Although results of the above study are interesting, a closer look shows several weaknesses in the findings.
- The study investigated only a very small number of people with type 2 diabetes, and most were male. This makes it difficult to apply the study findings to everyone with type 2 diabetes.
- The effect of vitamin C supplementation alone cannot be determined, because people were already being treated with different diabetes medicines, heart medicines, or lifestyle treatments.
Interestingly, the researchers found that glycated haemoglobin (HbA1c) levels did not improve with vitamin C supplementation.
The HbA1c level is important because a result of 48 mmol/mol (6.5%) or more can suggest a diagnosis of diabetes, and it can help track long-term blood sugar control.2
The authors suggested that this result may have been because the 1-month washout period was too short, meaning that vitamin C may still have had an effect in participants switched to placebo (and vice versa).
It is thought that damage to the body’s cells and tissues caused by substances known as free radicals may lead to the development of type 2 diabetes.1 Vitamin C is an antioxidant which is thought to have a protective role in diabetes by reducing the damage caused by free radicals.1,3 There are other ways you can reduce damage from free radicals, for example , not smoking and limiting alcohol intake.
More research studying a larger number of people is needed to determine whether people with type 2 diabetes can benefit from vitamin C supplements.
Initially, type 2 diabetes can often be managed with lifestyle changes such as healthy eating and regular exercise. Most people with type 2 diabetes will also need oral prescription medicines and many will eventually require insulin.4 Type 2 diabetes needs to be managed effectively to prevent complications.
If you are thinking about starting a vitamin C supplement or any other new medicine, including complementary medicines, we recommend that you talk to your GP or diabetes educator.