In a related study, extracts of cloves also were found to improve the function of insulin and to lower glucose, total cholesterol, LDL and triglycerides in people with type 2 diabetes. Earlier studies had shown these positive effects in laboratory studies; the study presented at Experimental Biology provides the first evidence of these beneficial effects in humans taking the equivalent of one to two cloves per day.
Earlier studies in the laboratory of one of the co-authors of all these papers, Dr. Richard A. Anderson, Beltsville Human Nutrition Research Center, United States Department of Agriculture, had shown that the equivalent of a quarter to half a teaspoon of cinnamon given to humans twice a day decreased risk factors for diabetes and cardiovascular disease, including glucose, cholesterol and triglycerides, by 10 to 30 percent. These new studies showing cinnamon's ability to block inflammation extend our understanding of the potential for the spice, says Dr. Anderson. As an anti-inflammatory agent, cinnamon may be useful in preventing or mitigating arthritis as well as cardiovascular disease. And as scientists increasingly understand the relationship between inflammation and insulin function in Alzheimer's (causing some to refer to the neurodegenerative disease as "type 3 diabetes"), cinnamon's ability to block inflammation and enhance insulin function may make it useful in combating that disease as well.
The cinnamon and clove studies presented April 4 at Experimental Biology 2006 in San Francisco are part of the scientific program of the American Society for Nutrition, Inc. The three studies are:
- Dr. Heping Cao of the Beltsville Human Nutrition Research Center and colleagues, including Dr. Anderson, investigated the biochemical basis for the insulin-like effects of cinnamon. Results showed that cinnamon, like insulin, increases the amount of three critically important proteins involved in the body's insulin signaling, glucose transport, and inflammatory response. Dr. Cao says the study provides new biochemical evidence for the beneficial effects of cinnamon in potentiating insulin action and suggests anti-inflammatory properties for the antioxidants in cinnamon. Other researchers involved in the study are Dr. Marilyn M. Polansky of the USDA-ARS Beltsville (Maryland) Human Nutrition Research Center, and Dr. Perry J. Blackshear of the National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina.
- Dr. Stephanie Mae Lampke, University of California, Santa Barbara (UCSB), and colleagues, used fractionation and electrospray mass spectrometry to identify the chemical structure of active ingredients in cinnamon. She worked with UCSB's James Pavolich and Donald Graves. This study provides information on how cinnamon works. Working with Dr. Lampe, Dr. Anderson, and Dr. Polansky (also involved in the paper above) were members of the USDA BHNRC. Research was supported in part by a grant from Cottage Hospital, Santa Barbara, to Dr. Graves.
- Dr. Alam Khan, Agricultural University, Peshawar, Pakistan, a former postdoctoral student and Fulbright Fellow in the Anderson laboratory, reports the first study of the effect of cloves on insulin function in humans. Thirty-six people with type 2 diabetes were divided into four groups, which then took capsules with either 0, 1, 2, or 3 grams of cloves for 30 days. There were no significance differences in responses among the three levels of cloves used – but there were markedly significant differences between those who took cloves and those who did not. At the end of the 30 days, individuals with diabetes who had been taking some level of clove supplementation showed a decrease in serum glucose from an average 225 to 150 mg/dL, triglycerides from an average 235 to 203 mg/dL, a decrease in serum total cholesterol from 273 to 239 mg/dL, and a decrease in LDL from 175 to 145 mg/dL. The individuals with diabetes who had not been taking clove capsules showed no differences. Serum HDL was not affected by consumption of cloves.
The people with diabetes who had been in the experimental group then were taken off clove supplementation and, after 10 days, their glucose, triglycerides, total cholesterol and LDL measured. Although these had begun to rise somewhat, all remained significantly lower than at the beginning of the study. Dr. Khan says the finding that intake of 1 to 3 grams of cloves per day lowered risk factors of diabetes without changing HDL concentration suggest strongly that cloves are beneficial for people with type 2 diabetes. Co-authors of the study in addition to Dr. Khan and Dr. Anderson are Dr. Syed Saceed Qadir, Agricultural University, Peshawar, Pakistan, and Dr. Khan Nawaz Khattak, HMC, Hayatabad, Peshawar, Pakistan. The research was supported by the Higher Education Commission of Pakistan.
The effect of cinnamon is a major research interest in Dr. Anderson's laboratory, where human studies are now taking place looking at how this ingredient can improve insulin functioning in women with polycystic ovary syndrome (a disease of insulin sensitivity in which perturbed hormone levels cause difficulty in getting pregnant, among other problems), people with type 2 diabetes and the prediabetic metabolic syndrome; and people who are very obese (because Dr. Anderson believes that improving insulin function will lead to improvements in weight and lean body mass).
A post doctoral fellow in the Anderson laboratory also is beginning to investigate whether improving insulin functioning will decrease the chance of developing Alzheimer's disease.
Two final bits of advice from Dr. Anderson: First, eating great quantities of cinnamon straight from the can is not a good idea. Table cinnamon is not water soluble, meaning it can build up in the body with unknown consequences. Second, the powered cinnamon has another limitation. Dr. Anderson's personal 60-point decline in total cholesterol occurred only after he switched from sprinkling cinnamon on his breakfast cereal to taking it in a capsule. Saliva contains a chemical harmful to cinnamon.