According to Gram research analysis of a 2026 study, severe illness appears to push nitrogen levels in teeth up by 1 to 3 parts per thousand, which can mimic a change in diet. Researchers tracked 13 captive rhesus macaques and found these spikes during bouts of diarrhea, dehydration, and weight loss, often after nursing ended.
Scientists often study nitrogen levels in teeth to learn what ancient people ate. A 2026 study in the American Journal of Biological Anthropology, according to research reviewed by Gram, suggests that serious sickness can distort that picture. Researchers examined teeth from 13 captive rhesus macaques, monkeys that ate nearly identical store-bought diets, and measured their nitrogen levels every few weeks. After nursing ended, the teeth showed sudden rises of 1 to 3 parts per thousand during periods of severe illness and weight loss. Every monkey in the study tested positive for Campylobacter, a bacteria that causes stomach illness, at least once. The findings suggest that a spike in tooth nitrogen may signal illness rather than a change in diet. This matters for interpreting the health history of ancient humans.
Key Statistics
A 2026 study of 13 captive rhesus macaques published in the American Journal of Biological Anthropology found that nitrogen levels in tooth dentin rose by 1 to 3 parts per thousand during periods of severe illness and weight loss.
In the same 2026 study, all 13 monkeys tested positive for Campylobacter at least once, and the end of nursing was identified in the first molars of eight individuals.
The Quick Take
- What they studied: Can changes in nitrogen levels inside teeth reveal periods of serious illness, or are they caused only by changes in diet?
- Who participated: 13 captive rhesus macaques, a monkey species, all fed similar commercial diets. Eight had their first molars analyzed and six had their second molars analyzed. Most were treated for stomach problems, dehydration, or being underweight.
- Key finding: After nursing ended, most monkeys showed sudden rises of 1 to 3 parts per thousand in tooth nitrogen during severe illness and weight loss. This is a very small chemical difference, but scientists treat jumps of this size as meaningful.
- What it means for you: This study was done in monkeys, so it does not tell you what to eat. It is a reminder that illness can affect body chemistry, and that tracking symptoms and weight alongside meals gives a fuller picture of your health.
The Research Details
Researchers worked with a captive colony of rhesus macaques that ate nearly the same diet. Colony staff kept detailed records of illnesses, treatments, and body weight. Because the diet was so consistent, any big changes in the monkeys’ body chemistry were more likely to come from something other than food.
Teeth grow in layers, much like tree rings. The team used a very precise ion-beam instrument to measure nitrogen at many points across the tooth, often every week to every month. They matched each measurement to the age when that layer formed. This allowed them to identify when nursing ended in eight of the monkeys.
Finally, the researchers compared the nitrogen readings with the colony’s health and weight records. This let them see whether nitrogen spikes lined up with real events like diarrhea, dehydration, or weight loss.
Most studies of teeth can only guess what happened in an animal’s life. This design links chemical readings to dated tooth layers and to real health records, so the researchers could check whether illness actually matched the spikes. That gives the findings more weight than a study that relies on guesses about the past.
The study was published in a peer-reviewed scientific journal, which means other experts reviewed it before publication. Its measurements were very detailed and were checked against colony records. However, the sample is small, with only 13 animals, and the monkeys were not randomly assigned to conditions. Results from captive monkeys may not apply directly to people living in the wild or to ancient humans.
What the Results Show
The researchers first identified when each monkey stopped nursing. In eight individuals, the change in tooth chemistry matched the end of breastfeeding. This shift marked a major dietary transition, since milk and solid food carry different nitrogen levels.
After weaning, most monkeys showed repeated jumps in tooth nitrogen of about 1 to 3 parts per thousand. These jumps appeared during periods of severe illness and weight loss. Because the monkeys ate almost the same food, the researchers concluded that the spikes were likely linked to the body’s response to sickness rather than to changes in diet.
All 13 monkeys tested positive for Campylobacter at least once. Campylobacter is a common bacteria that can cause diarrhea and stomach distress. Many of the monkeys were treated for idiopathic diarrhea, dehydration, and thin body condition, which suggests the infection and its effects may have contributed to the spikes. However, the study cannot prove that Campylobacter alone caused the changes.
The authors argue that tooth nitrogen could serve as a record of severe illness in ancient humans. They also caution that these records are complicated. Without accounting for illness, researchers could wrongly interpret a spike as a sudden change in diet, which could lead to inaccurate pictures of how ancient people lived and survived.
The monkeys did not all show the same pattern. Some had clearer spikes than others, which suggests that the strength of the body’s response to illness varies from one individual to another. This variation is important, because it means a single tooth may not capture every illness a person experienced.
The study also highlights how tooth records can preserve a timeline of early life. Because nursing changes are visible, researchers can use them as a reference point when reading other events in a tooth. This helps show that teeth can capture both developmental milestones and periods of hardship.
Scientists have long used nitrogen in teeth and bones to estimate diet and the age when breastfeeding stopped. This study supports those uses by showing that the nursing transition is clearly visible in the chemistry. At the same time, it challenges the idea that small nitrogen changes always reflect food choices. Recent claims that short-term stress can be read from teeth are partly supported here, but the authors urge caution and call for more research before drawing firm conclusions about individuals.
The most important limitation is the small number of animals, which makes it harder to know how well the patterns would hold for a larger group. The monkeys also lived in captivity on uniform diets, so their situation differs from the varied diets and environments of ancient humans. The study shows that illness and nitrogen spikes are linked, but it cannot prove that illness causes every spike. Finally, the research was done in macaques, not humans, so the findings are a starting point for human research rather than a final answer.
The Bottom Line
For researchers: Moderate to high confidence that illness and weight loss can raise nitrogen levels in teeth, so illness should be considered when reading diet from teeth. For the general public: Moderate confidence that sickness can affect body chemistry in ways that show up in tissue records. No changes to personal eating habits are supported by this study alone.
Archaeologists, bioanthropologists, nutrition students, and readers curious about how scientists read the past from teeth should find this research useful. People looking for personal diet advice should not apply these findings directly, since the study used monkeys and measured tooth tissue. Anyone dealing with ongoing illness or weight loss should talk with a healthcare professional.
Tooth nitrogen records reflect growth that happened over months and years, not short-term changes you can see in your own body. The study does not provide a timeline for personal health benefits or changes. Any improvements in how you feel during recovery from illness are best judged by a healthcare provider.
Frequently Asked Questions
Can illness change nitrogen levels in teeth?
A 2026 study of 13 captive rhesus macaques suggests it can. Researchers found nitrogen spikes of 1 to 3 parts per thousand during severe illness and weight loss, even when the monkeys ate nearly identical diets. The findings come from animal research and need confirmation in humans.
How do scientists use nitrogen in teeth to study ancient diets?
Teeth grow in layers, and the nitrogen in each layer reflects what a person ate at that time. Scientists measure these layers to reconstruct past diets and the age when breastfeeding ended. This study shows illness can also shift those readings, so health history should be considered during interpretation.
Does ending breastfeeding affect nitrogen levels in teeth?
Nursing changes are a major source of nitrogen shifts in teeth. In this 2026 study, researchers identified when breastfeeding ended in eight macaques by matching tooth layers to their growth ages. The shift marked a clear dietary transition that was easy to distinguish from illness-related spikes.
Should I change my diet based on this tooth research?
Dietary changes are not supported by this research alone. The study used captive monkeys on uniform diets and examined tooth tissue, not human eating habits. For personalized nutrition advice, talk with a doctor or registered dietitian.
Want to Apply This Research?
- Log each episode of diarrhea, vomiting, fever, or dehydration in the app, along with the date, duration, and fluid intake. Record your weight at the same time each week to create a measurable timeline you can review later.
- When you feel sick, use the app to log fluid intake and meals, and prioritize hydration. After recovery, note how your appetite and weight return to normal over the following weeks.
- Track weight, hydration, and illness episodes over several months to spot patterns. Bring these logs to a healthcare provider or registered dietitian to interpret trends, rather than trying to draw conclusions from tooth chemistry or animal research.
This article summarizes a study conducted in captive monkeys and is provided for general information only. It is not medical advice. If you are experiencing diarrhea, dehydration, unexplained weight loss, or other health concerns, consult a qualified healthcare professional.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.