Tag Archives: health

Misunderstood Salt: The Facts About Limiting Intake

For dec­ades we have been told, with cer­tainty, to lim­it our salt intake or risk heart dis­ease and high blood pressure—but is this advice based on sound sci­entif­ic find­ings? The short answer is No.

The evid­ence is incon­sist­ent, incon­clus­ive and con­tra­dict­ory, says prom­in­ent car­di­olo­gist Jeremi­ah Stamler (who used to be an advoc­ate for the eat-less-salt cam­paign back in the 60s and 80s), and there­fore the “eat-less-salt” mes­sage is pre­ma­ture and may even be harm­ful.

Last year, two [meta-ana­lyses] were pub­lished by the Cochrane Col­lab­or­a­tion, an inter­na­tion­al non­profit organ­iz­a­tion foun­ded to con­duct unbiased reviews of med­ic­al evid­ence. The first of the two reviews con­cluded that cut­ting back “the amount of salt eaten reduces blood pres­sure, but there is insuf­fi­cient evid­ence to con­firm the pre­dicted reduc­tions in people dying pre­ma­turely or suf­fer­ing car­di­ovas­cu­lar disease.” The second con­cluded that “we do not know if low salt diets improve or worsen health outcomes.”The idea that eat­ing less salt can worsen health out­comes may sound bizarre, but it also has bio­lo­gic­al plaus­ib­il­ity and is cel­eb­rat­ing its 40th anniversary this year, too. A 1972 paper in The New Eng­land Journ­al of Medi­cine repor­ted that the less salt people ate, the high­er their levels of a sub­stance secreted by the kid­neys, called ren­in, which set off a physiolo­gic­al cas­cade of events that seemed to end with an increased risk of heart dis­ease. In this scen­ario: eat less salt, secrete more ren­in, get heart dis­ease, die pre­ma­turely. […]

[Four stud­ies] involving Type 1 dia­bet­ics, Type 2 dia­bet­ics, healthy Europeans and patients with chron­ic heart fail­ure — repor­ted that the people eat­ing salt at the lower lim­it of nor­mal were more likely to have heart dis­ease than those eat­ing smack in the middle of the nor­mal range.

via The Browser

Illness Susceptibility and Sleep Quality

I’ve been ill for a few weeks and I was fairly sure (in my ama­teur opin­ion) that it was related to a sig­ni­fic­ant lack of sleep over the last couple of months. Upon return­ing to full health I decided to do some quick research on my favour­ite top­ic: sleep.

In one recent study look­ing at sleep habits and res­ult­ing sus­cept­ib­il­ity to the com­mon cold it was found that both sleep length and sleep qual­ity were “import­ant pre­dict­ors of immunity and, in turn, sus­cept­ib­il­ity”.

Spe­cific­ally, “those who slept an aver­age of few­er than sev­en hours a night […] were three times as likely to get sick as those who aver­aged at least eight hours”. Fur­ther­more, people who had 92% sleep effi­ciency were five and a half times more sus­cept­ible com­pared to those with 98% sleep effi­ciency (defined as the per­cent­age of time in bed actu­ally asleep).

The New York Times art­icle that led me to this study con­tin­ues:

Sleep and immunity, it seems, are tightly linked. Stud­ies have found that mam­mals that require the most sleep also pro­duce great­er levels of dis­ease-fight­ing white blood cells — but not red blood cells, even though both are pro­duced in bone mar­row and stem from the same pre­curs­or. And research­ers at the Max Planck Insti­tute for Evol­u­tion­ary Anthro­po­logy have shown that spe­cies that sleep more have great­er res­ist­ance against patho­gens.

The more you know… (the more you sleep?)

Update: I’ve briefly men­tioned this study on Lone Gun­man before, but I think the cog­nit­ive impact was the most inter­est­ing tit­bit in that Jonah Lehr­er art­icle.

The Brain on Food: Everyday Chemicals

Regard­ing all the foods that we con­sume as a drug­s is a won­drous way to exam­ine and com­pre­hend the com­plex inter­ac­tions and subtle forces behind how everything we put in our mouths affects “how our neur­ons behave and, sub­sequently, how we think and feel”.

In a com­pel­ling art­icle that sug­gests our shared evol­u­tion­ary his­tory with the plants and anim­als that we eat is the root cause of them hav­ing an affect on our body’s beha­viour, Gary Wenk, author of Your Brain on Food, briefly describes how some of the chem­ic­als present in ‘drugs’ such as chocol­ate, bana­nas, alco­hol and nut­meg affect us:

We have all exper­i­enced the con­sequences of our shared evol­u­tion­ary his­tory with the plants we eat. For example, unripe bana­nas con­tain the neur­o­trans­mit­ter sero­ton­in. When you eat an unripe banana, its sero­ton­in is free to act upon the sero­ton­in neur­ons with­in your digest­ive tract. The con­sequence is likely to be increased activ­a­tion of the muscles in the wall of your intest­ines, usu­ally exper­i­enced as diarrhea.

Many plants con­tain com­pounds that should be able to enhance your brain’s per­form­ance. For example, pota­toes, toma­toes, and egg­plants con­tain solan­ine and α-chaconine, sub­stances that can enhance the action of acet­ylcholine, a chem­ic­al in your brain that is vital to memory form­a­tion. Your mood might be enhanced slightly by eat­ing fava beans because they con­tain L-DOPA, a pre­curs­or to the pro­duc­tion of dopam­ine, the reward chem­ic­al in your brain. Wheth­er these food-borne com­pounds actu­ally affect your brain depends upon how much you con­sume and your own per­son­al physiology. This might explain why some people find it quite reward­ing to eat pota­toes or egg­plants.

Morphine-like chem­ic­als cap­able of act­ing upon the brain are pro­duced in your intest­ines when you con­sume milk, eggs, cheese, spin­ach, mush­rooms, pump­kin, and vari­ous fish and grains. Dairy products in par­tic­u­lar con­tain a pro­tein known as case­in, which enzymes in your intest­ines can con­vert into beta-caso­morph­in. In new­borns, that beta-caso­morph­in can eas­ily pass out of the imma­ture gut and into the devel­op­ing brain to pro­duce euphor­ia.

There’s much more like that in the art­icle, con­cluded with Wenk arguing that this shared evol­u­tion­ary his­tory is why plants and anim­als from oth­er plan­ets will prob­ably not harm or sus­tain us if we ever travel to dis­tant, Earth-like bod­ies.

Drinking Levels and Mortality Rates

Des­pite the vari­ous and severe health risks that come with drink­ing, abstain­ing from alco­hol appears to increase your risk of dying pre­ma­turely. The reas­ons for this are not clearly known, but it is thought to be because drink­ers are more likely to belong to a com­munity (albeit one that drinks), and a feel­ing of com­munity is strongly cor­rel­ated with hap­pi­ness and longev­ity.

Even after con­trolling for nearly all ima­gin­able vari­ables — socioeco­nom­ic status, level of phys­ic­al activ­ity, num­ber of close friends, qual­ity of social sup­port and so on — the research­ers […] found that over a 20-year peri­od, mor­tal­ity rates were highest for those who were not cur­rent drink­ers, regard­less of wheth­er they used to be alco­hol­ics, second highest for heavy drink­ers and low­est for mod­er­ate drinkers. […]

These are remark­able stat­ist­ics. Even though heavy drink­ing is asso­ci­ated with high­er risk for cir­rhosis and sev­er­al types of can­cer (par­tic­u­larly can­cers in the mouth and eso­phag­us), heavy drink­ers are less likely to die than people who don’t drink, even if they nev­er had a prob­lem with alco­hol. One import­ant reas­on is that alco­hol lub­ric­ates so many social inter­ac­tions, and social inter­ac­tions are vital for main­tain­ing men­tal and phys­ic­al health. […]

The authors of the new paper are care­ful to note that even if drink­ing is asso­ci­ated with longer life, it can be dan­ger­ous: it can impair your memory severely and it can lead to non­leth­al falls and oth­er mis­haps […] that can screw up your life. There’s also the depend­ency issue.

The cor­rel­a­tions between alco­hol intake and vari­ous health out­comes (both pos­it­ive and neg­at­ive) is con­fus­ing and var­ied. A few things seem to be for sure: it can be good and it can be bad; no caus­a­tion has been proven; and the effects dif­fer between the sexes.

Update: I for­got to link to the pub­lished study (Hola­han et al., 2010)… the Res­ults sec­tion is the one worth per­us­ing. For those without full access to the study (ahem), Over­com­ing Bias provides the full list of con­trols.

Update: Jonah Lehr­er dis­cusses this study in an art­icle titled Why Alco­hol Is Good for You, emphas­ising the social side of drink­ing as the key to longev­ity.

Food-Based Body Clock the Key to Jet Lag

The primary cause of jet lag (or desyn­chro­nos­is as it’s cor­rectly known) is the dis­rup­tion of our cir­ca­di­an rhythms based on the daily light–dark cycles we exper­i­ence. How­ever this is only the case when food is in plen­ti­ful supply, with new research sug­gest­ing that cir­ca­di­an rhythms based on food avail­ab­il­ity are able to over­ride those of the light-dark cycle. This could offer us a simple and effect­ive way of pre­vent­ing jet lag: fast­ing for six­teen hours pri­or to your new time zone’s break­fast time.

I men­tioned this in passing two years ago (just before under­tak­ing a 25-hour Sydney to Lon­don flight), but after recently com­ing across the study again I felt com­pelled to point to it in more detail.

Research­ers at Har­vard Med­ic­al School and Beth Israel Dea­con­ess Med­ic­al Cen­ter in Boston have now pin­pointed a second [bio­lo­gic­al clock] that is set by the avail­ab­il­ity of food. […]

Clif­ford Saper, the seni­or author of the study, said this second clock prob­ably takes over when food is scarce. It may have evolved to make sure mam­mals don’t go to sleep when they should be for­aging for food to stay alive.

Dr. Saper says long-dis­tance trav­el­lers can prob­ably use this food clock to adjust rap­idly to a new time zone.

“A peri­od of fast­ing with no food at all for about 16 hours is enough to engage this new clock,” he said in a state­ment released with the study. Once you eat again, your intern­al clock will be reset as though it is the start of a new day […] and you should just flip into that new time zone in one day.