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.