Not all supplement ingredients are created equal. This article explains the importance of ingredient form — from magnesium glycinate vs. oxide to methylfolate vs. folic acid.
In the supplement industry, bioavailability — the proportion of an ingested nutrient that is absorbed and utilised by the body — is one of the most important yet least understood concepts. Two products with identical label claims can deliver vastly different physiological effects depending on the form of the ingredient used. Understanding bioavailability is essential for formulating products that actually work.
Bioavailability is influenced by multiple factors: the chemical form of the ingredient, the delivery format (capsule, tablet, liquid, etc.), the presence of co-factors that enhance or inhibit absorption, individual physiological factors such as gut health and age, and the timing of consumption relative to food intake. Of these, the chemical form of the ingredient is the factor most directly within a formulator's control.
Magnesium is available in dozens of forms, with dramatically different absorption profiles. Magnesium oxide — the cheapest and most common form — has a bioavailability of approximately 4%. Magnesium citrate achieves around 30%. Magnesium glycinate (bisglycinate), a chelated form bound to the amino acid glycine, achieves bioavailability of 80% or higher and is also the gentlest on the digestive system. For a brand positioning around efficacy, the choice of magnesium form is a direct expression of product quality.
Folic acid — the synthetic form of folate used in most supplements — must be converted by the body into its active form, 5-methyltetrahydrofolate (5-MTHF), before it can be used. Approximately 40–60% of the population carries a variant of the MTHFR gene that impairs this conversion, meaning a significant proportion of consumers receive little benefit from folic acid supplementation. Methylfolate (5-MTHF) bypasses this conversion step entirely and is immediately bioavailable. Premium prenatal and general health formulations increasingly specify methylfolate for this reason.
Vitamin D2 (ergocalciferol) and D3 (cholecalciferol) are both used in supplements, but research consistently shows that D3 is significantly more effective at raising and maintaining serum 25(OH)D levels — the accepted marker of vitamin D status. D3 is also more stable in formulation. For any supplement intended to support vitamin D status, D3 is the scientifically preferred form.
At Nuteo, our R&D team specifies high-bioavailability ingredient forms as the default across our private label formulations. Our white label catalogue also features premium-form products clearly identified for brands that want to differentiate on quality. When developing a custom formulation, we work with clients to select the optimal ingredient forms for their target consumer, price point, and efficacy positioning.