Can Green Tea or Garlic Prevent Diabetes, Prediabetes?

Could drinking green tea and adding garlic reduce your risk of prediabetes and diabetes? Two recent studies—one on green tea and the other on aged garlic—found that extracts from these foods may be beneficial to individuals who have diabetes or who are at risk for developing the disorder.1,2

But don’t run out and buy green tea extract or garlic extract just yet! If they offer any health benefits, the best result occurs when they are taken along with other strategies, experts say.

 “Everybody wants that one-pill fix,” says Sherri Findley, MS, RD, a dietitian at University of Florida Health Shands Hospital in Gainesville, Florida, “Of course, it’s tempting to take a product and hope it will prevent these diseases.”

Findings of AntiDiabetes, Obesity Properties  

Small study suggests that garlic supplements improve glucose control, lessening diabetes risk.In the recent clinical trial on aged garlic extract that focused on adults with obesity,1 researchers focused on whether daily supplements of aged garlic extract might reduce inflammation and improve immune function. The results are promising given some evidence that taking aged garlic extract (3.6 grams) might improve blood cholesterol levels and have a favorable effect on the immune system.1

In a second study, also published in the journal Clinical Nutrition ESPEN, 120 women who were overweight (body mass index >24) were assigned to consume green tea extract (1 gram), metformin, or green tea with metformin.2 The evidence suggested that green tea extract outperformed metformin in terms of improving blood sugar control in women who did not have diabetes but were overweight and therefore considered at risk for developing the condition. 

Such Small Studies Only Offer a Bit of Hope, for Now

A small study suggests that green tea may help reduce the risk Angela Fitch, MD, FACP, associate professor and vice president of primary care at University of Cincinnati College of Medicine/UC Health in Ohio, says that the catechins in green tea do provide health benefits. “We know that these catechins can help with blood sugar regulation,” she says.

It is still unclear whether either of these extracts could prove useful in managing glucose in people with diabetes. Nearly half of all Americans have diabetes, or prediabetes,3 which is a condition that causes blood glucose levels to rise above normal but not high enough for a diagnosis of diabetes. Individuals with prediabetes, who are at risk of developing diabetes as well as cardiovascular disease,4 are often advised to make changes to their diet and to try to lose weight as the best way to reduce the risks associated with diabetes and cardiovascular disease.

While results from the two studies offer some promise of health benefits, it is important to keep in mind that they both involved a small number of people and that if the same research was conducted with larger numbers of subjects, the findings might end up being quite different, Dr. Fitch says. “The two studies show a benefit, but if we repeat these studies with 10,000 patients, they may show no connection between the extracts and improvements in diabetes symptoms,” she says.

Ms. Findley says taking aged garlic extract would not be a part of her current recommendation for obesity-related disease states including diabetes. “There is some evidence that these foods might be useful for concerns about heart disease and cholesterol levels,” says Dr. Fitch. 

Go with Known Strategies for the Greatest Benefits

While green tea extract and aged garlic extract may be helpful in reducing the risk of developing diabetes or prediabetes, it makes more sense to embrace more proven and sure measures as well, the experts say.

Here are a few things to try.

  • A little less weight matters most.  “Losing just five to 10 percent of your body weight is shown to reduce the risk of developing type 2 diabetes by 50 percent,” Fitch says.
  • Move a bit more. Physical activity—even walking—is a wonderful way to prevent the development of prediabetes, or diabetes, Findley says. “It’s a sure way to get the cells, the insulin, and your blood sugar to talk to each other better,” she says. Try to get in some form of activity, such as walking or Zumba, for at least 30 minutes on most days of the week, she says. Or use a walking app for motivation to track your steps; and, aim for 10,000 steps daily.
  • Pay attention to meal frequency, Findley says. What you eat and how often will have the greatest influence on your body weight, and ultimately your blood sugar levels. If you can, have a bigger breakfast and lunch and a smaller dinner. Others find it better to skip lunch and have a grain-free dinner most easily manage their weight and blood sugar.
  • Focus on protein. Add a bit of protein to every meal and snack to help keep your blood sugar stable. Spread some peanut butter on apple slices, or tuna salad on cucumber rounds for a snack, or top whole grain crackers with a slice of roast turkey. Nuts, hummus, and cheese sticks are also good sources of protein that can easily satisfy your hunger as part of a meal or just for a snack.
  • Avoid processed foods. Dr. Fitch says, “The more processed foods you eat, the more insulin resistance you will have. “And with insulin resistance, we effectively run out of insulin since we are using it up so fast. The more we use those cells in the pancreas to make insulin, the more tired they get.”
  • Increase Your Vegetables. “The Mediterranean diet is an excellent plan because it means eating more vegetables, not more whole wheat bread and cereal,” Dr. Fitch says, "If you can’t manage to eat at least eight servings of vegetables a day, try adding them into a smoothie for a good morning boost."

If you decide to take a supplement of either green tea or aged garlic extract, keep in mind that these pills are not regulated by the Food and Drug Administration, says Dr. Fitch. “You can’t be sure of the quality of the supplement you are taking,” she says. At the very least, be sure to look for products that carry the seal from independent testing labs such as, the USP, ConsumerLab, or NSF International, which offer some assurance that the ingredients have been evaluated.

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