[00:06] Cigarettes aren’t good for us.
[00:09] That’s hardly news--we’ve known 
about the dangers of smoking for decades.
[00:13] But how exactly do cigarettes harm us?
[00:16] Let’s look at what happens 
as their ingredients
[00:19] make their way through our bodies,
[00:20] and how we benefit physically 
when we finally give up smoking.
[00:25] With each inhalation,
[00:27] smoke brings its more than 5,000 
chemical substances
[00:31] into contact with the body’s tissues.
[00:33] From the start, tar, 
a black, resinous material,
[00:37] begins to coat the teeth and gums,
[00:39] damaging tooth enamel, 
and eventually causing decay.
[00:43] Over time, smoke also damages 
nerve-endings in the nose,
[00:47] causing loss of smell.
[00:50] Inside the airways and lungs,
[00:51] smoke increases 
the likelihood of infections,
[00:54] as well as chronic diseases
like bronchitis and emphysema.
[00:59] It does this by damaging the cilia,
[01:01] tiny hairlike structures whose job it is 
to keep the airways clean.
[01:07] It then fills the alveoli,
[01:09] tiny air sacs that enable the exchange 
of oxygen and carbon dioxide
[01:13] between the lungs and blood.
[01:15] A toxic gas called carbon monoxide 
crosses that membrane into the blood,
[01:20] binding to hemoglobin
[01:21] and displacing the oxygen
[01:23] it would usually have transported
around the body.
[01:26] That’s one of the reasons smoking 
can lead to oxygen deprivation
[01:30] and shortness of breath.
[01:32] Within about 10 seconds,
[01:35] the bloodstream carries a stimulant 
called nicotine to the brain,
[01:38] triggering the release of dopamine 
and other neurotransmitters
[01:42] including endorphins
[01:43] that create the pleasurable sensations 
which make smoking highly addictive.
[01:47] Nicotine and other chemicals 
from the cigarette
[01:50] simultaneously cause constriction 
of blood vessels
[01:53] and damage their delicate 
endothelial lining,
[01:55] restricting blood flow.
[01:57] These vascular effects lead 
to thickening of blood vessel walls
[02:00] and enhance blood platelet stickiness,
[02:03] increasing the likelihood 
that clots will form
[02:06] and trigger heart attacks and strokes.
[02:08] Many of the chemicals inside cigarettes 
can trigger dangerous mutations
[02:12] in the body’s DNA that make cancers form.
[02:15] Additionally, ingredients like arsenic 
and nickel
[02:18] may disrupt the process of DNA repair,
[02:21] thus compromising the body’s ability 
to fight many cancers.
[02:25] In fact, about one of every three 
cancer deaths in the United States
[02:29] is caused by smoking.
[02:31] And it’s not just lung cancer.
[02:33] Smoking can cause cancer 
in multiple tissues and organs,
[02:36] as well as damaged eyesight
[02:38] and weakened bones.
[02:40] It makes it harder 
for women to get pregnant.
[02:43] And in men,
it can cause erectile dysfunction.
[02:46] But for those who quit smoking,
[02:47] there’s a huge positive upside
[02:49] with almost immediate 
and long-lasting physical benefits.
[02:53] Just 20 minutes after 
a smoker’s final cigarette,
[02:57] their heart rate and blood pressure
begin to return to normal.
[03:00] After 12 hours, 
carbon monoxide levels stabilize,
[03:04] increasing the blood’s 
oxygen-carrying capacity.
[03:07] A day after ceasing,
[03:08] heart attack risk begins to decrease as
blood pressure and heart rates normalize.
[03:13] After two days,
[03:15] the nerve endings responsible 
for smell and taste start to recover.
[03:20] Lungs become healthier 
after about one month,
[03:23] with less coughing 
and shortness of breath.
[03:25] The delicate hair-like cilia 
in the airways and lungs
[03:28] start recovering within weeks,
[03:31] and are restored after 9 months, 
improving resistance to infection.
[03:35] By the one-year anniversary of quitting,
[03:37] heart disease risk plummets to half
as blood vessel function improves.
[03:42] Five years in,
[03:44] the chance of a clot forming
dramatically declines,
[03:46] and the risk of stroke 
continues to reduce.
[03:49] After ten years, the chances 
of developing fatal lung cancer
[03:53] go down by 50%,
[03:55] probably because the body’s ability 
to repair DNA is once again restored.
[04:00] Fifteen years in, the likelihood 
of developing coronary heart disease
[04:04] is essentially the same 
as that of a non-smoker.
[04:07] There’s no point pretending 
this is all easy to achieve.
[04:10] Quitting can lead to anxiety 
and depression,
[04:13] resulting from nicotine withdrawal.
[04:15] But fortunately, 
such effects are usually temporary.
[04:19] And quitting is getting easier,
thanks to a growing arsenal of tools.
[04:23] Nicotine replacement therapy through gum,
[04:26] skin patches,
[04:27] lozenges,
[04:28] and sprays
[04:29] may help wean smokers off cigarettes.
[04:32] They work by stimulating 
nicotine receptors in the brain
[04:35] and thus preventing withdrawal symptoms,
[04:37] without the addition 
of other harmful chemicals.
[04:40] Counselling and support groups,
[04:42] cognitive behavioral therapy,
[04:44] and moderate intensity exercise
[04:46] also help smokers stay cigarette-free.
[04:50] That’s good news,
[04:51] since quitting puts you and your body 
on the path back to health.