Sun exposure can accelerate ageing, cause skin burns, erythema (a skin reaction), skin cancer, melasmas (or sun spots) and other forms of hyperpigmentation – all triggered by solar ultraviolet radiation.

Approximately 80% of skin cancer cases in people engaged in outdoor activities are preventable by decreasing sun exposure. This can be done in lots of ways including wearing protective clothing or sunscreens.

But not all sunscreens work in the same way. You might have heard of “physical” and “chemical” sunscreens. What’s the difference and which one is right for you?

How sunscreens are classified

Sunscreens are grouped by their use of active inorganic and organic ultraviolet (UV) filters. Chemical sunscreens use organic filters such as cinnamates (chemically related to cinnamon oil) and benzophenones. Physical sunscreens (sometimes called mineral sunscreens) use inorganic filters such as titanium and zinc oxide.

These filters prevent the effects of UV radiation on the skin.

Organic UV filters are known as chemical filters because the molecules in them change to stop UV radiation reaching the skin. Inorganic UV filters are known as physical filters, because they work through physical means, such as blocking, scattering and reflection of UV radiation to prevent skin damage.

Nano versus micro

The effectiveness of the filters in physical sunscreen depends on factors including the size of the particle, how it’s mixed into the cream or lotion, the amount used and the refraction index (the speed light travels through a substance) of each filter.

When the particle size in physical sunscreens is large, it causes the light to be scattered and reflected more. That means physical sunscreens can be more obvious on the skin, which can reduce their cosmetic appeal.

Nanoparticulate forms of physical sunscreens (with tiny particles smaller than 100 nanometers) can improve the cosmetic appearance of creams on the skin and UV protection, because the particles in this size range absorb more radiation than they reflect. These are sometimes labelled as “invisible” zinc or mineral formulations and are considered safe.

So how do chemical sunscreens work?

Chemical UV filters work by absorbing high-energy UV rays. This leads to the filter molecules interacting with sunlight and changing chemically.

When molecules return to their ground (or lower energy) state, they release energy as heat, distributed all over the skin. This may lead to uncomfortable reactions for people with skin sensitivity.

Generally, UV filters are meant to stay on the epidermis (the first skin layer) surface to protect it from UV radiation. When they enter into the dermis (the connective tissue layer) and bloodstream, this can lead to skin sensitivity and increase the risk of toxicity. The safety profile of chemical UV filters may depend on whether their small molecular size allows them to penetrate the skin.

Chemical sunscreens, compared to physical ones, cause more adverse reactions in the skin because of chemical changes in their molecules. In addition, some chemical filters, such as dibenzoylmethane tend to break down after UV exposure. These degraded products can no longer protect the skin against UV and, if they penetrate the skin, can cause cell damage.

Due to their stability – that is, how well they retain product integrity and effectiveness when exposed to sunlight – physical sunscreens may be more suitable for children and people with skin allergies.

Although sunscreen filter ingredients can rarely cause true allergic dermatitis, patients with photodermatoses (where the skin reacts to light) and eczema have higher risk and should take care and seek advice.

What to look for

The best way to check if you’ll have a reaction to a physical or chemical sunscreen is to patch test it on a small area of skin.

And the best sunscreen to choose is one that provides broad-spectrum protection, is water and sweat-resistant, has a high sun protection factor (SPF), is easy to apply and has a low allergy risk.

Health authorities recommend sunscreen to prevent sun damage and cancer. Chemical sunscreens have the potential to penetrate the skin and may cause irritation for some people. Physical sunscreens are considered safe and effective and nanoparticulate formulations can increase their appeal and ease of use.

Yousuf Mohammed, Dermatology researcher, The University of Queensland and Khanh Phan, Postdoctoral research associate, Frazer Institute, The University of Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Beetroot has been in the news for all the wrong reasons. Supply issues in recent months have seen a shortage of tinned beetroot on Australian supermarket shelves. At one point, a tin was reportedly selling on eBay for more than A$65.

But as supplies increase, we turn our attention to beetroot’s apparent health benefits.

Is beetroot really vegetable Viagra, as UK TV doctor Michael Mosley suggests? What about beetroot’s other apparent health benefits – from reducing your blood pressure to improving your daily workout? Here’s what the science says.

What’s so special about beetroot?

Beetroot – alongside foods such as berries, nuts and leafy greens – is a “superfood”. It contains above-average levels per gram of certain vitamins and minerals.

Beetroot is particularly rich in vitamin B and C, minerals, fibre and antioxidants.

Most cooking methods don’t significantly alter its antioxidant levels. Pressure cooking does, however, lower levels of carotenoid (a type of antioxidant) compared to raw beetroot.

Processing into capsules, powders, chips or juice may affect beetroot’s ability to act as an antioxidant. However, this can vary between products, including between different brands of beetroot juice.

Is beetroot really vegetable Viagra?

The Romans are said to have used beetroot and its juice as an aphrodisiac.

But there’s limited scientific evidence to say beetroot improves your sex life. This does not mean it doesn’t. Rather, the vast number of scientific studies looking at the effect of beetroot have not measured libido or other aspects of sexual health.

How could it work?

When we eat beetroot, chemical reactions involving bacteria and enzymes transform the nitrate in beetroot into nitrite, then to nitric oxide. Nitric oxide helps dilate (widen) blood vessels, potentially improving circulation.

The richest sources of dietary nitric oxide that have been tested in clinical studies are beetroot, rocket and spinach.

Nitric oxide is also thought to support testosterone in its role in controlling blood flow before and during sex in men.

Beetroot’s ability to improve blood flow can benefit the circulatory system of the heart and blood vessels. This may positively impact sexual function, theoretically in men and women.

Therefore, it is reasonable to suggest there could be a modest link between beetroot and preparedness for sex, but don’t expect it to transform your sex life.

What else could it do?

Beetroot has received increasing attention over recent years due to its antioxidant and anti-tumour effect in humans.

Clinical trials have not verified all beetroot’s active ingredients and their effects. However, beetroot may be a potentially helpful treatment for various health issues related to oxidative stress and inflammation, such as cancer and diabetes. The idea is that you can take beetroot supplements or eat extra beetroot alongside your regular medicines (rather than replace them).

There is evidence beetroot juice can help lower systolic blood pressure (the first number in your blood pressure reading) by 2.73-4.81 mmHg (millimetres of mercury, the standard unit of measuring blood pressure) in people with high blood pressure. Some researchers say this reduction is comparable to the effects seen with certain medications and dietary interventions.

Other research finds even people without high blood pressure (but at risk of it) could benefit.

Beetroot may also improve athletic performance. Some studies show small benefits for endurance athletes (who run, swim or cycle long distances). These studies looked at various forms of the food, such as beetroot juice as well as beetroot-based supplements.

How to get more beetroot in your diet

There is scientific evidence to support positive impacts of consuming beetroot in whole, juice and supplement forms. So even if you can’t get hold of tinned beetroot, there are plenty of other ways you can get more beetroot into your diet. You can try:

• raw beetroot – grate raw beetroot and add it to salads or coleslaw, or slice beetroot to use as a crunchy topping for sandwiches or wraps
• cooked beetroot – roast beetroot with olive oil, salt and pepper for a flavour packed side dish. Alternatively, steam beetroot and serve it as a standalone dish or mixed into other dishes
• beetroot juice – make fresh beetroot juice using a juicer. You can combine it with other fruits and vegetables for added flavour. You can also blend raw or cooked beetroot with water and strain to make a juice
• smoothies – add beetroot to your favourite smoothie. It pairs well with fruits such as berries, apples and oranges
• soups – use beetroot in soups for both flavour and colour. Borscht is a classic beetroot soup, but you can also experiment with other recipes
• pickled beetroot – make pickled beetroot at home, or buy it from the supermarket. This can be a tasty addition to salads or sandwiches
• beetroot hummus – blend cooked beetroot into your homemade hummus for a vibrant and nutritious dip. You can also buy beetroot hummus from the supermarket
• grilled beetroot – slice beetroot and grill it for a smoky flavour
• beetroot chips – slice raw beetroot thinly, toss the slices with olive oil and your favourite seasonings, then bake or dehydrate them to make crispy beetroot chips
• cakes and baked goods – add grated beetroot to muffins, cakes, or brownies for a moist and colourful twist.

Are there any downsides?

Compared to the large number of studies on the beneficial effects of beetroot, there is very little evidence of negative side effects.

If you eat large amounts of beetroot, your urine may turn red or purple (called beeturia). But this is generally harmless.

There have been reports in some countries of beetroot-based dietary supplements contaminated with harmful substances, yet we have not seen this reported in Australia.

What’s the take-home message?

Beetroot may give some modest boost to sex for men and women, likely by helping your circulation. But it’s unlikely to transform your sex life or act as vegetable Viagra. We know there are many contributing factors to sexual wellbeing. Diet is only one.

For individually tailored support talk to your GP or an accredited practising dietitian.

Lauren Ball, Professor of Community Health and Wellbeing, The University of Queensland and Emily Burch, Lecturer, Southern Cross University

This article is republished from The Conversation under a Creative Commons license. Read the original article.