The Downside of a Vegetarian Diet

It's not always easy going green. A plant-based diet may leave you lacking in vitamin B12, finds a new research review in the Journal of Agricultural and Food Chemistry.

B12 is created by a particular type of bacteria that’s mainly found in the digestive tracts of animals, which means foods like milk, eggs, meat, and fish are the major dietary sources of the vitamin. So if you're a vegan or strict vegetarian, you'll have a tough time getting your daily dose, the study says.

"There can be some B12 in sea vegetables," says Alexandra Caspero, R.D., owner of weight-management and sports-nutrition service "But it varies so widely that it's not a reliable source."

Why do you need the vitamin in the first place? For starters, B12 helps your body break down homocysteine, an amino acid in the blood that’s linked to brain shrinkage and heart disease. The vitamin also assists with the production of red blood cells, which prevent you from developing pernicious anemia, a condition that lowers energy levels.

If you're worried you won't get enough of the nutrient because you don't eat animal-based foods, there's an easy backup plan: fortified cereals. Eat a bowl of 100 percent B12-boosted cereal, like Total or Multigrain Cheerios, every morning and you should be able to hit the daily quota of 2.4 micrograms. Or you could cover your nutritional bases with a multivitamin.

But it's important to note that any reduced-calorie diet can leave you lacking in certain nutrients. For example, in a University of Connecticut study, researchers analyzed the nutrient intake of people following either a low-carbohydrate or a low-fat diet. If a nutrient fell below 80 percent of the recommended dietary allowance (RDA), it was characterized as marginally deficient, whereas those less than 50 percent of the RDA were considered to be significantly deficient. The results:

Marginally Deficient
Low-carbohdydrate: folate
Low-fat: folate, calcium, magnesium, pantothenic acid

Significantly Deficient
Low-carbohydrate: vitamin D, chromium
Low-fat: zinc, vitamin D, chromium, molybedenum

These were just averages, of course. Nutrient intake can vary substantially from person to person depending on food preferences. A guy who eats several servings of vegetables a day will be far less likely to have a deficiency than one who doesn’t down any. Remember that, no matter what diet you adopt.

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