Phytoene is the colourless carotenoid that is the precursor of all the other carotenoids — it is the first and the rate-limiting intermediate in the carotenoid biosynthesis pathway, and it is produced from the geranylgeranyl pyrophosphate (GGPP) by the phytoene synthase enzyme (PSY). The phytoene is unique among the carotenoids because it has no colour (it is a colourless compound because it has only 3 conjugated double bonds, which is insufficient to give it a visible colour), and because it is the direct precursor of the coloured carotenoids (including the alpha-carotene, the beta-carotene, the lutein, the zeaxanthin, the lycopene, and the astaxanthin) through the action of the desaturation enzymes (PDS, ZDS, CRTISO, LCYB). Without adequate phytoene and carotenoid synthesis, the antioxidant defences are compromised, the skin ageing accelerates, and the light sensitivity increases — the hallmark of the phytoene deficiency and of the impaired carotenoid status that is associated with the poor diet, the malabsorption, and the genetic disorders of the carotenoid metabolism. The typical dietary phytoene intake from the foods (particularly the carrots, the tomatoes, the sweet potatoes, the pumpkin, and the winter squash) is approximately 10-50mg daily, and this is usually adequate for the maintenance of the normal carotenoid status and for the prevention of the phytoene deficiency. However, the phytoene supplementation is becoming increasingly popular as an antioxidant and as a skin health supplement — because the phytoene has a unique and potent antioxidant activity (despite its colourless nature) and because it is particularly effective at protecting the skin from the UV-induced damage and from the photo-ageing.
Phytoene and the Antioxidant Defence
Phytoene supports the antioxidant defence primarily through its role as a direct scavenger of the singlet oxygen and of the other reactive oxygen species — it has a high rate constant for the reaction with the singlet oxygen (1O2, kq approximately 10^9 M^-1 s^-1), and it is therefore one of the most effective singlet oxygen scavengers among the dietary compounds. The singlet oxygen is one of the most damaging reactive oxygen species in the skin (because it is generated by the UV radiation and because it causes the oxidative damage to the DNA, the proteins, and the lipids that is the primary driver of the photo-ageing and of the skin cancer). The phytoene also has a protective effect on the endogenous antioxidant enzymes (including the superoxide dismutase, the catalase, and the glutathione peroxidase) — it upregulates the expression of these enzymes and thereby enhances the overall antioxidant capacity of the skin. This dual mechanism of action (direct singlet oxygen scavenging plus upregulation of the endogenous antioxidant enzymes) makes the phytoene one of the most effective and most comprehensive antioxidants for the skin — and it explains why the phytoene supplementation has been shown to reduce the UV-induced skin damage, to improve the skin elasticity, and to reduce the appearance of the wrinkles in multiple clinical studies.
The clinical importance of the phytoene for the skin health is underscored by the observation that the phytoene supplementation reduces the UV-induced skin damage and improves the skin elasticity in humans. A study in 30 healthy volunteers (aged 40-65) found that the phytoene supplementation at 15mg daily for 12 weeks significantly reduced the skin roughness (by 20-30%, as measured by the VISIA imaging system) and improved the skin elasticity (by 15-25%, as measured by the Cutometer) — demonstrating the potent and clinically meaningful skin-protective effect of the phytoene in humans.
Practical Application
For general phytoene supplementation for the antioxidant defence and for the skin health, the evidence-based approach is to supplement with 10-30mg of phytoene daily (as the phytoene-rich carrot oil extract or as the pure phytoene supplement, taken with the meals that contain some fat to enhance the absorption). The phytoene should be taken with the other carotenoids (particularly the lutein, the zeaxanthin, and the lycopene — which work synergistically with the phytoene for the antioxidant defence and for the skin protection — the combined supplementation of the phytoene and the other carotenoids is more effective than any one of these carotenoids alone for the maintenance of the normal carotenoid status and for the prevention of the carotenoid deficiency). The phytoene is generally well-tolerated with no significant adverse effects at the doses that are used for the antioxidant support and for the skin health (up to 50mg daily), and it does not have any known drug interactions or contraindications. For comprehensive antioxidant defence and skin health, phytoene pairs well with the vitamin C (which is a potent antioxidant that works synergistically with the phytoene for the singlet oxygen scavenging and for the collagen synthesis — the combination of the phytoene and the vitamin C is one of the most effective combinations for the skin antioxidant defence and for the prevention of the photo-ageing), with the vitamin E (which is a lipid-soluble antioxidant that works synergistically with the phytoene for the membrane protection and for the skin health — the combination of the phytoene and the vitamin E is one of the most effective combinations for the prevention of the UV-induced skin damage and for the maintenance of the skin elasticity), with the collagen peptides (which support the skin structure and which work synergistically with the phytoene for the skin elasticity and for the reduction of the wrinkles — the combination of the phytoene and the collagen peptides is one of the most effective approaches for the skin ageing reversal and for the maintenance of the youthful skin appearance), and with the resveratrol (which is a potent sirtuin activator and antioxidant that works synergistically with the phytoene for the cellular protection and for the anti-ageing — the combination of the phytoene and the resveratrol is one of the most effective combinations for the prevention of the skin ageing and for the maintenance of the skin health).
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