Name: 防晒霜是BAD！？| 新研究解讀 (Sunscreen is BAD!? | New Research Explained)
Uploaded: 2021-01-14T11:04:07.000Z
Duration: 10 min 26 s
Description: 【看影片學英語】數萬部 YouTube 影片，搭配英漢字典即點即查，輕鬆掌握單字發音與用法，長久累積看電影不必再看字幕。

One day, we're told something is great for us, and the next we're told that ground

breaking new research proves that exact thing is now harmful.

Recently, an article was published titled Is Sunscreen the New Margarine?

claiming that sunscreen is actually bad for you because it blocks the formation of Vitamin D.

Welcome to the next installment of our Science Explained series.

In this video series, we explore scientific myths and misconceptions, and by diving into

the primary literature, determine what the body of scientific evidence currently has

Today we'll be exploring whether sunscreen is good or bad for you, and how you can decide

The article, posted on Outside Online, is largely based off the research of Richard

Weller is a dermatologist at the University of Edinburgh and Chief Medical Officer of

RelaxSol, a sunscreen company that proclaims to provide both sun protection while preserving

the health benefits of sun exposure in terms of Vitamin D and nitric oxide synthesis, as

Lindqvist is a senior research fellow in obstetrics and gynecology at the Karolinska Institute.

Lindqvist's paper, titled Avoidance of sun exposure as a risk factor for major

causes of death: a competing risk analysis of the Melanoma in Southern Sweden cohort

was published in the Journal of Internal Medicine in 2016.

The researchers conducted a series of questionnaires to 29,518 women between 1990 and 1992 asking

about sun exposure, alcohol consumption, smoking, marital status, education level, and parity,

They asked four questions in particular to assess sun exposure – (i) How often do you

(ii) Do you sunbathe during the winter, such as on vacations in the mountains?

(iv) Do you go abroad on vacation to swim and sunbathe?

These women were then followed for 20 years, with the researchers collecting data about

their development of diseases and causes of death.

The longer life expectancy amongst women with active sun exposure habits was related

to a decrease in CVD and non-cancer/non-CVD mortality, causing the relative contribution

In other words, women with active sun exposure habits were correlated with lower rates of

heart disease and non-cancer related causes of death.

However, the rates of death secondary to cancer increased, which is explained by the longer

If you live long enough, you're more likely to get cancer.

Now if you're confused how they arrived to this conclusion based off their methodology – don't

First, we can see that the groups are significantly different in just about every demographic

variable measured by the researchers, from education to marital status, parity, smoking,

alcohol consumption, age group, disposable income, and most importantly, any comorbidities.

While the researchers did attempt to control for these factors, the subgroups are so vastly

different that its comparing apples to oranges.

Additionally, they did NOT control for several other important confounding variables, such

as sun protective measures – did the women use hats or sunscreen?

They also didn't control for several other important factors relevant to their endpoint,

which is heart disease. These other factors include family history of heart disease, dietary factors, exercise,

BMI, diabetes, or hypertension, to list a few.

Given the drastic differences in each sub-group, it's safe to assume many of these other

factors would also be substantially varied.

If any of this confuses you, I recommend you watch my recent video on how to read research

The author also referenced research conducted by Richard Weller.

His study tracked blood pressure in over 300,000 individuals across the U.S., adjusting for

Preliminary findings suggest that people from sunnier climates have lower blood pressure.

However, it is difficult to assess the validity of the claims or the methods without seeing a

That being said, these results aren't all that surprising, as other published articles

have demonstrated an inverse association between sunlight exposure and blood pressure.

The overarching conclusions are already on

shaky grounds given the dataset and methods used.

But perhaps there is truth to these claims – for that, we'll need to dig a bit deeper.

The author claims that sunscreen blocks all

UV radiation and therefore all Vitamin D production.

Ask anyone who has gotten sunburned despite using sunscreen and you'll understand the

The effectiveness of sunscreen is measured in SPF, standing for Sun Protection Factor,

which is a measurement of how effectively UVB rays are blocked.

This is not a linear scale, but higher numbers correlate to a greater percentage of UVB rays

An SPF of 15 corresponds to 93% blockage, SPF of 30 corresponds to 97%, and SPF 50  corresponds

That being said, the overwhelming majority of people do not apply enough sunscreen.

For best results, you should apply 2mg/cm2 of skin, reapplied every two hours.

Most people under apply, using only 1/4 to 1/2 of the recommended

amount, and are generally not great with reapplication.

In the real world, even with regular use of sunscreen, a great deal of sunlight and radiation

Studies have also demonstrated that despite sunscreen

use, adequate Vitamin D production occurs due to the imperfect nature of sunscreen and

lack of perfect skin coverage at all times.

Now while UVB rays are at the right wavelength to help catalyze vitamin D synthesis, they

also cause major damage to our skin, including carcinogenesis, meaning the formation of cancer.

The article glosses over the real risks associated with skin cancer.

In medical school and plastic surgery residency, I've seen some nasty skin cancer cases.

And skin cancer is surprisingly common too.

One in five Americans will develop skin cancer by the age of 70.

There's basal cell carcinoma, squamous cell carcinoma, and worst of all, melanoma. And like any cancer, it can be quite serious.

Skin cancer can metastasize, require major surgery, radiation, and immunotherapy.

字幕列表影片播放

防晒霜是BAD！？| 新研究解讀 (Sunscreen is BAD!? | New Research Explained)

recommend

demonstrate

evidence

convince