Brushing your teeth after eating starchy foods may be more important for some people than others, according to new research from Cornell University. Scientists have found that variations in a specific gene that affects starch digestion can negatively impact the concentration of bacteria in the mouth—potentially increasing the risk of tooth decay and gum disease. The findings are published in the journal Microorganisms (“The Impact of Human Salivary Amylase Gene Copy Number and Starch on Oral Biofilms“).
The study found that the number of copies of the AMY1 gene—which produces salivary amylase, the enzyme that breaks down starch in the mouth—influences how oral bacteria react to starchy foods. This effect could explain why some people experience more dental problems than others, even with similar oral hygiene habits. Depending on the number of AMY1 copies you have, you may want to be just as careful about brushing your teeth after consuming these digestible starches.
Which people attract bacteria?
The number of copies of the AMY1 gene varies widely among individuals, from 2 to 20 copies. People with more copies produce more amylase in their saliva and break down starchy foods more efficiently. This genetic variation evolved as humans switched to agricultural diets with higher starch content thousands of years ago.
The research team cultured bacteria from saliva samples from 31 adults with different numbers of AMY1 copies in the laboratory. They created cultures that resembled dental plaque both with and without starch to observe how the bacteria would react. The questions the scientist included in the study were: a). what happens in our mouths when we eat starch? and b). What is the difference in the behavior of bacteria in those with high and low copy numbers?
The study concluded and explained that:
- Those with high AMY1 copies responded differently to starch than those with low copies. Specifically, when starchy foods were consumed, two types of bacteria – Veillonella and Atopobium – were less abundant in samples from donors with high AMY1. Both of these bacteria have been linked to tooth decay and gum disease
- Someone with high copies efficiently breaks down starch and the bacteria that are attracted to these sugars, resulting in a higher number of “fighter” bacteria in their mouths.
- Populations that historically had greater access to starch had more copies, which would give us a survival advantage when food is scarce, being able to better break down starchy foods
- Samples from donors with periodontitis had significantly lower bacterial diversity compared to those from individuals with healthy gums
- Populations with high AMY1 copy numbers were found to have increased concentrations of Streptococcus bacteria that feed on starch breakdown products. Furthermore, while some Streptococcus species cause tooth decay, others are beneficial and may help inhibit harmful bacteria
Starchy treats that are dangerous for teeth
- white bread and rolls
- pasta and noodles
- white rice
- crackers and pretzels
- potato chips
- french fries
- mashed potatoes
- breakfast cereals (especially refined ones)
- candy and donuts
- cookies and cakes
- pizza dough
- bagels
- corn-based snacks
- instant oats
- refined flour tortillas
Less dreaded starchy foods
- brown rice
- whole wheat bread
- steel cut oats
- quinoa
- barley
- beans and legumes
- sweet potatoes
- whole wheat pasta.
