What is Cinnamon?

Cinnamon is a spice found in the inner bark of trees from the Cinnamomum genus. There are two main species of these trees from which the two major types of cinnamon are derived: Cinnamomum zeylanicum, which produces ceylon (or ‘true’) cinnamon spice and Cinnamomum aromaticum which produces cassia (or Chinese) cinnamon spice. Ceylon cinnamon is indigenous to Sri Lanka and southern India whereas cassia cinnamon is grown in China (1,2).

What does Cinnamon Contain?

Many aspects of the cinnamon tree regardless of the species possess various compounds in varying proportions. However, it is the bark of the cinnamon tree which contains cinnamaldehyde in the highest proportions (1). The main constitutes of oil derived from the bark of ‘true’ cinnamon are trans-cinnamaldehyde (the main constitute), eugenol and linalool (1).

Cassia, unlike Ceylon cinnamon is very high in coumarins. Coumarins are a family of compounds to which the drug warfarin also belongs. Hence, ingesting high levels of cassia cinnamon can be dangerous due to its anticoagulant, hepatotoxic and potentially carcinogenic properties (1,2). As a result, taking cassia cinnamon as a supplement is not recommended as levels of 1 teaspoon per day or greater are over the recommended daily amount of coumarin per day (1).

Health Benefits of Cinnamon

Ceylon cinnamon has also been shown to exhibit effects on blood pressure, glycaemic control and blood lipid profile in both in vitro and in vivo. Most interestingly, some research on animals has suggested that supplementation with ceylon cinnamon may aid with weight loss, reduce fasting blood glucose, increase HDL (whilst lowering LDL) and increase insulin levels within the blood (1). The process by which Ceylon cinnamon can lower blood glucose levels is due to the spice reducing carbohydrate breakdown in the small intestine as a result of enzyme inhibition meaning blood glucose levels do not rise as highly. Furthermore, recruitment of GLUT4, a glucose transporter, into the membranes of cells (mainly adipose and skeletal muscle), glucose metabolism and the synthesis of glycogen are all promoted whilst liver gluconeogenesis is inhibited. All of these factors aid with lowering blood glucose levels. Additionally, insulin release and recruitment of insulin receptors are also stimulated. The overall effect is insulin sensitivity is much improved (2). In a recent clinical trial with 28 healthy human participants, ceylon cinnamon was associated with reductions in systolic and diastolic blood pressure, a reduction in LDL and elevation in HDL after three months. However, no changes in BMI, weight, waist or hip circumference were recorded. Such findings are similar to previous studies, yet it is possible that in diabetic patients, more benefit could be garnished from Ceylon cinnamon (3).

Essential oils from Ceylon cinnamon have also been shown to exhibit powerful antioxidant properties (1,4). Participants in studies have shown marked reductions in markers of oxidative stress such as lipid peroxidation level (LPO) whilst raising other biomarkers indicative of low oxidative stress including total antioxidant power (TAP) and total thiol molecules (TTM) (1).

Furthermore, ceylon cinnamon has been shown to inhibit the tau protein aggregation and filament formation associated with Alzheimer’s disease in vitro and in mice models which may mean it could be used as a preventative medication or therapeutic for the condition (1,4,5).

Ceylon cinnamon has also been shown to stimulate type I collagen production within the skin. Type I collagen is by far the most abundant form of collagen within the skin responsible for maintaining skin structure and also its function. Application of Ceylon cinnamon onto the skin may make skin appear fuller and younger, or at least delay the effects of ageing (6), as it has been shown that compounds within cinnamon can penetrate the skin (7). However, cinnamaldehyde is known to induce contact dermatitis in some individuals (7,8). In combination with its known antimicrobial and antifungal effects, it appears that Ceylon cinnamon may have a role in skin care (1).

If this wasn’t enough, ceylon cinnamon has also been shown to be an inhibitor of osteoclastogenesis, the process by which bone breakdown cells are produced, in vitro. Due to this property, Ceylon cinnamon may have be useful in treating patients with low bone density or osteoporosis (1,9).

In a study involving mice injected with melanoma cancer cells, it was shown that after 30 days of oral cassia cinnamon administration, tumour weight was approximately half in the treated group versus the control group. Levels of NFκB and AP1, transcription factors involved in melanoma gene activation, were shown to be decreased and the activation of their associated genes were also reduced leading to tumour apoptosis (10). Cinnamaldehyde has been associated with suppression of tumour growth by various different mechanisms in a range of human cancers including hepatocellular carcinoma and ovarian carcinoma (11).

Cinnamon as a Sports Supplement?

Metabolic syndrome is a prediabetic condition involving central obesity, hypertension, hyperglycaemia, and dyslipidaemia. It is thought that cinnamon supplementation may have a beneficial role when combined with high intensity exercise (12).

WNT5A is a growth factor which is secreted by some cells and can influence cell proliferation, behaviour, and survival. Generally, it is associated with fat accumulation and inflammation. In healthy patients, their adipocytes can also release SFRP5 which can keep the actions of WNT5A under control. However, in obese patients there are reductions in SFRP5 and hence more inflammation and fat accumulation can occur which can contribute to insulin resistance (12). A study involving female rats involved the induction of metabolic syndrome in the intervention group via the removal of the rats’ ovaries. This process successfully raised serum glucose levels, insulin resistance, LDL and visceral fat in the rats. However, after supplementation with ceylon cinnamon for 3 months, the rats who were also subject to an intense exercise regime showed the greatest reductions in the previously raised indicators of metabolic syndrome when compared with the rats receiving cinnamon supplementation or exercise alone. Interestingly, WNT5A was only reduced in the rats who received cinnamon supplementation and exercise, yet SFRP5 was increased in all groups regardless of their treatment (12).

With regards to injury, a study involving mice showed that topical application of Ceylon cinnamon extract led to accelerated wound healing compared with placebo. The mice were all given full thickness (into the hypodermis) 7mm diameter wounds via a surgical procedure. After 14 days, the two groups which received 1.5% and 3% Ceylon cinnamon extract had significantly smaller wounds than control groups as well as proceeded to the chronic phase of healing faster. It was however the rats which received 3% Ceylon cinnamon extract which, on day 14, had an average wound diameter of 2.2mm versus the placebo group which had an average injury diameter of 4.89mm (13).

In a small study analysing the anti-inflammatory properties of Ceylon cinnamon, it was determined that a 9-day supplementation period with cinnamon using 3g per day was effective at reducing muscle soreness in athletes who undertook weight training exercises to the point of failure. It was not shown however that cinnamon supplementation can improve sports performance (14).

Further Thoughts

Since ceylon cinnamon may improve insulin sensitivity, it may have a potentially beneficial effect on those taking creatine supplementation. It is known that creatine is better absorbed when taken along with carbohydrates since this can elevate insulin levels. Perhaps, supplementation of cinnamon may improve insulin sensitivity to the point at which creatine could be taken with less carbohydrates yet still be optimally absorbed. This may help athletes who are calorie restricting stick to their strict diets more easily. Whilst this is an interesting idea, it is important to note that most studies which have managed to demonstrate improvements in insulin sensitivity with cinnamon supplementation (not all have) have been in participants who already have issues with insulin sensitivity - this would not be the case with most athletes.

Whilst there has been little research to investigate the impact of cinnamon extract on the wound healing in humans, cinnamon extract applied topically may aid the healing of traumatic injury or tissue damage. This could be partly due to the anti-inflammatory properties or the ability to stimulate skin tissue which cinnamon possesses.

Conclusion

Cinnamon clearly has many interesting health benefits, yet the extent of many of them are still in the very early research stages. Overall, it is likely the supplementation with cinnamon is something that may improve the health of anyone taking it. With a view to cinnamon as a sports supplement, its inhibition of osteoclastogenesis is interesting, since prophylactic or therapeutic supplementation may allow elderly people to continue to remain active longer than would otherwise be possible. Plus, there may be a role for cinnamon supplementation in injured athletes to prevent losses in bone density. For those with diabetes or metabolic syndrome, the benefits shown from animal studies via the combination of endurance exercise and cinnamon supplementation are very promising. The potential for cinnamon to balance blood sugar levels could be beneficial for athletes to feel more energetic and ready for training sessions. The additional advantages cinnamon supplementation confers over exercise alone in animal models may transfer across to humans when that research is completed. Hopefully, this will further reinforce and boost the positive role exercise can have in improving the health of those with metabolic syndrome or diabetes. Finally, it is not surprising that some research already suggests that the anti-inflammatory properties translate to sports performance. If cinnamon supplementation can truly reduce muscle inflammation after intense exercise or improve wound healing, then it may be used by athletes to train harder more frequently which may then open doors to improved performance late down the line.

Sources

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