Sprague-Dawley rat aorta. J Nutr Biochem. 2006 Feb;17(2):109-16. Epub 2005 Jun 20.
  • Norton C, Kalea AZ, Harris PD, Klimis-Zacas DJ. Wild blueberry-rich diets affect the contractile machinery of the vascular smooth muscle in the Sprague-Dawley rat. J Med Food. 2005 Spring;8(1):8-13.
  • Jakab L. [Glycosaminoglycans, proteoglycans, atherosclerosis] Orv Hetil. 2004 Apr 11;145(15):795-803. Review. Hungarian.
  • Jakab L. [The pathogenesis of atherosclerosis] Orv Hetil. 2003 Jun 8;144(23):1121-8. Review. Hungarian.
  • Drubaix I, Viljanen-Tarifa E, Robert AM, Robert L. [Role of glycosoaminoglycans in venous disease. Mode of action of some flavonoid drugs] Pathol Biol (Paris). 1995 May;43(5):461-70. Review. French.

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