{"id":2731,"date":"2016-05-11T07:00:00","date_gmt":"2016-05-11T07:00:00","guid":{"rendered":"http:\/\/www.beanthinking.org\/?p=2731"},"modified":"2016-05-10T13:33:10","modified_gmt":"2016-05-10T13:33:10","slug":"a-connection-between-cold-brew-and-blood-pressure","status":"publish","type":"post","link":"https:\/\/www.beanthinking.org\/?p=2731","title":{"rendered":"A link between high blood pressure and drinking cold brew through a straw"},"content":{"rendered":"
\"Straws<\/a>
Drinking milkshake through a straw or two.<\/figcaption><\/figure>\n

How do you drink your cold-brew? How about iced-coffee or iced-tea? Would you drink it through a straw? Maybe a smoothie or a milkshake would be ok. Perhaps you’ve noticed that you need a large straw to drink that milkshake while a small straw works for ‘thinner’ drinks. But what is the connection between this and the measurement of your blood pressure? It is not that drinking coffee gives you high blood pressure or the reverse. That question can be left for discussion on other websites. No, the question is, can drinking a milkshake through a straw give you an insight into the problems of high blood pressure caused by the build up of cholesterol?<\/p>\n

If you are currently in a caf\u00e9, why not try an experiment. Get two straws and try drinking a cold drink using both of them together. It’s tricky but it is do-able, you can drink your drink. Now place one straw such that it is ‘sucking’ on the air outside the glass with the other straw still in the drink. Without cheating you can no longer ‘suck’ up that cold brew. Plugging either end of the ‘free to air’ straw enables you once again to drink your coffee. This experiment demonstrates that you are not really ‘sucking’ the liquid through the straw, rather you are generating a pressure difference between the top of the straw (a lower pressure in your mouth) and atmospheric pressure (higher pressure, around the drink) that pushes the liquid through the straw. Attempting\u00a0to drink through two straws when\u00a0one is open to the atmosphere cancels out that pressure difference.<\/p>\n

\"2<\/a>
The straw on the left has a diameter of 3mm, on the right, 6mm.<\/figcaption><\/figure>\n

Now another experiment. How do straws of different diameters affect the amount of liquid you can ‘pull’ through the straw? Try it. I have two straws in this picture, the smaller one has a diameter of 3mm, the larger one a diameter of 6mm. It takes a lot longer to drink a quantity of liquid through the smaller straw than it does the larger straw (assuming that you are drinking the same drink with each straw). For example, I drank 200ml of water in 10-12 sec with the larger straw but 26 sec with the smaller straw.<\/p>\n

Back in the early nineteenth century two people were each investigating how liquid flowed through narrow tubes. Jean Leonard Marie Poiseuille (1797-1869)<\/span><\/a> was investigating tubes of diameter 0.013-0.65mm in order to understand the flow of blood through capillaries in the body. Gotthilf Heinrich Ludwig Hagen (1797-1884)<\/span><\/a> was investigating tubes between 2.3-6mm diameter (the same as the straws in the picture). Although they came to their conclusions independently, their work now forms the basis of parts of our understanding of the circulation of blood in the body\u2020. What is now known as the Hagen-Poiseuille law states that the flow of liquid through the straw (or blood vessel) is proportional to the pressure difference between the two ends of the straw (how much you ‘suck’ so to speak) and the radius of the straw raised to the fourth power*. That is, it is the radius x radius x radius x radius. Doubling the radius of the straw results in a 2x2x2x2 (= 16) increase in flow rate.<\/p>\n

Experimenting with the two straws does not give you quite the 16x difference that you may expect from this law perhaps partly because the flow into the straw is turbulent. If you maintained a uniform flow through the straws, you should find that the difference in flow rate between the two straws would be closer to 16x.<\/p>\n

\"straw,<\/a>
A straw in water, another physics-phenomenon that is worth contemplating for a while.<\/figcaption><\/figure>\n

Of course, what applies to straws applies equally well to arteries or even the alveoli in your lungs. If your arteries get clogged by too much cholesterol, the reduction in the diameter of the artery leads to a reduced flow of the blood. A decrease in the diameter of an artery by just twenty\u00a0percent more than\u00a0halves the flow rate of blood<\/span><\/a> through it (thereby increasing the blood pressure required to maintain ‘normal’ flow rate). Similarly the constriction of the alveoli in the lungs of asthmatics reduces the flow rate of air<\/span><\/a> through the lungs in an asthma attack.<\/p>\n

So it is not quite the fact that drinking cold-brew through a thin straw can give you high blood pressure. It is rather that thinking about how liquid moves through straws can help you to think about what is going on in your body. Those arteries of yours may be worth thinking about as you sip your cold brew this summer, whether or not you do so through a straw.<\/p>\n

 <\/p>\n

*The Hagen-Poiseuille law states that the flow rate F = \u0394P.(r\u00b2)\u00b2\/(8\u03b7l) where \u0394P is the pressure difference, r the radius of the straw,\u00a0\u03b7 is the viscosity of the liquid and l the length of the straw (or artery). Perhaps you can see why you will need a larger diameter straw to drink a milkshake.<\/span><\/p>\n

\u2020Blood Pressure Measurement, An Illustrated History by NH. Naqvi and MD Blaufox, Parthenon Publishing (1998)<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

How do you drink your cold-brew? How about iced-coffee or iced-tea? Would you drink it through a straw? Maybe a smoothie or a milkshake would be ok. Perhaps you’ve noticed that you need a large straw to drink that milkshake while a small straw works for ‘thinner’ drinks. But what is the connection between this … <\/p>\n

Continue reading “A link between high blood pressure and drinking cold brew through a straw”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[4,77],"tags":[1012,1013,1011,1003,1014,1005,1008,1010,1018,1020,1019,1001,1002,1016,1017,1006,1015,1000,1007,1009,1004],"class_list":["post-2731","post","type-post","status-publish","format-standard","hentry","category-general","category-science-history","tag-alveoli","tag-artery","tag-asthma","tag-blood-pressure","tag-cholesterol","tag-cold-brew","tag-diameter","tag-does-drinking-cold-brew-through-a-straw-give-you-high-blood-pressure","tag-flow-rate","tag-fluid-dynamics","tag-fluid-flow","tag-hagen","tag-hagen-poiseuille-law","tag-iced-coffee","tag-iced-tea","tag-liquid-flow","tag-milkshake","tag-poiseuille","tag-radius","tag-rate-of-flow","tag-straws"],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p4Z8Nz-I3","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.beanthinking.org\/index.php?rest_route=\/wp\/v2\/posts\/2731","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.beanthinking.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.beanthinking.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.beanthinking.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.beanthinking.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2731"}],"version-history":[{"count":19,"href":"https:\/\/www.beanthinking.org\/index.php?rest_route=\/wp\/v2\/posts\/2731\/revisions"}],"predecessor-version":[{"id":2760,"href":"https:\/\/www.beanthinking.org\/index.php?rest_route=\/wp\/v2\/posts\/2731\/revisions\/2760"}],"wp:attachment":[{"href":"https:\/\/www.beanthinking.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2731"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.beanthinking.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2731"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.beanthinking.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2731"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}