Pearls of Wisdom: Dietary Interventions for Diabetes

Question: Albert is a 56-year-old man with diabetes and a hemoglobin A1c level of 7.2% on maximum doses of a sulfonylurea and metformin. He has attended a series of educational sessions with a certified diabetes educator and has consulted a dietitian to better manage his diabetic diet. He also exercises 210 minutes a week, including jogging for 30 minutes a day.

The goal is to maintain his A1c at less than 7.0%, but Albert would rather not add an additional medication, nor does he want to switch either of his current medications, which have successfully lowered his A1c from 8.9% to 7.2%.

Which dietary intervention might bring him to his A1c goal?

A. Chinese oolong tea
B. Probiotics
C. Eicosapentaenoic acid supplements
D. Switching to a high glycemic index diet

What is the correct answer?
(Answer and discussion on next page)

Louis Kuritzky, MD, has been involved in medical education since the 1970s. Drawing upon years of clinical experience, he has crafted each year for almost 3 decades a collection of items that are often underappreciated by clinicians, yet important for patients. These “Pearls of Wisdom” often highlight studies that may not have gotten traction within the clinical community and/or may have been overlooked since their time of publishing, but warrant a second look.


Answer: Chinese oolong tea

Albert is the type of patient that makes our job much easier. He is adherent with his medication regimen, he exercises beyond the minimum amount required for maintenance of cardiovascular health, and he has shown initiative to learn more about his diabetes by attending educational sessions with a certified diabetes educator and consulting a dietitian. As a result, he has drastically improved his dysglycemia.

Although it would not be inappropriate to add another pharmacologic agent at this time, even a small dose of a dipeptidyl peptidase-4 inhibitor would probably easily bring him below the American Diabetes Association's 2016 recommended goal of less than 7.0%. This would also increase his risk for hypoglycemia, add complexity to his regimen, and increase expense.

A Supplement to Consider

Chinese oolong tea to the rescue. I do not claim to be a tea expert, but am told that green tea, oolong tea, and black tea all come from the same tea plant and actually reflect the degree of fermentation. Green tea is not fermented, while oolong tea is partially fermented, and black tea is fully fermented. There is even a difference between Chinese and Taiwanese oolong. Reportedly, Chinese oolong tea has more polymerized polyphenols than the Taiwanese variety due to differences in fermentation. So, what difference might ingestion of Chinese oolong tea make?

Why Chinese Oolong Tea?1



A study by Hosoda et al1 included Taiwanese participants (N=20) with diabetes who were on either a sulfonylurea (n=11) or a sulfonylurea plus a biguanide (n=9). The participants were randomly assigned to consume either 1500 mL of tea or water daily for 30 days, with each group then crossing over to the comparator regimen. The participants were allowed to drink Chinese oolong tea but were restricted from consuming any other tea varieties.

The instructions for brewing the tea were explicit: Place 5 teabags (or 15 g of tea leaf) in 1500 mL of boiling water and steep for 10 minutes. The Chinese oolong tea (or water) was to be consumed 5 times daily in 300-mL servings each time.

The Results

During ingestion of Chinese oolong tea, participants' fasting glucose levels declined from 229 mg/dL to 162 mg/dL, whereas during ingestion of water (the placebo control), no change was reported.

What’s the “Take Home”?

This is a small study, yet it was published in one of the most respected journals in the world—Diabetes Care, the primary publication of the American Diabetes Association. It certainly doesn’t seem unreasonable to consider a trial inclusion of Chinese oolong tea for persons who wish to modify dysglycemia without the addition of further pharmacologic agents—and really, what do you have to lose?


1. Hosoda K, Wang M-F, Liao M-L, et al. Antihyperglycemic effect of oolong tea in type 2 diabetes. Diabetes Care. 2003;26(6):1714-1718.