Vitamin B12 deficiencies can arise when you aren’t getting the right nutrients in your diet or your body can’t absorb nutrients properly. Crohn’s and celiac disease, weight loss surgery, and chronic alcoholism can all affect a person’s ability to absorb enough of the nutrients they need. The bulk of B12 in our diets comes from animal products, and vegans are at risk of B12 deficiency. Seniors have more trouble with nutrient absorption and hunger, as well as those with persistent hunger and other digestive system disorders as a result of hunger and weight loss surgery. Www.vitamin.com/vitamin-12 for more details.