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Antioxidants May Help Reduce Diabetes Risk

Study shows high carotenoid serum concentration may prevent development of type 2.

Diabetes is a global health problem. According to the World Health Organization, diabetes is estimated to affect 25.8 million Americans and 346 million people worldwide. The risk factors of developing type 2 diabetes include diet, sedentary lifestyle, body mass index, and genetics. Consistently eating fruit and vegetables can help people maintain healthy body weight. Other than that, a new study published in BMJ Open Diabetes Research & Care reported Japanese people with high carotenoids serum concentration showed low risk of developing type 2 diabetes.

This study conducted in Japan tried to assess the relationship between antioxidant vitamins like carotenoids and the development of type 2 diabetes. Many fruits and vegetables contain high carotenoids such as carrots, cantaloupe, sweet potato, and kale. In the previous study, oxidative stress was linked to the cause of type 2 diabetes, because reactive oxygen species produced by oxidative stress causes the development of insulin resistance, beta-cell dysfunction, and impaired glucose tolerance. Therefore, researchers suggested consuming antioxidant food should help people fight against the development of type 2 diabetes.

This was a population-based prospective survey and a follow-up study from the Mikkabi prospective cohort study. 910 participants ages 30 to 79 years were included in the follow-up study between 2003 to 2013. After excluding participants with diabetes or with a history of diabetes, a total of 264 male and 600 female patients were included in the final results. Researchers found that carotenoids concentration at baseline survey included lutein, lycopene, alpha-carotene, beta-carotene, beta-cryptoxanthin, and zeaxanthin. Participants’ heights, body mass index, and blood pressure were recorded during the study. On the other hand, participants were required to fill out a self-administered questionnaire used to collect information about their chronic disease, medication, lifestyle, and dietary intake.

Results showed that a total 55 participants (22 males and 33 males) developed diabetes during 7.8 years of follow-up. After adjusting for age, sex and BMI, people with the highest groups of serum alpha-carotene, beta-cryptoxanthin and total provitamin A carotenoids showed significantly lower incidence of type 2 diabetes. Other carotenoids like beta-carotene, lutein, lycopene, and zeaxanthin showed the tendency to fight against the development of diabetes, but those results were not statistically significant in the study.

The study further concluded that a diet with a high content of alpha-carotene and beta-cryptoxanthin protected the development of type 2 diabetes in middle-aged and older Japanese. They also pointed out some limitation of this study. For example, researchers did not access the role of other antioxidants like vitamins C and E in the development of diabetes in participants, and the numbers of participants was not large. Therefore, further studies are needed to draw a definitive conclusion.

Although the conclusion of this study focused on Japanese population, similar conclusions had been made in studies conducted in the United States. A study published in Nutrition Research in 2014 collected data from the National Health and Nutrition Examination Survey 2003 to 2004, which showed people eating fruit and vegetables that were enriched in carotenoids could reduce the toxicity of persistent organic pollutants, such as polychlorinated biphenyls. Polychlorinated biphenyls could be found in food, soil, and air, and it was one of the causes of oxidative stress, which led to type 2 diabetes.

In another study published in Diabetes Care,  people whose diets had the highest levels of vitamin E were found to be 30% less likely to develop type 2 diabetes than those who ate the least amounts of the antioxidant.  In addition, researchers found that people who ate a lot of carotenoids, a type of antioxidant found in colorful fruits and vegetables, also had a lower risk of developing type 2 diabetes.

But the study showed one of the most popular antioxidants, vitamin C, seemed to offer no protection against the disease.  In the study, researchers looked at the antioxidant content of the diets of more than 4,000 men and women between the ages of 40 and 69 who were free of diabetes at the start of the study. Specifically, they tracked the amount of vitamin E, vitamin C, carotenoids, and other forms or derivatives of vitamin E, such as tocopherols.  After 23 years of follow-up, the study showed that people who consumed more vitamin E and carotenoids had a lower risk of type 2 diabetes compared with people who consumed lower levels of the antioxidant, but no such effect was linked to vitamin C intake.

In the United States, fast food and high -sugar-containing foods are popular at the dinner table. The finding of this study should encourage people to add more foods that are rich in carotenoids to help deter the development of type 2 diabetes.

Practice Pearls:

  • A follow-up cohort study of Japanese participants accessed the association of high serum carotenoids and the risk of development of type 2 diabetes.
  • The results showed the higher concentration of alpha-carotene, beta-cryptoxanthin and total provitamin A carotenoids was linked to the lowest risk of type 2 diabetes.
  • In the United States, foods that had high carotenoids also helped people reduce the risk of diabetes.

WHO. [Accessed January 3, 2014];Diabetes Programme Facts and Figures. 2011. <http://www.who.int/diabetes/facts/en/>

Sugiura M, Nakamura M, Ogawa K, Ikoma Y, Yano M. High-serum carotenoids associated with lower risk for developing type 2 diabetes among Japanese subjects: Mikkabi cohort study. BMJ Open Diabetes Research Care 2015.

Hofe CR, Feng L, Zephyr D, Stromberg AJ, Henning B, Gaetke LM. Fruit and vegetable intake, as reflected by serum carotenoid concentrations, predicts reduced probability of PCB-association for type 2 diabetes: NHANES 2003 -2004. Nutrition Research. 2014 Apr:34(4); 285-293.

Montonen, J. Diabetes Care, February 2004; vol 27: pp 362-366.