Have you ever wondered what happens when we eat 'DNA'? Considering that most of our daily food contains cells with DNA, it's worth exploring what becomes of the external DNA we consume
This thought never occurred to me, although I have been associated with DNA and chromatin research for around 20 years. It is surprising considering most of our food, whether vegetables, fruits, nuts, grains, or meat, is made from cells that eventually contain DNA. So what happens to that external DNA we consume?
It is believed and accepted that when cooking at a higher temperature, DNA is broken down into smaller pieces that are eventually degraded by our digestive system. Most of the DNA entering our digestive system is broken down and degraded to mono-nucleotides by nuclease enzymes present in pancreatic and intestinal juices. However, very tiny fractions of fragmented or broken DNA can pass through the digestive system and eventually end up in the bloodstream and organs.
So what happened to the DNA, which ultimately reaches tissues and organs? Since its fate and adverse effects were not identified, it was considered non-harmful. However, a recently published article (Jun, Y. W., et al. 2023) explores this idea of DNA entering our system. Authors claim that cooking at higher temperatures results in higher levels of damaged DNA, such as deamination and oxidation of DNA bases. They provide evidence that damaged DNA can enter cells, potentially triggering a DNA damage response, as observed in cultured cells and mice intestines. While the direct or indirect effects are yet to be fully understood, it's evident that damaged DNA has the potential to incite reactions within cells.
So how much DNA is consumed by our food? surprisingly astonishing amount! For instance, consuming 500 grams of steak results in ingesting more than a gram of DNA! Organ meats like liver or heart contain even higher amounts of DNA (refer to the original article for precise values). In contrast, vegetable-based food sources offer a better option as they typically contain lower DNA content, making this a point worth considering for those contemplating a vegan diet.
It is to be noted that this study offers early findings, future studies will shed more light on the adverse effects of consumption of DNA, particularly in humans. Additionally, this study reports adverse effects caused by damaged DNA. Does it mean that undamaged DNA is not harmful? or damaged DNA is not easily degraded by our digestive tract and hence ends up inside cells. Future research will clarify these questions.
Do we need to worry if human cells or tissues take foreign DNA from the digestive system? The simple answer would be ‘yes’, particularly if it is damaged DNA resulting from various reasons, including high-temperature cooking. But my worry will not be for human cells but for the microbes present in our gut system. Our gut microbial population is estimated to be over 100 trillion microbial cells, whereas our whole body contains roughly 37.2 trillion cells. Even if you ignore the numbers, as it is impossible to estimate them with accuracy, it is clear that microbes will outnumber us by a large fraction. Now the question is, How do these microbes see foreign DNA? Since most microbes fall in the lower part of the evolutionary scale, they lack either sophistication or defense mechanisms to deal with foreign DNA invasions, unlike their eukaryotic counterparts.
We are all born with sterile guts, but when we reach the end of toddlerhood, we have fully developed gut microbiota, for whom we will be hosts throughout our lives. Since, there is mutual benefit for both, a synergy exists between the host and microbial population. This inevitable partnership is put under stress due to antibiotic consumption, aging, stress, illness, and lifestyle changes such as a bad diet. Damaged DNA from what we consume due to elevated temperature cooking could be another way to kill the synergy between our digestive system microbes. Since we are all grown with these microbes, it will be challenging to discard and rebuild the entire gut microbiota.
In conclusion, the notion of consuming DNA through our food offers a fascinating avenue for exploration. While current findings raise intriguing possibilities, more research is needed to comprehend the full impact of DNA consumption, particularly damaged DNA, on our health and gut microbiota.
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