Mice with advanced stages of the disease had improved cognitive abilities
Researchers from the U.S. and Italy found mice with advanced stages of Alzheimer’s disease had shown improved cognitive abilities when fed a protein restricted diet supplemented with non-essential amino acids every other week for four weeks.
When mice were placed on this diet not only did their cognitive abilities improve but few of their neurons contained abnormal levels of the highly soluble damaging protein called tau.
Dietary protein is the major dietary regulator of a growth hormone known as IGF-1, which has been associated with aging and diseases in mice and several diseases in older adults such as age-related degenerative disease.
Dr. Valter Longo, PhD, Edna Jones Professor in Gerontology and Professor in Biological Science, Director of the USC Longevity Institute and corresponding author of the study collaborated with Dr. Pinchas Cohen, MD, Dean of USC Davis School, USC graduate students Edoardo Parrella, Tom Maxim, Lu Zhang, Junxiang Wan and Min Wei; Francesca Maialetti of the Istituto Superiore di Sanità in Rome; and Luigi Fontana of Washington University in St. Louis.
Dr. Longo stated "We had previously shown that humans deficient in Growth Hormone receptor and IGF-I displayed reduced incidence of cancer and diabetes. Although the new study is in mice, it raises the possibility that low protein intake and low IGF-I may also protect from age-dependent neurodegeneration.”
In animals Calorie Restriction (CR) protects against aging, oxidative stress and neurodegenerative pathologies. Reduced levels of growth hormone and IGF-1, which mediate some of the protective effects of CR, can also extend longevity and protect against age-related diseases in rodents and humans, according to the study’s abstract.
The reduced levels of IGF-1 circulating through the body by 30 to 70 percent and caused an eight-fold increase in a protein that blocks IGF-1's effects by binding to it.
Exploring dietary solutions to those diseases as opposed to generating pharmaceuticals to manipulate IGF-1 directly allows Longo's team to make strides that could help sufferers today or in the next few years.
Dr. Cohen commented "Alzheimer's Disease and other forms of neurodegeneration are a major burden on society, and it is a rising priority for this nation to develop new approaches for preventing and treating these conditions, since the frequencies of these disorders will be rising as the population ages over the next several decades.” "New strategies to address this, particularly non-invasive, non-pharmacological approaches such as tested in Dr. Longo's study are particularly exciting."
Dr. Longo adds "Developing a drug can take 15 years of trials and a billion dollars.”
"Although only clinical trials can determine whether the protein-restricted diet is effective and safe in humans with cognitive impairment, a doctor could read this study today and, if his or her patient did not have any other viable options, could consider introducing the protein restriction cycles in the treatment” says Longo.
Upcoming studies by Dr. Longo will attempt to determine whether humans respond similarly, while simultaneously examining the effects of dietary restrictions on cancer, diabetes and cardiac disease.
Many elderly individuals may have already been frail, have lost weight or may not be healthy enough to eat a protein-restricted diet every other week.
Dr. Longo emphasis that any dieting be monitored by a doctor or registered dietician to make sure that patients do not become amino acid deficient, lose additional weight or develop other side effects.
The results of their study were published online by Aging Cell last month.
Low protein diets are usually prescribed for those with kidney and liver disease and inherited metabolic disorders.
Adults in the U.S. are encouraged to get 10% to 35% of their day's calories from protein foods. That's about 46 grams of protein for women and 56 grams of protein for men, according to WebMD. However, low amounts of protein can produce dire negative effects such as muscle loss and nutrient deficiencies.
Information on a low-protein diet can be found at NYU Langone Medical Center.