Vitamin B12 deficiency is very common, especially in vegetarians, vegans, and older adults. The most common symptoms include blood disorders, impaired brain function, and elevated homocysteine levels.
Vitamin B12 is an essential nutrient that your body can’t make on its own, so you need to get it from your diet or supplements. Before you start supplementing with B12 you need your doctor to do a blood test to whether you have a gene mutation MTHFR which detects if you can absorb B12. This test needs to be done - MTHFR 677 and MTHFR 1298
If positive for a methylation defect you need to take a special B12 - methylcyanocobalamin. You can start eating foods that are high in B12 as organ meats. eggs, and of course leafy greens.
Organ meats are some of the most nutritious foods out there. Liver and kidneys, especially from lamb, are rich in vitamin B12. A 3.5-ounce (100-gram) serving of lamb liver provides an incredible 1,500% of the RDI for vitamin B12. Leafy greens are also high in B12. I prefer sardines as my source of B12 A one-cup (150-gram) serving of drained sardines provides more than double the RDI for vitamin B12. Salmon is another one of my favorite choices for B12. A half fillet (178 grams) of cooked salmon can pack more than 80% of the RDI for vitamin B12