Ceramides, barrier first.

Wheat-derived "phytoceramides" (Lipowheat, Ceramosides, Ceratiq) are the category leaders. A systematic review and meta-analysis of seven RCTs (426 participants, 6–20 weeks, 0.4–30 mg ceramide/day) found a small-to-moderate hydration effect (SMD +0.40) and lower TEWL (SMD −0.29). The classic Lipowheat trial (51 women, 350 mg/day, 12 weeks) improved arm and leg hydration versus placebo — but not the face, and dermatologist-scored dryness didn't differ.

Two honest footnotes: every trial is manufacturer-linked, and wheat "ceramide" products are mostly galactolipids (DGDG) with a sliver of glucosylceramide — the active may not be the ceramide at all. Regulatory: Seppic's wheat lipids hold a US FDA GRAS notice; no EFSA-authorised health claim exists, so "hydration from within" on EU packaging is an unauthorised claim.

For anyone avoiding wheat, rice and konjac extracts have their own (small) trials. Oryza Ceramide (44 women, 40 mg/day, 12 weeks, double-blind) lowered cheek TEWL at weeks 4 and 12 — though its β-sitosterol glucoside raises skin ceramides on its own in reconstructed epidermis, so the credit is shared. Konjac glucosylceramide reduced surfactant-induced TEWL in a 100-person double-blind study; a 2024 wine-lees ceramide RCT (29 completers) improved TEWL at week 12 but not hydration, itch, or quality of life.

Same pattern as wheat: measurable instrument changes, sponsor authorship, small samples. Reasonable to try for body dryness; expect nothing visible on the face.

Wrinkle claims for capsules rest on thin ground: Seppic's 60-volunteer study (60 days, 30 mg Ceramosides) reported reduced wrinkle parameters alongside hydration; a 12-week milk-ceramide RCT measured elasticity and eye wrinkles; a 2024 Seppic trial in women with mild-to-moderate aging exists. No wrinkle endpoint has been pooled, and no independent replication exists. If hydration rises, fine dehydration lines soften — that is the honest ceiling.

The only clinical-population trial is striking and lonely: Kimata 2006 gave 25 children with moderate atopic dermatitis 1.8 mg/day of konjac ceramide for two weeks and reported lower eczema scores, prick-test reactivity, and dust-mite IgE versus 25 controls. Big immunological claims from a tiny dose over 14 days, two decades ago, with no replication — a hypothesis, not a treatment. Keep the emollients and the dermatologist.

Because plasma ceramides are now a heart-risk biomarker (see the safety section), a fair question is whether swallowing ceramides raises them. Nobody has checked — no supplement trial measured blood ceramides. Biology argues against a meaningful effect: plant glucosylceramides are not absorbed intact but hydrolysed to sphingoid bases, which are actively pumped back into the gut and largely burned as fatty acids; and supplement doses (1–30 mg) are trivial against the ~300–400 mg of sphingolipids a European eats daily in dairy, eggs, and soy. Implausible — and untested. Neither "heart-safe" nor "heart-risky" claims have data.

Rather than importing ceramides, niacinamide makes your skin build more. Tanno's British Journal of Dermatology study found nicotinamide raised ceramide synthesis 4–5-fold in cultured keratinocytes via the rate-limiting enzyme, and topical use increased stratum-corneum ceramides and free fatty acids while lowering TEWL in dry skin; a 2025 study extends the hydration and structure data. Niacinamide's broader trial record — barrier, pigmentation, fine lines — is larger than that of ceramides themselves, at a fraction of prestige-cream prices. The logical pairing: niacinamide serum under a ceramide cream.

The oral route with the most consistent barrier data is not ceramides but essential fatty acids. In a 12-week double-blind trial, flaxseed oil reduced skin sensitivity, TEWL, roughness, and scaling while raising hydration; flaxseed and borage oil both improved roughness and scaling in the British Journal of Nutrition; krill-oil pilots point the same way. Trials of 13 women per arm, so "moderate" for consistency rather than size — and cheap enough that a 12-week experiment costs less than one prestige cream.

Urea is a humectant and keratolytic with decades of clinical documentation for xerosis — Cochrane-level support as an emollient active. It is also reported to up-regulate barrier-lipid gene expression, which is why it appears on "ceramide booster" lists; the clinical case, though, was already made by hydration and scaling outcomes long before that mechanism was described. Rough shins, heels, and winter arms: 5–10% urea cream is the evidence-cheap answer.

Beyond exfoliation, lactic acid has a specific ceramide story: Rawlings' 1996 study found the L-isomer raised keratinocyte ceramide production ~300% in vitro and stratum-corneum ceramides +38% in vivo, with better resistance to dryness — the D-isomer did nothing, so the form matters. A single Unilever-origin study, seldom replicated: a plausible bonus from an exfoliant you might use anyway, not a reason to start one.

Kao's eucalyptus-leaf extract (macrocarpal A) raised ceramide, glucosylceramide, and sphingomyelin synthesis dose-dependently in keratinocytes — and appears in every Curél trial alongside the pseudo-ceramide, which means the clinical credit can't be separated. Mechanistic support, no solo human data: a fine ingredient to see on the label, not one to chase.

Hair cuticle lipids do contain ceramides, and ceramide-2 analogues in conditioners improve combability and break-strength in ingredient-supplier tress studies. A lab-synthesised ceramide stimulated dermal-papilla cells in culture — no human hair-growth trial followed. The one clinical scalp study is Kao's leave-on pseudo-ceramide lotion for dry scalp. Verdict: pleasant conditioning chemistry; "repairs hair" is a tress-test claim, and shampoo is the wrong vehicle for it.