Genetic ancestry and genotype-by-diet interactions shape plasma carotenoid metabolism in humans
By integrating multi-ancestry genomic data with a longitudinal dietary intervention trial, this study reveals how genetic ancestry and specific genotype-by-diet interactions, particularly at loci like 3q13 and PKD1L2-BCO1, significantly shape individual plasma carotenoid metabolism and response to supplementation, thereby advancing the framework for precision nutrition.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer
Every time we eat a carrot or a leafy green, our bodies begin a complex process of turning those foods into the nutrients that keep us healthy. Some of these nutrients, called carotenoids, are the pigments that give fruits and vegetables their bright red, orange, and yellow colors. They act as powerful antioxidants in our blood, helping to protect our cells from damage and lowering the risk of chronic diseases like heart disease and certain cancers. For decades, scientists have assumed that if two people eat the same amount of these colorful foods, their blood levels of these nutrients should be roughly the same. However, in the real world, this is rarely true. One person might have high levels of a specific nutrient after a meal, while another has very low levels, even if their diets are identical. This variation suggests that something inside our bodies, beyond just what we eat, is deciding how much of these nutrients we absorb and keep.
A new study brings together genetics, diet, and diverse human populations to solve this mystery. Researchers wanted to understand why our bodies handle these nutrients so differently. They focused on the idea that our genetic makeup, or the unique set of instructions in our DNA, interacts with what we eat. This interaction means that the same food can have different effects on different people. To find the answer, the team looked at a group of people from various racial and ethnic backgrounds, measuring the levels of carotenoids in their blood and comparing those levels to their genetic code. They also conducted a controlled experiment where participants drank a specific amount of carotenoid-rich juice every day for six weeks to see how their bodies responded to a known dose of the nutrient.
The researchers discovered that the amount of these nutrients in our blood is not just a simple reflection of our diet. Instead, it is shaped by a combination of our ancestry and our specific genes. They found that for some types of carotenoids, genetics plays a very small role, but for others, it is a major factor. One specific nutrient, called beta-cryptoxanthin, which is found in foods like oranges and peaches, showed the strongest link to our genes. The study revealed that people with certain genetic variations had much higher levels of this nutrient in their blood than others, even when they ate similar amounts of food. This suggests that for beta-cryptoxanthin, our genes act like a filter, determining how much of the nutrient our bodies actually keep.
To pinpoint exactly which genes were responsible, the team scanned the DNA of hundreds of participants. They identified specific locations in the human genome that were strongly linked to beta-cryptoxanthin levels. One of these locations is near a gene called IGSF11, and another is near a gene called R3HDM4. People who carried specific versions of these genes had significantly different blood levels of the nutrient. The study showed that these genetic differences could explain a large portion of the variation seen in the group, proving that our DNA is a powerful driver of how we process these healthy compounds.
The most revealing part of the study came from the six-week experiment where people drank carotenoid-rich juice. The researchers wanted to see if the genetic differences they found actually changed how people responded to eating more of the nutrient. They found that the answer was yes. People with certain versions of the gene near IGSF11 responded very differently to the juice than those with other versions. Some saw a large increase in their blood levels after drinking the juice, while others saw very little change, even though they all drank the same amount. This proves that the effect of a healthy diet is not the same for everyone; it depends on the genetic instructions each person carries.
The team also looked for rare genetic changes that might cause extreme results. They found that a few individuals with unusually high or low levels of carotenoids carried rare, damaging mutations in genes that help process fats and nutrients. For example, one person with a very low level of beta-carotene had a rare mutation in a gene called BCO1, which is known to help break down carotenoids. This finding reinforces the idea that while common genetic variations create subtle differences in the general population, rare genetic glitches can cause dramatic differences in how a single person handles these nutrients.
This research changes how we should think about nutrition. It shows that blood levels of nutrients are not just a simple report card on what we ate, but a complex picture drawn by our diet, our ancestry, and our unique genetic code. The study suggests that a "one-size-fits-all" approach to dietary advice might not work for everyone. What is a perfect amount of a specific nutrient for one person might be too much or too little for another, depending on their genes. While the study does not yet provide a way to prescribe specific diets based on DNA, it lays the groundwork for a future where nutrition is tailored to the individual. By understanding that our genes shape how we absorb and use the food we eat, scientists can move closer to a world where dietary advice is as unique as the person receiving it.
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