It has been known for some time that severe caloric restriction can retard the aging process and prolong the life of mice. But would the same be true for humans? Frankly, I’ve been skeptical.
But now new research shows that caloric restriction works in a primate species, making it all the more likely that it just might work in humans. In a new study published this week, researchers report that macaque monkeys that have been on a calorie-restricted diet (by 30%) for the past 20 years are living longer and are healthier than their age-matched control counterparts. The study is still ongoing, but after excluding animals that died of non-age-related causes (accidents for example), 50% of the animals on a normal diet are dead of age-related causes, compared to only 20% in the restricted-diet group. The calorie-restricted animals also have fewer age-associated diseases such as diabetes, cancer, and cardiovascular disease.
It has often been said that over millions of years of food shortages, evolution has endowed us with a natural impulse to seek out foods high in calories in order to survive. If this is true, it may be extremely difficult to get humans to voluntarily restrict their caloric intake even if they saw the value in it; they’d be fighting a natural, and very strong, evolutionary survival mechanism. Do you agree, or do you think it is more cultural – for example, that heavy advertising has convinced us that foods high in calories are desirable?
Saturday, July 11, 2009
Wednesday, July 8, 2009
Wildfires, Evolution, and Ecosystems
Fires set by the forces of nature have existed on the Earth since the dawn of time, and as a result some plants have evolved to survive fires rather well. A few plants even require an occasional fire in order to release their seeds. But here’s an interesting notion; did certain plants evolve to encourage the spread of wildfires once they’ve started? After all, if the plant could survive the fire it might be a good way to kill off the competition. For those of you interested in evolutionary processes, see the recent well-referenced opinion article in the New York Times.
Sunday, July 5, 2009
Swine Flu Takes Hold in Argentina
Swine flu just won’t go away. A recent a sharp uptick in the number of deaths from swine flu in Argentina has moved that country into third place for the most swine flu deaths, after Mexico and the United states. And the timing couldn’t be worse; it’s winter in South America, the season when influenza viruses typically spread the easiest. Of special concern is that the death rate in Argentina (1.6%) is more than three times the world average.
We need to keep an eye on this pesky bug. Who knows what it could do in North America NEXT flu season? For the latest information on swine flu (also now called Pandemic H1N1), see the World Health Organization website.
We need to keep an eye on this pesky bug. Who knows what it could do in North America NEXT flu season? For the latest information on swine flu (also now called Pandemic H1N1), see the World Health Organization website.
Wednesday, July 1, 2009
Is Being "Overweight" Bad For Your Health?
There is no doubt that gross obesity is a worsening health problem. But what about being just “overweight”, defined by the U.S. government and the World Health Organization as a Body Mass Index (BMI) of between 25 and 30 - is it also bad for your health?
It depends on the question - bad for what? As a group, people who are overweight apparently do have a slightly increased risk for certain diseases, such as heart disease and diabetes. But for other parameters, such as risk of death, the evidence is not that clear-cut (See “Is ‘Overweight’ Overstated?”, pp. 346-347, Human Biology 5th ed.). To add fuel to the controversy, a recent study of over 11,000 Canadian adults reveals that as a group, people who are defined as overweight have a slightly lower risk of death than the normal-weight group, though not by much.
Taking this new mortality data into account and reviewing the graph on p. 346 of Human Biology, one wonders whether the range of “normal” weight shouldn’t be shifted about 3 BMI to the right. A word of caution, however; the shape of the weight-vs.-risk curve is likely to be different for every disease, age group, etc. It’s probably going to be impossible to come up with a functional definition of overweight, no matter how much we’d like to.
It depends on the question - bad for what? As a group, people who are overweight apparently do have a slightly increased risk for certain diseases, such as heart disease and diabetes. But for other parameters, such as risk of death, the evidence is not that clear-cut (See “Is ‘Overweight’ Overstated?”, pp. 346-347, Human Biology 5th ed.). To add fuel to the controversy, a recent study of over 11,000 Canadian adults reveals that as a group, people who are defined as overweight have a slightly lower risk of death than the normal-weight group, though not by much.
Taking this new mortality data into account and reviewing the graph on p. 346 of Human Biology, one wonders whether the range of “normal” weight shouldn’t be shifted about 3 BMI to the right. A word of caution, however; the shape of the weight-vs.-risk curve is likely to be different for every disease, age group, etc. It’s probably going to be impossible to come up with a functional definition of overweight, no matter how much we’d like to.
Sunday, June 28, 2009
The Pandemic of 2009
The World Health Organization has officially declared a pandemic as a result of the rapid worldwide spread of Influenza A (H1N1), formerly known as swine flu. But that does NOT mean that a lot of people will die. By definition, a pandemic is simply a widespread outbreak of a new human flu virus that spreads rapidly from human to human, causing human illness.
Some flu pandemics cause only mild symptoms and few deaths – others can be quite deadly. The best-known pandemics of the last century were the deadly Spanish flu of 1918 (20-40 million deaths), and the milder Asian flu of 1957 (1-4 million deaths) and Hong Kong flu of 1968 (also 1-4 million deaths). In contrast, the milder seasonal flu that many of us get nearly every year kills “only” about a quarter of a million people each year.
Pandemics are of concern to public health officials (and the public!) because the virus spreads so quickly and because the consequences of the spread cannot always be predicted in advance. Fortunately, it now appears that this pandemic will be no more deadly than the typical seasonal flu that many of us get nearly every year. Most people who become infected with Influenza A (H1N1) are recovering without the need for medical care. But it could have been otherwise, and that’s why health officials were so concerned at first and why they are still watching it closely.
The other flu we worry about is avian flu (see Human Biology 5th ed., pp. 540-541). Avian flu is VERY deadly in the few cases in which it has been caught from birds, but human-to-human transmission is still exceedingly rare.
Some flu pandemics cause only mild symptoms and few deaths – others can be quite deadly. The best-known pandemics of the last century were the deadly Spanish flu of 1918 (20-40 million deaths), and the milder Asian flu of 1957 (1-4 million deaths) and Hong Kong flu of 1968 (also 1-4 million deaths). In contrast, the milder seasonal flu that many of us get nearly every year kills “only” about a quarter of a million people each year.
Pandemics are of concern to public health officials (and the public!) because the virus spreads so quickly and because the consequences of the spread cannot always be predicted in advance. Fortunately, it now appears that this pandemic will be no more deadly than the typical seasonal flu that many of us get nearly every year. Most people who become infected with Influenza A (H1N1) are recovering without the need for medical care. But it could have been otherwise, and that’s why health officials were so concerned at first and why they are still watching it closely.
The other flu we worry about is avian flu (see Human Biology 5th ed., pp. 540-541). Avian flu is VERY deadly in the few cases in which it has been caught from birds, but human-to-human transmission is still exceedingly rare.
Wednesday, June 24, 2009
Freeze Your Eggs
Okay, so you’re a woman in her thirties who wants to have children some day but has not yet met “Mr. Right”. What to do? Well, some women have made the decision to freeze some of their eggs before their reproductive clock stops ticking, just in case. The basic techniques are readily available at any fertility clinic; stimulate egg maturation hormonally, harvest some eggs, and then (instead of fertilizing and implanting them) just freeze them.
Worldwide, only about a thousand children have been born from previously frozen eggs. In contrast, over 50,000 babies are born each year in the U.S as a consequence of in vitro fertilization and implantation (Human Biology 5th ed., p. 394). Obviously, the idea of older single women freezing their eggs has not yet caught on. But it just might!
See “Why I Froze My Eggs”, by Rachel Lehmann-Haupt. Newsweek May 11, 2009, pp. 50-52.
Worldwide, only about a thousand children have been born from previously frozen eggs. In contrast, over 50,000 babies are born each year in the U.S as a consequence of in vitro fertilization and implantation (Human Biology 5th ed., p. 394). Obviously, the idea of older single women freezing their eggs has not yet caught on. But it just might!
See “Why I Froze My Eggs”, by Rachel Lehmann-Haupt. Newsweek May 11, 2009, pp. 50-52.
Tuesday, June 23, 2009
Steve Jobs' New Liver
It’s not official, but there are reports in the news media that Steve Jobs, CEO of Apple computers, received a liver transplant recently at an undisclosed location in Tennessee (The New York Times, June 23; “A Transplant That is Raising Many Questions”).
Normally, patients who need an organ transplant place themselves on the transplant list of one of eleven regional Organ Procurement Organizations (OPOs) in the U.S. Waiting times can vary. When an organ becomes available the regional OPO offers it to a patient already on its list, with the highest priority given to the sickest patients and those who have been on the list the longest time.
Most patients sign up for the transplant list at only one OPO, because insurance companies will only pay for an organ transplant performed in a person’s “home” OPO. Nevertheless, patients who are willing to pay for the transplant themselves (and with access to a plane so they can get to the hospital within six hours) can increase their odds for a transplant by placing themselves on the transplant lists of several different OPOs simultaneously. No one has said whether or not Mr. Jobs was on more than one list at the time of his transplant, or how long he waited for his new liver.
For a discussion of whether the current organ allocation system is fair, see “How Should We Allocate Scarce Organs?” in Human Biology 5th ed., pp. 368-369.
Normally, patients who need an organ transplant place themselves on the transplant list of one of eleven regional Organ Procurement Organizations (OPOs) in the U.S. Waiting times can vary. When an organ becomes available the regional OPO offers it to a patient already on its list, with the highest priority given to the sickest patients and those who have been on the list the longest time.
Most patients sign up for the transplant list at only one OPO, because insurance companies will only pay for an organ transplant performed in a person’s “home” OPO. Nevertheless, patients who are willing to pay for the transplant themselves (and with access to a plane so they can get to the hospital within six hours) can increase their odds for a transplant by placing themselves on the transplant lists of several different OPOs simultaneously. No one has said whether or not Mr. Jobs was on more than one list at the time of his transplant, or how long he waited for his new liver.
For a discussion of whether the current organ allocation system is fair, see “How Should We Allocate Scarce Organs?” in Human Biology 5th ed., pp. 368-369.
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