The failure of supply-side social policy

The US is in the midst of two social crises. The first is an opioid epidemic that is decimating parts of rural and now urban America and the second is a surge in the number of migrants crossing the southern US border primarily from Central America. In any system that involves flow, either physical (e.g. electricity) or social (e.g. money), the amount of flow (i.e. flux) is dependent on the amount of supply (e.g. power station/federal reserve) and the amount of demand (e.g. air conditioner/disposable income). So if you want to reduce opioid consumption or illegal immigration you can either shut down the supply or reduce the demand.

During the twentieth century there was a debate over the causes of booms and busts in the economy. I am greatly simplifying the debate but on one side were the demand-side Keynesians who believed that the business cycle is mostly a result of fluctuating demand. If people suddenly decide to stop spending then businesses would lose customers, which would lead them to lay off workers, who would then have less money to spend in other businesses and thus reduce demand further and so forth, leading to a recession. On the other side there were the supply-siders who believed that the problem of economic downturns was inadequate supply, which would be solved by cutting taxes and reducing business regulations. The Great Recession of 2008 provided a partial test of both theories as the US applied a demand-side fix in the form of a stimulus while Europe went for “expansionary austerity” and cut government spending, which slashes demand. The US has now experienced over a decade of steady growth while Europe went into a double dip recession before climbing out after the policy changed. That is not to say that demand-side policies always work. The 1970’s were plagued by stagflation with high unemployment and high inflation for which the Keynesians had no fix. Former Fed Chairman Paul Volcker famously raised interest rates in 1979 to reduce the money supply. It triggered a short recession, which was followed by nearly three decades of low inflation economic growth.

In terms of social policy, the US has really only tried supply-side solutions. The drug war put a lot of petty dealers and drug users in jail but did little to halt the use of drugs. It seems to me that if we really want to solve or at least alleviate the opioid and drug crisis, we need to slash demand. Opioids are pain killers and are physically addictive. Addicted users who try to stop will experience withdrawal, which is extremely painful. If you do succeed you will no longer be physically addicted. However, you can always relapse if you use again. The current US opioid epidemic started with a change in the philosophy of pain management by the medical establishment with a concurrent development of new supposedly less addictive opioid pills. So doctors, encouraged by the pharmaceutical industry, began prescribing opioids for all manners of ailments. Most doctors were well intentioned but a handful participated in outright criminal activity and became de facto drug dealers. In any case, this led to the initial phase of the opioid epidemic. When awareness of over prescription started to enter public consciousness there was pressure to reduce the supply. Addicts then turned to illicit opioids like heroin, which started phase 2 of the epidemic. However, as this supply was targeted by drug enforcement, a new highly potent and cheaper synthetic opioid, fentanyl, emerged. This was something that was easy to produce in makeshift labs anywhere and also provided a safer business model for drug dealers. However, fentanyl is so potent that this is has led to a surge in overdose deaths. Instead of targeting supply we need to reduce demand. First we need to understand why people take them in the first place. While some drugs are taken for the experience or entertainment, opioids are mostly being used to alleviate pain and suffering. It is probably no coincidence that the places most ravaged by opioids are also those that are struggling most economically. If we want to get a handle on the opioid crisis we need to improve these areas economically. People probably also take drugs for some form of escape. This is where I think video games and virtual reality may be helpful. We can debate the merits of playing Fortnite 16 hours a day but it is surely better than taking cocaine. I think we should take using video games as a treatment for drug addiction seriously. We could and should also develop games for this purpose.

Extra border security has not stemmed illegal immigration. What does slow immigration is a downturn in the US economy, which quenches demand for low-skilled labour, or an improvement in the conditions of the originating countries, which reduces the desire to leave in the first place. The current US migrant crisis is mostly due to the abhorrent and dangerous conditions in Guatemala and Honduras. For Europe, it is problems in Africa and the Middle East. In both cases, putting up more barriers or treating the migrants inhospitably is not really doing much. It just makes the journey more perilous, which is bad for the migrant and a moral and public relations nightmare for host countries. Perhaps, we could try to stem demand by at least making it safer in the originating countries. The US could provide more aid to Latin America including stationing American troops if necessary to curb gang activity and restore civil order. This would at least help diminish those seeking asylum. Reducing economic migration is much harder since we really don’t know how to do economic development very well but more investment in source countries could help. While globalization and free trade may have hurt the US worker and contributed to the opioid epidemic by decimating manufacturing in the US, it has also brought a lot of people out of abject poverty. The growth miracles in China and the rest of Asia would not be possible without international trade and investment. Thus the two crises are not independent. More free trade could help to reduce illegal immigration but it could also lead to worsening economic conditions for some regions spurring more opioid use. There are no magic bullets but we at least need to change the strategy.

The low carb war continues

Last month, a paper in the British Journal of Medicine on the effect of low carb diets on energy expenditure, with senior author David Ludwig, made a big splash in the popular press and also instigated a mini-Twitter war. The study, which cost somewhere in the neighborhood of 12 million dollars, addressed the general question of whether a person will burn more energy on a low carbohydrate diet compared to an average or high carb diet. In particular, the study looked at the time period after weight loss where people are susceptible to regaining weight. The argument is that it will be easier to maintain weight loss on a low carb diet since you will be burning more energy. Recent intensive studies by my colleague Kevin Hall and others have found that low carb diets had little effect if any on energy expenditure, so this paper was somewhat of a surprise and gave hope to low carb aficionados. However, Kevin found some possible flaws, which he points out in an official response to BMJ and a BioRxiv paper, which then prompted a none-too-pleased response from Ludwig, which you can follow on Twitter. The bottom line is that the low carb effect size depends on the baseline point you compare too. In the original study plan, the baseline point was chosen to be energy expenditure prior to the weight loss phase of the study. In the publication, the baseline point was changed to after the weight loss but before the weight loss maintenance phase. If the original baseline was chosen, the low carb effect is no longer significant. The authors claim that they were blinded to the data and changed the baseline for technical reasons so this did not represent a case of p-hacking where one tries multiple combinations until something significant turns up. It seems pretty clear to me that low carbs do not have much of a metabolic effect but that is not to say that low carb diets are not effective. The elephant in the room is still appetite. It is possible that you are simply less hungry on a low carb diet and thus you eat less. Also, when you eliminate a whole category of food, there is just less food to eat. That could be the biggest effect of all.

Science and the vampire/zombie apocalypse

It seems like every time I turn on the TV, which only occurs when I’m in the exercise room, there is a show that involves either zombies or vampires. From my small sampling, it seems that the more recent incarnations try to invoke scientific explanations for these conditions that involve a viral or parasitic etiology. Popular entertainment reflects societal anxieties; disease and pandemics is to the twenty first century what nuclear war was to the late twentieth. Unfortunately, the addition of science to the zombie or vampire mythology makes for a much less compelling story.

A necessary requirement of good fiction is that it be self-consistent. The rules that govern the world the characters inhabit need to apply uniformly. Bram Stoker’s Dracula was a great story because there were simple rules that governed vampires – they die from exposure to sunlight, stakes to the heart, and silver bullets. They are repelled by garlic and Christian symbols. Most importantly, their thirst for blood was a lifestyle choice, like consuming fine wine, rather than a nutritional requirement. Vampires lived in a world of magic and so their world did not need to obey the laws of physics.

Once you try to make vampirism or zombism a disease and scientifically plausible in our world, you run into a host of troubles. Vampires and zombies need to obey the laws of thermodynamics, which means they need energy to function. This implies that the easiest way to kill one of these creatures is to starve them to death. Given how energetically active vampires are and how little caloric content blood has by volume, since it is mostly water, vampires would need to drink a lot of blood to sustain themselves. All you need to do is to quarantine all humans into secure locations for a few days and all vampires should either starve to death or fall into a dormant state. Vampirism is self-limiting because there would not be enough human hosts to sustain a large population. This is why only small animals can subsist entirely on blood (e.g. vampire bats weight about 40 grams and can drink half their weight in blood). Once, you make vampires biological, it makes no sense why they can only drink blood. What exactly is in blood that they can’t get from eating flesh? Even if they don’t have a digestive system that can handle solid food, they could always put meat into a Vitamix and make a smoothie. Zombies eat all parts of humans so they would need to feed less often than vampires and thus be harder to starve. However, zombies are usually non-intelligent and thus easier to avoid and sequester. It seems like any zombie epidemic could be controlled at very early stages. Additionally, why is it that zombies don’t eat each other? Why do they only like to eat humans?  Why aren’t they hanging around farms and eating livestock and poultry?

Vampires and sometimes zombies also have super-strength without having to bulk up. This means that their muscles are much more efficient. How is this possible? Muscles are pretty similar at the cellular level. Chimpanzees are stronger than humans by weight because they have more fast twitch than slow twitch muscles. There is thus always a trade-off between strength and endurance. In a physically plausible world, humans should always find an edge in combating zombies or vampires. The only way to make a vampire or zombie story viable is to endow them with nonphysical properties. My guess is that we have hit peak vampire/zombie; the next wave of horror shows will feature a more plausible threat – evil AI.

Arsenic and Selenium

You should listen to this podcast from Quirks and Quarks about how University of Calgary scientist Judit Smits is trying to use selenium rich lentils from Saskatchewan, Canada to treat arsenic poisoning in Bangladesh. Well water in parts of rural Bangladesh have high levels of natural arsenic and this is a major health problem. Professor Smits, who is actually in the department of veterinary medicine, has done work using arsenic to treat selenium poisoning in animals. It turns out that arsenic and selenium, both of which can be toxic in high doses, effectively neutralize each other. They each seem to increase excretion of the other into the bile. So she hypothesized that selenium might counter arsenic poisoning but the interaction is nontrivial so it is not a certainty that it would work. Dr. Smits organized a study to transport ten tons of lentils from Canada to Bangladesh this past summer to test the hypothesis and you can hear about the trials and tribulations of getting the study done. The results are not yet in but I think this is a perfect example of how cleverness combined with determination can make a real difference. This study is funded entirely from Canadian sources but it sounds like something the Gates and Clinton foundations could be interested in.

2016-9-26. Corrected a typo, changed Saskatchewan to Bangladesh

New Papers

Li, Y., Chow, C. C., Courville, A. B., Sumner, A. E. & Periwal, V. Modeling glucose and free fatty acid kinetics in glucose and meal tolerance test. Theoretical Biology and Medical Modelling 1–20 (2016). doi:10.1186/s12976-016-0036-3

Katan, M. B. et al. Impact of Masked Replacement of Sugar-Sweetened with Sugar-Free Beverages on Body Weight Increases with Initial BMI: Secondary Analysis of Data from an 18 Month Double–Blind Trial in Children. PLoS ONE 11, e0159771 (2016).

These two papers took painfully long times to be published, which was completely perplexing and frustrating given that they both seemed rather straightforward and noncontroversial. The first is a generalization of our previously developed minimal model of the fatty acid and glucose as a function of insulin to a response to an ingested meal, where the rate of appearance of fat and glucose in the blood was modeled by an empirically determined time dependent function. The second was a reanalysis of the effects of substituting sugar-sweetened beverages with non-sugar ones. We applied our childhood growth model to predict what the children ate to account for their growth. Interestingly, what we found is that the model predicted that children with higher BMI are less able to compensate for a reduction of calories than children with lower BMI. This could imply that children with higher BMI have a less sensitive caloric sensing system and thus could be prone to overeating but on the flip side, can also be “tricked” into eating less.

The hazards of being obese

One of my favourite contrarian positions is that being overweight is not so bad. I don’t truly believe this but I like to use it to point out that although most everyone holds that being obese is not healthy, there is actually very little evidence to support this assertion. However, this recent rather impressive paper in the Lancet finally shows that being overweight or obese is really bad. The paper is a meta-analysis of hundreds of studies with a combined study size of over 10 million! The take home message is that the hazard ratio for dying is significantly greater than one but not too bad for overweight and mildly obese people (BMI < 30) but increases sharply after that. It is over two and rapidly increasing for BMI greater than 35. The hazard ratio gives the relative probability of mortality (or any outcome) per unit time (i.e. mortality rate) in a survival analysis, which in this case was a Cox proportional hazards model. The hazard ratio as a function of BMI is well fit by a quadratic function with a minimum around 22 kg/m^2. The chances of dying increase if you are thinner or fatter than this. The study was careful to not include smokers and anyone with a chronic disease and also did not start the analysis until 5 years after the measurement to avoid capturing people who are thin because they are already ill. They also broke the model down into various regions. Surprisingly, the chances of dying when you are obese is worse if you are in Europe or North America compared to Asia. Particularly surprising is the fact that the hazard ratio rises slowest in South Asia for increasing BMI. South Asians have been found to be more susceptible to insulin resistance and Type II diabetes with increased body fat but it seems that they die from it at lower rates. However, the error bars were also very large because the sample size was smaller so this may not hold up with more data. In any case, I can no longer use the lack of health consequences of obesity to rib my colleagues so I’ll have to find a new axe to grind.