"A mushroom used for centuries in Chinese medicine reduces weight gain in animals," BBC News reports.
A supplement from the Ganoderma lucidum mushroom (more commonly known as "reishi") slowed the pace of weight gain by apparently altering bacteria inside the digestive system of mice.
In this study, the researchers aimed to see if reishi was effective in preventing obesity. They gave mice different amounts of reishi or placebo and either a normal diet or a high-fat diet for eight weeks. All mice on the high-fat diet gained a lot of weight and body fat, but those given reishi did not gain as much weight or body fat. The reishi supplement did not have an effect on mice fed a normal diet. The supplement appeared to work by improving the number of "good" bacteria in the gut and through reducing inflammation. Some studies have suggested that chronic inflammation and an increased number of "bad" bacteria in the gut are linked to obesity in humans.
Randomised controlled trials in humans would be required to see if it is safe and effective.
Even if it is, it is unlikely to be useful in tackling obesity by itself; you would still need to eat a balanced diet and take plenty of exercise. Sadly, as far as we know, there is no such thing as a single superfood that will magically enable you to lose weight.
Where did the story come from?
The study was carried out by researchers from Chang Gung University and other institutes in Taiwan, and the University of the Pacific and Rockefeller University in the US. It was funded by the Ministry of Science and Technology of Taiwan and Chang Gung Memorial Hospital in Taiwan. Two of the authors have financial interests in Chang Gung Biotechnology, a company that produces Ganoderma lucidum products. The other authors declared no conflict of interest.
The study was published in the peer-reviewed scientific journal Nature Communications.
The BBC and Mail Online reported the study accurately and included expert commentary from microbiologist Professor Colin Hill.
What kind of research was this?
This was a laboratory study on mice. The researchers aimed to see if reishi has any effect on body weight and obesity.
Chinese medicine has used a number of different mushrooms to treat a variety of conditions over thousands of years. One of these is called reishi, or Ganoderma lucidum, which is believed to improve health and lifespan. It has also been tested as a possible cancer treatment as some research has suggested it is beneficial to the immune system. However, the effect against cancer remains uncertain, as a recent Cochrane systematic review highlighted the lack of large and high-quality randomised controlled trials in this area.
A similar lack of robust studies was found in a Cochrane review of Ganoderma lucidum to improve cardiovascular risk factors such as blood pressure or cholesterol in people with type 2 diabetes.
Some studies have suggested that obesity is linked to chronic inflammation, and Ganoderma lucidum is linked to an improvement in the immune system, so the researchers wanted to assess whether Ganoderma lucidum has an effect on obesity in mice.
This type of animal study is useful in determining whether a particular treatment shows promise and investigates its biological effects, as there can be several different groups whose diets and living conditions are strictly controlled, allowing them to be directly compared. If a treatment does show promise at this stage and appears safe then it would usually progress to trials in primates, which would indicate whether a treatment is more likely to work in humans, as they are more similar to us than mice. Human clinical trials would then follow if the treatment appeared to be sufficiently safe and effective in the animal trials.
What did the research involve?
The researchers split mice into six groups and fed them either a high-fat diet or a normal "chow" diet for eight weeks. Each group either had a supplement of different amounts of Ganoderma lucidum extract in water or just water alone (as a control). They then compared their weight, body fat and insulin resistance.
The amount of food each mouse ate was measured, as was the amount of energy they extracted from the food, by measuring the energy left in the faeces.
Finally, as the researchers thought the effects might be related to bacteria in the gut, they transplanted faeces from mice given Ganoderma lucidum supplement into mice without the supplement to work out if the effects could be passed on this way (!horizontally transmitted").
What were the basic results?
The Ganoderma lucidum supplement reduced the amount of weight gain and fat deposits in mice fed a high-fat diet. The most weight gain was seen in mice given the control (about 18g), and the least weight gain in mice given the highest dose of Ganoderma lucidum (about 12g). This was despite each group eating the same amount of food and extracting the same amount of energy from it (by measuring the energy left in the faeces).
The Ganoderma lucidum supplement did not have any effect on mice fed a normal diet, with both groups gaining around 4g.
Markers of inflammation were increased in the mice fed a high-fat diet, but this was reduced by Ganoderma lucidum.
Ganoderma lucidum also reduced insulin resistance in mice fed a high-fat diet.
Ganoderma lucidum reversed an imbalance in gut bacteria in the mice fed a high-fat diet, increasing the number of "good" bacteria. This effect was also achieved by transferring the faeces of mice fed Ganoderma lucidum to mice not given the supplement. This supported the possibility that the effect could be due to gut bacteria.
How did the researchers interpret the results?
The researchers concluded that the water extract of Ganoderma lucidum reduces obesity and inflammation in mice fed a high-fat diet. They say that this may be due to changes in the gut bacteria, evidenced by the fact that the effects were replicated when they transplanted these gut bacteria (through faeces samples) into other mice.
This study of Ganoderma lucidum in mice eating a high-fat diet found that it may help to reduce weight and fat gain, reduce inflammation and improve the levels of "good" gut bacteria in the gut. It also appeared to reduce the risk of insulin resistance. Ganoderma lucidum was not seen to have a significant effect for mice fed a normal diet.
The results of this study suggest a possible use for the extract, but randomised controlled trials in humans are required to determine safety and effectiveness for preventing weight gain. The same is true for any other conditions that Ganoderma lucidum is currently believed to improve.
Either way, it is clear that eating a high-fat diet was the cause of the increased weight gain and body fat in these mice. Even if the mushroom extract is found to help prevent weight gain in humans, it is likely to be healthier to avoid a diet very high in fat. Eating a balanced diet including plenty of fruit and vegetables and taking regular exercise based on your ability is the best way to combat obesity.
Ganoderma lucidum supplements are available to buy online but we wouldn’t recommend doing so. Just because something is “natural” doesn’t mean it is safe. The supplements can cause thinning of the blood, which could be very dangerous for people with high blood pressure. They are also known to interact in adverse ways with certain medications.
Always check with your GP before taking any kind of herbal or plant-based supplement.