Who needs it?

Vitamin B12 is needed for protein synthesis .Helps the blood to carry oxygen to the cells, so it is necessary for the body's energy production process. Required for DNA synthesis .Necessary for nerves. Detoxifies nicotine (for smokers) and other toxins.

Signs of deficiency

Weak hair, eczema or dermatitis, special sensitivity of the oral mucosa to heat and/or cold , irritability , anxiety and tension , lack of energy, constipation, strained and aching muscles , pale skin.

How much ?

RDA (recommended daily intake) 1 mcg
OPN (optimal daily intake) 25 mcg

Toxicity

Not known for oral use (tablets).A rare allergic reaction at the injection site.

Recommended foods

Oysters (15 mcg), sardines (25 mcg), tuna (5 mcg), Lamb (footprints) , eggs (1.7 mcg), shrimp(1 mcg), cottage cheese (5 mcg), milk (0.3 mcg) , Turkey and chicken (2 mcg) , Cheese (1.5 mcg).

Assistants

Acts in combination with folic acid.It is best to take with a vitamin B complex and food.

Thieves

Alcohol, smoking, low acidity of the stomach.

Source
Patrick Holford" the new Bible of optimal nutrition " P. 478-479 book publisher (Medical Research and Consulting Center)