Study under review: Cinnamon supplementation positively affects obesity: A systematic review and dose-response meta-analysis of randomized controlled trials.
With the increasing prevalence of obesity, interest in the potential slimming effects of commonly consumed plants and spices has been increasing. Plant species contain bioactive substances called phytochemicals that can have many distinct physiological effects, several of them positive in the context of modern chronic diseases. Examples of well-studied substances with bioactive properties contained in foods are curcumin (in turmeric), epigallocatechin-3-gallate (EGCG, in green tea), resveratrol (in wine), among others. These, along with a few more, are depicted in Figure 1.
For instance, EGCG has shown to attenuate body fat accumulation in mice by reducing the availability of dietary energy and increasing fat oxidation. Similar effects have been noted for curcumin and other dietary plant polyphenols, suggesting a possible therapeutic utility for the treatment of obesity and related diseases.
Phytochemicals, as their name suggests, are chemicals present in plants (“phyton” means “plant” in Greek). In the context of nutrition research, they are commonly referred to as compounds that have physiological effects on organisms that consume them. These compounds are classified by their chemical structure and include polyphenols, alkaloids, and carotenoids. Due to the wide range of plant species consumed by humans, many different types of phytochemicals are present in a mixed diet. Some data suggest that consumption of these chemicals in whole foods is better than in an isolated, supplemental form, due to interactions between them. As there are about 8,000 phytochemicals in whole foods, their effect should be studied also in the context of ingestion of a dietary mixture rather than only as an isolated supplement. It is very likely that their effect under normal dietary conditions differs from what is observed when studying isolated compounds. Finally, it is worth noting that some of these substances have been developed as defense strategies from plants to avoid being eaten, and therefore, can also be toxic. Hence, it is important to avoid lumping them together as beneficial for humans.
One commonly used spice that contains compounds with promising health effects is cinnamon. The cinnamon spice is obtained from the bark of different Cinnamomum species, and is rich in four characteristic compounds: cinnamic acid, cinnamaldehyde, eugenol, and coumarin. These have shown distinct properties in several systems. For example, eugenol and cinnamaldehyde have anti-inflammatory properties in vitro, as well as when given to animal models in some studies. These compounds also appear to have antimicrobial effects against some bacteria.
On the other hand, in the context of obesity and metabolic abnormalities (and in addition to it’s anti-inflammatory effects), there is also promising data to support cinnamon supplementation. In healthy participants, cinnamon supplementation has a positive impact on insulin sensitivity and glycemic control, which suggests its utility for obesity-induced insulin resistance. In addition, cinnamaldehyde can directly boost thermogenesis in human fat cells, and cinnamon extract can reduce lipogenesis, induce the browning of subcutaneous adipose tissue, and alter the composition of the gut microbiota and increase the integrity of the gut barrier.
Due to the aforementioned observations, cinnamon consumption (either as part of the normal diet as a spice or as a supplement) might be beneficial for the treatment of obesity. However, despite the amount of mechanistic and animal model data, studies in humans regarding bodyweight or fat mass have shown either a small or no effect compared to placebo. Therefore, the authors of the current study performed a systematic review and dose-response meta-analysis of available randomized controlled trials (RCTs) to assess the effects of cinnamon supplementation on bodyweight, body mass index, waist circumference and fat mass percentage in overweight and obese adults.
Compounds present in plants appear to have many different effects, some of which can be beneficial for modern chronic diseases, such as obesity. Cinnamon contains compounds that have shown anti-inflammatory, anti-hyperglycemic and anti-microbial properties, and studies in animal models using cinnamon extract have shown a reduction in fat mass and lipid accumulation, as well as beneficial effects directly on fat cells. However, studies in humans have found contradictory results and no study to date has summarized evidence on its effects on obesity in humans. Therefore, the study under review assessed the effects of cinnamon on bodyweight, body mass index, waist circumference and fat mass using data from randomized controlled trials.
Other Articles in Issue #54 (April 2019)
- ERD Mini: What’s magnesium good for?
- Investigating arginine for erectile dysfunction
- Does physical activity prevent depression or does depression prevent physical activity?
- A D-fence against cancer?
- ERD Mini: Folic acid intake and neural tube defects
- The (mild) health risks of energy drinks
- Peppermint oil soothes symptoms of irritable bowel syndrome