GLA (Gamma-Linolenic Acid).

In the body GLA is elongated to dihomo-gamma-linolenic acid (DGLA), and delta-5-desaturase carries some of that DGLA onward to arachidonic acid. EPA slows that same enzyme and competes for the shared desaturase and eicosanoid steps, so taking it alongside GLA holds more of the pool as DGLA and tilts the body's prostaglandin balance toward the DGLA-derived side.

GLA is a polyunsaturated fat whose double bonds make it quick to oxidize, both sitting in the softgel and once it is worked into cell membranes. Vitamin E is the fat-soluble antioxidant that settles into those same lipids and absorbs the oxidative hit, which is why more polyunsaturated fat in the diet raises the vitamin E requirement and why GLA oils are usually bottled with a little added.

GLA is elongated to dihomo-gamma-linolenic acid, which can either make series-1 prostaglandins or be desaturated onward to arachidonic acid. EPA slows that delta-5 desaturase step, so DGLA accumulates on the series-1 route instead.

DHA occupies membrane phospholipid positions that would otherwise hold arachidonic acid derived from the omega-6 chain. That keeps the eicosanoid balance from tilting as GLA intake rises.

The delta-6 and delta-5 desaturases that sit on either side of GLA in the omega-6 chain both need zinc. Zinc status therefore governs how GLA is handled once absorbed.

GLA carries three double bonds and oxidises readily in the lipid phase. Astaxanthin spans the membrane and intercepts peroxyl radicals in that same phase.

Carnosic and rosmarinic acids interrupt peroxidation chains in a bottled polyunsaturated oil. That keeps the GLA content intact through shelf life.

Phospholipids reduce oil droplet size so bile salts and lipase act faster. The fatty acids in a GLA oil become available for absorption sooner.

Alpha-linolenic acid from flaxseed and the omega-6 chain that GLA belongs to queue at the same delta-6 desaturase and elongase enzymes. Large amounts of one slow the handling of the other, which is why the ratio is set deliberately.

Series-1 prostaglandins made from DGLA reduce platelet aggregation, and garlic organosulfur compounds do the same by a separate route. Their effects on normal clotting add together.

Delta-6-desaturase inserts a double bond into linoleic acid to give gamma-linolenic acid, and this is the rate-limiting step of the whole n-6 conversion sequence. Supplemental GLA starts one step past that bottleneck, which is the entire pharmacological rationale for taking it. The two are precursor and product, not two interchangeable oils.

Evening primrose oil carries GLA esterified in triglycerides alongside a much larger linoleic acid fraction. A formula containing both a GLA concentrate and evening primrose oil is supplying the same fatty acid twice, at different concentrations and in different matrices. This matters for dose accounting rather than being a mechanistic partnership.

Borage, also sold as starflower oil, delivers GLA in triglyceride form at a higher percentage of total fatty acids than evening primrose or black currant oils, so less oil is needed for a given GLA amount. The trade-off is that borage is a species where pyrrolizidine alkaloid carry-over from the plant is the relevant purity specification, which is why certified alkaloid-free grades exist. Combining borage with another GLA source is duplication of the same active rather than complementary chemistry.

Conversion of linoleic acid to GLA depends on delta-6-desaturase, whose activity in the nutrition literature is tied to adequate B6, zinc and magnesium. Because supplemental GLA already sits downstream of that enzyme, the cofactor matters more for endogenous production than for the supplemented fraction. The relationship is enzymatic dependency in normal metabolism.

The desaturase and elongase steps that build long-chain polyunsaturated fatty acids from dietary precursors are described as magnesium-dependent, alongside the ATP-consuming activation of fatty acids to their CoA esters. Magnesium adequacy therefore supports the whole conversion sequence rather than any one step. This is cofactor biochemistry and not a tested oil-plus-mineral combination.

Polyunsaturated fatty acids with three double bonds oxidise readily, and the selenium-dependent glutathione peroxidases are the main enzymes that reduce the resulting lipid hydroperoxides in tissue. Selenium status therefore bears on how oxidised fatty acids are handled after absorption, which is a different problem from oxidation in the bottle. This is established enzymology, not a combination outcome.

Coenzyme Q10 is a large lipophilic molecule that needs dietary fat and bile for micellar solubilisation, so an oil-filled softgel is a functional vehicle for it. A GLA-rich oil serves that role as well as any other triglyceride. The enabling effect belongs to the lipid vehicle, not specifically to gamma-linolenic acid.

Fat-soluble vitamins are absorbed with dietary lipid through micelles, which is why oil-based softgels are a standard carrier. A GLA-containing seed oil provides that lipid phase. Again the mechanism is vehicle chemistry rather than any specific property of gamma-linolenic acid.

GLA is elongated to DGLA, which cyclooxygenase converts to prostaglandin E1, a mediator that reduces platelet aggregation. Ginkgo extracts carry a long-standing caution about platelet-related interactions in clinical references. Combining the two is a plausible additive direction on platelet behaviour and is worth flagging rather than presenting as a benefit; anyone on anticoagulant or antiplatelet medication should be discussing it with their prescriber.