"Dear Doctor: Can vitamin D help people with high-risk pre-diabetes avoid developing overt diabetes?"

From oregonlive.com/advice

By Dr. Keith Roach

DEAR DR. ROACH: I was diagnosed with prediabetes over 30 years ago. My parents had diabetes. I just turned 84, and my weight is 135 pounds. I am 5 feet and 3.5 inches tall.

I watch my diet and take four blood pressure pills, and my blood pressure is under control. My cholesterol is very low (my total cholesterol is 130 mg/dL) since I’ve been on 20 mg of simvastatin for over 30 years. I take berberine and other supplements to help keep my A1C level between 6.1% to 6.4%. I prefer not to add more medicine.

I also take bitter melon, alpha-lipoic acid, chromium, cinnamon, gymnema, and other supplements like vitamin D3, zinc and B12. What is your opinion? -- E.G.

ANSWER: It sounds like what you are doing is working since you haven’t developed diabetes. However, I can’t make any definitive statements on whether it’s one or more of your supplements that’s helping or whether it’s your healthy weight for your height.

Supplements are medicines. You are taking them, it seems, specifically to help prevent the development of diabetes. Of all the ones you mention, the one with the strongest evidence of benefit is vitamin D, which may help people with high-risk prediabetes prevent overt diabetes. The Endocrine Society recently published a guideline recommending it specifically for this purpose.

While I can find influencers and marketers who will tell you that these are all very helpful, the clinical trials on these tend to follow a pattern. Small trials suggest a large benefit, but larger and more rigorous studies show a much smaller benefit (or none). None of them are harmful in recommended doses, but I do think you may be wasting your money.

Good diet and exercise habits are probably the most critical for long-term prevention of diabetes. Getty Images Getty Images

You haven’t talked about your diet and exercise habits, which are probably the most critical for long-term prevention of diabetes. While 30 minutes of moderate exercise daily is a good rule of thumb for most people, if you want personalized information, you can talk to a diabetes educator or bring in a detailed food diary to a registered dietician/nutritionist. Both can help you sort out the truth from fiction and make recommendations. It’s a good investment.

https://www.oregonlive.com/advice/2025/07/dear-doctor-can-vitamin-d-help-people-with-high-risk-pre-diabetes-avoid-developing-overt-diabetes.html