Getting the right amount of certain vitamins in your diet can help you regulate your appetite. In some cases, getting too much or too little of a vitamin can cause you to lose your appetite or experience an increased appetite. Generally, vitamins aren't likely to greatly affect your appetite either way.
Multivitamins and Appetite
Multivitamin use doesn't appear to increase appetite. A multivitamin and mineral supplement given to patients with HIV helped improve their nutritional recovery but didn't seem to affect appetite in a study published in the "Journal of Acquired Immune Deficiency Syndromes" in April 2015.
In some cases, taking multivitamins may actually result in decreases in appetite. A study published in the "British Journal of Nutrition" in 2008 found that women who took multivitamins while following a reduced-calorie diet had lower appetite ratings after eating than women who weren't taking multivitamins.
Vitamin Deficiencies and Appetite
Being deficient in folic acid, or folate, can cause a loss of appetite, so treating this deficiency with an increased intake of folic acid may help increase your appetite back to normal levels. Adults should get at least 400 micrograms of folic acid each day. Don't take extra folate unless your doctor recommends it, because this could cause an imbalance of the other B vitamins, and folate can interact with certain medications. Dark green leafy vegetables, citrus fruits, broccoli, asparagus and beans all provide folic acid.
Vitamin K deficiency can also cause appetite loss, as well as bone loss, lethargy, easy bruising and slowed growth. Adults should consume at least 90 micrograms of vitamin K per day to avoid deficiency symptoms. You can increase your vitamin K intake by eating green leafy vegetables, asparagus, prunes and soybeans.
Vitamin Toxicity and Appetite
Although changes in appetite are more common with vitamin deficiency than vitamin toxicity, getting too much of certain vitamins can interfere with your appetite. For example, taking very large amounts of vitamin D supplements can cause toxicity symptoms that include appetite loss, diarrhea, weakness, mental changes and vomiting. The recommended dietary allowance for vitamin D is 600 international units per day for adults under 70 and 800 international units per day for older adults. Vitamin D is available in fortified foods, mushrooms, eggs, tofu, pork and oily fish.
Ways to Increase Appetite
If you're experiencing decreased appetite levels because of a serious illness, try eating a number of smaller meals per day rather than just a few large meals and increasing the amount of calories and protein in your snacks. Liquid protein drinks and eating more of your favorite foods may also be helpful, according to MedlinePlus. Consider adding more high-calorie but nutrient-rich foods to your meals, such as nuts, seeds, avocados, olives and cheese, if you're trying to gain weight.
Exercise can help regulate your appetite, according to a study published in the "Journal of Obesity" in April 2012. Walking may be better than running if you're trying to eat more, because walking caused an increase in appetite hormones but didn't also cause an increase in satiety hormones, as running did in this study. Strength training may also help you increase your weight in a healthy way.