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November 28, 2013
What if you could eat all you wanted at Thanksgiving dinner? A new in vitro study in the journal Food Chemistry may give you a good excuse. Researchers from Poznan University of Life Sciences in Poznan, Poland have found that cranberries reduce the generation of fat cells and make those cells slimmer as well.
“These results are the first to point out the anti-adipogenic properties of cranberries,” said Katarzyna Kowalska, lead author of the study and a PhD student at Poznan University. “Generally we should eat fruits and vegetables, but it’s good to know which of them exhibit anti-adipogenic properties.”
Cranberries grow wild throughout the marshy New England coast and were a staple of native Wampanoag cooking; they were likely an ingredient in the first Thanksgiving feast. For years, researchers have known that cranberries are packed with healthful compounds, from vitamins to minerals to polyphenols, and have investigated cranberries’ effect on numerous human conditions, such as urinary tract infections and cardiovascular disease. But Kowalska was curious about whether they had any effect on fat, so she and her team gathered Polish cranberries, Vaccinium oxycoccos, small, pale pink berries with a sharp acidic flavor.
The researchers added varying concentrations (0–50 mg/ml) of a solution made from freeze-dried, powdered cranberries dissolved in complete cell culture medium to mouse embryo 3T3-L1 preadipocytes, which are destined to become fat cells. After 48 hours, they saw an effect: preadipocyte proliferation slowed and the cells became less viable in a concentration-dependent manner.
Kowalska and colleagues then stimulated differentiation of the preadipocytes into mature adipocytes and found that high doses of the cranberry solution reduced the viability of mature adipocytes and also increased production of reactive oxygen species (ROSs) known to play a role in apoptosis.
Additionally, when the cranberry solution was added to preadipocytes actively maturing into adipocytes, cell number, viability, and metabolic activity dwindled depending on the cranberry concentration. The resulting adipocytes also contained less fat. Cranberries stimulated lipolysis in mature adipocytes as well, depending on concentration and also appeared to inhibit lipogenesis in the first place.
The molecular mechanism for how this happened was unclear, so using real-time PCR, the team examined the expression of transcription factors (PPARgamma, C/EBPalpha, SREBP1) thought to be involved in the regulation of adipocyte differentiation and found that the cranberry solution suppressed expression of those genes in differentiating preadipocytes.
So which one of the many biologically active compounds in cranberries was at work here? The researchers theorize that quercetin may play a role. Cranberries contain as much as 25 mg quercetin per 100 g of fresh fruit, and other studies have shown that the compound prevents proliferation and can induce apoptosis in 3T3-L1 cells. Previous research has also shown that quercetin interferes with adipogenesis by interacting with the transcription factors mentioned above. Anthocyanins, another group of compounds in cranberries, have also been shown to inhibit proliferation of preadipocytes and adipocytes. More likely, said the authors, is that the many polyphenols in cranberries work together.
The researchers emphasize that they need to conduct animal and clinical studies to know for sure whether cranberries’ effects will extend beyond the lab. But, for now, enjoying a bit of the berries in your stuffing or salsa can’t hurt. Stay away from sauces with lots of sugar, however.
“The best will be fresh fruits or frozen fruits or low caloric juice,” said Kowalska. “Probably once we add sugar to cranberries, we change the anti-obesity power of this fruit.”
Kowalska K, Olejnik A, Rychlik J, Grajek W. Cranberries (Oxycoccus quadripetalus) inhibit adipogenesis and lipogenesis in 3T3-L1 cells. Food Chem. 2014 Apr 1;148C:246-252
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