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What exactly happens to the food we eat?

What exactly happens to the food we eat?

Have you ever wondered what happens to food after we put it in our mouths? Paweł Jedynak from the Faculty of Biochemistry, Biophysics and Biotechnology describes the journey the food takes through our organisms, and uses this opportunity to discuss and debunk a recently popular myth – the leaky gut syndrome.

1Question is a series of articles by the University Marketing science communication unit, in which specialists and experts from various fields briefly discuss interesting issues related to the world, civilisation, culture, biology, history, and many more.

The food we eat is, of course, digested. Proteins are broken down to amino acids, and starch releases glucose, an important source of energy. Not all compounds of the food we eat are useful to us. More complex compounds, such as fibre, will not be absorbed by our bodies – the will leave them unchanged. Even the most delicious-looking meals will eventually turn into metabolic waste.

Microparticle ingredients of our diet are much more interesting. Some of them are so small that they can easily penetrate cell membranes. Others combine with fats and enter our organism along with them. Several of them are mistaken for carbohydrates or amino acids and collected by specialised transporters which line our small intestines. This holds true for humans and animals alike. That’s also the way toxins can enter our organisms. However, most of the substances we ingest has little to no effect on our health and mood.

There and back again

Some of the ‘foreign’ compounds may be temporarily deposited in tissues and organs. In this sense, the saying ‘you are what you eat’ is true. Indeed, even cooks in the Middle Ages and Renaissance knew that! Weeks before animals were butchered, cooked and served at the table, they were fed with fragrant herbs. The metabolites in those herbs were stored in the animals’ muscles, enriching the meals’ flavour. The same goes for our bodies – the body of someone who frequently eats in fast food bars will greatly differ from the body of a strict vegetarian in terms of the compounds found in them. Practically everyone can recognise the striking colour of the meat of salmon or rainbow trout, fish that are fed copious amounts of carotenoids. Carotenoids are also responsible for the colour of flamingos’ feathers – if the birds don’t get enough of them, their pink plumage wans.

The compounds we ingest don’t stay with us forever. From tissues, they can travel through the bloodstream to the liver, which brakes them down or neutralises them by binding them with carbohydrates (it increases the solubility of the compounds, but also hampers their interactions with proteins and enzymes). After that, the compounds are transferred to the kidneys, where they are filtered out and excreted with urine. This journey is not always quick – it can take a week for the caffeine from a cup of coffee to leave our body.

Travelling betanin

The name 'betalain' comes from the Latin name of the common beet (Beta vulgaris), from which betalains were first extracted. The deep red color of beets, bougainvillea, amaranth, and many cactuses results from the presence of betalain pigments.

Sometimes it is possible to see the compounds travelling through our organisms. After we consume beets, the betanin and its derivative betalain (red food dyes) which they contain can be absorbed by intestinal cells. The exact details of this process are unknown, but we do know that they can spread through cell membranes. Nevertheless, betalain is absorbed at a very low rate and is easily transformed into compounds that are yellowish in colour. It's estimated that about 50% of betanin is broken down in the stomach.

When the dye finds a way into our bloodstream, it's excreted with urine. Depending on various factors, we may expect the urine to turn reddish about from about 2 to 4 hours after we consume beets. Only about 3% of the betalain we ingest has the chance of travelling through our bodies – unless we eat more beets, that is. As of now, we haven't found
any relation between the absorption and exctretion
of betalain and health or genetic conditions.

Changes in the colour of urine can also be induced by artificial colourings added to food. Researchers studying the behaviour of wild animals can use this to their advantage by adding such substances to baits and follow the trail that the animals leave behind.

Leaky gut

Beet juice has recently risen to popularity because of the so-called ‘leaky gut syndrome’, an alleged medical condition mostly proposed by nutritionists and practitioners of alternative medicine. To determine if a person is suffering from the leaky gut syndrome, they have to drink some beet juice and observe if the colour of their urine changes. Such change is claimed to be the evidence of leaky gut. Meanwhile, the reason for this is much simpler. Betaine, just as many other compounds, is actively drawn by the intestinal cells regardless of any pathological conditions. The leaky gut syndrome is not a medically confirmed condition.

The leaky gut syndrome is not a medically confirmed condition

The origins of this hypothetical affliction probably has its origin in the very rare cases of chronic enteritis related to diseases such as the congenital Crohn’s disease. In these cases, intestines are indeed damaged, but it is the result of the disease, not its cause. The intestines of the patients are tested using a highly specialised method involving a compound 250 times more massive than betaine, unavailable to the general public. Websites that warn people about the dangers of the leaky gut syndrome very frequently advertise a wide range of expensive dietary supplements at the same time. Therefore, our concern for health is often preyed upon by people wishing to make money out of it.

It’s important to note that blood is not only used by our organism to produce urine, but also other important fluids, such as tears or saliva. This means a lot of ‘foreign’ compounds are also present there. Scientists use this fact to develop non-invasive tests for xenobiotics (food ingredients that are alien to both our organisms and natural foods), such as the omnipresent bisphenol A.

Original text:

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