Marine or bovine collagen: what actually differs

Almost every collagen powder on sale in the UK is one of two things. Marine collagen comes from fish skin and scales, usually cod, tilapia or snapper. Bovine collagen comes from cattle hide. Both are hydrolysed, meaning the long protein strands are broken into much shorter chains so they dissolve in liquid and are absorbed rather than passing through.

The differences that get advertised are not always the differences that matter to you as a buyer.

The type of collagen differs

Marine collagen is predominantly type I. Bovine is typically a mix of type I and type III. Type I is the dominant collagen in skin; type III is more associated with connective tissue and blood vessels. That is the basis for the claim that marine is the skin one and bovine is the joint one.

It is a reasonable simplification but it is a simplification. Once collagen is hydrolysed into short peptide chains, what your body absorbs is amino acids and small fragments, not intact type I or type III protein. Your body then uses those building blocks wherever it is currently building.

Absorption is often overstated

Marine collagen is frequently described as having smaller peptides and therefore better absorption. Peptide size does vary, and lower molecular weight fractions do appear in the bloodstream more readily. Whether that difference is large enough to change anything you would notice is much less clear, and the studies that would answer it directly are thin on the ground.

If a brand claims a specific absorption advantage, look for whether the claim names a molecular weight and cites a study, or whether it simply asserts it.

Where the real differences are

For most people choosing between the two, these are the factors that will actually affect the decision:

• Price. Bovine is generally cheaper per gram because hide is a more abundant by-product than fish skin.
• Serving size. Marine products often sell 2.5g to 5g servings; bovine products more commonly sell 10g. Compare the amount, not the tub.
• Diet and belief. Neither is vegan or vegetarian. Bovine raises questions for some religious diets unless certified; marine raises questions for people avoiding fish.
• Allergens. Marine collagen contains fish and must be declared. If you have a fish allergy, this is not a preference question.
• Taste. Bovine has a slightly more savoury note in plain water. In coffee or a smoothie, most people cannot tell.

A sensible way to choose

Decide your serving size first, then your dietary constraints, then compare cost per serving between the products that remain. That order will get you to a defensible answer faster than trying to adjudicate the type I versus type III argument, which for a hydrolysed powder is a smaller factor than the price difference between brands.

Whichever you choose, collagen supplements sit alongside a varied diet rather than replacing anything in it, and if you are pregnant, breastfeeding or taking prescription medication, that is worth a conversation with a pharmacist or GP first.