Every day, our body breaks down the food we consume into its molecular components. This allows us to utilize fats, carbohydrates, and proteins. But all the secondary plant substances, minerals, vitamins, and micronutrients also find their way into our body through the intestines. How exactly this works is complicated in detail. There are various absorption pathways to ensure that all molecules reach their site of action.
So that you know better in the future, why, for example, the bioavailability of magnesium varies between 4 and 80%, why we should add certain secondary plant substances oil, what bioavailability actually is and which absorption pathways exist in our body, this article will provide you with information.
Absorption pathways – everything starts in the stomach
To help you better visualize the different absorption pathways, let's look at an example together. Let's say you eat an apple. In the mouth, it is already broken down and mixed with the first digestive enzymes. Generally speaking, digestive enzymes are helpers that can break down food into smaller pieces. Amylase can z.B. cut long-chain carbohydrate chains into shorter pieces.
But back to our apple. It now ends up chopped in an acid bath – the stomach. In this harsh environment, as many germs as possible are to be destroyed by the acid, and the food is further softened. But this is not the only task of the stomach. It also produces the Intrinsic Factor (IF). This protein is essential for us to absorb vitamin B12. Without the Intrinsic Factor, this would hardly be possible.
200m2 Intestine for absorption
After our apple has already been partially digested by stomach acid, it now moves into the duodenum, where additionally bile and pancreatic juice meet the chyme. The pancreatic secretion contains peptidases that ensure that the proteins in our food are broken down into individual amino acids.
Now that almost everything is broken down, the crucial question arises. How can we absorb the remaining molecules?
The answer to this question is hidden in our small intestine. This is a fascinating development of evolution.In an adult human, it is about 5m long and its surface area is more than 200m², which is slightly less than an entire tennis court. On this huge area, there are a lot of transporters that help us absorb all the important components from our food. For example, our intestinal cells have a special transporter to absorb iron ions. We need these for the red pigment in our blood, hemoglobin. However, we can also take in iron (in the form of hemoglobin) through the heme transporter, which is found in meat. First Pass Effect – the liver is in charge here We have overcome the first hurdle.Our molecules have made the journey from food, through the intestines, into our bodies. Through the portal vein – a vessel that collects all the blood from the digestive tract – they now reach the liver. It serves as the first detoxification site in the body.
All nutrients that have been absorbed through the intestines must first pass through the liver, where they are processed by liver cells. Through various biochemical processes, the molecules are processed – and this has significant consequences for the further course. In medicine, this phenomenon is called First Pass Effect.
Perhaps an example will help you better understand the significance of the First Pass Effect. In medicine, different forms of opioids are used.This class of medications binds to the opioid receptors and thus provides strong pain relief. However, there is an opioid derivative that is used not for pain but for diarrhea. Loperamide. This binds in the intestine to the enterocytes (intestinal cells) and thus causes a slower intestinal passage. However, like all other medications, it also enters the bloodstream, where it is detoxified by over 99% in the liver and thus shows hardly any effect in the rest of the body.
Parenteral, sublingual, buccal, and Co. – who is who?
Our liver is therefore a kind of preemptive shield. Before a molecule reaches the brain or the heart, it must pass the "entry check" in the liver.This makes sense from an evolutionary perspective, but can sometimes be a hindrance in medicine. One can partially circumvent this first-pass effect by increasing the concentration of the starting substance, so that the liver cannot manage to "detoxify" all molecules. However, this is often associated with some side effects. A more elegant solution in this case is to change the method of application. Instead of orally, we have additional parenteral (besides the intestine) absorption pathways available. When it needs to be quick, the buccal (via the cheek mucosa) or sublingual (under the tongue) application of medications can be performed. These are predominantly pain medications that dissolve in the mouth or under the tongue.Through the blood vessels, these molecules go directly to the heart. The liver is bypassed. To help you better understand the pathways, we have provided a graphic.
It works very similarly with suppositories. The blood from the rectum no longer goes to the liver, but instead goes directly to the heart via the inferior vena cava. This is especially a popular method for children to bypass the liver with active ingredients.
You probably know the last method from the hospital. We can also administer medications directly through the vein. This also allows us to bypass the liver and the first-pass effect.
Liposomal vs. Hydrophilic
By now, we have made it into the bloodstream, but there are still more hurdles waiting for us.In principle, we can distinguish between molecules that are fat-soluble (lipophilic ), such as vitamins A, D, E, K and water-soluble ones like vitamin C . Water-soluble substances can be easily transported in the blood, but have a harder time getting into the cells. For fat-soluble substances, it is exactly the opposite. In the blood, they often require special transport proteins, but they can pass through the phospholipid layer of the cells more easily.
When we talk about blood fat levels, these fat particles do not float freely in the blood, but are bound to transport proteins, such as apolipoprotein B . Thus, these blood fats can be made water-soluble.If you want to learn more about which blood lipid values are important for your longevity, feel free to read our article on the subject. Bioavailability using magnesium as an example Not everything we eat reaches our blood in the same way. Roughly simplified, this is how you can imagine bioavailability. One measures the concentration of the substance in the blood plasma (after it has passed through the liver) and compares it with the initial concentration. Significant differences can arise.
A good example is Magnesium. This occurs naturally in various compound forms, such as magnesium oxide, magnesium citrate or magnesium bisglycinate . The bioavailability of magnesium varies greatly between these compounds.
The well-known magnesium oxide has a bioavailability of only 4% ! This means that while this form is quite effective for constipation, other forms are significantly more effective for magnesium supplementation. Magnesium citrate and magnesium bisglycinate are both absorbed by our body at 80% for example. Additionally, magnesium bisglycinate can also cross the blood-brain barrier into the brain.
Secondary plant substances – the difficulty with bioavailability
Secondary plant substances have a number of health benefits. We have already provided you with an overview in a separate article.
The problem with secondary plant substances is, on the one hand, their concentration. In studies, large amounts of the pure substance are used. To z.B.the amount of quercetin we would need to take in order to match what is used there would be up to 100 apples – daily. For resveratrol , it varies by study, 12l of red wine and for sulforaphane , it would be up to 40kg of broccoli – all per day.
Some of the secondary plant substances, such as resveratrol or quercetin are fat-soluble. This means we can absorb them less effectively for the reasons mentioned above, and the bioavailability is low.To circumvent this, we can pack the molecules into a phospholipid layer and thus increase the bioavailability multiple times.
For the blood sugar-lowering berberine , this formulation can increase bioavailability by up to 10 times and for quercetin by up to 20 times! This is made possible on one hand by the combination of a lipid layer and on the other hand by the addition of adjuvants, which are molecules that can assist in absorption. For quercetin, this is vitamin C and for berberine a mineral complex.
Bioavailable Berberine with Chromium and Zinc in the Mineral Complex Berbersome
Absorption of secondary plant compounds - the devil is in the details
Not only quercetin and berberine need a little help to increase bioavailability, but also the sulforaphane contained in broccoli Sulforaphane. In this green vegetable, this anti-inflammatory molecule is still in its precursor, glucoraphanin . This is converted in our intestines with the help of the enzyme myrosinase into sulforaphane .The efficiency, however, is not very high – it is around 10% and usually even lower, as individual substances are washed out due to prolonged cooking. For this reason, Sulforapro contains both glucoraphanin and myrosinase. And there is another trick to ensure that the active ingredient reaches exactly where it is needed. In the intestine. The magic word here is: stomach-resistant capsules.
Sulforaphane from molecular precursors combined with the finest broccoli extract - a natural source of sulforaphane
Size matters
The molecules we consume daily come in very different sizes. Some of them are too large to be absorbed directly – z.B. Collagen and Hyaluronic acid, both important molecules for skin health. These substances form long molecular chains that are not absorbable by our body. Therefore, if we want to consume collagen or hyaluronic acid through food, we need to package the molecules smaller, in so-called peptide shells. These contain already crushed pieces of the starting substance. Here it gets a bit complicated.
In collagen the studies have shown that it is beneficial if the fragments in the peptide shells are as small as possible. In hyaluron it is exactly the opposite. Larger fragments, known as high molecular weight hyaluron, showed better results in studies with humans.
Conclusion on absorption pathways
The path from food to our cells is not always as simple as one might think. Fat-soluble and water-soluble molecules are absorbed differently.The liver metabolizes many molecules before they even enter the bloodstream, and the bioavailability of the substances depends on the composition.
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