How low-fat yoghurt could make spots worse

... while chocolate may not be as bad for your skin as you think

FOR YEARS, scientific dogma has held that there is no link between skin conditions and diet. Yet the idea persists that certain foods — whether it’s chocolate or cheese — can aggravate conditions such as acne and eczema.

And there’s no shortage of food bloggers and books claiming to have found a diet that can help. Just twoe of the latest contributions include: The Clear Skin Diet, ‘an accessible guide to curing acne . . . using the simple principles of a low-fat vegan diet’ and The Eczema Detox from Australian nutritionist Karen Fischer, a ‘low-chemical diet for eliminating skin inflammation’.

In many ways it seems inconceivable that diet should not have an impact on our skin. After all, the skin is the body’s largest organ, it is constantly renewing itself and, as with all bodily processes, requires a number of different nutrients in order to do this.

For instance, fatty acids — found in seeds, nuts and oily fish — are needed for maintaining the barrier function of the skin, while protein — found in pulses, meat, fish and eggs — is essential for the production of collagen, the protein that gives skin its elasticity and structure.

We also know that in some people, food allergies can manifest in the form of skin rashes. Yet the medical authorities are categorical. On its website, the NHS states that there is ‘no evidence’ that diet plays a role in acne. While the Psoriasis Society concludes that ‘scientific research has not yet found a definite link, or found a diet that works for everybody’.

Similarly, the National Eczema Society reports that ‘the research evidence for nutritional approaches is patchy’.

But is it really the case that what you eat makes no difference at all? Here, we look at the latest evidence on the link between diet and skin.

YES, YOU ARE WHAT YOU EAT

‘THE physiology of how what we eat ends up in our skin is very complex,’ says Dr Anjali Mahto, a dermatologist at the Cadogan Clinic in London.

‘What you put into your body goes through so many processes that the bioavailability — meaning what actually gets to your skin — of what’s left is very low.

‘ That’s why things like high doses of vitamin C, often contained in skin health supplements and recommended for boosting skin elasticity and firmness, just don’t make sense — your body excretes most of it.’

She also cautions against the idea that what we eat can have such a significant hormonal impact that it would cause levels of testosterone — the main hormone thought to cause acne — to rise. However, according to Dr Mahto, ‘there are always going to be holes in our knowledge in this area’.

This is because it’s very hard to design a robust scientific study around nutrition.

‘One of the reasons why the link between diet and nutrition and disease — not just skin disease, but many other medical conditions — is so controversial is because it’s really hard to carry out highquality clinical trials on nutrition as there are so many confounding factors,’ Dr Mahto explains.

‘Most foods are not single nutrients so it’s very hard to say what specifically is beneficial. A lot of food studies also rely on asking people to remember what they ate — known as retrospective data — which is notoriously unreliable.

‘For example, studies might be asking adults to recall how much dairy they consumed 20 years ago as teenagers to find a link.

‘ Finally, because of monthly fluctuations in female hormones, you can’t extrapolate data that you get from studies on men to women.’

CONTROL YOUR SWEET TOOTH

DR MAHTO says that there isn’t a single diet that’s ‘good for skin’. ‘If a diet is good for your general health, it’s good for skin,’ she says. ‘That means all the classic dietary advice; eating a rainbow of fruit and vegetables to get a broad range of vitamins and minerals.’

Likewise, oily fish — so often advised as a key component of an all-round healthy diet — is likely to be good for our skin, she says.

‘There are some small studies, including several cited in a recent review published in the Journal of Dermatology & Therapy, that show diets high in omega-3 fatty acids might have an anti-inflammatory effect and, as many skin conditions are related to chronic inflammation, it’s possible that getting two to three portions of oily fish a week could be of benefit.’

What about things to avoid? In general, Dr Mahto says, cutting out entire food groups, such as meat, dairy or gluten, without advice from a dietitian, is likely to be of questionable benefit.

‘However, reducing the amount of sugar you consume is not a bad idea,’ she says. ‘There is some evidence that refined sugar can potentially contribute to acne.’

The exact mechanism by which sugar affects acne is not known. According to Dr Mahto, one theory is that a spike in blood sugar levels leads to spike in insulin ( the hormone that we release to help use sugar as energy) and when insulin spikes, so too does a compound called insulin growth factor 1 (IGF-1), which is thought to have similar effects to testosterone, increasing the size and activity of the oil glands in the skin, thus promoting acne.

However Dr Mahto wouldn’t advocate cutting out sugar entirely as, like most medical professionals, she believes in creating a diet that is sustainable.

LOW-FAT DAIRY CAN BE TO BLAME

DAIRY is often demonised in skin conditions and, according to Dr Mahto, in the Fifties and Sixties, though there was no robust science to support it, the standard advice was to cut out dairy and sugar.

Then new research came along in the Sixties and Seventies saying there was no link between diet and acne, but more recently methodological flaws have been found in those studies.

This has led to the pendulum starting to swing in the opposite direction, though nobody is really sure why dairy might lead to acne. ‘Anecdotal evidence and small observational studies seem to suggest that when body builders switch from taking dairy-based whey protein to a vegetable alternative, some may see an improvement in their acne,’ says Dr Mahto. Generally, studies that suggest a link between dairy and acne interestingly also tend to suggest that low-fat dairy is more of an issue than full fat. ‘There are various hypotheses about why — it might be that the hormones cows are given are having an impact that is only apparent when you remove some of the fat,’ says Dr Mahto. ‘ But nobody really knows for sure.’

WHAT ABOUT CHOCOLATE?

SOME studies, including one small study on 14 men published in the Journal of Clinical and Aesthetic Dermatology in 2014 seemed to show that chocolate was associated with an increase in the number of acne lesions.

However, the prevailing medical opinion remains that there is no strong evidence that milk, highfat foods, or chocolate increase the risk of acne.

So where does the oft-repeated idea that chocolate causes spots come from? It could actually be the refined sugar content that is the problem, rather than the chocolate component itself.

WHY DIETS MIGHT SEEM TO WORK

WHAT dermatologists agree on is that their patients can be sorely tempted to try a ‘skin saving’ diet, especially when their proponents promise such ‘miraculous’ results.

Asked to explain how people seem to ‘cure’ skin conditions through diet, Dr Mahto points out that many conditions — eczema, acne, psoriasis, rosacea — are chronic conditions that, by their very nature, have periods of flareup and apparent remission.

‘It’s difficult to state categorically that a change in diet affected the change in skin,’ she says. ‘And it may well be that three or six months down the line, the condition is back again.’

She also points out that very often when people make dietary changes, they also make wholesale changes to their exercise routine or lifestyle, making it hard to identify what exactly is making the difference.

Not least because such a lifestyle overhaul can reduce stress levels, and, as stress is known to have a negative impact on many skin conditions, this can also improve skin health.

Dr Mahto points out that dermatologists aren’t biased against dietary approaches — after all if dietary advice could cure the eczema, it’s cheaper than the £169 million a year spent on prescription medication for the condition.

But, she says, dermatologists need to see good scientific evidence before giving advice to patients which is likely to cause more harm than good.

‘Having a good approach to lifestyle, eating well, reducing stress, and regular exercise is important — there is no doubt that is part of the solution when it comes to managing chronic skin disease,’ she says. ‘However, based on current knowledge, it would be a mistake to think chronic skin problems can be cured with diet alone.

‘ Clearly more research is required, but until then recommendations need to remain rooted in science, not pseudoscience.’