Understanding Antioxidants

Antioxidants play an important role in preventing or slowing the process of cutaneous ageing, and while the consumption of antioxidants in food and supplements can be of benefit, there is growing evidence that topical use of antioxidants has clinical benefit.

Many topical rejuvenation formulations contain vitamins and vitamin derivatives that perform both protective and reparative functions. Vitamin B3 is an umbrella term denoting several related molecules, including nicotinic acid (niacin) and niacinamide.

These molecules are important components of the enzymes nicotinamide adenine dinucleotide and nicotinamide adenine dinucleotide phosphate, which play critical roles in mitochondrial oxidative phosphorylation. It has long been established that niacinamide exerts an anti-inflammatory effect, demonstrated by the efficacy of topical niacinamide in the treatment of inflammatory acne vulgaris. More recently, niacinamide has been shown to mitigate the skin’s inflammatory response elicited by exposure to environmental stressors, such as UVR and pollution, by inhibiting cellular senescence and maintaining epidermal homeostasis.

Clinically, topical niacinamide is extremely well tolerated by facial skin and provides several beneficial effects for ageing skin, such as improved barrier function, and decreased appearance of signs of facial photo-ageing such as texture, pore size, hyperpigmented spots, red blotchiness, sallowness and reduced sebum production. Although the facial rejuvenating effects of niacinamide are similar to those reported for tretinoin, topical tretinoin 0.025% continues to be a more potent technology with niacinamide reported to be one-third to one-fifth as effective at improving wrinkles and hyperpigmentation.

Vitamin C is a potent water-soluble nonenzymatic antioxidant that has the capacity to rejuvenate photoaged skin following its topical application. One of the main difficulties with vitamin C products is instability. The most stable formulation of vitamin C is L-ascorbic acid with a pH of 3.5, as acidity improves its penetration and stability. When used topically, ascorbic acid can significantly improve photo-ageing scores for cheek and the perioral area, and reduce skin roughness and wrinkling.

These clinical improvements are thought to be mediated via the proliferation of keratinocytes and fibroblasts, increased expression of collagen I and collagen III, newly synthesized elastic fibres in the papillary dermis, and also increased expression of ECM protease inhibitors such as TIMPS. In addition to increased expression of collagen, topical ascorbic acid also improves collagen fibre organization and cross-linking, which together enhance the strength and stability of the ECM. Vitamin C is also a potent cosmeceutical for the treatment of hyperpigmentation. Vitamin C is thought to inhibit the enzyme tyrosinase (responsible for the conversion of tyrosine to melanin) by interacting with copper ions at tyrosinase active sites, thus reducing melanin synthesis. Therefore, topical vitamin C has some value in improving the pigmentary changes associated with sun exposure, but high-quality clinical trial data are lacking.

Skin ageing is inevitable, but measures can be taken to reduce the impact, particularly changes that are caused by environmental factors. Prevention of UVR-induced accelerated skin ageing, with the regular use of broad-spectrum photoprotection, should be an integral part of the skincare routine. This can be supplemented with topical antioxidant products that provide additional photoprotection, and may also help to neutralise other sources of oxidative stress, such as air pollution. Optimisation of barrier function with the use of simple emollients can also play a role: a healthy stratum corneum is the first line of defence against environmental assault. Topical retinoids and some peptides, in addition to epidermal effects, demonstrate dermal repair with a more profound clinical impact on deeper cutaneous wrinkles, although cellular changes will take months, not days.

Furthermore, realistic expectations with regard to overall impact on facial morphology are needed, as even the best skin rejuvenation programme will not mitigate potentially more dramatic volumetric changes due to underlying fat redistribution, atrophy and deeper bone loss!

For more information please refer to the full article, which is taken from:

Tamara W Griffiths, Rachel E B Watson, Abigail K Langton, Skin ageing and topical rejuvenation strategies, British Journal of Dermatology, Volume 189, Issue Supplement_1, October 2023, Pages i17–i23, https://doi.org/10.1093/bjd/ljad282