Fasting doubles stem cells' regenerative capacity: Study

The US biologists found that a 24-hour fast can reverse the age-related loss of intestinal stem cell function that can regenerate new intestinal cells.

The study, published on Thursday in the journal Cell Stem Cell, revealed that fasting dramatically improves stem cells' ability to regenerate, in both aged and young mice, Xinhua reported.

In fasting mice, cells begin breaking down fatty acids instead of glucose, a change that stimulates the stem cells to become more regenerative.

The researchers found that they could also boost regeneration with a molecule that activates the same metabolic switch and such an intervention could potentially help older people recovering from gastrointestinal infections or cancer patients undergoing chemotherapy.

"Fasting has many effects in the intestine, which include boosting regeneration as well as potential uses in any type of ailment that impinges on the intestine, such as infections or cancers," said Omer Yilmaz, an assistant professor of biology in Massachusetts Institute of Technology (MIT), and one of the senior authors of the study.

"This study provided evidence that fasting induces a metabolic switch in the intestinal stem cells, from utilising carbohydrates to burning fat," said David Sabatini, an MIT professor of biology and the paper's another senior author.

"Interestingly, switching these cells to fatty acid oxidation enhanced their function significantly. Pharmacological targeting of this pathway may provide a therapeutic opportunity to improve tissue homeostasis in age-associated pathologies."

Intestinal stem cells are responsible for maintaining the lining of the intestine, which typically renews itself every five days. When an injury or infection occurs, stem cells are key to repairing any damage. However, as people age, the regenerative abilities of these intestinal stem cells decline, so it takes longer for the intestine to recover.

After mice fasted for 24 hours, the researchers removed intestinal stem cells and grew them in a culture dish, allowing them to determine whether the cells can give rise to "mini-intestines" known as organoids.

The researchers found that stem cells from the fasting mice doubled their regenerative capacity.

The researchers sequenced the messenger RNA of stem cells from the mice that fasted and revealed that fasting induces cells to switch from their usual metabolism, which burns carbohydrates such as sugars, to metabolise fatty acids.

This switch occurs through the activation of transcription factors called PPARs, which turn on many genes that are involved in metabolizing fatty acids, according to the researchers.

The researchers found that if they turned off this pathway, fasting could no longer boost regeneration and they could reproduce the beneficial effects of fasting by treating mice with a molecule that mimics the effects of PPARs.

The findings suggest that drug treatment could stimulate regeneration without requiring patients to fast, which is difficult for most people.

One group that could benefit from such treatment is cancer patients who are receiving chemotherapy, which often harms intestinal cells.

It could also benefit older people who experience intestinal infections or other gastrointestinal disorders that can damage the lining of the intestine.

Three days of fasting can renew your entire immune system

A person’s entire immune system can be rejuvenated by fasting for as little as three days as it triggers the body to start producing new white blood cells, a study suggests
Fasting for as little as three days can regenerate the entire immune system, even in the elderly, scientists have found in a breakthrough described as “remarkable”.

Although fasting diets have been criticised by nutritionists for being unhealthy, new research suggests starving the body kick-starts stem cells into producing new white blood cells, which fight off infection.

Scientists at the University of Southern California say the discovery could be particularly beneficial for people suffering from damaged immune systems, such as cancer patients on chemotherapy.

It could also help the elderly whose immune system becomes less effective as they age, making it harder for them to fight off even common diseases.

The researchers say fasting “flips a regenerative switch” which prompts stem cells to create brand new white blood cells, essentially regenerating the entire immune system.

“It gives the ‘OK’ for stem cells to go ahead and begin proliferating and rebuild the entire system,” said Prof Valter Longo, Professor of Gerontology and the Biological Sciences at the University of California.

“And the good news is that the body got rid of the parts of the system that might be damaged or old, the inefficient parts, during the fasting.

“Now, if you start with a system heavily damaged by chemotherapy or ageing, fasting cycles can generate, literally, a new immune system.”

Prolonged fasting forces the body to use stores of glucose and fat but also breaks down a significant portion of white blood cells.

During each cycle of fasting, this depletion of white blood cells induces changes that trigger stem cell-based regeneration of new immune system cells.

In trials humans were asked to regularly fast for between two and four days over a six-month period.

Scientists found that prolonged fasting also reduced the enzyme PKA, which is linked to ageing and a hormone which increases cancer risk and tumour growth.

“We could not predict that prolonged fasting would have such a remarkable effect in promoting stem cell-based regeneration of the hematopoietic system,” added Prof Longo.

“When you starve, the system tries to save energy, and one of the things it can do to save energy is to recycle a lot of the immune cells that are not needed, especially those that may be damaged,” Dr Longo said.

“What we started noticing in both our human work and animal work is that the white blood cell count goes down with prolonged fasting. Then when you re-feed, the blood cells come back. So we started thinking, well, where does it come from?”

Fasting for 72 hours also protected cancer patients against the toxic impact of chemotherapy.

“While chemotherapy saves lives, it causes significant collateral damage to the immune system. The results of this study suggest that fasting may mitigate some of the harmful effects of chemotherapy,” said co-author Tanya Dorff, assistant professor of clinical medicine at the USC Norris Comprehensive Cancer Center and Hospital.

“More clinical studies are needed, and any such dietary intervention should be undertaken only under the guidance of a physician.”

“We are investigating the possibility that these effects are applicable to many different systems and organs, not just the immune system,” added Prof Longo.

However, some British experts were sceptical of the research.

Dr Graham Rook, emeritus professor of immunology at University College London, said the study sounded “improbable”.

Chris Mason, Professor of Regenerative Medicine at UCL, said: “There is some interesting data here. It sees that fasting reduces the number and size of cells and then re-feeding at 72 hours saw a rebound.

“That could be potentially useful because that is not such a long time that it would be terribly harmful to someone with cancer.

“But I think the most sensible way forward would be to synthesise this effect with drugs. I am not sure fasting is the best idea. People are better eating on a regular basis.”

Dr Longo added: “There is no evidence at all that fasting would be dangerous while there is strong evidence that it is beneficial.

“I have received emails from hundreds of cancer patients who have combined chemo with fasting, many with the assistance of the oncologists.

“Thus far the great majority have reported doing very well and only a few have reported some side effects including fainting and a temporary increase in liver markers. Clearly we need to finish the clinical trials, but it looks very promising.”

Benefits of Fasting

Most religions use periods of fasting as a means of demonstrating faith or penitence, and an opportunity for spiritual reflection. Fasting has also historically been a means to express political views and a form of protest.

Though it may not be the most practical -- or safest -- diet, some people use fasting as a way to lose weight or to cleanse the body of toxins, although some experts say our bodies are perfectly equipped with organs that already do the job. How fasting is used for weight loss varies by diet. Some fasting diets involve drinking nothing but water or eating only raw foods for a period of one or more days, while others restrict food on alternate days. Certain fasting diets only allow liquids like water, juice, or tea, while others dramatically cut calories but do not eliminate food altogether.

Does Fasting Help You Lose Weight?

When you fast, your body is forced to dip into energy stores to get the fuel it needs to keep going, so you will lose weight. The big question is how long you will keep that weight off. Because food was often scarce for our ancestors, our bodies have been genetically programmed to combat the effects of fasting. When you eat less food, your metabolism slows down to conserve energy. Then, when you go back to your usual diet, your lowered metabolism may cause you to store more energy, meaning that you will probably gain back the weight you lost and possibly even put on more weight when eating the same calories you did before the fast.

As you fast, your body will adjust by reducing your appetite, so you will initially feel less hungry. But once you have stopped fasting, your appetite hormones will kick back into gear and you may actually feel hungrier and be more likely to binge.

Research has shown that fasting on alternate days can help people lose weight, but not for long. In one study, people who followed an alternate-day fasting diet shed weight, even when they ate all they wanted on the nonfasting days. However, they could not maintain the weight loss over time.
Can Fasting Detoxify the Body?

Some fasting diets claim that they can cleanse the body of impurities. However, there is no evidence that fasting detoxifies your body, or that your body even needs to be detoxified. It is naturally designed to remove toxins through the skin (by sweating), liver, colon, and kidneys.
Could Fasting Help You Live Longer?

Studies of fasting in both rodents and humans appear to indicate a connection between calorie restriction and longevity. In one study of overweight men and women, a calorie-restricted diet improved markers of aging, such as insulin level and body temperature.

Fasting might also improve longevity by delaying the onset of age-related diseases including Alzheimer's, heart disease, and diabetes. One study showed that skipping meals once a month, as members of the Mormon religious group do, reduces the risk of clogged arteries (the build-up of plaque that can lead to heart attacks and strokes). However, it is not clear from this research whether fasting alone or the Mormons' generally healthier lifestyle (they also abstain from coffee, alcohol, and smoking) is responsible for the improved heart health. 

Researchers do not yet know whether the effects of fasting translate into an actual increase in lifespan, because they have not followed people for long enough periods of time. However the concept of intermittent fasting, such as skipping a meal purposefully on an intermittent basis, is gaining attention. It appears to be a relatively safe way to reduce caloric intake that is easier for some people to do. The data however is not there yet nor is this an accepted practice.
Is Fasting Safe?

Fasting for a day or two probably won't hurt people who are generally healthy, provided they maintain an adequate fluid intake. However, fasting entirely for long periods of time can be harmful. Your body needs a variety of vitamins, minerals, and other nutrients from food to stay healthy. Not getting enough of these nutrients during fasting diets can lead to symptoms such as fatigue, dizziness, constipation, dehydration, gallstones, and cold intolerance. It is possible to die if you fast too long.

Even short-term fasting is not recommended for people with type I diabetes, because it can lead to dangerous dips and spikes in blood sugar. Women who are pregnant or breastfeeding, or anyone with a chronic disease, should not fast.

Before you go on any type of new diet, particularly one that involves fasting, talk to your doctor to find out whether it is safe and appropriate for you. Also ask your doctor to refer you to a registered dietitian, who can show you how to design a healthy eating plan.