Answer:Many different supplements may help lower or control blood sugar in people with prediabetes or type 2 diabetes who experience hyperglycemia (when blood glucose rises higher than normal). These supplements are discussed below. More details about each, including dosage, drug interactions, potential side effects, and ConsumerLab.com's reviews of products on the market, can be found by clicking on the links.
Due to the seriousness of hyperglycemia, it is important to consult with your physician regarding use of these supplements.
Cinnamon supplements may modestly improve blood sugar in people with type 2 diabetes whose blood sugar is not well controlled with medication. In addition, one small study found that a branded cinnamon extract reduced fasting blood sugar by an average of about 10 mg/dL in prediabetic men and women with metabolic syndrome. Keep in mind, however, that only certain varieties of cinnamon have been shown to have this effect, and long-term safety studies have not been conducted.
Increased intake of magnesium from the diet and supplements has generally been associated with a decrease in the risk of developing type 2 diabetes — particularly among people with low intakes. Magnesium supplementation has been shown to insulin sensitivity in people with type 2 diabetes, and may lower blood sugar levels in people with prediabetes or metabolic syndrome.
Curcumin (from turmeric) may improve blood sugar levels, according to preliminary studies, and one study found curcumin to dramatically lower the chances of prediabetes in middle-aged, slightly overweight men and women with somewhat higher than normal blood sugar levels.
Alpha lipoic acid may improve insulin sensitivity and blood sugar control in people with type 2 diabetes, although it may only slightly reduce levels of glycosylated hemoglobin (HbA1c).
Chromium picolinate may help some people with type 2 diabetes decrease fasting blood glucose levels as well as levels of insulin and glycosylated hemoglobin (HbA1c). However, be aware that high doses may worsen insulin sensitivity in healthy people who are not obese or diabetic.
Several small, preliminary studies suggest that apple cider vinegar, taken as a liquid, may reduce the rise in blood sugar that occurs after eating, although it's not clear if it is beneficial to people with type 2 diabetes. Apple cider vinegar tablets and pills do not appear to have the same effect on blood sugar.
Having adequate blood levels of vitamin D may reduce the risk of insulin resistance in people who are obese. There is some evidence that a certain blood level of vitamin D is needed for normal glucose metabolism in women who are overweight and obese (but not diabetic), but it is not clear whether any further benefit is gained with higher blood levels.
In healthy people, consuming a moderate amount of extra virgin olive oil with a meal has been shown to reduce increases in blood sugar after the meal compared to the same meal consumed with corn oil. In people with type 1 or type 2 diabetes, olive oil may improve glucose metabolism.
Increasing dietary fiber, especially insoluble fiber from cereal and grains, is associated with a reduced risk of diabetes and has been shown to reduce fasting blood glucose and modestly lower HbA1c in people with type 2 diabetes (Martin, J Nutr 2008; Post,J Am Board Fam Med 2012). In people with type 1 diabetes, 50 grams of dietary fiber per day has been shown to significantly improve blood sugar control and reduce hypoglycemic events (Giacco, Diabetes Care 2000). The American Dietetic Association states that "diets providing 30 to 50 g fiber per day from whole food sources consistently produce lower serum glucose levels compared to a low-fiber diet. Fiber supplements providing doses of 10 to 29 g/day may have some benefit in terms of glycemic control." (Slavin, J Am Diet Assoc 2008). In people with type 2 diabetes, there is limited evidence that psyllium fiber can help. (Note: A concern with psyllium fiber supplements is that tests by ConsumerLab found many to have relatively high levels of lead, a toxic heavy metal. See the results in ConsumerLab's Psyllium Fiber Supplements Review, which includes more information about psyllium, its uses, dosage, and safety.)
Ginseng, both American and Korean Red ginseng (from Panax ginseng), may reduce blood sugar levels in people with diabetes, according to preliminary research.
Drinking whey protein before a high glycemic meal may help to lessen increases in blood sugar after the meal in people with well-controlled type 2 diabetes.
Silymarin, a component of milk thistle, may decrease blood sugar and hemoglobin A1c in people with type 2 diabetes, and reduce insulin resistance in people with coexisting diabetes and alcoholic cirrhosis.
Inulin, a type of prebiotic, may improve measures of blood sugar control in women with type 2 diabetes, although it did not improve blood sugar levels or insulin resistance in a study of prediabetic men and women.
Berberine (a compound found in plants such as barberry, Oregon grape and goldenseal) may reduce blood sugar levels in people with metabolic syndrome or type 2 diabetes, according to a few small studies.
Fenugreek may help to lower blood sugar, according to preliminary studies, and one study found fenugreek extract to significantly improve some measures of blood sugar control and insulin response in people with type 2 diabetes (Gong, J Ethnopharmacol 2016).
D-ribose, often promoted for energy or sports performance, may also lower blood sugar levels (Fenstad, Internet J Nutr Wellness 2007).
Gymnema sylvestre may decrease average blood sugar levels in people with type 1 or type 2 diabetes, according to two small, preliminary studies using 400 mg of a standardized extract (GS4 from Sabinsa, standardized to 25% gymnemic acid) for six months or more (Baskaran, J Ethnopharmacol 1990; Shanmugasundaram, J Ethnopharmacol 1990).
White mulberry (Morus alba or Morus indica) has been traditionally used in Asia to help treat type 2 diabetes, and there is some preliminary evidence to support this use. Mulberry leaf extract (species not given) may lessen increases in blood sugar after ingestion of table sugar in healthy people and people with type 2 diabetes (Mudra, Diabetes Care 2007). Among people with type 2 diabetes, taking 1 gram of powdered white mulberry leaf three times daily (after breakfast, lunch and dinner) for four weeks was found to lower fasting blood sugar by 27%, while taking 5 mg of the anti-diabetes drug glibenclamide lowered fasting blood sugar by only 8% (Andallu, Clin Chim Acta 2001).
There is mixed evidence as to whether CoQ10 may lower blood sugar. To be safe, people with diabetes or who take medication to lower blood sugar should consult a physician before using.
Amla (Emblica officinalis), also known as Indian gooseberry, has been traditionally used in Ayurvedic medicine for type 2 diabetes, and some preliminary evidence supports this use. One small study in Pakistan that included 32 people has shown that taking 1, 2, or 3 grams of powdered amla fruit once daily with breakfast can lower both pre- and post-meal blood sugar levels in people with or without diabetes after about 2-3 weeks of use (Akhtar, Int J Food Sci Nutr 2011). However, more research is needed to determine which form and dosage of amla has greatest benefit, whether the short-term effects persist long-term, and whether amla has benefit when taken with prescribed medicines for diabetes.
Preliminary evidence suggests certain other supplements, including aloe, ashwagandha, ginkgo, green coffee bean extract, glucosamine, black cohosh, rhodiola, reishi mushroom and tart cherry juice may lower blood sugar. While there is not enough clinical research to support the use of these supplements for this purpose, it's important to keep this in mind, as they could enhance the blood sugar lowering effect of other supplements or medications you may be taking.
There are a few supplements which may worsen blood sugar control or insulin sensitivity in certain people: excessive amounts of niacin may elevate blood sugar levels, and prescription digestive enzymes may cause an increase or decrease in blood sugar levels in people with exocrine pancreatic insufficiency. CLA (conjugated linoleic acid), a popular supplement for slimming, may worsen blood sugar control in diabetics and in obese people without diabetes.
Although fish oil does not appear to adversely affect blood sugar levels in people with diabetes, one study reported that a large daily dose of krill oil (providing a modest amount of EPA and DHA) reduced insulin sensitivity in overweight, middle-aged men by about 27% -- which could potentially increase the risk of diabetes.
Vitamin C may lower blood sugar levels after eating in people with type 2 diabetes, but be aware that high doses may interfere with certain blood sugar tests.
Consumption of coffee (caffeinated and decaffeinated) has been associated with a lower risk of developing type 2 diabetes (Ding, Diabetes Care 2014), yet caffeinated coffee has been shown to raise blood sugar levels (Keijzers, Diabetes Care 2002; Roberston, Br J Nutr 2015). A study in 29 healthy adults (average age 21) who experienced a single night of disrupted sleep found that drinking strong black coffee (providing 300 mg of caffeine) in the morning 30 minutes before drinking a sugary beverage impaired blood sugar response by 50% compared to disrupted sleep without drinking coffee (Smith, Br J Nutr 2020).
Interestingly, one study found that drinking coffee with added milk (1.7 oz) and sugar (just under 2 teaspoons) before a meal actually resulted in less sugar in the blood after the meal compared to consuming the coffee black, suggesting a possible benefit from these additives (Wong, Br J Nutr 2020). In addition, decaffeinated coffee seems to have a lesser effect (Greenberg, Diabetes Care 2010).
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