Scientists think that Nerve Growth Factor plays an important role in cognitive function, mood, inflammation & more. Learn about the proposed effects of NGF & factors that may increase it. What is Nerve Growth Factor?
Science now accepts that the brain continues to reorganize itself and create new brain cells throughout life. The birth of new neurons in the brain is referred to as neurogenesis .
Nerve growth factor (NGF) is one of a group of small protein-like molecules called neurotrophins ( BDNF is another) that are responsible for neurogenesis or the development of new neurons and for the health and maintenance of mature ones.
Based on animal findings, researchers consider that NGF may promote the growth, maintenance, and survival of neurons and axons. It’s also thought to help repair the myelin sheath, which is the insulating coating around the axons [ 1 ].
Animal experiments found that as the production of NGF decreases in the brain, the animals’ ability to form new connections and to retain and access memories becomes impaired. They believe NGF might save degenerating nerves and help restore their function, but human data are lacking [ 2 ].
Dr. Rita Levi-Montalcini, an Italian American neurologist, won a Nobel Prize for discovering nerve growth factor in 1996. She shared the prize with biochemist Stanley Cohen.
Some of her later claims surrounded her personality with controversy. For example, she said that she used NGF eye drops to increase her life- and health-span.
Rita did live to be a centenarian. She died in 2012, aged 103 years old. Of course, the true secret to her longevity remains unknown. As far as science is concerned, evidence is lacking to claim that NGF has lifespan-increasing properties. Plus, the safety of NGF use in humans hasn’t been established.
Studies investigating NGF levels in people are in the early stages. Findings so far have been inconclusive. We simply don’t yet know how NGF levels relate to health and disease.
In a study of 157 normal people, NGF levels were on average 194 pg/ml. Age didn’t make a significant difference amongst the participants, but NGF was significantly lower in women (112 pg/ml) than in men (243 pg/ml) [ 3 ].
Another study found lower NGF levels in people with common, so-called Western diseases , including atherosclerosis, obesity, type 2 diabetes and metabolic syndrome [ 4 ].
On the other hand, high NGF levels are found in a number of autoimmune diseases, accompanied by increased numbers of mast cells, which produce histamine and which are also able to produce NGF [ 5 ].
Some researchers have also suggested a link between higher NGF and BDNF levels in schizophrenia. They hypothesize that neurotrophins do not always support health – as is often popularly thought [ 6 ].
It’s important to realize that NGF levels can be different in different places. For example, NGF can be measured in the blood, cerebrospinal fluid (CDF), and in specific brain regions. No correlations between these measures have yet been established, as is the case with BDNF. We also don’t know if NGF from the blood can enter the brain [ 7 , 8 ].
Far more NGF human research is needed to understand this little brain-active protein and its roles. Proposed Health Effects of NGF
This section explores associations between NGF and aspects of health.
The majority of studies covered in this article deal with associations only, which means that a cause-and-effect relationship hasn’t been established.
For example, just because mood problems have been linked with low NGF in certain brain areas doesn’t mean that mood disorders are caused by low NGF. Nor does it mean that increasing NGF will improve mood, unless clinical data about a direct link are available. However, data are lacking to make such claims.
Additionally, even if a study did find that low brain NGF contributes to depression, NGF levels are highly unlikely to be the only causative factor. Complex mood disorders like depression always involve multiple possible factors – including brain chemistry, environment, health status, and genetics – that may vary from one person to another. 1) Mood
The link between NGF and mood disorders is still unclear.
In one small study, Blood levels of NGF were lower in those with Major Depressive Disorder compared to controls. Larger human studies are needed [ 9 ].
In rats, Exercise increased NGF (and BDNF & synapsin I), which was suggested to have improved the survival of neurons in the hippocampus and mood by increasing the serotonin -producing cells in the brain stem. This hasn’t been confirmed in humans [ 10 ].
Chrysin is a flavonoid found in honey and some plants. Some scientists think that the chrysin may improve mood in lab animals by raising NGF, but this hasn’t been proven [ 11 ]. 2) Myelin & Multiple Sclerosis
There’s no evidence about the effects of NGF on myelin and multiple sclerosis in humans.
In an animal model of human brain demyelinating diseases (e.g. Multiple Sclerosis), NGF delayed onset, lowered inflammation, and lessened tissue injury [ 12 ]. Scientists are investigating whether NGF can:
Promote the growth and repair of myelin damage [ 13 ].
Induce the production of BDNF , which is also thought to be important for the myelination of nerves [ 13 ]. Play a role in brain disorders, including Multiple Sclerosis, Alzheimer’s disease, and Parkinson’s disease [ 14 ]. None of these effects have been proven. We can’t apply the existing animal data to humans. 3) Alzheimer’s Disease According to one theory, substances that raise acetylcholine may be beneficial in Alzheimer‘s disease . Recent animal studies proposed that NGF might protect acetylcholine activated neurons, but its effectiveness and safety in Alzheimer’s patients has never been properly investigated [ 15 ].In a study of 10 Alzheimer’s patients receiving NGF gene transfer therapy, the authors observed degenerating neurons sprouting from their axons, tissue growth, and improvement of function. Larger clinical trials are needed [ 16 ].Some researchers hold that the ability of the brain to convert proNGF to mature NGF is faulty […]