How much sun you really need to get enough vitamin D

It’s FAR more than you think! A top NHS dermatologist draws on nearly 20 years’ experience to reveal some surprising truths about your skin . . .

Will drinking milk give you spots? How much sun do i need to get enough vitamin D? What’s the best ointment for a burn? Everywhere you look there are articles, advertisements and health advice columns telling you how you should look after your skin — with often conflicting messages.

i’ve worked as a hospital dermatologist for nearly 20 years and based on my clinical experience — and close scrutiny of the scientific evidence — here i explain what really will help keep your skin healthy . . .

MOST PEOPLE DON’T NEED MOISTURISER

PEoPlE who have normal skin generally don’t need body moisturisers — their skin is in its own natural balance and doesn’t need adjusting.

But even those with normal skin will notice that with age, skin becomes drier, especially on our hands and lower legs.

This seems to start from the age of 20 years onwards. That’s because we produce 1 per cent less collagen each year (so the skin retains less water); the surface cells (keratinocytes) tend to accumulate in clumps on the skin surface, leading to the appearance of dry flakes.

The fat cells underneath start to shrink and this leads to a reduction in water transferred from the blood into the upper skin layers.

Finally, from age 50 onwards the sebaceous (oil) glands start to shrink, leading to less oil in the skin. The areas of our skin with the smallest number of sebaceous glands are the most susceptible to this drying effect, namely the lower legs and hands.

So as we get older we want to try to preserve the natural oil in our skin.

To try to combat dry skin conditions, moisturisers (‘emollients’) have been used for hundreds of years.

There are two main types of ingredients in an emollient: humectants, or water- holding ingredients, attract water from the depths of the skin. Humectants include urea, propylene glycol, glycerine and hydroxyl acids. The other type of ingredient, occlusives, creates an oily barrier at the skin surface, sealing in water and reducing evaporation — ingredients include paraffin, lanolin and mineral oils.

The most effective moisturisers contain humectants and occlusives. Different parts of our skin need different types of emollients.

Generally, it is recommended we avoid heavy, oily emollients on our face where clogging pores can lead to acne. lower legs and feet/hands tend to be much drier than the rest of our skin and rich, oily emollients are needed.

look for an emollient that contains an oil, such as a coconut or cocoa butter or paraffin, plus one of the humectants listed above.

TRUTH ABOUT STRETCH MARKS

Your risk of stretch marks is greater if there is a family history, if you’re overweight before pregnancy or have a large baby. (And if you have stretch marks, you’re also more likely to experience a ‘tear’ during childbirth.)

But can you prevent them? Sadly, the short answer, research shows, is no — there is no strong, reliable evidence that the ‘ standard’ remedies such as topical cream, bitter almond oil, olive oil and cocoa oil can prevent or reduce their severity. These might make your skin feel soft, but they won’t stop you getting stretch marks.

SUNBURN VERSUS VITAMIN D

AvoiDinG sunburn is clearly very important, but there’s no doubt that the sun is also important for health: most of us know that vitamin D is vital for our bones and immune systems — and that it’s made in the skin when it’s exposed to sunlight. But how much skin do you need to expose and for how long? The general consensus is that our bodies need around 20-25 mcg of vitamin D a day — as you might expect, how much sun exposure this requires depends on the intensity of the sunlight, the cloud cover and your skin type.

And now scientists at the norwegian institute for Air research have devised a calculator that will take all these factors into account and then estimate what you need. To give you an idea, here is an example based on london as to what different skin types would need on alternate days at different times of the year: Blond Caucasian: April 1: eight minutes; August 1: five minutes; December 1: two hours, 20 mins. Mediterranean: April 1: 13 minutes; August 1: seven minutes; December 1: four hours, eight mins. Black: April 1: 44 minutes; August 1: 24 minutes; December 1: more than 24 hours.

Because the exposure needed in the sunniest seasons to get vitamin D is so short, there is no risk of sunburn. it’s also worth pointing out that in the winter in london we would all have a lot of difficulty in making sufficient vitamin D in our skin from the sun.

luckily, in the winter we can usually rely on our vitamin D stores to tide us over until the spring. We

can also get additional vitamin D from our diet. Vitamin D is oil soluble which means you need to eat fat to absorb it (bear this in mind if you are on a low-fat diet).

Foods naturally high (or artificially fortified) in vitamin D include oily fish, mushrooms, cheese, eggs, tofu, fortified cereals, fortified milk, soya and almond milk.

To work out how much sun exposure you need where you live, go to fastrt.nilu.no.

DO SUPPLEMENTS FOR NAILS WORK?

Fingernails grow about twice as quickly as toenails, and the longer the finger (or toe) the more rapid the growth of the nail.

so our middle fingernail grows faster than our thumb/little fingernails. The average rate of growth of most fingernails is 4.8 mm/month and toenails 2mm/month.

if you have ever damaged your nail, by hitting it with a hammer for example, you will notice it takes months for the blood patch in the nail to ‘grow out’.

On average it takes nine months to grow a new fingernail and 12 to 14 months to grow a new toenail.

if we are seriously ill for a few weeks or more, our nails can temporarily stop growing and then, when we recover, they start growing again.

The episode of nail growth arrest is subsequently seen as a horizontal line called Beau’s line — a bit like rings on a tree trunk showing good or bad growing seasons.

similarly, a white spot or streak on your nail is not due to calcium deficiency, but are caused by little knocks or bumps.

Can taking supplements improve the texture and strength of your nails? in fact, there is little evidence it can, but there is some evidence that rubbing oily moisturisers on to dry nails can enhance their hydration and reduce brittleness.

Fats and oils made up of glycolic and stearic acids, such as coconut oil, help to keep nails water resistant, maintaining the water level of nails at around 18 per cent.

if the water content of our nails drops below 16 per cent, nails can become brittle.

HAVING AN OP? READ THIS FIRST

MOsT of us will have some sort of surgical procedure at some point in our lives that will involve cutting through our skin.

so you might be surprised to hear that currently there is no consensus among surgeons as to whether it is best to keep wounds dry and covered after surgery for a few days/weeks, or whether it is best to start washing wounds the next day for optimal healing for the wound — and hence minimise the healing of scars.

There are generally two schools of thought. One is that early washing could help patients to get back to normal more quickly and wash any germs, dirt or sweat off the wounds.

The other is that early washing may lead to poor wound healing, through irritation and maceration (making the skin soggy and fragile). But it’s not clear what is best.

in fact, most dermatologists opt for early washing of wounds at either 24 or 48 hours, and then ask people to apply Vaseline to the fresh wound daily. Yes, Vaseline.

BEST REMEDY FOR WOUNDS

BuT what about Manuka honey, aloe vera, Bio- Oil etc, you might think?

in fact there is a lack of goodquality research into the use of these products.

However, it is fair to say that there is certainly no compelling evidence that aloe vera topical agents or dressings help acute or chronic wound healing.

Honey has been used for thousands of years as a wound dressing, but it’s only recently that its active biological properties have been uncovered.

Honey is acidic, and this acidity effectively stops the breakdown of proteins that the body produces to promote wound healing. Honey also helps to draw fluid out of wounds, which can be helpful if they are very wet and weepy, but less so if they are dry.

Manuka honey (produced in new Zealand) has been much prized and promoted for its ability to kill bacteria which can be helpful in keeping a wound clean and free from infection.

But is Manuka honey any better at killing bacteria than just standard honey?

Manuka honey can cost from £10£40, whereas standard honey sells for around £2-£10 per pot. all honey contains hydrogen peroxide ( a natural bleach) which kills bacteria, but unfortunately a lot of this activity is neutralised by catalase (an enzyme) which is present in wound tissues.

Manuka honey has an additional antibacterial agent called methylglyoxal, which is not deactivated by the catalase.

But Manuka honey is not superior to plain Vaseline, according to a study conducted in 2006 which compared Manuka honey dressings with paraffin (Vaseline)-impregnated dressings in 100 patients following toenail surgery.

Many of my patients mention they have bought Bio-Oil to apply to cuts, grazes, stretch marks and surgical wounds.

When you look at the ingredients it looks like perfumed mixed oils. The main oils include PurCellin, chamomile, lavender, rosemary and calendula plus vitamins a and e. The company suggests the PurCellin oil is effective at improving the appearance of scars (the oil is actually a synthetic form of preening oil produced by ducks to keep their feathers watertight).

When you look at its published study (which only had 37 participants), it claims that after eight weeks 92 per cent showed improvement in the appearance of the scars compared with a placebo.

But there is no detail as to what the placebo was, what the improvement was and what type of scars were being treated.