The study found a fasting-mimicking diet reduced symptoms in mouse models of MS - even reversing them in 20 percent of animals - and suggests it holds promise for use in human patients.
The research, led by the University of Southern California (USC) in Los Angeles, is published in the journal Cell Reports.
Senior investigator and professor Valter Longo, who directs the Longevity Institute at USC's Davis School of Gerontology, says they found the fasting-mimicking diet (FMD) triggers a cellular death-and-life process that appears critical for bodily repair. He explains:
"During the fasting-mimicking diet, cortisone is produced and that initiates a killing of autoimmune cells. This process also leads to the production of new healthy cells."
Multiple sclerosis (MS) is an autoimmune disease where the immune system gradually disrupts the blood-brain barrier and attacks the myelin sheath of proteins and fats that insulates nerve fibers in the spinal cord and brain.
As the unpredictable disease progresses, the onslaught on the myelin sheath eventually causes the electrical signals carried by the nerves to leak out. This gives rise to symptoms that get worse and worse, ranging from mild numbness in the arms and legs to paralysis and blindness.
MS is thought to affect around 2.3 million people worldwide. In the United States, estimates suggest around 350,000 Americans have MS.
'Complete recovery in 20 percent of mice'
In earlier work, Prof. Longo and his team had tested cycles of a similar FMD to the one in the new study with anti-cancer drugs and found the combination protected healthy cells and weakened cancer cells.
The results from those earlier studies prompted them to investigate the potential for the FMD to have a similar effect in MS. Prof. Longo says they asked themselves perhaps it could it clear out the bad cells and help generate good ones.
The new study is in two parts: tests on mice and a small pilot trial on humans.
First, the researchers started with two groups of mice with autoimmune disease. One group was put on a low-calorie and low-protein FMD comprising three cycles of fasting that lasted for 3 days out of every 7. The other group - the controls - were put on a normal diet.
The authors note the FMD reduced symptoms in all the mice and "caused complete recovery for 20 percent of the animals."
Further tests revealed the FMD mice had increased levels of corticosterone, a steroid hormone released by the adrenal glands to control metabolism.
The FMD mice also had increased levels of immune T cells and reduced levels of inflammation-causing cytokines - proteins that instruct other cells to repair sites of trauma, infection, or other pain.
And last - but not least - the researchers found the FMD mice showed signs of regeneration of myelin that had been damaged by the autoimmunity.
'Kills bad cells, generates good and myelin-producing cells'
In people with MS, it is the T cells that attack the myelin sheath and damage the nerves. From the results in the mice, it appears that the cycles of fasting in the FMD may interfere with this process, while also promoting regeneration, as Prof. Longo explains:
"On the one hand, this fasting-mimicking diet kills bad immune cells. Then, after the mice return to the normal diet, the good immune cells but also the myelin-producing cells are generated, allowing a percentage of mice to reach a disease-free state."
In the second part of the study, the researchers tested the safety and potential efficacy of the FMD on 60 patients with relapsing-remitting MS (RRMS). RRMS is the most common form of MS, where patients have symptom flare-ups interspersed with periods of recovery.
The patients were randomly assigned to a control diet, a high-fat, ketogenic diet (KD group), or a modified human FMD for 7 days, followed by a Mediterranean diet for 6 months (FMD group).
The researchers note the FMD and KD groups "displayed clinically meaningful improvements" in a scale that measures overall change in health, quality of life, physical health, and mental health.
The team emphasizes the preliminary nature of the findings, and notes the study is also limited by the fact it did not test whether the Mediterranean diet alone would lead to similar improvements. Plus, it did not include any imaging or immune function analyses.
However, Prof. Longo suggests the results are promising enough to warrant further investigation that tests the potential for FMD to help patients with MS and other autoimmune diseases in larger clinical trials.
Meanwhile, he notes that some FMDs have been tested and found safe in trials, and suggests patients with autoimmune disorders who have run out of treatment options should raise the possibility of trying FMD or joining a clinical trial with their doctors.
"We are optimistic. What we don't want is patients trying to do this at home without involvement of their specialist or without understanding that larger trials are necessary to confirm that the diet, as a treatment, is effective against multiple sclerosis or other autoimmunities."
Prof. Valter Longo