If you have a nagging, mysterious cough that just won’t go away, you may want to check your B12 levels, especially if you’re a vegetarian. Vitamin B12 is a key nutrient found naturally only in animal sources (fortified products, like cereals and soymilk, contain it too). Deficiency is linked to a whole host of serious health problems — from brain shrinkage to depression to anemia. Now Italian researchers have added chronic coughing to that list.

The new University of Turin study found that among patients suffering from persistent, unexplained cough, two-thirds had low levels of vitamin B12. When patients increased their B12 intake to normal levels, their cough disappeared. The connection? “Nerves need vitamin B12 to function, so not getting enough can lead to inflammation which can irritate airways,” says lead researcher Caterina Bucca, M.D. Keep in mind that the body’s ability to absorb B12 declines with age, so make sure to meet your requirements by choosing from sources like those listed below:

Top Sources   Quantity  Daily Value
Clams  3 oz  3,503%
Oysters  3 oz  1,020%
Alaskan King Crab  6 oz  815%
Cereal  3/4 cup  250%
Wild Salmon  6 oz  216%
Soy Milk  1 cup  125%
Halibut  6 oz  97%
Nonfat Yogurt  1 cup  48%
Yellowfin Tuna  6 oz  43%
Turkey Breast  6 oz  28%

Source: USDA Standard Nutrient Database

Bonus: Bananas and pineapple may also help you breathe easier. Children who ate one banana a day had 34% lower incidence of asthma, while other research suggests pineapple’s bromelain may reduce asthma-related inflammation.

Published April 1, 2010