Body parts like teeth can be analyzed for isotope concentrations.

The human body continuously changes in reaction to its environment and the nutrients that enter it. This characteristic means that analyzing the isotopes that are present in the body, or tracing the path of isotopes that have just been introduced into the body, can give scientists and medical professionals lots of useful information.

Diagnosis of Disease

Radioactive isotopes are used in medicine for producing diagnostically useful images. The patient inhales, swallows or is injected with the radioactive isotope, and then a detector follows its path and where it ends up. The radioactive movement can show whether the normal pathways, such as the blood vessels of the brain, contain blockages. It can also show whether an organ does not collect as much isotope as it should, or if it takes up more than it should.

Nutritional Uptake Studies

When nutrients enter the body, being able to identify their path through the body is useful knowledge for nutrient metabolism in general, and is also helpful in identifying issues of malabsorption in people with medical problems. For example, tracking where calcium isotopes end up in people with weak bones can identify whether calcium absorption is an issue, or if the calcium ends up in the bones as it should.

Identifying What Someone Ate

The human body takes nutrients from foods to maintain and renew the cells, so it makes sense that the isotopes in a particular person's body reflects their diet. Carbon and nitrogen isotopes are especially important for this type of information, as they are common in plant foods and animal foods respectively.

Identifying Where Someone Lived

The level of isotopes in a human body varies according to where the person was born, lived and moved to. For example, strontium can come in strontium 87 and strontium 86 isotopes. Each geographical location has a particular ratio of one strontium to another. Growing children absorb strontium from water and food, and this settles in the permanent set of teeth to remain at the same level for life. Strontium also collects in bone, but changes every decade or so. This difference means that analysis of these isotopes in the body can identify where the person spent her childhood, and where she spent the last decade of her life.