Capsules and Tablets: What Nobody Tells You About Absorption | GenerAcion Vita
What labels don't have the space to tell you about capsules and tablets
Capsules and Tablets: What No One Tells You About Absorption
Discover why your supplement's form might be compromising its absorption. Excipients, mineral competition, and gastric pH, all explained with verified sources.
Have you ever wondered why you have been taking supplements for months without feeling a difference?
The answer is rarely the brand, but rather the form.
Most supplements you find on the shelves—whether in a pharmacy, health store, or online—come in capsules or tablets. It is the most common format, the cheapest to produce, and the easiest to store, but there is important information that simply doesn't fit on a label and that completely changes the way you should look at what you are taking.
The problem starts before the supplement reaches your blood
When you swallow a capsule or tablet, the active ingredient does not go straight into your bloodstream; first, it must pass through a series of barriers:
Dissolution in the stomach → Absorption in the small intestine → Transport to the bloodstream
Each of these stages is an opportunity for part of what you took to be lost, and there are factors that make this loss much more likely than you imagine.
1. Excipients — the ingredients no one mentions
Open the label of any capsule or tablet and you will find, beyond the active ingredient, a list of substances with unfamiliar names: for example, magnesium stearate, silicon dioxide, microcrystalline cellulose, hypromellose.
These are excipients, substances added to give the product form, stability, and consistency. For decades, they were considered pharmacologically inert, meaning they had no effect on the body.
Recent research suggests otherwise.
A systematic review published in ScienceDirect in 2025 analyzed about 180 studies and demonstrated that certain excipients can alter intestinal permeability, modulate absorption transporters, and interfere with metabolic enzymes, thereby directly affecting the amount of active ingredient that reaches circulation.¹
This does not mean that all excipients are problematic, but it does mean that the formulation matters and that two supplements, with the same active ingredient, can have very different bioavailabilities.
2. Mineral competition — the problem no one sees
Imagine you decide to take a multimineral supplement, for example, calcium, iron, zinc, magnesium, and copper in a single capsule... it seems practical and efficient, but in reality, you are creating an internal competition within your own gut.
These minerals share the same intestinal transporters, in particular the DMT1 (Divalent Metal Transporter 1) transporter, and when they are present simultaneously and in high doses, they compete with each other for entry into intestinal cells. The result: the absorption of each is compromised by the presence of the others.²
Some documented examples:
- Calcium and iron — calcium inhibits the absorption of non-heme iron in a dose-dependent manner, especially at doses ≥300 mg in the same meal³
- Zinc and copper — excess zinc increases intestinal metallothionein, a protein with higher affinity for copper, which can cause copper deficiency even with adequate intake⁴
- Magnesium and zinc — they share common absorption pathways; high doses of magnesium can inhibit zinc absorption
The chelated form partially solves this problem by binding the mineral to an amino acid and utilizing dipeptide transporters, an alternative, less saturated pathway. But in a conventional multimineral tablet or capsule, this advantage rarely exists.
3. Gastric pH — the silent factor
The dissolution of a capsule or tablet depends directly on the stomach's pH.
The problem is that gastric pH is not constant and varies according to:
- Time of day — it is more acidic in the morning while fasting
- Age — gastric pH tends to increase (become less acidic) with aging
- Medication — proton pump inhibitors (PPIs) and antacids significantly raise gastric pH
- Health status — gastritis, H. pylori infection, and other conditions affect acidity
A high gastric pH can drastically reduce the dissolution of inorganic mineral forms and compromise the release of the active ingredient from enteric-coated tablets.⁵
In a liquid or liposomal form, this variable is practically eliminated, since the ingredient is already dissolved or encapsulated in lipid vesicles that do not depend on pH to be absorbed.
4. Inorganic forms — cheap to produce and (usually) less effective for absorption
The vast majority of mineral supplements in capsules or tablets use inorganic forms: oxide, carbonate, sulfate, chloride.
Why? Because they are significantly cheaper to produce.
A systematic review of 14 studies published in the journal Nutrition in 2021 concluded that organic forms of magnesium, such as bisglycinate, citrate, and glycinate, are consistently more bioavailable than inorganic forms.⁶
Magnesium oxide, for example, is one of the most common forms on the market and one of the least absorbed. Studies point to absorption rates of less than 15%, meaning that more than 85% of what you take is simply eliminated from the body.
What this means in practice
We are not saying that all capsules and tablets are ineffective. We are saying that the chemical form of the active ingredient, the presence and type of excipients, and the time and context in which they are taken make a real and documented difference in the amount your body effectively uses.
Before choosing a supplement, the right questions are:
- What is the chemical form of the active ingredient?
- Does it contain excipients that might interfere with absorption?
- Am I taking minerals that compete with each other?
- Is my gastric pH optimized for this form?
At GenerAcion Vita, these are the questions we ask before selecting any product, and they are the questions we want you to ask as well when choosing a food supplement.
References
¹ Systematic review of pharmaceutical excipients and intestinal drug absorption. ScienceDirect, 2025. sciencedirect.com
² Interaction and competition for intestinal absorption by zinc, iron, copper, and manganese. PubMed, 2024. PMC11920315
³ Hallberg L et al. Calcium: effect of different amounts on nonheme- and heme-iron absorption. Am J Clin Nutr. 1991. PubMed 1984335
⁴ Duncan A et al. Iatrogenic copper deficiency: risks with zinc prescribing. Br J Clin Pharmacol. 2023. doi:10.1111/bcp.15749
⁵ The Bioavailability of Drugs — The Current State of Knowledge. PMC, 2023. PMC10745386
⁶ Uberti F et al. Bioavailability of magnesium food supplements: A systematic review. Nutrition. 2021. ScienceDirect
Want to know which supplementation forms have higher bioavailability? Explore the GAV Academy or discover your absorption profile in 2 minutes.
