A single ingestion of the active compound cinnamaldehyde increased energy expenditure by nearly four more calories over a 90 minute period compared to placebo. The researchers say cinnamaldehyde may offer a more tolerable thermogenic alternative to compounds like capsaicin found in chilli peppers.
Transient receptor potential (TRP) channels are located throughout the body and mediate sensations such as pain, taste and temperature.
TRP channels can be activated by natural compounds such as chilli peppers' capsaicin and previous animal studies have suggested this may impact energy balance and have an 'anti-obesity' effect. Capsaicin can increase metabolism in humans through sensory nerve stimulation.
The study published in Nature's journal Scientific Reports looked at whether the stimulation of other TRP channels using cinnamon's cinnamaldehyde would have an anti-obesity effect comparable to capsaicin.
In the exploratory clinical trial, scientists from the Nestlé Research Centre and University of Tokyo compared the impact of 1 mg capsaicin or 70 mg cinnamaldehyde and a cooling flavour (0.2 ml) in 200ml of tomato juice versus a placebo on TRP channels and energy expenditure.
They also compared the impact on activation of the sympathetic nervous system (SNS) due to proposed thermogenic effects.
A total of 16 healthy subjects received all the treatments and the placebo in a double-blinded randomised order. Energy expenditure, fat and carbohydrate oxidation, heart rate variability and blood pressure were measured in the 90 minutes following ingestion. Facial thermography was also used to track activation of the SNS.
A single ingestion of cinnamaldehyde significantly increased energy expenditure by 3.6 kcal over the 90-minute period of the experiment when compared to placebo. Capsaicin and cinnamaldehyde enhanced postprandial fat oxidation and increased nose temperature until 15 minutes after ingestion.
Cinnamaldehyde also increased the cheek and chin temperature, the facial thermography revealed. Heart rate variability analysis did not show any changes to the nervous system.
The participants also judged cinnamaldehyde to be less intense than capsaicin.
‘More powerful than capsaicin’
The authors concluded that cinnamaldehyde may be a more tolerable solution to improve thermogenesis via spicy ingredients than capsaicin.
"The present concentration of cinnamaldehyde (350 ppm) is in the range of its occurrence as a flavouring in food. Cinnamaldehyde potentially is more powerful than capsaicin at improving energy expenditure and fat oxidation through thermogenic effects.
"Even though the effect appears subtle, a cumulative approach (combining dietary, exercise and behavioural aspects) is believed to be the most efficient for sustainable weight loss or maintenance," they wrote.
They recommended further long-term studies to confirm the impact of cinnamaldehyde and explore other compounds that affect TRP channels on metabolism, insulin sensitivity and body weight.
Source: Scientific Reports
Published online, DOI: 10.1038/srep20795
“Effects of TRP channel agonist ingestion on metabolism and autonomic nervous system in a randomized clinical trial of healthy subjects”
Authors: S. Michlig et al.