[www.ncbi.nlm.nih.gov]

Vitamin B12 is a water-soluble vitamin synthesized by the bacteria present in the human body.

Deficiency of this particular vitamin can lead to fatigue, weakness, constipation, balance issues, mental fogginess, peripheral tingling, depression, and cognitive issues [4,5].

Micronutrients are known to affect the normal structure and functions of the brain.

Some clinical studies have shown that higher Vitamin B12 levels in the body resulted in better outcomes in patients suffering from depressive and other mental health disorders [6], whereas some studies have also stated that adolescents with borderline levels of serum Vitamin B12 levels develop cognitive changes requiring treatment [7].

Higher homocysteine levels are associated with a phenomenon called "methionine loading." A deficiency of Vitamin B12 along with B6 and folate usually prevents the conversion of homocysteine to methionine, increasing the levels of homocysteine.

Higher levels of homocysteine affect the DNA formation and overall turnover of red blood cells (RBCs), causing the development of megaloblastic or pernicious anemia, ultimately affecting the cognitive ability and mood of the patient [14-17].

Vitamin B12 is interdependent with other micronutrients, mainly Vitamin B6 and folate. This interdependence affects multiple neuronal pathways that are not directly controlled by Vitamin B12. Neurotransmitters are required to conduct the signals from one neuron to another, with the help of pre- and post-synaptic junctions. The malfunctioning of any of these pathways can lead to depression [4]. Lower Vitamin B12 levels are also known to increase the risk of cognitive decline, Alzheimer's disease, and dementia. According to Vogiatzoglou et al., higher Vitamin B12 levels have proven to protect patients against brain atrophy [18].

Daily supplementation of oral Vitamin B12 (100 mcg) and folic acid (400 mcg) has been shown to increase cognitive function in a randomized controlled trial performed by Walker et al. in 2012 [26].

Melancholic depressive symptoms were more relatively associated with lower plasma Vitamin B12 levels.

I recall a Dr. saying that there's no point getting B-12 shots, that the tablets are just as effective. Do you know anything about this?

[www.aafp.org].

This study agrees with you

Thanks. However, someone I know insists that she HAS to have injections after several years of being vegan, i.e., her digestion is so poor that B12 tablets or drops won't work. At least that is what the doctor told her and she just loves those injections.

Sublingual bypasses the digestive system.

Doesnt require intrinsic factor

Directly into bloodstream

Allegedly

Yes, it seems to be about "intrinsic factor". "Allegedly". I wonder if there is a way to fundamentally heal the weakness in the stomach so that the body can manufacture intrinsic factor once again, ie, I assume that the person with low or no IF was not born that way, but that the deficiency wa acquired.

Who knows what the real situation is. I do read everywhere that injections just are not necessary.

I would think yes intrinsic factor could be improved

...

Vitamin B-12 injections are generally prescribed when B-12 deficiency has become so severe that a quick restoration is necessary.

The AAFP says B-12 injections demonstrate more rapid results than their oral counterparts, so they are more appropriate for patients with a severe deficiency.

B-12 injections are ordinarily administered intramuscularly, meaning the injection is administered into a muscle, and around 10 percent is absorbed directly into the body. This makes it an effective means of rapid replacement for severely deficient patients.

@Fresh. Many thanks for your info. What you say makes sense. I guess it hinges on "severe" deficiency VS "moderate" deficiency.