Lancet editors miss bogus reference on Japanese longevity and salt intake

Is it too much to ask of medical journal editors to verify references for key claims? After all, just because a study author footnotes a claim, should that act automatically enshrine the claim with credibility?

If you want to know how lazy editors can help launch diet and health myths, you need look no further than a new article in The Lancet entitled, “What has made the population of Japan healthy?

The study’s media release stated,

[Japanese] life expectancy increased rapidly throughout the 1950s and 60s as first infectious disease mortality dropped markedly, which was swiftly followed by stroke mortality falling. High blood pressure was also controlled through salt reduction campaigns and increased use of antihypertensive drugs and better health technologies. [Emphasis added]

Curious about the salt reduction claim, I read the full article which spotlighted it in a summary box entitled “Key Messages”:

The control of blood pressure improved through population-based interventions such as salt reduction campaigns…

The text of the article went on to read,

A reduction in dietary salt intake has been very important for the health improvement of the Japanese population. Average salt intake among middle-aged men decreased from 30 g/day in the 1950s to 14 g/day in the 1980s…

Two factors that might be important in contributing to the falling trend in blood pressure in the population are the increased coverage of antihypertensive drugs in patients with hypertension and improved lifestyles that include reduced dietary salt intake.38

“Two factors that might be important”? I though the article said that blood pressure was controlled by salt reduction. So I went to check out footnote 38, which directed me to the following study,

Ikeda N, Gakidou E, Hasegawa T, Murray CJ. Understanding the decline of mean systolic blood pressure in Japan: an analysis of pooled data from the National Nutrition Survey, 1986–2002. Bull World Health Organ 2008; 86: 978–88.

It didn’t take long thereafter for The Lancet article’s claim to begin to teeter. The abstract in Ikeda et al. stated,

Declining mean systolic blood pressure (SBP) in Japan between 1986 and 2002 was partly attributable to the increased use of antihypertensive medications, especially in the older population, and lowered mean BMI in young women. However, a substantial part of the decline was left unexplained and needs to be investigated further. A still greater decline in SBP would be expected through improvements in body weight management, salt and alcohol intake, and treatment and control of hypertension. [Emphasis added]

So lower blood pressure was linked with medications, not reduced salt intake, which only merited a hopeful “would be expected.”

Adding detail to this observation, the Ikeda et al. study stated,

Reduced mean daily salt intake contributed [in a statistically significant manner] to the decline of mean SBP by −0.4 to −0.2 mmHg in all age groups in both sexes.

But SBP is meaningless on a population level, and fractional mmHg changes in SBP are miniscule and likely not even detectable on a clinical basis for an individual — after all, “ideal” SBP is on the order of 120 mmHg. It’s no wonder that Ikeda et al. go on to acknowledge that,

Lifestyle-related factors such as physical activity, alcohol drinking and dietary salt intake made only limited contributions to the decline of mean SBP in this study.

And even that assertion is an overstatement as there is no evidence that reducing dietary salt intake even made a “limited” contribution.

So The Lancet article makes a prominent claim that is actually debunked, as opposed to sustained, by its reference.

The added bizarre twist, here, is that Ikeda is the lead author of the article in The Lancet. So Ikeda debunked his own claim before he made it, but made it anyway, and then had the nerve to cite his prior debunking as support for the new claim.

I guess The Lancet‘s editors were too busy rushing the article to publication to actually “edit” it. The Lancet‘s editors were also apparently too busy in 1998 to uncover the scientific misconduct behind the study that fraudulently linked the MMR vaccine with autism — a study that launched anti-vaccine hysteria.

We’ll see if and how the media plays Ikeda’s new article. But if you ever hear someone bloviating about how low-salt diets help the Japanese live longer, you’ll know where the myth came from and how bogus it is.

15 thoughts on “Lancet editors miss bogus reference on Japanese longevity and salt intake”

  1. I don’t know the numbers but I think Japanese people still consume a lot
    of salt and know that it isn’t good for them.

    I suspect that their diet which has a lot more fish and vegetables has
    a lot to do with their health and as incomes rise they are able to consume
    more of these items.

  2. One of my favorite .sig lines follows:

    1950. Salt causes hypertension.
    1960. Salt does not cause hypertension.
    1970. Salt causes hypertension.
    1980. Salt relieves hypertension.
    1998. The AMA Journal concludes that “salt does not affect hypertension in any way.”
    –PAUL HARVEY

    Add this to the “food pyramid”… uh, that is, the new “food plate,” and the “new improved breathless CPR technique” (guess all the people saved with the old breathy one over the last four decades need to drop dead now). How much more evidence do we need to realize that experts don’t always know what’s best??

  3. Can’t speak to the issue of salt in Japan, but the new CPR practices DO WORK better. The new CPR practices are built on a scientific basis of keeping the pressure of blood in the cardiac-supplying arteries at a consistently high level, which drops precipitously when compressions are stopped. The CPR compressions have to start again to get the pressure of blood in the coronary arteries back to a useful level. There is enough latent oxygen in the blood to keep vital tissues from dying without frequently stopping compressions to give a breath or two. It is the sustained coronary artery pressure of the new CPR that allows for MUCH improved cardiac survival, and, thus, treatment of dysrhythmias. Non-EMS CPR done by trained bystanders using the new practices will keep a person more viable longer than the old CPR. When EMS arrives, and they have the device to do so, CPR sustained with a mechanical device that does the actual compressions has resulted in an even more impressive increase in successful resuscitations!

    So, your comparison of Japanese salt science and CPR practices is a bit off. If you or anyone you love has heart disease in the family, go to the local fire station or ambulance service and ask them how they plan on trying to resuscitate you if you go down.

    Now, pass the salt….

  4. So how is this different than many other credulous studies coming out of many “respected” publications? On top of that, the media spins and cherry picks quotes for sensationalism every day. It’s all boiling down to readership of the newspaper, TV segment or blog entry.

  5. Recent study of Ashkenazi Jews showed that genetics (having long-lived parents) over-rode personal smoking, drinking, and moderate obesity. Japanese men are among the heaviest smokers and both genders love soy sauce, pickles, beer, and sake. Doesn’t stop them from being the longest-lived of the larger populations.

  6. You mean salting down my radishes and bell peppers is (choose below)?

    A. unhealthy
    B. Healthy
    C. none of the above

  7. 30 years and never got a patient’s BP to normalize with decreased salt intake. Weight loss of 20# -yes. Decrease ethanol intake to 1 a day or less – yes. Medication – yes.

    This is likely a prelude to legislation to limit NaCl, involving testers, tasters, and informative labels required, so attorneys can practice medicine without having to having had the annoyance of attending medical school or having done a residency.

  8. I wonder if they considered some of the less obvious causes of Japanese mortality in the 30s and 40s? One being WWII. Aside from the obvious death-by-combat aspect of war-time Japan, diets suffered terribly during the war as resources were restricted and redirected.

  9. Sadly enough, Dr. Bob may be on to something. There simply aren’t enough street criminals to defend and human rights issues to discover for all the law school grads to hope to make a decent living.

  10. From the POV of evolutionary biology, it simply makes no sense that a substance as abundant in the environment as NsCl, which is *also* an essential nutrient, would also have such a low threshold of daily intake (a few mg/kg of body weight) for adverse effects to occur. The body has several means of maintaining optimum salt levels (sweat, tears, mucus, etc.).
    I have not been able to determine the original reports that demonized salt, but I would bet a week’s salary that they were not double-blind controlled studies and they had serious methodological problems. Nonetheless they made for easy copy in the popular press, and most people are willing to blindly accept the first pronouncements they hear on any specific topic (in this case the health effects of dietary salt) as Gospel Truth.
    Some of us are old enough to remember the backstory behind Ghandi’s famous Salt March to protest the British Salt Tax – because even in 1930 salt was known to be as important to nutrition as water and grain. Hyponatremia kills. A 7% drop in salt levels causes illness, a 10% drop causes seizures and/or coma. Better too much than too little.

  11. Have you seen the numbers for daily consumption of Soy Sauce in that country? Have you checked the amount of sodium in soy sauce?

    I cannot believe that Japan really has a near-hyponatric amount of salt intake. That flies straight in the face of known facts

  12. “TOKYO — Japan has long boasted of having many of the world’s oldest people — testament, many here say, to a society with a superior diet and a commitment to its elderly that is unrivaled in the West.
    That was before the police found the body of a man thought to be one of Japan’s oldest, at 111 years, mummified in his bed, dead for more than three decades. His daughter, now 81, hid his death to continue collecting his monthly pension payments, the police said.

    Alarmed, local governments began sending teams to check on other elderly residents. What they found so far has been anything but encouraging. ”

    http://www.nytimes.com/2010/08/15/world/asia/15japan.html

  13. The actual data says that reducing the amount of salt one eats will substantially reduce lifespan.

    I am a man of 75, and I consume salt as I feel I need it . . .and as I do physical work, I consume a good amount of it and I would compare my health to anyone 10 years. less than my age. Just a lot of horse-pucky, by idiots.
    The sweat glands excrete salt as needed, and in fact, salt stores up water for use by the body’s natural cooling system.

    If you don’t do physical labor, which I love to do, things might be different.

  14. Salt is a natural parasite control. All animals need salt, thus, the importance of salt lick on every continent. Every culture has used it in their diets and our body knows how to regulate it. Maybe we should talk more about the difference of processed (useless) salt and natural salts. I have always strongly believed, and have found much confirmation in health statistics, that salt is not harmful but helpful. S.M. Yale Masters of Public Health

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