Vitamin C and skin health

(Source)

 From SciTechDaily

A new study led by researchers at the University of Otago, Faculty of Medicine – Christchurch (Ōtautahi), has revealed that the skin’s ability to produce collagen and renew itself is directly influenced by how much vitamin C a person consumes.

According to findings published in the Journal of Investigative Dermatology, the amount of vitamin C present in the skin closely mirrors the level circulating in the blood (plasma). The researchers also found that these levels can rise through greater fruit consumption.

The investigation involved two dozen healthy adults from Aotearoa, (New Zealand) and Germany. Participants who ate two vitamin C-rich SunGold kiwifruit each day showed an increase in plasma vitamin C, which in turn raised the vitamin’s concentration in the skin. This change supported greater skin thickness (collagen production) and encouraged renewal and regeneration in the outer layers of the skin.

Lead author Professor Margreet Vissers from Mātai Hāora (Centre for Redox Biology and Medicine, part of the Department of Pathology and Molecular Medicine), describes the connection between vitamin C intake and skin thickness as “compelling.”

“We were surprised by the tight correlation between plasma vitamin C levels and those in the skin – this was much more marked than in any other organ we have investigated,” Professor Vissers says.

“We are the first to demonstrate that vitamin C in the blood circulation penetrates all layers of the skin and is associated with improved skin function. I am very proud of my team and excited about what the data is telling us.”

Dietary Vitamin C More Effective Than Topical Forms

Professor Vissers says the study results suggest that beauty really does come from within, supporting your skin function from the inside-out by delivering vitamin C to the skin the way nature designed it – via the bloodstream.

“We know that vitamin C is required for collagen production. This fact has inspired the addition of vitamin C to many skin cream formulations. However, vitamin C is highly water-soluble and poorly absorbed through the outer skin barrier. Our study shows that the skin is extremely good at absorbing vitamin C from the blood circulation. Uptake into the outer epidermal skin layer also seems to be prioritized,” she says.

Funded by New Zealand company Zespri International, along with a University of Otago Research Grant, the study comprised two stages. The first stage established the association between plasma and skin vitamin C levels, using healthy skin tissue from patients undergoing elective surgical procedures at Te Whatu Ora Canterbury (with support from the Otago campus’s He Taonga Tapu – Canterbury Cancer Society Tissue Bank).

The second stage involved a before-and-after, dietary vitamin C intervention study at two sites (in Christchurch and Germany), each with 12 healthy participants.

“All were instructed to consume two Kiwi Gold kiwifruit daily – the equivalent of 250 micrograms of vitamin C – for eight weeks. We then collected skin samples before and after the intervention, with separate analyses allowing us to look at the skin basal layers in Christchurch and the outer dermal skin layer and skin function tests in Germany,” Professor Vissers explains.

Advanced Skin Testing Confirms Structural Improvements

The German participants were recruited and tested by the SGS Institute Fresenius in Hamburg, which had the technical capability to collect the outer dermal skin layer (the blister “roof”). The Institute measured skin sample regeneration – including ultrasound-tested measures of skin thickness, elasticity UV protection, and renewal of epidermal cells – giving a complete picture of skin function.

“The other really substantial finding showed a significant increase in the participants’ skin thickness levels, reflecting collagen production and an upsurge in the regeneration of their epidermal cells, in other words, skin renewal,” Professor Vissers says.

She says SunGoldTM kiwifruit was chosen for the trial due to its proven high vitamin C levels, but it’s anticipated that other foods rich in vitamin C, particularly fresh fruit and vegetables such as citrus, berry fruit, capsicums, and broccoli, would have similar beneficial effects.

“We suggest that increasing your dietary vitamin C intake will result in effective vitamin C uptake into all compartments of the skin,” Professor Vissers says.

“The important thing is to keep your plasma levels optimal, which we know can be easily achieved in a healthy person with a vitamin C intake of around 250mg per day. The body however, does not store the vitamin, so we recommend 5+ [of fruit] a day, every day, with one of those five being a high vitamin C food, as a good habit to cultivate.”

Reference: “Improved Human Skin Vitamin C Levels and Skin Function after Dietary Intake of Kiwifruit: A High-Vitamin-C Food” by Juliet M. Pullar, Stephanie M. Bozonet, Dörte Segger, Astrid von Seebach, Emma Vlasiuk, Helen R. Morrin, John F. Pearson, Jeremy Simcock and Margreet C.M. Vissers, 29 October 2025, Journal of Investigative Dermatology.
DOI: 10.1016/j.jid.2025.10.587

They do not discuss whether vitamin C supplementation is as beneficial.  The disadvantages of natural vitamin C is that fruit quickly loses its vitamins if it isn't fresh.  However, frozen fruit or vegetables are usually snap-frozen immediately after picking so will contain more vitamin C.

Daily omega-3 might delay the aging process

From the Guardian 

A daily dose of omega-3 oils may slow the aging process, according to a major clinical trial of interventions that aim to extend humans’ healthspan – the number of years spent in good health before a decline in old age.

Healthy older people who took one gram of the essential fatty acid for three years were found to have aged three months less than others on the trial, as measured by biological markers. Additional vitamin D and regular exercise boosted the effect to nearly four months, researchers found.

Heike Bischoff-Ferrari, the first author on the study and professor of geriatric medicine and healthy longevity at the University of Zurich, said: “While the effects may appear small with three to four months rejuvenation of biological age in three years, if sustained, they may have relevant effects on population health.”

Previous studies had hinted that omega-3, an unsaturated fatty acid found in oily fish and other foods such as nuts and seeds, could affect the ageing process. But whether humans would see any meaningful benefits from consuming it was unclear.

The researchers used biological tools called epigenetic clocks to assess how rates of ageing were affected in a clinical trial involving nearly 800 people aged 70 and over in Switzerland. Epigenetic clocks measure DNA methylation, chemical modifications that build up on DNA and reflect the biological rather than the chronological age of the tissue.

Volunteers on the trial were divided into eight groups and each took a gram of algae-based omega-3 a day, or 2,000 international units of vitamin D, or performed 30 minutes of exercise three times a week, or a combination of these.

Three different epigenetic clocks suggested that omega-3 slowed ageing, while one found an additional benefit when it was accompanied by vitamin D and exercise, the authors write in Nature Aging.

The same European trial, Do-Health, has reported other beneficial effects of omega-3, including a 10% lower rate of falls in seniors and 13% fewer infections. Meanwhile, the combination of omega-3, vitamin D and exercise lowered the risk of entering pre-frailty – when people show one or two signs of physical or mental decline that typically precede frailty – by 39% and reduced invasive cancers by 61%.

The work raises the prospect of inexpensive and readily available ways to improve healthspan, which even if modest at the individual level could be valuable at the population scale. But the results are tentative and it is not yet clear whether any slowing in the ageing process translates to people living healthier for longer.

There are two categories of strokes: ischaemic and haemorrhagic.  The former are caused by a blockage in an artery (or, rarely) a vein.  The latter are caused by bleeding/breaking capillaries.   Because omega-3 supplements "thin the blood", they tend to reduce ischaemic (blockage) strokes, which make up 87% of all strokes, but may increase the risk of haemorrhagic (bleeding) strokes (13 % of all strokes)  The blockages tend to be caused by cholesterol plaque build-up, so if you're a meat eater, omega-3 oils improve your health.  As the article continues:

While previous work has signalled health benefits from consuming omega-3, one recent study reported that fish oil supplements might only reduce the risk of serious heart problems in those with cardiovascular disease. For healthy people, the supplements may raise the risk of heart conditions or stroke. The NHS does not recommend omega-3 supplements but advises people to eat two portions of fish per week, or the equivalent from a vegetarian source, to get enough of the essential fatty acid.

If you have a low risk of heart disease, as I do, being vegan, and take omega-3 oils, you should probably take 500-1000 mg a day of vitamin C with your omega-3 oils, as this vitamin is necessary for collagen synthesis, which is important for blood vessel integrity (a factor in haemorrhagic strokes).  Unfortunately, although freshly picked vegetables and fruit have high vitamin C content, it immediately starts decaying as soon as they're harvested.  Hence the need for supplemental vitamin C. 

Collagen, which is necessary to blood vessel health, is made from proteins you eat, so if you are vegan, you should also make sure you have enough protein.   Good protein sources are from soy products (soy milk, tofu, tempe, etc.), pulses/beans, and nuts and seeds (preferably raw, so the omega-3 oils in them aren't degraded).   Also, you should keep your omega-3 oil supplements in the fridge, as the chemical bonds in their molecules are easily broken by heat (and light, which is why they are sold in dark bottles).

Actually, even if you are a meat-eater, you too should take a vitamin C supplement. 

If you are on blood-thinners (for example, warfarin), it may be unwise to also take omega-3 oil supplements.  Check with your doctor.

Please note that you should check with your doctor before taking supplements.