First-ever clinical trial links berry-enriched diets to reductions in risk factors for fatty liver disease and pre-diabetic metabolic syndrome
by Craig Weatherby
The good news about colorful fruits just keeps rolling in, as you can see by searching our news archive.
And last month, Finnish scientists published the results of the first clinical trial testing the effects of berries on human liver function.
While the trial's positive outcomes hold promise for people at risk for fatty liver disease, they also indicate that berries may help deter diabetes.
What is fatty liver disease?
Ten to 25 percent of American adults have non-alcoholic fatty liver disease (NAFLD), which is defined as having more than 10 percent of your liver's weight as fat.
Fatty liver occurs most often in people who meet any one of several often-overlapping risk factors: diabetes, obesity, very high blood triglyceride levels, or excessive alcohol intake.
Gradual buildup of excess fat in liver cells leads to inflammation of the liver, which damages the organ and can lead to liver failure.
Fatty liver can even occur in children who eat high-calorie diets dominated by junky foods low in polyunsaturated fats (such as omega-3s) and high in saturated fats and sugars (Mager DR et al. 2010).
Earlier this year, Scottish researchers linked higher omega-3 intakes to reduced risk of NAFLD, while an Israeli team associated sweet soda with increased liver risk (See “Omega-3s Deter Fatty Liver; Sweet Drinks Raise the Risk”).
Now it looks like the antioxidants in berries may join fish-derived omega-3s as potential liver-protectors.
Finnish trial finds that berries improve liver health markers
Researchers from Finland's University of Turku conducted the first human clinical trial linking berries to improved liver function and reductions in key components of metabolic syndrome (Lehtonen HM et al. 2010).
A team led by Dr. Heikki Kallio recruited 61 women (average age 43) and randomly assigned them to one of two groups for a trial that lasted 20 weeks.
One group (31 women) replaced all snacks with commercial snack foods that contained an average of 163 grams of popular, locally harvested Scandinavian berries: lingonberry, sea buckthorn berry, bilberry, and black currant.
The control group (30 women) received no special foods, supplements, or instructions, so increased berry consumption was the only lifestyle difference between the two groups.
The scientists measured the participants' blood levels of an enzyme called alanine aminotransferase (ALAT)
—a well-established marker of non-alcoholic fatty liver disease
—at the beginning and end of the trial.
People in the berry group averaged a 23 percent drop in their ALAT levels… a sign of enhanced liver function.
And, the berry group enjoyed a rise in blood levels of adiponectin: a hormone that discourages storage of excess dietary calories as abdominal fat.
This beneficial effect on adiponectin levels could help deter fatty liver itself, and the pre-diabetic state known as metabolic syndrome, which promotes fatty liver.
As the Finnish team wrote, “This study showed that the daily consumption of more than 150 grams of northern berries… had a positive effect on ALAT and adiponectin levels.
While the Finns saw no rise in the total antioxidant capacity of the berry group's blood, they detected lower levels of inflammation in the berry group.
Those findings make sense, given that the polyphenol-type antioxidants in berries reduce the expression of genes related to inflammation.
(Similar sets of polyphenol-type antioxidants also abound in grapes, tea, cocoa, coffee, and whole grains.)
The Finns noted that the small amount of berries the control group members consumed as part of their normal diets was not enough to produce the benefits seen in the berry group.
However, the trial showed that berries affect the liver and key hormones in positive ways.
So it seems reasonable to propose that eating smaller amounts of berries routinely could help protect liver health and deter metabolic syndrome.
- Lehtonen HM, Suomela JP, Tahvonen R, Vaarno J, Venojärvi M, Viikari J, Kallio H. Berry meals and risk factors associated with metabolic syndrome. Eur J Clin Nutr. 2010 Mar 3. [Epub ahead of print]
- Mager DR, Patterson C, So S, Rogenstein CD, Wykes LJ, Roberts EA. Dietary and physical activity patterns in children with fatty liver. Eur J Clin Nutr. 2010 Mar 10. [Epub ahead of print]