Question

Emma is a 25-year-old woman who has been following a vegan diet for two years and has not consumed any food from animal sources. Her food intake on a vegan diet has been well balanced. She generally follows Canada's Food Guide by consuming a variety of vegetables including spinach, romaine lettuce, broccoli, carrots, sweet potato, squash, tomatoes and sweet peppers, and fruits like berries, bananas, apples melons, and pears. She consumes only whole grains, such as whole grain breads, oatmeal and brown rice, and chooses her proteins from nuts, seeds, and a variety of legumes. She takes no supplements. When Emma visits her doctor for a check-up, she orders blood work to assess Emma's vitamin B12 status and finds that Emma's blood levels are insufficient, i.e. low but, fortunately, not yet so low that she is considered deficient.

Answer 1

Option 1st is the correct answer. Vitamin B12 plays a major role in the synthesis and maintenance of myelin sheath (an outer covering on neurons).

Vitamin B12 is very crucial for the synthesis of methionine because it acts as a cofactor in a very important step of the methionine synthesis. Methionine is an amino acid that provides the methyl groups required for methylation reactions in the synthesis of mylein. Without methionine, the synthesis of myelin and neurotransmitters that are needed for neurological development, maintenance, and functions, is not possible.

In addition, The precursor for the synthesis of methionine is homocysteine. Homocysteine is an amino acid that is related to many neurodegenerative disorders. An increased level of homocysteine may results into brain damage and cognitive disturbances. Thus, the synthesis of methionine prevents the accumulation of this harmful amino acid in the brain.