Glucomannan is a fiber with many beneficial effects. It lowers cholesterol, helps control blood sugar in diabetes, and may even help with weight loss. Surprisingly, it also decreases inflammation, potentially helps with allergies, protects the skin from UV radiation, and may delay aging. Read this article to discover more glucomannan health benefits and why you should take this supplement with care.
What Is Glucomannan?
Glucomannan is a complex sugar and soluble fiber. The most commonly used type is konjac glucomannan, which is taken from the tubers of konjac, a plant native to Asia .
It is also extracted from :
- Eastern white pine
It absorbs water extremely well and has the highest viscosity of any known dietary fiber .
A few grams of glucomannan powder can turn a whole glass (eight ounces) of water into a gel.
It has gained in popularity as a dietary supplement, mainly due to its potential weight-reducing effects.
Mechanisms of Action
Glucomannan works by:
- Taking up space in the stomach, making you feel full and eat less
- Decreasing the amount of the hunger hormone ghrelin 
- Decreasing the absorption of nutrients (proteins, fats, and sugars) [4, 1]
- Removing bile acids 
- Promoting the growth of good bacteria in the gut [6, 7]
Health Benefits of Glucomannan
1) Lowers Cholesterol
Bile acids are made from cholesterol. Glucomannan binds to bile acids and helps remove them from the body. As a result, the body has to convert more cholesterol into bile acids, lowering cholesterol levels .
Two meta-analyses, one including 12 studies and the other including 14 studies, showed that this supplement significantly lowered LDL and non-HDL cholesterol types. LDL and non-HDL cholesterol increase the risk of heart disease when elevated [8, 9].
2) Beneficial in Diabetes
Glucomannan causes a more gradual absorption of sugar, which reduces spikes in blood sugar levels .
A study of 34 pregnant women showed that this fiber safely decreased blood glucose levels in both diabetic and non-diabetic patients .
3) May Help with Weight Loss
Glucomannan may help with weight loss in certain groups of people but doesn’t seem to have an effect on others. Hopefully, future studies will explain why this supplement works for some and not others, and show which groups benefit most from glucomannan supplementation.
4) Helps with Constipation
However, there is also a study in 72 children (DB-RCT), that showed this fiber was not more effective than the placebo in treating constipation .
5) Is a Prebiotic
6) Is Beneficial in Polycystic Ovary Syndrome
7) Helps Lower Thyroid Hormones in Hyperthyroid Patients
In a study with 48 hyperthyroid patients, those who received glucomannan, in addition to standard therapy, had significantly lower thyroid hormone levels during the first weeks of treatment .
8) May Help Combat Acne
Glucomannan and probiotic bacteria blocked the growth of acne-causing bacteria in a cell study .
9) May Decrease Inflammation
10) May Help with Allergies
11) Promotes Antioxidant Activity
12) May Protect Skin from UV radiation
Glucomannan decreased UV-induced skin redness in human volunteers and protected skin cells against UVB-induced damage .
13) May Delay Aging
14) Reduces Cholesterol
In a DB-RCT with 120 people with high cholesterol, glucomannan combined with policosanol or chromium-polynicotinate was effective in reducing total and LDL cholesterol but didn’t affect HDL or triglyceride levels .
In another trial, 2.4 g/day of chitosan and glucomannan reduced total, LDL, and HDL cholesterol but not triglycerides in 21 overweight people .
15) Protects the Skin from UV
A 0.5% glucomannan emulsion applied on skin decreased UV-induced skin injuries in people .
Risks and Side Effects of Glucomannan
To prevent it from expanding prematurely and blocking the gut, make sure you take enough water or other liquids. Also, don’t take it immediately before going to bed.
This supplement lowers blood glucose. Mixed with diabetic medication, it can cause low blood sugar .
Users say glucomannan is good for:
- Controlling blood sugar levels
- Weight loss
- Hunger control
- Lowering cholesterol
- Insulin resistance in PCOS
However, some also report:
- Bloating and gas
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