Berry study examined mice predisposed to atherosclerosis
The USDA study compared the size of artery lesions in 30 young laboratory mice.
All of the mice had a variant of the gene that provides instructions for making a large protein compound called apolipoprotein E or APOE.
APOE combines with fats (lipids) in the body to form molecules called lipoproteins, which carry cholesterol and other fats through the bloodstream.
Because the mice lacked the gene that directs cells to make APOE, they were highly susceptible to forming lesions in their arteries.
For five months, half of the animals were fed diets enhanced with freeze-dried blueberry powder while the other half received the same diet without any berry powder.
The blueberry-spiked diet contained one percent blueberry powder… the equivalent in humans of eating about one half-cup of fresh blueberries daily.
The researchers measured the size of artery lesions at two sites on the main artery leading from the animals' hearts—called the aorta—at the beginning and end of the study.
After five months, the lesions found at two sites in the blueberry group were 39 and 58 percent smaller than the aorta lesions in the control mice.
Findings may apply to people with a problematic genetic profile
Maintaining normal blood cholesterol levels is essential for the prevention of disorders that affect the heart and blood vessels (cardiovascular diseases), including heart attack and stroke.
Apolipoprotein E is a major component of very low-density lipoproteins (VLDLs), which remove excess cholesterol from the blood and carry it to the liver for processing.
There are at least three slightly different versions (alleles) of the APOE gene, called e2, e3, and e4. The most common allele is e3, which is found in more than half of the general population.
People who carry at least one copy of the APOE e4 allele have an increased chance of developing atherosclerosis, which leads to a progressive narrowing of the arteries and increases the risk of clots that produce heart attacks and stroke.
If the new results in mice hold true for humans, blueberries could benefit all people but especially those who don't make sufficient APOE.
USDA team will dig deeper to learn berries' artery-aiding secret
The USDA scientists say they will seek to determine how the blueberry powder helped control lesion size in the APOE-deficient mice.
They speculate that blueberries may help APOE-deficient mice (and people) in a “nutrigenomic” fashion.
That is, they may influence the expression of genes in ways that boost the activity of the body's own antioxidant enzymes, thereby reducing free-radical-generated “oxidative stress” …a known risk factor for atherosclerosis.
If so, it seems likely that other blue-purple berries—which possess similar chemical profiles—would deliver the cardiovascular benefits seen in the APOE-deficient mice (e.g., blackberries, elderberries, black currants, chokeberries, bilberries, and boysenberries).
And if the berry powder aided the APOE-deficient mice by boosting their internal antioxidant network, then there is good reason to suspect that berries would aid animals and people who do not lack APOE, though probably not as dramatically.
The USDA team also wants to determine whether eating blueberries in infancy, childhood, and young adulthood would help protect against onset and progression of atherosclerosis in later years.
Early prevention seems especially important in light of America's epidemic of childhood obesity, since being overweight or obese increases the risk of developing atherosclerosis.