Personalized nutrition: Researchers identify connection between genetic variation and gut bacteria

Researchers uncovered a previously unknown link between genetic variation and gut bacteria which could help nutritionists personalize their recommendations. In a paper published in the journal Cell Host & Microbe, American and Egyptian researchers reported that having many copies of the gene alpha-amylase 1 (AMY1) is associated with increased populations of gut bacteria that play an important role in digestive and oral health.

How genetic variation affects the gut

The researchers analyzed existing genetic and stool sample data from 100 British individuals to examine whether the number of copies of AMY1, which codes for the starch-splitting amylase enzyme, influence gut bacterial composition. Half of the individuals had high copy numbers while the other half had low.

The researchers found that high AMY1 copy numbers correlate with increased populations of Ruminococcaceae bacteria, which proliferate in the intestine when amylase levels are high. These bacteria break down resistant starch so it can be digested — a feat that human amylase cannot do.

Being able to break down hard-to-digest starch is beneficial for your health. In prehistoric times, people with more AMY1 copies fared better than those with fewer copies when food was scarce.

“It likely provided additional nutrition from starch,” said Angela Poole, an assistant professor of nutrition at Cornell University and the lead author of the study. (Related: Study: Almost ALL our genes are influenced by the food we eat.)

However, higher copy numbers also correlated with increased populations of the mouth bacteria Porphyromonas, which are associated with periodontal disease.


The researchers then recruited 25 participants in New York with AMY1 copy numbers that ranged from high to low and put them on a high-starch diet for two weeks. After analyzing saliva and stool samples from the participants, the researchers found that AMY1 copy numbers correlated with increases in the same bacteria.

These findings can help advance personalized nutrition, according to Poole. Health professionals can take patients’ AMY1 copy numbers into account when giving dietary advice.

What is personalized nutrition and is it effective?

Personalized nutrition goes by many names, including “precision nutrition,” “individualized nutrition” and “nutritional genomics.” Each term carries nuances in meaning, but experts agree that the goal of personalized nutrition is to improve health by tailoring dietary recommendations and interventions to people’s specific needs.

“In general, people define it as nutrition based upon the individual,” registered dietitian Tanya Freirich told Very Well Fit.

Personalized nutrition isn’t new, but it’s on the rise partly because personalized data has become so accessible recently.

“DNA tests are cheaper and more readily available than ever,” Freirich said. “Most people can track their activity levels, heart rates, and oxygen saturation with a smart watch or activity tracker.”

Lauren Harris-Pincus, a registered dietitian-nutritionist, says there’s a scale of complexity when it comes to personalized nutrition. It can be as simple as working with a person to implement behavioral changes or as complex as using a person’s genetic code to determine which foods and lifestyle interventions will fit them best.

But is personalized nutrition actually effective?

In a review of personalized nutrition trials, researchers from Deakin University in Australia found that people are more likely to eat healthy when they receive personalized advice than generalized dietary advice.

“We know that overall, diets don’t work,” Harris-Pincus said. “Most people who lose weight gain it all back plus more.”

But personalized nutrition is not just about weight loss. According to Harris-Pincus, it can also tell you how to better control your blood sugar and cholesterol and determine which types of exercise are best for you.

So yes, personalized nutrition can benefit you whether you’re trying to lose weight, manage diabetes or just wish to stay healthy.

Learn more about the benefits of personalized nutrition at

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