What happens if you only eat vegetables for a month

While a healthy vegetarian diet that includes a variety of different foods can provide all of the nutrients you need, a diet consisting of only vegetables doesn't. Vegetables don't contain sufficient amounts of certain vitamins and minerals, including vitamin B-12 and vitamin D. You need to consume a wider variety of foods to get the recommended amount of essential omega-3 fats and all of the necessary amino acids.

Protein

Protein is important as a source of amino acids, which you need for creating new cells. While animal foods provide all nine of the essential amino acids in sufficient amounts, soybeans and soy products are the only vegetable source that provides them all. Adding grains and nuts to your diet or consuming dairy or eggs will allow you to get the amino acids you need, since animal products and the grain quinoa are complete proteins and grains and nuts provide the amino acids not found in vegetables.

Omega-3 Fats

You need a certain amount of fat each day for good health, including omega-3 fats, which are essential. Vegetables only contain a small amount of fat and don't contain omega-3 fats in significant amounts. Fish are the best source of omega-3 fats, providing docosahexaenoic acid, or DHA, and eicosapentaenoic acid, or EPA, but you can get some omega-3 fats from nuts, flaxseeds, green leafy vegetables, soybeans and algae. However, the vegetarian sources of omega-3 fats contain alpha-linolenic acid, or ALA, which isn't very efficiently converted into the DHA and EPA you need.

Vitamin B-12

Vitamin B-12 is another nutrient that you can't get from vegetables, since it is only found in animal foods. You need vitamin B-12 for forming healthy red blood cells to transport oxygen around your body. Vegetarians need to either eat foods that are fortified with vitamin B-12, like some breakfast cereals, or take a vitamin B-12 supplement.

Vitamin D

Vegetables don't provide any significant amount of vitamin D. You need vitamin D for absorbing calcium and keeping your bones and teeth strong. Sunlight provides some vitamin D, but usually not enough to meet your vitamin D needs. Other sources of vitamin D include fortified milk, liver and egg yolks.

Considerations

Some other essential nutrients, including iron and zinc, aren't as well absorbed from vegetable sources as those from animal sources, so the recommended intake of these nutrients is higher for vegetarians to compensate for this. For example, vegetarians need to consume about twice as much iron as non-vegetarians, according to MayoClinic.com. The healthiest diets are those that include a wide variety of foods, so don't restrict yourself to eating foods from only one food group.

While you may enjoy perfect health on a varied, well-planned vegetarian diet, restricting food choices to vegetables only can have serious health consequences. With no other food groups, it's not only likely that you won't get the energy you need to fuel everyday activities, but you might also become deficient in an assortment of nutrients. To promote good health, include foods such as fruits, nuts, legumes and whole grains in your diet -- all of which qualify as vegetarian and vegan -- along with plenty of vegetables.

Calorie Deficiency

Most moderately active men burn between 2,400 and 2,800 calories per day, while most women burn 1,800 to 2,200 calories. It's extremely difficult to meet these numbers with vegetables alone. For example, 1 cup of raw, chopped carrots contains just 52 calories, while the same amount of boiled broccoli contains 55 calories. You'd need to eat 38 cups of carrots or 36 cups of broccoli just to consume 2,000 calories. With too few calories, you'll likely feel lethargic and have a harder time focusing and performing vigorous activities.

Macronutrient Deficiency

Although vegetables are good sources of fiber and carbohydrates, they lack significant amounts of the macronutrients, fat and protein. Fat is necessary for healthy mental function, energy and nutrient metabolism, while you need protein for strong muscles and an effective immune system. The "2010 Dietary Guidelines for Americans" recommends getting 20 to 35 percent of your daily calories from fat and 10 to 35 percent from protein. Beans, peas and tofu are good protein sources, while nuts, avocado and olive oil are healthy sources of fat.

Vitamin and Mineral Deficiency

With a vegetable-only diet, you'll miss out on the broad range of vitamins and minerals present in a balanced meal plan. In particular, you may grow deficient in vitamin B-12 and vitamin D. You also run the risk of an iron deficiency. Even though some vegetables, such as dark, leafy greens, are rich in iron, they also contain chemicals called phytates that block absorption of the mineral. A diet deficient in vitamin B-12 or iron can cause anemia, a condition in which your blood doesn't supply your body with enough oxygen.

Disordered Eating

Severely restricting food can be a sign of an eating disorder, particularly if you are trying to lose weight. Healthy weight loss does not involve drastic calorie reduction -- and putting your physical image over your well-being could be a sign of deeper issues. Only a qualified health professional can diagnose such a condition. However, if you feel overwhelmed by your weight or your diet, speak with a counselor or other expert to help ensure optimal physical and mental health.

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