Homocysteine is a compound that is an intermediate of the the methylation process. Methylation is critical to synthesizing and modifying DNA, neurotransmitters, and other important molecules within the body. Homocysteine can accumulate when there are deficiencies of vitamins B2, B6, B9 and B12, or nutrients choline, betaine, or glycine. It has numerous deleterious effects, contributing to oxidative stress, inflammation, mitochondrial dysfunction and excess excitation in the brain. All of these can contribute to various symptoms, such as digestive distress, fatigue and brain fog. Elevated homocysteine has been found in numerous inflammatory conditions.