SMOKING AND BONE HEALTH
Claudia Wallis nicely summarizes the issues surrounding bone health and calcium metabolism in “A Diet for Better Bones” [The Science of Health]. She mentions the likely harmful effects of excessive alcohol and coffee intake in the article. To this list I would add cigarettes – in any quantity and at almost any time in life.
A routine part of my practice as a neurosurgeon was the evaluation of patients with osteoporosis and the performance of spinal surgery, including fusion. I soon saw that almost all of my osteoporosis patients had smoked, although many of them would initially deny a history of cigarette consumption until specifically asked if they had smoked as a teenager. Even a brief history of cigarette use during the most important period for bone growth and bone formation – adolescence and early adulthood – was correlated with a significant increase in the risk of osteoporotic fractures in late adulthood.
Similarly, the rate of successful spinal surgeries – especially discectomy and fusion – was significantly lower in active smokers than in non-smokers, so I would delay non-urgent surgery until the patient was at least four – and ideally six – weeks free from cigarette smoke. Over the ensuing decades, numerous studies have confirmed my anecdotal observations.
As Wallis points out, vitamin D supplementation probably has little benefit for most people who want to prevent osteoporosis. But quitting smoking – or better yet, never smoking – is certainly a great benefit.
DANIEL SPITZER Piermont, New York
METABOLIC WAY LESS GIVEN
I enjoyed “The Human Engine,” Herman Pontzer’s article about rigorous experiments determining age- and lean-mass-adjusted trends in human metabolism. The “Measuring Metabolism” box shows these data in two graphs, and the large degree of dispersion across their respective regression curves leads to even more interesting questions.
Each scatter point represents a unique human who is most likely not ‘average’. Could the spread explain why certain individuals have more difficulty losing weight or why a particular diet doesn’t work for everyone? How much of it is linked to genetics versus environment? Is it ethical to make health recommendations based on a sample mean when those who fall outside the regression curve may be harmed? In addition, new cancer therapies tailor treatments to an individual’s genetics. Are such considerations applied to studies of nutrition and metabolism?
MARK G. KUZYK Regent Professor of Physics, Washington State University
I was surprised that Pontzer’s article on human metabolism did not mention the gut microbiota. Each of us lives with a complex gut ecosystem that contains more organisms than there are cells in our body. Recent discoveries have made it clear that the gut microbiota influences many aspects of our physiology, from immune function to mental health, and changes in it caused by widespread use of antibiotics and highly processed foods most likely play a critical role in explaining the epidemic of obesity. The gut microbiota is also the filter through which all our food is processed, making it inseparable from human metabolism. It’s not just “we” who use the calories we consume, making the “calories in, calories out” phrase quoted by Pontzer incomplete.
IRA S. NASH Scarsdale, New York
PONTZER’S ANSWERS: Understanding the significant variability we see between individuals in their daily energy expenditure is the next step in metabolic research. We now have a good idea of how body size, fat percentage, lifestyle and age affect the calories we burn each day, but as readers Kuzyk and Nash point out, there’s a lot of unexplained variation. The extent to which these differences reflect genetics or environment is not currently well understood. Our microbiome may be a crucial piece of the puzzle. However, evidence on that front is currently sparse. Time and more study will tell.
We don’t usually find that a “fast” or “slow” metabolism (burning more or less energy than we would expect given a person’s height and age) predicts weight gain or obesity. I suspect the metabolic variation we see tells us something about overall body function and health, but those possible connections have yet to be tested.
LOCALITY TRUNK
“The Universe Is Not Locally Real,” by Daniel Garisto, reports on how the Bell test has been used to rule out the existence of hidden variables, unseen factors that could explain quantum mechanical phenomena while preserving local realism. But I still wonder why answering the question of hidden variables has not been declared unsolvable by this technique.
Garisto says “any previous physical connection between components, however far in the past [emphasis mine], has the ability to distort the validity of the results of a Bell test. He then describes a “cosmic Bell test” in which researchers used stars that were “sufficiently spaced” that light from one wouldn’t reach the other for centuries. But assuming the big bang and cosmic inflation are true, that doesn’t mean there’s an inevitable loophole. each Bubble test because in a distant past everything was physically connected?
GARY RECTOR Cave Creek, Ariz.
ANSWER GARISTO: There have been more cosmic Bell tests since the one I described in my article, including one that used light from quasars billions of light years apart. Rector is right that even these tests only go back to a point. As he suggests, this does imply that the Big Bang remains an inevitable loophole. It is worth considering what such a mesh-sized theory would assume: that hidden variables were encoded at the beginning of time and space, setting everything deterministically in motion until the end of spacetime..
Superdeterminism, as this idea is called, could save local realism from quantum mechanics, but it robs the universe of chance in favor of a conspiratorial approach to experimentation. Everything we can measure suggests that quantum mechanics is correct, that local realism is incorrect. It’s worth being aware of superdeterminism as a possibility. But believing in things because they’re impossible to rule out is a bad way to approach science – or for that matter, whatever.
AT INTELLIGENT
Bumblebees apparently “play”, according to the study reported in “Bee-Ball” by Grace van Deelen [Advances]. This raises a question: Are bees individually intelligent? What about ants? Within a colony, these insects continuously exchange information in the form of pheromones and other chemicals. A bee or ant colony shows more intelligence than would be expected by adding up the intelligence of the individuals.
FROM SNYDER La Crescenta, California.
ERRATUM
In ‘Primary Soup’ by Clara Moskowitz [March 2023], the “Quark Soup” box should have said that Brookhaven National Laboratory’s sPHENIX and STAR detectors each have a powerful magnet at their core, not a powerful superconducting magnet. Only the magnet of sPHENIX is superconducting.
