Richard Weller: Could the sun be good for your heart?

88,013 views ・ 2013-01-17

TED


Please double-click on the English subtitles below to play the video.

00:00
Translator: Morton Bast Reviewer: Thu-Huong Ha
0
0
7000
00:15
So, before I became a dermatologist,
1
15640
2407
00:18
I started in general medicine,
2
18047
2552
00:20
as most dermatologists do in Britain.
3
20599
2216
00:22
At the end of that time, I went off to Australia,
4
22815
2048
00:24
about 20 years ago.
5
24863
1896
00:26
What you learn when you go to Australia
6
26759
2121
00:28
is the Australians are very competitive.
7
28880
2726
00:31
And they are not magnanimous in victory.
8
31606
2057
00:33
And that happened a lot:
9
33663
2064
00:35
"You pommies, you can't play cricket, rugby."
10
35727
2432
00:38
I could accept that.
11
38159
2118
00:40
But moving into work --
12
40277
2330
00:42
and we have each week what's called a journal club,
13
42607
2538
00:45
when you'd sit down with the other doctors
14
45145
2458
00:47
and you'd study a scientific paper
15
47603
2120
00:49
in relation to medicine.
16
49723
1841
00:51
And after week one, it was about cardiovascular mortality,
17
51564
2749
00:54
a dry subject -- how many people die of heart disease,
18
54313
3680
00:57
what the rates are.
19
57993
1384
00:59
And they were competitive about this:
20
59377
1976
01:01
"You pommies, your rates of heart disease are shocking."
21
61353
3096
01:04
And of course, they were right.
22
64449
1896
01:06
Australians have about a third less heart disease than we do --
23
66345
3981
01:10
less deaths from heart attacks, heart failure, less strokes --
24
70326
3791
01:14
they're generally a healthier bunch.
25
74117
2060
01:16
And of course they said this was because of
26
76177
1691
01:17
their fine moral standing, their exercise,
27
77868
2064
01:19
because they're Australians and we're weedy pommies, and so on.
28
79932
4068
01:24
But it's not just Australia that has better health than Britain.
29
84000
5031
01:29
Within Britain, there is a gradient of health --
30
89031
3528
01:32
and this is what's called standardized mortality,
31
92559
1936
01:34
basically your chances of dying.
32
94495
2088
01:36
This is looking at data from the paper about 20 years ago,
33
96583
3344
01:39
but it's true today.
34
99927
1475
01:41
Comparing your rates of dying 50 degrees north --
35
101402
3090
01:44
that's the South, that's London and places --
36
104492
2267
01:46
by latitude, and 55 degrees --
37
106759
3352
01:50
the bad news is that's here, Glasgow.
38
110111
2384
01:52
I'm from Edinburgh. Worse news, that's even Edinburgh.
39
112495
2848
01:55
(Laughter)
40
115343
4124
01:59
So what accounts for this horrible space here
41
119467
3306
02:02
between us up here in southern Scotland
42
122773
2204
02:04
and the South?
43
124977
1010
02:05
Now, we know about smoking,
44
125987
1418
02:07
deep-fried Mars bars, chips -- the Glasgow diet.
45
127405
2702
02:10
All of these things.
46
130107
1328
02:11
But this graph is after taking into account
47
131435
2792
02:14
all of these known risk factors.
48
134227
2064
02:16
This is after accounting for smoking, social class, diet,
49
136291
3769
02:20
all those other known risk factors.
50
140060
1743
02:21
We are left with this missing space
51
141803
2224
02:24
of increased deaths the further north you go.
52
144027
3860
02:27
Now, sunlight, of course, comes into this.
53
147887
2637
02:30
And vitamin D has had a great deal of press,
54
150524
2320
02:32
and a lot of people get concerned about it.
55
152844
2002
02:34
And we need vitamin D. It's now a requirement that children have a certain amount.
56
154846
3992
02:38
My grandmother grew up in Glasgow,
57
158838
2232
02:41
back in the 1920s and '30s when rickets was a real problem
58
161070
3586
02:44
and cod liver oil was brought in.
59
164656
2198
02:46
And that really prevented the rickets that used to be common in this city.
60
166854
3944
02:50
And I as a child was fed cod liver oil by my grandmother.
61
170798
3920
02:54
I distinctly -- nobody forgets cod liver oil.
62
174718
3024
02:57
But an association: The higher people's blood levels of vitamin D are,
63
177742
4782
03:02
the less heart disease they have, the less cancer.
64
182524
3327
03:05
There seems to be a lot of data suggesting that vitamin D is very good for you.
65
185851
3842
03:09
And it is, to prevent rickets and so on.
66
189693
2294
03:11
But if you give people vitamin D supplements,
67
191987
2720
03:14
you don't change that high rate of heart disease.
68
194707
3432
03:18
And the evidence for it preventing cancers is not yet great.
69
198139
3728
03:21
So what I'm going to suggest is that vitamin D is not the only story in town.
70
201867
4857
03:26
It's not the only reason preventing heart disease.
71
206724
3311
03:30
High vitamin D levels, I think, are a marker for sunlight exposure,
72
210035
4369
03:34
and sunlight exposure, in methods I'm going to show,
73
214404
3215
03:37
is good for heart disease.
74
217619
2439
03:40
Anyway, I came back from Australia,
75
220058
1961
03:42
and despite the obvious risks to my health, I moved to Aberdeen.
76
222019
3496
03:45
(Laughter)
77
225515
2552
03:48
Now, in Aberdeen, I started my dermatology training.
78
228067
3151
03:51
But I also became interested in research,
79
231218
1945
03:53
and in particular I became interested in this substance, nitric oxide.
80
233163
3175
03:56
Now these three guys up here,
81
236338
1376
03:57
Furchgott, Ignarro and Murad,
82
237714
1570
03:59
won the Nobel Prize for medicine back in 1998.
83
239284
3262
04:02
And they were the first people to describe
84
242546
2143
04:04
this new chemical transmitter, nitric oxide.
85
244689
3345
04:08
What nitric oxide does is it dilates blood vessels,
86
248034
3025
04:11
so it lowers your blood pressure.
87
251059
1871
04:12
It also dilates the coronary arteries, so it stops angina.
88
252930
4167
04:17
And what was remarkable about it
89
257097
1386
04:18
was in the past when we think of chemical messengers within the body,
90
258483
4071
04:22
we thought of complicated things like estrogen and insulin,
91
262554
3170
04:25
or nerve transmission.
92
265724
1470
04:27
Very complex processes with very complex chemicals
93
267194
3295
04:30
that fit into very complex receptors.
94
270489
2288
04:32
And here's this incredibly simple molecule,
95
272777
2361
04:35
a nitrogen and an oxygen that are stuck together,
96
275138
3338
04:38
and yet these are hugely important for [unclear] our low blood pressure,
97
278476
4630
04:43
for neurotransmission, for many, many things,
98
283106
2606
04:45
but particularly cardiovascular health.
99
285712
3402
04:49
And I started doing research, and we found, very excitingly,
100
289114
3302
04:52
that the skin produces nitric oxide.
101
292416
2610
04:55
So it's not just in the cardiovascular system it arises.
102
295026
2897
04:57
It arises in the skin.
103
297923
1867
04:59
Well, having found that and published that,
104
299790
1866
05:01
I thought, well, what's it doing?
105
301656
2056
05:03
How do you have low blood pressure in your skin?
106
303712
1480
05:05
It's not the heart. What do you do?
107
305192
2091
05:07
So I went off to the States, as many people do if they're going to do research,
108
307283
4071
05:11
and I spent a few years in Pittsburgh. This is Pittsburgh.
109
311354
3737
05:15
And I was interested in these really complex systems.
110
315091
2613
05:17
We thought that maybe nitric oxide affected cell death,
111
317704
4041
05:21
and how cells survive, and their resistance to other things.
112
321745
2480
05:24
And I first off started work in cell culture, growing cells,
113
324225
3367
05:27
and then I was using knockout mouse models --
114
327592
2120
05:29
mice that couldn't make the gene.
115
329712
1737
05:31
We worked out a mechanism, which -- NO was helping cells survive.
116
331449
4410
05:35
And I then moved back to Edinburgh.
117
335859
3821
05:39
And in Edinburgh, the experimental animal we use is the medical student.
118
339680
2782
05:42
It's a species close to human,
119
342462
2058
05:44
with several advantages over mice:
120
344520
1902
05:46
They're free, you don't shave them, they feed themselves,
121
346422
3456
05:49
and nobody pickets your office saying,
122
349878
2120
05:51
"Save the lab medical student."
123
351998
2400
05:54
So they're really an ideal model.
124
354398
3263
05:57
But what we found
125
357661
1961
05:59
was that we couldn't reproduce in man the data we had shown in mice.
126
359622
4617
06:04
It seemed we couldn't turn off the production
127
364239
3240
06:07
of nitric oxide in the skin of humans.
128
367479
3080
06:10
We put on creams that blocked the enzyme that made it,
129
370559
2792
06:13
we injected things. We couldn't turn off the nitric oxide.
130
373351
4384
06:17
And the reason for this, it turned out, after two or three years' work,
131
377735
3264
06:20
was that in the skin we have huge stores
132
380999
4048
06:25
not of nitric oxide, because nitric oxide is a gas,
133
385047
3088
06:28
and it's released -- (Poof!) -- and in a few seconds it's away,
134
388135
3152
06:31
but it can be turned into these forms of nitric oxide --
135
391287
3224
06:34
nitrate, NO3; nitrite, NO2; nitrosothiols.
136
394511
3632
06:38
And these are more stable,
137
398143
1416
06:39
and your skin has got really large stores of NO.
138
399559
4160
06:43
And we then thought to ourselves, with those big stores,
139
403719
2825
06:46
I wonder if sunlight might activate those stores
140
406544
3311
06:49
and release them from the skin,
141
409855
1744
06:51
where the stores are about 10 times as big as what's in the circulation.
142
411599
3392
06:54
Could the sun activate those stores into the circulation,
143
414991
2840
06:57
and there in the circulation do its good things for your cardiovascular system?
144
417831
5240
07:03
Well, I'm an experimental dermatologist,
145
423071
2528
07:05
so what we did was we thought
146
425599
1305
07:06
we'd have to expose our experimental animals to sunlight.
147
426904
3527
07:10
And so what we did was we took a bunch of volunteers
148
430431
4080
07:14
and we exposed them to ultraviolet light.
149
434511
2698
07:17
So these are kind of sunlamps.
150
437209
1729
07:18
Now, what we were careful to do was,
151
438938
2696
07:21
vitamin D is made by ultraviolet B rays
152
441634
2960
07:24
and we wanted to separate our story from the vitamin D story.
153
444594
3976
07:28
So we used ultraviolet A, which doesn't make vitamin D.
154
448570
3847
07:32
When we put people under a lamp
155
452417
2281
07:34
for the equivalent of about 30 minutes of sunshine in summer in Edinburgh,
156
454698
5076
07:39
what we produced was, we produced a rise
157
459774
2540
07:42
in circulating nitric oxide.
158
462314
1992
07:44
So we put patients with these subjects under the UV,
159
464306
2848
07:47
and their NO levels do go up,
160
467154
2416
07:49
and their blood pressure goes down.
161
469570
2136
07:51
Not by much, as an individual level,
162
471706
2377
07:54
but enough at a population level
163
474083
2367
07:56
to shift the rates of heart disease in a whole population.
164
476450
3720
08:00
And when we shone UV at them,
165
480170
2424
08:02
or when we warmed them up to the same level as the lamps,
166
482594
3662
08:06
but didn't actually let the rays hit the skin, this didn't happen.
167
486256
3262
08:09
So this seems to be a feature of ultraviolet rays hitting the skin.
168
489518
3864
08:13
Now, we're still collecting data.
169
493382
1824
08:15
A few good things here:
170
495206
1448
08:16
This appeared to be more marked in older people.
171
496654
3147
08:19
I'm not sure exactly how much.
172
499801
1613
08:21
One of the subjects here was my mother-in-law,
173
501414
1773
08:23
and clearly I do not know her age.
174
503187
2952
08:26
But certainly in people older than my wife,
175
506139
3432
08:29
this appears to be a more marked effect.
176
509571
3133
08:32
And the other thing I should mention
177
512704
1251
08:33
was there was no change in vitamin D.
178
513955
2056
08:36
This is separate from vitamin D.
179
516011
2120
08:38
So vitamin D is good for you -- it stops rickets,
180
518131
1536
08:39
it prevents calcium metabolism, important stuff.
181
519667
2240
08:41
But this is a separate mechanism from vitamin D.
182
521907
3032
08:44
Now, one of the problems with looking at blood pressure
183
524939
2576
08:47
is your body does everything it can
184
527515
1552
08:49
to keep your blood pressure at the same place.
185
529067
1583
08:50
If your leg is chopped off and you lose blood,
186
530650
1649
08:52
your body will clamp down, increase the heart rate,
187
532299
2905
08:55
do everything it can to keep your blood pressure up.
188
535204
2224
08:57
That is an absolutely fundamental physiological principle.
189
537428
2976
09:00
So what we've next done
190
540404
1807
09:02
is we've moved on to looking at blood vessel dilatation.
191
542211
3656
09:05
So we've measured -- this is again,
192
545867
1497
09:07
notice no tail and hairless, this is a medical student.
193
547364
5328
09:12
In the arm, you can measure blood flow in the arm
194
552692
2618
09:15
by how much it swells up as some blood flows into it.
195
555310
3232
09:18
And what we've shown is that doing a sham irradiation --
196
558542
3475
09:22
this is the thick line here --
197
562017
1469
09:23
this is shining UV on the arm so it warms up
198
563486
2400
09:25
but keeping it covered so the rays don't hit the skin.
199
565886
2824
09:28
There is no change in blood flow, in dilatation of the blood vessels.
200
568710
3912
09:32
But the active irradiation,
201
572622
1849
09:34
during the UV and for an hour after it,
202
574471
3352
09:37
there is dilation of the blood vessels.
203
577823
2097
09:39
This is the mechanism by which you lower blood pressure,
204
579920
2600
09:42
by which you dilate the coronary arteries also,
205
582520
2376
09:44
to let the blood be supplied with the heart.
206
584896
1711
09:46
So here, further data that ultraviolet -- that's sunlight --
207
586607
4393
09:51
has benefits on the blood flow and the cardiovascular system.
208
591000
4879
09:55
So we thought we'd just kind of model --
209
595879
2343
09:58
Different amounts of UV hit different parts of the Earth at different times of year,
210
598222
6249
10:04
so you can actually work out those stores of nitric oxide --
211
604471
4024
10:08
the nitrates, nitrites, nitrosothiols in the skin --
212
608495
2256
10:10
cleave to release NO.
213
610751
2872
10:13
Different wavelengths of light have different activities of doing that.
214
613623
3825
10:17
So you can look at the wavelengths of light that do that.
215
617448
2079
10:19
And you can look -- So, if you live on the equator, the sun comes straight overhead,
216
619527
3985
10:23
it comes through a very thin bit of atmosphere.
217
623512
1816
10:25
In winter or summer, it's the same amount of light.
218
625328
2439
10:27
If you live up here, in summer
219
627767
2513
10:30
the sun is coming fairly directly down,
220
630280
2656
10:32
but in winter it's coming through a huge amount of atmosphere,
221
632936
3307
10:36
and much of the ultraviolet is weeded out,
222
636243
3221
10:39
and the range of wavelengths that hit the Earth
223
639464
2352
10:41
are different from summer to winter.
224
641816
2328
10:44
So what you can do is you can multiply those data
225
644144
1942
10:46
by the NO that's released
226
646086
1993
10:48
and you can calculate how much nitric oxide
227
648079
3184
10:51
would be released from the skin into the circulation.
228
651263
3169
10:54
Now, if you're on the equator here --
229
654432
2000
10:56
that's these two lines here, the red line and the purple line --
230
656432
3427
10:59
the amount of nitric oxide that's released is the area under the curve,
231
659859
4397
11:04
it's the area in this space here.
232
664256
2031
11:06
So if you're on the equator, December or June,
233
666287
2697
11:08
you've got masses of NO being released from the skin.
234
668984
3256
11:12
So Ventura is in southern California.
235
672240
2464
11:14
In summer, you might as well be at the equator.
236
674704
2216
11:16
It's great. Lots of NO is released.
237
676920
2056
11:18
Ventura mid-winter, well, there's still a decent amount.
238
678976
3943
11:22
Edinburgh in summer, the area beneath the curve is pretty good,
239
682919
3961
11:26
but Edinburgh in winter, the amount of NO that can be released
240
686880
4215
11:31
is next to nothing, tiny amounts.
241
691095
3858
11:34
So what do we think?
242
694953
1805
11:36
We're still working at this story,
243
696758
1592
11:38
we're still developing it, we're still expanding it.
244
698350
1912
11:40
We think it's very important.
245
700262
1648
11:41
We think it probably accounts for a lot of the north-south health divide within Britain,
246
701910
3593
11:45
It's of relevance to us.
247
705503
1631
11:47
We think that the skin --
248
707134
1688
11:48
well, we know that the skin has got very large stores
249
708822
2888
11:51
of nitric oxide as these various other forms.
250
711710
2224
11:53
We suspect a lot of these come from diet,
251
713934
1873
11:55
green leafy vegetables, beetroot, lettuce
252
715807
2271
11:58
has a lot of these nitric oxides that we think go to the skin.
253
718078
3320
12:01
We think they're then stored in the skin,
254
721398
2144
12:03
and we think the sunlight releases this
255
723542
2400
12:05
where it has generally beneficial effects.
256
725942
2633
12:08
And this is ongoing work, but dermatologists --
257
728575
2479
12:11
I mean, I'm a dermatologist.
258
731054
1720
12:12
My day job is saying to people, "You've got skin cancer,
259
732774
2528
12:15
it's caused by sunlight, don't go in the sun."
260
735302
1880
12:17
I actually think a far more important message
261
737182
2736
12:19
is that there are benefits as well as risks to sunlight.
262
739918
3424
12:23
Yes, sunlight is the major alterable risk factor for skin cancer,
263
743342
5753
12:29
but deaths from heart disease are a hundred times higher
264
749095
2871
12:31
than deaths from skin cancer.
265
751966
1952
12:33
And I think that we need to be more aware of,
266
753918
2649
12:36
and we need to find the risk-benefit ratio.
267
756567
2079
12:38
How much sunlight is safe,
268
758646
1472
12:40
and how can we finesse this best for our general health?
269
760118
4200
12:44
So, thank you very much indeed.
270
764318
2180
12:46
(Applause)
271
766498
6897
About this website

This site will introduce you to YouTube videos that are useful for learning English. You will see English lessons taught by top-notch teachers from around the world. Double-click on the English subtitles displayed on each video page to play the video from there. The subtitles scroll in sync with the video playback. If you have any comments or requests, please contact us using this contact form.

https://forms.gle/WvT1wiN1qDtmnspy7