But there are some foods and nutrients, such as dark chocolate and magnesium, that warrant further investigation, Dr Michael Quon, chief of the diabetes unit of the US National Center for Complementary and Alternative Medicine (NCCAM) told NutraIngredientsUSA.com.
Dr Quon recently presented the findings of a NCCAM study on high-dose oral vitamin C, shown to improve endothelial dysfunction in diabetes patients when given intraarterially.
The researchers had hypothesised that high dose vitamin C supplements could also have this effect and in turn improve insulin resistance (endothelial dysfunction has been shown to contribute to insulin resistance).
But while Quon's team are still analyzing the data, presented at the American Diabetes Association's scientific sessions last week, he said that "it doesn't look like the dose of vitamin C that we used could improve either of these parameters".
However the initial findings will prompt further investigation.
"We found that vitamin C levels in people with diabetes are extremely low. But with high doses, their vitamin C levels did not improve as much as they would have in normal people."
"The findings are consistent with studies showing that oral vitamin C is not really effective [on diabetes-related conditions] but it may be that these patients have a defect in vitamin C handling. We want to investigate this further," added Quon.
The researcher is also planning a trial to evaluate the effects of epicatechins in dark chocolate, which have shown 'intriguing' effects, and magnesium.
Other studies being wholly or partly funded by NCCAM are looking at gingko biloba, chromium and the safety of glucosamine, which can cause insulin resistance in high doses.
The significant research in this area suggests that "there is quite strong interest and at least some evidence that warrants further investigation", noted Dr Quon.
"If there is public interest, it is in the government's interest to invest in the research."
He added that while practitioners "don't object to supplements that aren't harmful, we would like to recommend things that have proven efficacy."
Supplement makers have to be careful however when marketing to diabetes patients, noted Victor Ferrari, chief operating officer and executive vice president at Horphag Research, maker of Pycnogenol. The pine bark extract has been shown in studies to offer heart health benefits, including lower bad (LDL) cholesterol, reduce platelet activity, relax artery constriction and improve circulation.
"The difficulty is how we position ourselves in a disease environment. We don't want to compete with drugs and are clearly a food supplement. But there are claims that can be proved for diabetes management," said Ferrari.
He noted that there are "lots of aspects regarding daily issues, such as blood sugar control. Improved circulation is also high on our target list."
Chromium supplements company Nutrition 21 has also focused closely on diabetes management and is currently recruiting patients for a major trial on the benefits of its chromium picolinate in blood sugar control.
Better safety and efficacy data will certainly help a wide range of supplement makers, not only in the US, target a sizeable market. While diabetes has increased rapidly as a result of rising obesity, it is also increasing in areas with an ageing population. There are currently more than 194 million people with diabetes worldwide but if nothing is done to slow the epidemic, the number will exceed 333 million by 2025, according to the International Diabetes Federation.