October 23, 2008
Cherries Reduce Body Fat In Rats
Eat tart cherries to help keep off excess weight?
CHICAGO, IL, October 26 – New research continues to link tart cherries, one of today's hottest "Super Fruits," to lowering risk factors for heart disease. In addition to lowering cholesterol and reducing inflammation, the study being presented by University of Michigan researchers at next week's American Dietetic Association annual meeting, found that a cherry-enriched diet lowered body weight and fat – major risk factors for heart disease.
Maybe the inflammation reduction causes a change in signaling that reduces body weight.
In the study, at-risk, obese rats that were fed a cherry-enriched diet saw significant decreases in body weight and fat (especially the important "belly" fat with known risk for heart disease) while maintaining lean muscle mass. After twelve weeks, the cherry-fed rats had 14 percent lower body fat compared to the other rats who did not consume cherries (cherry-fed rats were approximately 54% body fat; rats eating the Western diet alone were 63% body fat). The researchers suggested cherry consumption could have an effect on important fat genes and genetic expression. According to the American Heart Association, being overweight or obese, in particular when the weight is concentrated in the middle, is a major risk factor for heart disease . Nearly two out of three Americans are overweight.
The animals were fed a "Western diet," characterized by high fat and moderate carbohydrate – in line with the typical American diet – with or without added whole tart cherry powder, as 1 percent of the diet. The study was funded by the Cherry Marketing Institute, which provided an unrestricted grant to the University of Michigan to conduct the research and was not directly involved in the design, conduct or analysis of the project.
Would blueberries or cranberries deliver the same benefit? Would this work in humans?
My quick web search showed that cherries have a low glycemic index, possibly the lowest of any fruit inspite of their high sugar content. Some flavonoids delay carbohydrate digestion and uptake (this is one of pycnogenol's claims). Possibly, tart cherries contain some of these and reduce insulin spikes, even when consumed with other carbs. Some carb blockers may also interfere with carb uptake - so the isocaloric control diet in this study may actually provide more absorbable calories than the cherry diet.
There are many papers online presenting evidence that several anthocyanins and flavonoids reduce inflammation markers IL-6 and TNF-alpha levels. There are conflicting reports online, but IL-6 and (less often) TNF-alpha reduction sometime leads to improved glucose tolerance.
Cherry salicylates may account for some of the anti-inflammatory effect also.
More information is at:
The adjusted dose for humans would be 1.5 cups/day, but if carb blocking is responsible, a single dose might not work very well. Furthermore, in this study, lean rats experienced an even greater reduction in IL-6 and TNF-alpha levels than obese rats.
I am curious whether enzymatically reducing cherry sugars would make them even more effective.
So that's why people put cherries on their ice cream sundaes.
Another example of folk wisdom.
1.5 cups a day seems like a lot. On the other hand, I probably eat that much per day in cranberries.
What we need: feed the rats different pure flavonoids and other compounds one or a few at a time to try to trace down which compounds are causing the effect. Also, of course try with different berries and cherries to see if tart cherries are most potent.
Recall my recent comments about the USDA Procyanidin Database:
That USDA Procyanidin Database makes for interesting reading (at least to me). Raw pinto beans are up there with unsweetened chocolate in terms of procyanidin antioxidants and you can eat a lot more pinto beans than chocolate. But cooked pinto beans have about 2 orders of magnitude less of the good stuff. Is that accurate? Blueberries and cranberries are excellent sources. Ditto hazelnuts, pecans, and pistachios. Sorghum is highly excellent. I had no idea. But that's typically cooked. Whereas you can eat the berries and nuts raw. My advice: eat the berries and nuts.
Maybe nuts and berries will keep off weight. You think?
I am not sure that the anti-digestive effects of various phytonutrients are separable.Combinations probably produce nonlinear interractions. According to the study, the tart cherries they used are highest in anthocyanin content. Since cherries have such a low glycemic index, my bet is that they contain carb enzyme inhibitor. The literature indicates that many phytonutrients interfere with digestion of proteins, carbs and fats.
For instance, tea polyphenols inhibit a set of such enzymes.
"Effects of tea polyphenols on the activities of α-amylase, pepsin, trypsin and lipase"
Bean tannins inhibit protein digestion.
"Dry bean tannins: A review of nutritional implications"
Persimmons may both inhibit carb digestive enzymes and nonenzymatic glycation.
"Inhibitory Activities of Proanthocyanidins from Persimmon against Oxidative Stress and Digestive Enzymes Related to Diabetes"
Phytic acid (available as the supplement IP-6, aka inositol hexaphosphate, or from sesame seeds) also inhibits carb digestion, and BTW, also chelates metals.
"The effect of phytic acid on in vitro rate of starch digestibility and blood glucose response"
You may find the following interesting also:
"Suppressive Effect of a Hot Water Extract of Adzuki Beans (Vigna angularis) on Hyperglycemia after Sucrose Loading in Mice and Diabetic Rats"
"The effects of sorghum proanthocyanidins on digestive enzyme activity in vitro and in the digestive tract of chicken"
"Chestnut Astringent Skin Extract, an α-Amylase Inhibitor, Retards Carbohydrate Absorption in Rats and Humans"
"Inhibitory effect of pine extract on alpha-glucosidase activity and postprandial hyperglycemia"
Also note that food preparation, even chewing has a major impact on digestibility.
"Measurement of resistant starch: factors affecting the amount of starch escaping digestion in vitro" http://www.ajcn.org/cgi/reprint/56/1/123.pdf
Here is an unbiased review of the benefits and risks of plant polyphenols:
"Toxic and anti-nutritional substances: Phenolics and antioxidants"
Regards glycemic index and cherries:
1) Fructose does not elicit an insulin response.
2) Fruits have lots of fructose and not so much glucose.
So is there really an additional effect from compounds inhibiting sugar uptake? If so, I'd expect more flatulence as bacteria feasted on what didn't get absorbed.
A good theory.
Setting aside the desiccated fruits (dates, raisins, figs, and prunes) which have much higher fructose/weight ratios because the drying process removes water, only pears and grapes have a higher fructose content. See the table at:
"Triglycerides-Lowering Diet: What About Fructose?"
Most of the other fruits have only a modestly lower fructose content, yet cherries have a substantially lower glycemic index. See the "Glycemic Index of Fruits and Fruit Juice" at:
Note that pears and grapes (as well as some of the dried fruits) have a much higher GI than cherries.
So I am not convinced that your theory is right.
Lou, the GI index for cherries you found was for sweet cherries, not the tart cherries in the UM study. Any idea if that makes a difference? Tart cherries probably are rather lower in sugar content - it's hard to find them in a dried form without added sugar, because they're so tart.
The site to head for when it comes to GI is glycemicindex.com. Choose Database. Then type in cherries. I get two hits. Some Canadian cherries get 22 GI. But some Australian cherries get 63 GI. You can also search on cherry. That gives mostly foods that contain cherry as a flavoring. Even the"Fromage Frais, red fruit: red cherry (Healthy Living)" is a cheese.
Also see Rick Mendosa's GI list. Neither list has blueberries.
That reducetriglycerides.com link has a much shorter sucrose than fructose list. So we are left not knowing how much sucrose is in these various fruits that have differing GI values. I would expect GI to vary as a function of sucrose most of all. Though if the fruits have digestible polysaccharides they will contribute as well.
The GI tables seem to be inconsistent - probably there is no consistent measurement methodology.
Only looking at cherries' fructose content, you would expect the diet to worsen cardiac risk factors, contrary to what the study found. I do believe that certain phytonutrients impede carb digestion.
I will try to get a copy of the paper for more detail.
There is a product called "Plevalean" which is made of ground beef and tart cherries.
I'll bet this report boosts sales.
As any wine maker knows, the sugar content and acidity of fruits can vary drastically from one year to the next or from one location to the next due to relatively small differences in weather during the growing season. Even if two vines receive the exact same amounts of rain and sun, different distributions or patterns of rain and sun can make a big difference.
Getting consistent GI measurements for fruit will be impossible simply due to variations in sugar from year to year even in the same plant.