外刊阅读 | 华盛顿邮报 | 如何才能拥有更健康的头发？

Prior to general relativity, the leading theory of gravity was Isaac Newton's law of universal gravitation, which unified the description of moving massive bodies both on Earth and in the Solar System. 

在广义相对论之前，引力的主要理论是艾萨克·牛顿的万有引力定律，该定律统一了对地球和太阳系中运动的大质量物体的描述。

How can I get healthier hair?

如何才能拥有更健康的头发？

1

My hair has been dry and brittle lately. How can I take better care of it? And what can my hair tell me about my health?You may not know this, but your scalp has its own microbiome. It’s a special part of the microbiome that exists elsewhere all over your skin, contending with a high density of hair follicles and their oil-producing sebaceous glands.

The scalp microbiome contains many common bacteria but is also home to a number of fungi, like the Malassezia species that is associated with seborrheic dermatitis, an inflammatory condition of the scalp causing red, itchy skin and dandruff. Which microbes inhabit your scalp is influenced by your age, sex, hair texture, the environment — including moisture, UV exposure and air pollution — and your behaviors, such as bleaching or coloring your hair or wearing a head covering.Most dermatologists agree that the first step toward healthy hair is a healthy scalp, and how you care for it can affect the health of your hair at every age. This means using “gentle” or “sulfate-free” hair care products that you massage onto your head — not scrub into a voluminous lather — with warm instead of scalding water. For many people, it also means not washing your hair every day.

The right frequency to wash your hair depends on the individual — washing daily can strip away the skin’s oils leading to brittle hair or an overly dry scalp (for women, sebaceous gland production drops after menopause, so what worked in your 30s may not be what works best in your 60s). The American Academy of Dermatology recommends washing once weekly or every other week for African Americans.

As we age, our hair becomes thinner and more brittle, and both men and women start to bald, typically in different patterns, around the scalp. Though these changes are normal — due to alterations in the stem cells of our hair follicles and hormonal shifts such as with menopause — they can feel distressing because of how deeply they can impact our perception of ourselves.Men tend to start to notice balding or hair thinning as early as their 20s. By their 50s, about half have experienced hair loss. Symptoms in women can show up a bit later — by age 70, half of women notice some degree of hair thinning.

Humans have about 5 million hair follicles on our bodies. While 80 to 90 percent of our hair is in the “growing” phase of their life cycle at any one moment — a phase that can last about two to six years — each hair eventually enters a shedding period at the end of the cycle. It may sound wild, but because of this, it’s normal to lose around 100-200 hairs per day from the scalp.Much of the time, changes in hair are nothing scary. But if your hair starts falling out in clumps, or the skin underneath the hair appears red and irritated, talk to your physician. Excessive hair loss may be a sign of telogen effluvium, a condition in which at least half of the scalp hair transitions out of the “growing” phase and becomes easily pulled from the scalp. Telogen effluvium can happen when the body experiences major stressors such as after a surgery or if you’re malnourished.

Journal：washingtonpost(July 22, 2024 )

Title：How can I get healthier hair? Here’s what the science says.

Category：Health

The right frequency to wash your hair depends on the individual.

正确的洗头频率因人而异。

If and how fast we “go gray” is largely determined by our genetics, but smoking and alcohol use have also been shown to speed up the rate at which our hair loses color.

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