A healthy diet, exercise and certain medications are the cornerstones of diabetes prevention and treatment.
However, some herbs and supplements may also have potential benefits.
Interestingly, many of them have been shown to have anti-diabetic properties, including lowering blood sugar and improving blood lipids and insulin sensitivity.
This is a list of the most promising herbs and supplements for diabetes.
Turmeric is an herb that gives curry its yellow color. It contains a compound called curcumin, which has several medicinal properties, including anti-diabetic effects.
Studies have shown that curcumin has the ability to lower blood sugar levels. One recent study found that taking just 300 mg a day of highly purified curcuminoids decreased blood sugar levels by almost 18% (1, 2).
Another study of more than 200 prediabetics found that taking 1.5 grams of curcumin for 9 months improved beta-cell function and prevented the development of type 2 diabetes during the study (3).
Bottom Line: Turmeric is the spice that gives curry its yellow color. It contains an active compound called curcumin, which may lower blood sugar and decrease the risk of developing diabetes.
Ginger is a popular spice used in cooking and home remedies.
It may also improve some diabetes symptoms.
One study of 88 participants found that taking 3 grams of ginger daily for eight weeks reduced fasting blood sugar and HbA1c levels, which are a measure of average blood sugar levels over the past 2–3 months (9).
Lastly, evidence also suggests that the active compounds found in ginger can help prevent changes in proteins caused by high blood sugar. These changes can damage cells, nerves and blood vessels (16, 17).
Bottom Line: Ginger is a medicinal and culinary plant that may help moderate blood sugar levels, fight inflammation and prevent some negative outcomes of diabetes.
Cinnamon is a well-known supplement for diabetes. However, the evidence for its use is conflicting.
Many lab studies have shown that cinnamon may help improve insulin resistance, lower the absorption of glucose after a meal and fight inflammation. However, many large reviews of studies in humans have not found consistent results (18, 19, 20, 21).
Some studies show no significant effects, while others find improvements in fasting blood sugar, total cholesterol, "bad" LDL cholesterol and "good" HDL cholesterol.
Another problem with recommending cinnamon as a supplement for diabetes is that the two main types of cinnamon — Ceylon and Cassia — have varying effects. Moreover, neither has been studied well.
Some evidence suggests that Cassia cinnamon may be more effective at lowering blood sugar levels, and most studies in humans have used Cassia cinnamon or not specified which type was used (26).
However, Cassia cinnamon has a high content of coumarin, which has the potential to cause liver damage if taken in excess. Although current studies have not found this effect, they have been too small and too short to say for sure (27).
Therefore, if cinnamon is used as a supplement, Ceylon cinnamon is the safer choice.
Bottom Line: Cinnamon may improve blood sugar and blood lipid levels. However, the evidence is conflicting. It's also important to choose the right form of cinnamon.
Unfortunately, only a few studies have explored these effects in humans. Nevertheless, the results are encouraging.
One study in type 1 and type 2 diabetics found that simply consuming 100 grams of raw, red onion caused a significant decrease in high blood sugar levels in both types of patients when consumed with a meal that contained sugar (31).
While the evidence is only preliminary, adding onion to your diet appears to be an easy way to help keep your blood sugar levels under control.
Bottom Line: The use of onion to treat diabetes has not been extensively studied in humans. However, some evidence suggests that adding onion to your diet may help keep your blood sugar in check.
Black seed, or black curry (Nigella sativa), is the seed of a flower that has a history of use in traditional medicine.
A recent review of 23 human studies including over 1,500 participants found that black seed significantly reduced fasting blood sugar and HbA1c in more than half of the studies examined (42).
However, more research is necessary to confirm these effects and determine the appropriate dosage.
Bottom Line: Black seed or black curry is a seed that shows promise in improving blood sugar and blood lipid levels, as well as protecting the heart and liver from disease.
Fenugreek is an herb often used in cooking and home remedies for many conditions.
Studies on the use of fenugreek in diabetics have not been consistent, but a large review found that fenugreek significantly decreased fasting blood sugar, post-meal blood sugar, average blood sugar over 2–3 months (HbA1c) and cholesterol (47).
Other reviews have also found that fenugreek helped lower blood sugar, but just how much of an impact it has is not clear. One review found that fenugreek helped lower blood sugar by 17 mg/dl on average, which is relatively small (48, 49, 50).
Interestingly, fenugreek may help prevent diabetes in the first place. Another recent study found that daily supplementation of fenugreek over three years significantly reduced the number of people who developed diabetes during the study (51).
However, an upset stomach may be a side effect.
Bottom Line: Results have been inconsistent, but fenugreek may improve several different measures of blood sugar or even reduce the risk of developing diabetes. However, side effects may be a concern.
Aloe vera is a common house and garden plant that is also well known for its health benefits, perhaps most famously for soothing the pain of a sunburn.
However, it's currently being extensively studied for other uses as well, including as an oral supplement to improve symptoms of diabetes.
Reviews of recent studies have found that aloe vera can significantly reduce fasting blood sugar.
One study found that aloe vera reduced HbA1c, a measure of average blood sugar over the past several months, by 1.05%, which is very promising (52).
Bottom Line: Several reviews have found that aloe vera can help lower high blood sugar. However, more studies are needed to confirm its effectiveness and safety.
Berberine is a supplement derived from plants. It has long been studied for its anti-diabetic effects.
In one three-month study of 36 patients, berberine supplements were nearly as effective as metformin, a diabetes medication that helps control blood sugar levels.
In fact, berberine decreased HbA1c from 9.47% to 7.48%. Interestingly, less than 7.0% is well-controlled for diabetics and less than 6.0% is considered normal. It also decreased fasting blood sugar by 36% and post-meal blood sugar by 44% (61).
Unfortunately, berberine is very poorly absorbed, meaning the dosage is usually rather high. In one study, up to 34.5% of patients experienced side effects, including diarrhea, flatulence and stomach pain (57).
However, berberine appears to be effective and scientists are continuing to research ways to improve its ability to be absorbed.
Bottom Line: Berberine is a supplement that appears to be effective at lowering high blood sugar, blood lipid levels and inflammation. However, it is poorly absorbed and side effects may be common.
Several berries from the Vaccinium family, such as bilberries, blueberries and whortleberries, may help fight symptoms of diabetes.
Large observational studies have found that consuming berries is associated with a lower risk of developing type 2 diabetes (62).
A few studies in humans have also found promising results.
One study found that taking whortleberry extract three times per day for two months lowered fasting blood sugar by 16.3%, post-meal blood sugar by 13.5% and HbA1c by 7.3% (65).
Another study found that bilberry supplements significantly reduced post-meal blood sugar (66).
Also, drinking a blueberry smoothie for six weeks was found to improve insulin sensitivity in people with prediabetes (67).
While the evidence about berries and diabetes is still very preliminary, it does seem promising.
Bottom Line: A few small studies have found that berries from the Vaccinium family can help lower several measures of blood sugar levels. However, more studies are needed.
Chromium supplements for diabetes are controversial.
Unfortunately, most of the studies conducted in humans have been small or had significant design flaws, making their results unreliable (48).
Chromium may help lower blood sugar in people with diabetes, but more high-quality studies are needed to confirm its effectiveness and determine the proper form and dosage.
Bottom Line: Some evidence shows that chromium is effective at lowering blood sugar levels. Unfortunately, many of these studies were small and had design flaws, so stronger evidence is needed.
Researchers have recently learned that magnesium may play a role in diabetes.
While it's known that high levels of insulin can cause blood magnesium levels to decrease, that doesn't mean that supplementing with magnesium is beneficial.
However, one review including over 600,000 participants found that people who consumed the highest amounts of magnesium from their diets had a 17% lower risk of developing diabetes than those who consumed the least magnesium (71).
The same study found that for every 100-mg increase in dietary intake of magnesium per day, the risk of diabetes decreased by up to 13%.
This evidence is only observational, so it alone cannot prove that supplementing or increasing dietary intake of magnesium is beneficial. But it does demonstrate the importance of getting enough magnesium from your diet.
Furthermore, several reviews have also examined the effects of magnesium supplements.
However, it's not clear if magnesium supplements are beneficial for all people who have or are at risk of diabetes. It may only be beneficial to those who are not getting enough magnesium from their diet in the first place (72).
Bottom Line: Getting enough magnesium is important for controlling blood sugar levels in diabetics. However, magnesium supplements may only benefit those who have low magnesium blood levels.
Countless herbs and supplements have been studied for their possible benefits for diabetes, but most only have preliminary evidence behind them.
- Vitamin C: Vitamin C is an antioxidant that may fight inflammation and improve insulin sensitivity. However, the evidence is very contradictory, and it's unclear if it has any real benefit (74, 75, 76, 77).
- Coenzyme Q10: Coenzyme Q10, or ubiquinone, is an enzyme involved in the production of energy. Some preliminary evidence suggests it may fight oxidative damage and protect kidney and nerve function in diabetics (78, 79, 80).
- Coriander: Coriander, or cilantro, is a common herb. In the lab, coriander extract has inhibited enzymes that help break down complex carbs into sugars. It may also have antioxidant and lipid-lowering effects (81, 82, 83).
- Rosemary: Rosemary is a popular culinary herb with a wide range of health properties. It may benefit diabetics, but all studies to date have been conducted in test tubes or animals (84, 85, 86).
- Garlic: Garlic has well-documented anti-diabetic effects, including lowering high blood sugar and fighting inflammation. However, most of these effects have only been studied in animals (87, 88, 89, 90).
Bottom Line: Many more herbs and supplements, including garlic, coriander and vitamin C, have properties that might be useful for diabetics. However, they have not yet been studied enough in humans.
Many herbs and supplements may benefit those with or at risk of diabetes. However, most need to be better studied in regards to safety, effectiveness and dosage.
While none of these options should be used to replace diet and lifestyle changes or medications, they may help improve some symptoms or risk factors for diabetics.
If you're thinking about trying herbs or supplements, talk to your doctor to determine how they can fit into your treatment plan. This is especially important if you are currently taking medications, which may need to be adjusted.
Lastly, because the US supplement market is not well regulated, do your research to ensure that you're buying from a reputable supplier.