Strontium is a trace mineral that is good for bone health. It is a silver-gray metal that occurs naturally in nature. Strontium is assimilated in the body in the same way as calcium. In the body, strontium is absorbed into the bloodstream and also behaves similarly to calcium, according to the Argonne National Laboratory. Several types of foods are rich in strontium.

Milk and dairy products contain strontium. Cows' digestive processes reduce the strontium/calcium ratio. Pasteurized milk contains an average value of 0.86 milligrams of strontium per liter. Strontium levels in North American milk range from 0.43 mg/liter to 1.51 mg/liter, according to a study by Georgia L. Rehnberg, et al., published in the February 1969 issue of Environmental Science & Technology. Cream has half the amount of strontium of whole milk, while skim milk has slightly higher amounts of strontium than whole milk. Cheddar cheese is even higher in strontium than whole milk.

Strontium-90 is another form of strontium. It is a radioactive isotope that is fallout from atmospheric testing of nuclear weapons. Current levels of strontium-90 are very low and do not pose health risks at low doses, according to the Environmental Protection Agency. Although strontium-90 levels in milk are small, they contribute half the total strontium-90 intake in the adult diet. Strontium-90 averages 15 micromicrocuries per liter of milk.

The amount of strontium in vegetables varies according to the region they were grown. Lettuce from California is a rich source of strontium. Stable strontium levels in vegetables are high. Vegetables with the highest amounts of strontium include spinach, lettuce, carrots, peas, beans, potatoes and celery.

Radioactive strontium is found in small amounts everywhere, according to the Centers for Disease Control. Levels of radioactive strontium-90 are relatively low in vegetables and are safe for human consumption. Lettuce has 17 micromicrocuries, mmc, per kilogram of strontium-90. California cabbage has 5.1 mmc/kg and celery 3.4 mmc/kg.

Grains are another food source rich in strontium. The level of strontium in the soil affects the amount of strontium in grains. Wheat, barley and other grains used to make bread have significant levels of strontium. Flour, grains and breads average 2 mmc/kg of strontium-90 and 2,150 mg per gram of stable strontium.

Low levels of strontium-90 are also found in grains. These levels are so low, around 11 picocuries/day, that they are not a health concern.

Oysters, mollusks, fish and other seafood are rich sources of strontium. Shellfish tend to have higher levels of strontium because they are filter feeders.