Sunday, May 21, 2017

My Meta-Analysis on Saturated Fat, Polyunsaturated Fat and Coronary Heart Disease

I just published a paper in Nutrition Journal titled ‘The effect of replacing saturated fat with mostly n-6 polyunsaturated fat on coronary heart disease: a meta-analysis of randomised controlled trials’.  Nutrition Journal is an open access journal and the paper shouldn’t be too technical so I encourage you to read it but I’ll also summarise it below:

I begin in the introduction by discussing the effect that saturated fat (SFA), monounsaturated fat (MUFA) and polyunsaturated fat (PUFA) have on cholesterol levels and how this formed the basis of the diet heart hypothesis, which is that replacing SFA with PUFA would be expected to reduce the risk of coronary heart disease (since MUFA didn’t affect total cholesterol it was largely ignored at this time).  Several clinical trials were conducted, mostly in the 1960s and 1970s, to test the diet heart hypothesis.

More recently, several meta-analyses have pulled the results of the diet heart trials and most came to the conclusion that replacing SFA with PUFA would reduce the risk of coronary heart disease.  However, there is a lot of controversy surrounding the diet heart hypothesis, and it is an important topic since the advice to reduce saturated fat is very influential in conventional dietary advice.  So I thought it would be useful to do my own research.

I researched the clinical trials included in the previous meta-analyses and found that the dietary advice or the foods given to the participants in the trials would be expected to result in the high PUFA group having a lower intake of trans fats (to varying degrees) compared to the high SFA group.  I also found other confounding variables such as two trials where the high PUFA group received a multifactorial dietary intervention, one trial where the high SFA group was given a vitamin E deficient diet, and another trial where the high SFA group received more antipsychotic medication that was found to be cardiotoxic.  These issues were rarely discussed or taken into account by the previous meta-analyses.

Therefore I conducted my own meta-analysis by including the trials in previous meta-analyses and then categorising them as ‘adequately controlled’ or ‘inadequately controlled’ based on the degree of confounding variables in each trial.  I considered the adequately controlled trials to be those that most accurately tested the effect of replacing SFA with PUFA, while the inadequately controlled trials to have too much of a difference between the groups to be a valid test of replacing SFA with PUFA.

The main findings are:

  • The results from the adequately controlled trials suggest that replacing SFA with PUFA is unlikely to increase or decrease the risk of coronary heart disease or all-cause mortality
  • This is the case regardless of whether the Sydney Diet Heart Study is included or excluded
  • The suggestion of benefits reported in earlier meta-analyses is due to the inclusion of inadequately controlled trials

In the discussion, I mention that there are issues in drawing conclusions from risk factors (such as cholesterol) and observational studies, and that the issues inherent in these types of studies are likely due to them having discordant results with this meta-analysis.  I also discuss that similarly there are issues in drawing conclusions from nutrients (like SFA) to foods, as foods are made up of many nutrients and other substances that may affect outcomes you’re interested in, such as the risk of coronary heart disease.

So what are the implications of this paper?

  • Saturated fat is unlikely to increase the risk of coronary heart disease
  • Replacing saturated fat with polyunsaturated fat (such as butter with margarine or vegetable oil) is unlikely to increase or decrease the risk of coronary heart disease
  • Results from observational studies and enthusiasm from discovering a new risk factor or discovering a target for an existing risk factor should be tempered with a degree of caution and scepticism until they are tested
  • Dietary guidelines and public health policy should focus on other things that are more likely to be effective at preventing coronary heart disease

If you like talks, the content of the meta-analysis is similar to a talk I have in 2015 at the Ancestral Health Society of New Zealand’s (AHSNZ) international symposium in Queenstown.  You can view the talk here and the other talks here.  There were a lot of great speakers there talking about a diverse range of topics such as nutrition, exercise, behaviour change, sustainability, active transport and mental health.  So it shouldn't be too hard to find something that interests you.

AHSNZ is holding another international symposium in October at Queenstown which you can find out more about the symposium here.  I’ll be speaking again, this time about insulin resistance, which is the focus of my PhD (so this paper is very unlikely to count towards my PhD and has mostly been a weekend project) and will be a focus on the blog over the next several months.

Tuesday, April 18, 2017

Public Health Strategies Part 4C: Bans

Bans on Unhealthy Foods

In earlier blog posts I discussed taxes and subsidies as public health strategies, mainly related to the current more popular calls to tax sugar sweetened beverages (SSBs) and subsidise fruit and vegetables.  In researching those posts I came to the conclusion that both strategies have some potential to influence consumer choices and therefore population health when implemented broadly (e.g. tax ‘extra’ foods instead of just SSBs) and strongly (e.g. 50-100% tax rather than 10-20% tax).  However, the narrow range of targets combined with the weak tax/subsidy is unlikely to substantially improve population health.  In addition, assuming consumption wouldn’t be affected, a 100% tax on SSBs would only increase the average household budget of low income earners by 1% [1], which is something that even most low income earners in an affluent country like Australia could shrug off (not to mention those on higher incomes).  This raises the question of whether more aggressive market controls such as bans on the marketing, sales and/or possession (the latter has actually been proposed [2]) of foods like SSBs are required to truly reduce the prevalence of obesity and metabolic disease

Bans can apply to the ability of producers to market a product or sell a product and the ability of consumers to possess a product.  Bans are not necessarily universal, it may only apply to certain times (such as advertising on TV when children are most likely to be watching and bands on selling alcohol after a certain hour of the night), places (such as bans on selling SSBs in schools) and very specific products (such as the proposed New York City ban on big gulps).  Non-universal bans on selling products are intended to lower consumption by reducing convenience, while universal bans on selling products or being in possession of them (such as illicit drugs) are intended to eliminate consumption

Like any other policy, putting a ban on unhealthy foods is likely to have unintended consequences and these will depend on what kind of ban is implemented.  A universal ban on unhealthy foods with little to no redeeming qualities like SSBs is unlikely to happen, and it could result in unintended consequences similar to the war on drugs and the American prohibition on alcohol, in addition to losing an opportunity for tax revenue.  Alternatively, a non-universal ban that reduces convenience can be easily circumvented by a determined consumer who can plan in advance to take extra drinks with them to consume late at night, to take SSBs with them to a school/university campus and to simply order to small size drinks instead of the big gulp.  Of course, not everyone will be the determined consumer and the point is that small changes in convenience can have large impacts in behaviour.

The rationale of banning something like SSBs (as opposed to TFA, asbestos, etc) is to save people from themselves, but is it the government’s job to do this?  Some people would object to the nanny-statism and demand the freedom to eat/drink what they choose, although if you’re asking the government to pay for your healthcare one could argue that you are implicitly trading some liberty for security.

Bans to reduce the consumption of unhealthy foods by children are another story.  Unlike adults, we do not hold children completely legally responsible for their actions (which scales with age of course), and so there is an argument to be made to protect children from themselves, or from their parents*.  With health issues like obesity and tooth decay being an issue among some young children, perhaps banning the sale of SSBs for children or to children (SSBs would be an 18+ substance like cigarettes and alcohol) would be help to reduce these issues.  Unfortunately, my look at the research at the moment suggests that just banning sodas at high schools results in an increased consumption of other SSBs [3], while banning the sale of all SSBs at middle schools only seems to reduce consumption at school and doesn’t appear to reduce overall consumption [4].  Perhaps there would be more success at primary schools, but also it seems people will get their sugar fix no matter what, and so the narrower the ban, the less likely it is to be effective at all

* Bit of a rant: sorry Guardian author, if a 2 year old needs 20 teeth removed due to tooth decay, that’s not an issue with oral health prevention [5], that’s child abuse from parents who don’t sufficiently care.  This is similar to issue that sometimes comes up where children fed a vegan diet are malnourished, leading to an Italian proposal to jail parents feeding young children a vegan diet [6].  I don’t want to necessarily jail vegan parents or vilify parents who give their children SSBs, just when there is evidence of harm, because it’s about the outcome (in the absence of losing the genetic lottery), not the methods to get there.  Vilifying ‘wrong’ methods regardless of any feedback from outcomes could lead to a hideously broad application of that Italian proposal (‘oh, you’re feeding your child a low carb diet?  That’s against the dietary guidelines.  It doesn’t matter that there’s nothing wrong with your child, you’re going to jail’) and leads to dogmatically sticking with the ‘right’ method, such as the dietary guidelines, rather than updating your methods based on the feedback from outcomes in research and clinical practice (outcome based medicine > evidence based medicine).  If you think I’m being harsh, consider how you would feel if you had your teeth removed, got type 2 diabetes or suffered developmental issues before you had the chance to make your own choices or because your mother smoked and drank heavily while pregnant with you.  The right as a parent to bring your child up their own way should not trump their responsibilities to bring them up well.

** The Torba province of Vanuatu is aiming to impose strong restrictions on junk food while promoting locally grown, organic food [7].  It will be interesting to see how that goes.  They have a fairly special advantage from being isolated and a small community which might lead to it working out very well (but good luck trying to implement the same in Australia, etc)

*** Alternatively if you see obesity and lifestyle diseases as an product of market failure, you could just ban capitalism and adopt socialism or communism, which is proving to be a really effective policy at reducing obesity in Venezuela at the moment :p

Ban on Trans Fats

This leads me to the FDA ban on partially hydrogenated oils (PHOs).  In the US, the FDA has ruled that PHOs are not generally recognised as safe for use in human food.  The response to this seems to generally be positive, with a small number of doubts and concerns coming from some libertarians.  I agree that banning PHOs won’t have much effect as consumption of PHOs is quite low and they aren’t actually that bad.  In Australia in 2009, the average intake of TFA is 0.5% of total energy intake, with 60-75% coming from animal foods, so only 0.125-0.2% from PHOs, though intakes in the US seem to be quite a bit higher [8].  A recent study using the Nurses’ Health Study and the Health Professionals Follow-up Study found that each 1% increment of total energy intake from TFA was associated with just a 10% increase in total mortality (the effect would be diluted as TFAs from animal foods are pretty neutral, but still) [9]

Even though at current intakes, PHOs aren’t that bad, they are still a great example of something that should be banned.  (1) PHOs are really only convenient for the food industry and consumers don’t seek them out (copha is disgusting) (no black market).  (2) They will likely just be replaced with SFA rich fats/oils (no negative unintended consequence for consumers, just a drop in sanity from the Heart Foundation).  (3) It’s unlikely that this will translate to regulation on ‘unhealthy’ foods like red meat because PHOs don’t have any nutritionally redeeming qualities, whereas red meat certainly does (particularly when most people could use more protein, iron and zinc, etc) (so the libertarian concern of increasing government regulation is unlikely)

Some objections to a ban on PHOs is the false dichotomy that SFA is a larger issue [10], concerns that the PHOs would be replaced with SFA rich fats/oils, and concerns that that enforcing a ban would be too hard [11].  The ban would be hard to enforce 100%, but would be just as hard to enforce accurate labelling [12] which seems to be the Australian Heart Foundation’s preferred method, at least initially.  Mandatory labelling hasn’t been implemented because TFA intake in Australia is less than the WHO target of 1% [13], but I still think consumers should still have a right to know

Down the Conspiracy Theory Rabbit Hole

Given that the FDA is banning PHOs due to their adverse health effects and having no redeeming qualities, why aren’t cigarettes also going to be banned?  Cigarette smoking is associated with far worse health outcomes than PHOs and also results in second-hand smoke and more litter.  About 15% of Australians still smoke despite decades of health messaging stating the adverse effects of smoking, cigarettes been heavily taxed, advertisements for cigarettes been banned, plain packaging laws, and graphic imagery depicting some potential consequences of smoking.  Surely banning the sale and possession of cigarettes entirely would be one of the most productive policies for public health (and even poverty), and potentially a popular policy for the vast majority who don’t smoke (cleaner air and environment) and especially for ex-smokers.  One could speculate that the reason why governments haven’t banned the sale and possession of cigarettes is that the tax revenue they get from them exceeds the healthcare costs from smoking.  When looking at the costs of smoking, you see stats along the line of ‘smoking costs $X’, but these stats are probably irrelevant if not compared with the costs of not smoking.  I came across a study from the Netherlands (so could be different elsewhere) that predicted that the healthcare costs of smokers and of people with obesity are actually lower per person because they live shorter lives [14], and haven’t yet seen another study with a similar type of analysis.  Another consequence of smokers and people with obesity or diet and lifestyle diseases tending to die younger is that on average you would expect them to cost the government less money on pensions.  I wonder if these reason are a factor why many governments aren’t aggressively addressing diet and lifestyle diseases.  After all, even if the average life expectancy suddenly increased by 10 years because the government implemented rigourous public health policies, people will still want their pension at 65 and moving the pension age up to 75 might be more politically unpalatable than getting people to stop having pizza and coke for dinner.  (That might be a bit of a stretch, but I think you could make a reasonable case for pensions being a factor (alongside more major ones like debt) behind the constant drive for economic and therefore population growth and for the migrant crisis in Europe, but that’s getting quite off topic).  But this is hardly a flawless conspiracy theory given that government had a major role in the reduction in smoking, the investment governments make in medical research, and the demographics that receive most of the healthcare expenditure (i.e. not working)

Sunday, February 26, 2017

Public Health Strategies Part 4B: Subsidies

In an earlier blog post I discussed taxation as a public health strategy, particularly related to the proposed tax on sugar sweetened beverages (SSBs) in Australia.  In this post I’m going to look at the opposite of taxation: subsidies.

Putting a tax on unhealthy foods would generate extra tax revenue and so the question becomes whether the government should reduce taxes in other areas (or use it to help pay off national debt) or put that extra revenue into something, and if so, what?  Generally I have seen calls to tax unhealthy foods being coupled to calls to subsidise health foods, like fruit and vegetables (F&V).  There are a few rationales for subsidising healthy foods like fruit and vegetables:

  • Reducing the cost of fruit and vegetables would increase the consumption of them and displace unhealthy foods, which will ultimately improve population health and reduce healthcare costs
  • Coupling a fruit and vegetable subsidy to a tax on unhealthy foods (like sugar sweetened beverages) is also a means to reduce the increase to cost of living as a result of the tax, provided people purchase fruit and vegetables 

However, there may be a few problems if a health food subsidy was put in practice

  • A recently published Australian modelling study estimated that a F&V subsidy ($0.14 per 100g of fresh and preserved F&V*) would increase F&V consumption by 42g (a serving of fruit and vegetables is considered 150g and 75g respectively).  However, it was estimated that the subsidy would also increase sodium consumption by 48mg and energy consumption by 236kJ (56.6 calories), because “however, using price subsidies or discounts as an incentive to purchase more fruits and vegetables may have the effect of increasing real income available to buy food, including unhealthy products, and could therefore lead to an overall increase in dietary measures such as saturated fat, sodium, or total energy intake”**.  As a result, their model predicted that a F&V subsidy would actually have adverse health outcomes [1].  The major benefit of food taxes is that they generate revenue [2].  This revenue should go towards initiatives that are at least cost effective, but with a F&V subsidy there’s this study says there’s a 89% chance that it wouldn’t be.  Not a great policy
  • A subsidy on F&V isn’t likely to offset the increase in cost of living from a tax on unhealthy foods such as SSBs.  The estimates show that there isn’t going to be much change in behaviour.  So the people who are already low SSB consumers and high F&V consumers are the ones who will benefit.  This got me thinking if the promotion of taxes + subsidies in some people (not all) may at least partly driven by financial self-interest, but you can defend this motivation in countries with socialised healthcare.  (By the way, my diet is very rich in F&V, with no SSBs and low added sugar, so I would benefit a lot from such policies) 

In my opinion as a stingy student currently on an unflattering income, many F&V are already very cheap as there’s a lot you purchase for < $4-5 per kg or much less.  I think the reason why so many people don’t consume the recommended intake of F&V [3] is because other foods simply taste better, the structure of their habitual meals is not conducive to eating many F&V (cereal for breakfast, sandwiches for lunch, etc), and they don’t value/are empowered about their health enough to change.  When people say cost is important, they are comparing apples with apples, and not apples with muffins.  The apple wins easily on cost, but the café bought muffin wins on palatability and reward, and because most Australians have that money to spend, that’s what most people choose

A tax on unhealthy foods should be coupled with a subsidy or health initiative that is actually cost effective in itself.  An idea circulating around AHSNZ is that a tax on SSBs could be coupled to subsidy on dental health or free dental for children.  This would disproportionately benefit lower income families who are less likely to have private health insurance, see the dentist less often and more likely to have worse diets.  It is also likely to be more cost effective as healthcare spent in younger people has a greater return on investment, and dental health is one of the major health issues for children, and one (rampant tooth decay) that is potentially not reversible unlike obesity and type 2 diabetes.  Some people may be against the government using taxes and subsidies to save people from themselves, but may concede that something should be done as tooth decay is so common in children [4].  I would still like to see an estimate of the cost effectiveness of any policy, as good intentions are not a guarantee of good policies

* For example, if a fruit or vegetable was priced at $4 per kg, this subsidy would cover 35% of the costs.  This method of subsidising has a greater effect on cheaper F&Vs such that it wouldn’t be practical as very cheap F&Vs like carrots would be almost free.  In fact, at the time of writing this Coles has a special on carrots at $1.20 per kg, so they would be paying the customer to purchase them, pretty crazy! (but don’t forget that F&V are expensive and cost of healthy foods is a limiting factor in population health…)

** I think this point is debatable.  Paying less for F&V would result in consuming more F&V and this may have the opposite effect on calorie intake as F&V are more satiating than most foods per calorie.  In addition, the sodium > blood pressure data they used was based on a large effect from observational studies [5] rather than the small effect in RCTs [6], although sodium could be a surrogate marker for highly processed foods and such foods are unhealthy for other reasons besides sodium.  That being said, if the estimates on calorie and sodium intake were ignored, increasing F&V intake by 42g alone isn’t going to have that much impact on population health

*** The study also modelled the effect of taxes on SSBs, sugar, saturated fat and sodium.  The study estimated that all these taxes combined, plus the F&V subsidy, would reduce 470,000 disability adjusted life years (DALYs, or years with chronic disease) and would reduce health healthcare expenditure by $3.4 billion.  These figures seem impressive, but need to be put in context.  The study used a population of 22 million, so this works out to average reduction of 0.0214 DALYs per person (7.8 days) and average reduction in healthcare costs of $155.55 per person across their lifetime (or a few dollars per year, depending on how long you think the average person will live for (e.g. 40 years = $3.86 per person per year)).  This magnitude of response is consistent with another Australian study I discussed previously.  Modest taxes on unhealthy foods are somewhat useful at generating revenue for the diseases they increase the risk of, and will very marginally improve population health, but they won’t come close to solving the obesity/chronic disease epidemic

Sunday, February 5, 2017

Health Associations and Censorship

In an earlier post I discussed education as a public health strategy.  In that post I levelled some criticisms against health associations, particularly that they should revise some of their content and offer more detail, depth and complexity than the bare minimum to sufficiently inform and empower the early majority.

I care about health associations because they strongly influence health policy and what the public thinks on health.  And I think they should.  The purpose of health associations is for a large number of experts to come together and arrive, and arrive at a consensus and publish their collective ideas in a centralised place.  As a result, statistically speaking, the average person is more likely to find information from health associations and this information is more likely to be accurate.

However, the rise of the Internet has resulted in increasingly more information that is decentralised, crowd-sourced, and diverse than ever before, the opposite form of information from health associations.  Much of this kind of information is likely to be of a lower quality than the former, but due to the great diversity of ideas in the latter, some of those ideas may be better.  The hope is that this crowd-sourced information undergoes a process akin to evolution wherein in the free marketplace of ideas, good ideas are generally promoted and bad ideas are generally discarded, and that the average person is able to discern this

This dichotomy was described by Tom Naughton as the vision of the anointed vs the wisdom of crowds (also see his four part series on the anointed and free speech regarding the call for retraction by the ironically named Centre for Science in the Public Interest (CSPI) on Nina Teicholz's BMJ article criticising the dietary guidelines)  And health associations, much like the 'anointed' that Thomas Sowell discusses in his book, are generally pretty dismissive of ideas that challenge their consensus, particularly when coming from non-experts.  Perhaps more importantly, there are few notable instances where health associations have attempted to censor people who promote opposing ideas:

Tim Noakes is a highly regarded South African emeritus professor in exercise science and recent advocate for LCHF diets.  After providing rather general and unindivdualised advice on Twitter, the dietitian Claire Strydom, president of the Association for Dietetics in South Africa, said it was “Dangerous to wean an infant onto #LCHF diet” (evidence for that claim?) and reported Tim Noakes to the Health Professional Council of South Africa (HPCSA) for unprofessional conduct [1], which lead to the HPCSA setting up a hearing.  Tim Noakes doesn’t practice medicine, so could easily give up his license, but wanted to put both conventional dietary advice on trial and defend LCHF.  If you want to learn more about the Tim Noakes trial I would highly recommend Marika Sboros’ coverage of the trial and the following article.  Meanwhile, veganism actually has a history of failure to thrive and (rare) child deaths [2], but you don’t hear about people promoting veganism in children being taken to court

Gary Fettke is an Australian orthopedic surgeon who had been advising his diabetic patients to eat a LCHF diet until a complaint led to an investigation by the Australian Health Practitioner Regulation Agency (AHPRA), where APHRA found he was not qualified to give nutritional advice and told him to stop doing so.  The case led to senate inquiry into the AHPRA (see link) [3] [4] [5] [6] [7] [8]

Jennifer Elliot is an Australian dietician who was giving advising people with metabolic syndrome and type 2 diabetes to eat a LCHF diet.  When an anonymous complaint was lodged with the Dietitians Association of Australia (DAA) the DAA deregistered her and then her employer fired her and stated that “Nutritional advice to clients must not include a low carbohydrate diet. Jennifer will be advised on the information that she may provide to clients…” [9] [10].  If dieticians are told what advice to give, then what’s the point, is their function just a meal plan generator?

Steve Cooksey was a type 2 diabetic who decided to manage/treat his condition with a low carb Paleo diet.  He started a blog, which included dietary advice in an advice column that the North Carolina Board of Dietetics/Nutrition deemed was illegal (giving dietary advice without a licence).  Steve Cooksey and the Institute for Justice, filed a free speech lawsuit against the board [11].  Fortunately, the case was successful [12]

Even if you disagree with some or all their ideas you should still defend their right to express them both on principle and in self-interest (taking away one person’s rights sets a precedent to take away everyone’s).  When someone aims to censor speech, they are communicating that they aren’t interested in having a conversation or that they are in the pursuit of truth.

There are a perhaps two broad motivations for censorship.  The first is a concern that they won’t win in the free marketplace of ideas and so resort to censorship to protect the public from ‘dangerous’ ideas.  However, this motivation is based on a patronising belief that the public is too stupid to hear both sides of an argument and come to the right conclusion.  In addition, it may reveal some anxiety in how well they can express their ideas, how convinced they are of them and how convincing the ideas are to others.  You may be able to draw a parallel here between the political correct authoritarianism, which aims to censor ‘hate speech’ (which these days basically means anything someone finds offensive) and is associated with low verbal cognitive ability, high interpersonal disgust sensitivity, mood or anxiety disorder, and intolerance of nuance and the unknown [13].  As an unintended consequence, the act of censorship signals to others that they have something to hide or that their arguments are weak, and so the idea they are trying to censor gains more visibility and credibility than otherwise (the Streisand effect)

Secondly, the individual or organisation doing the censorship may have a conflict of interest.  Dietetic associations are particularly suspect here.  They function more like a trade union in that their primary function to benefit dieticians collectively rather than the health of the public [14].  They have an incentive to pass anti-competition laws to give them have a monopoly over dietary advice (Steve Cooksey’s case + other evidence [14]).  Also, dietetic associations receive sponsorship from the food industry (see ‘And Now a Word From Our Sponsors’ US [15] and Australia [16] + the conflicts of interest in the Tim Noakes trial [17]),  and the food industry also employs many individual dieticians.  Finally, and this applies to many organisations, they have an incentive to shut down opposing ideas so that the public perceives them to be the ultimate gate-keepers of knowledge, and that acknowledging other ideas or previous errors will cede the monopoly and make them appear less relevant, rather than more honest

With the internet providing increasingly more diverse ideas and information, the increasing partisan bias of the media and the rise of fake news, the solution cannot be to silence everyone you disagree with, as this will be both logistically challenging and counterproductive.  Instead the solution must be to teach people how to think, not what to think.  And instead of presenting an uninspiring version of conventional wisdom and dismissing/censoring opposing ideas, I would like to see health associations hosting debates similar to the Sugar and the State debate hosted by the Cato Institute The Protein Debate hosted by the Performance Menu

Sunday, January 8, 2017

Public Health Strategies Part 4A: Taxes

In an earlier post I mentioned a few different commonly proposed public health strategies, and how most of them fit quite nicely into a political spectrum characterised by an authoritarian-libertarian axis and a left-right axis.   In this post I’ll discuss the strategy of taxation/subsidies, which I thought fits nicely into the authoritarian left quadrant.  This is because this strategy holds the food environment primarily responsible for people not adopting healthy lifestyle behaviours rather than personal responsibility, and then uses government controls to manipulate the free market


Rationale

There are a few targets people have suggested to tax or subsidise.  There was the failed Danish tax on saturated fat, and sometimes there are suggestions that fruit + vegetables and even gym memberships (because you couldn’t possibly exercise without one) should be subsidised, but this isn’t very common.  At the moment, a tax on sugar sweetened beverages (SSBs) is far more commonly proposed and is actually being implemented in a few areas, so I’ll focus on that

There are two main rationales to support a tax on SSBs.  The first is that a tax on SSBs will increase their price and this would reduce the consumption of them, particularly in people on lower incomes, who consume more SSBs on average, as they are more sensitive to changes in price.  This is textbook supply and demand, as price goes up demand decreases.  In this respect, a tax on unhealthy food or a subsidy on healthy food could be seen as a form of nanny statism.  Generally, implicit in the support for a tax on SSBs is the belief that education programs haven’t or will not work on some people (the laggards).  This usually isn’t mentioned when a tax on SSBs is proposed (probably out of political correctness and not risking alienating others), but it is an important premise to justify taxes/subsidies, because otherwise why not use education instead?  And so a tax on SSBs appears necessary to reduce SSB consumption and therefore improve health, or, to save some people from themselves.  Or perhaps more importantly, to save the overweight/obese children with a mouthful of tooth decay from negligent parents.  But people who are against many forms of nanny statism argue that what right does the government have to control/influence individual choices that don’t adversely affect others?*  In addition, cigarettes are heavily taxed but plenty of people still smoke, and as David Gillespie points out, there is already a tax in Australia on many processed foods including SSBs in the form of the GST [1]

This leads into the second rationale for taxing SSBs which counters the previous argument.  In countries with a socialised healthcare system the consumption of SSBs creates a negative externality.  When people purchase SSBs they are paying the costs for the product but are mostly or totally externalising the increase in healthcare costs from SSB consumption increasing the risk of several chronic diseases.  As a result, it could be said that they are not paying the ‘true costs’ of a SSB.  Let’s say 1 litre of SSBs costs the consumer $1.50 but each litre of SSBs is associated with an increase in healthcare costs at about $0.30.  Therefore, in this scenario a 20% tax on SSBs is necessary to internalise the healthcare costs.  With this rationale of internalising externalities, a tax on SSBs could be considered a successful policy even if no one changes their behaviour as a result of the tax, and also doesn’t make it about nanny statism or a moral judgement (a ‘sin tax’)

Of course, the government (and health associations [2]) also has a motivation to tax things that are politically acceptable as a form of cash grab, particularly if they’re the kind of government that likes to spend money, which seems to be the main motivation for the Danish tax on saturated fat [3].  “A lesson learnt from this chain of events is that if a tax on fat is to survive it needs more than merely to be passed. It probably needs to be politically supported for health rather than fiscal reasons and to be supported or at least accepted by prominent actors in the food arena including researchers.” [3]

* This can also apply to laws against recreational drug use (that doesn’t expose people to second hand smoke for example), ‘unsafe’ playgrounds and bike helmet and seatbelt laws

Efficacy

Danish tax on saturated fat: some people in public health have praised the Danish fat tax because it reduced the intake of saturated fat [3].  However, simply implementing a well-intentioned policy doesn’t mean it’s necessarily going to have good outcomes.  The most important outcome of such policies should be related to health rather than consumption, and in this respect even diet-heart diehards should judge it to be a failure.  Based on ecological data, the Danish tax on saturated fat appears to have reduced SFA, MUFA and PUFA by 0.3%, 0.2% and 0.1% of total calories respectively (this is because foods high in SFA are often high in MUFA and PUFA on a grams per weight basis).  As a result, LDL-C would be expected to decrease by 0.008 mmol/l and HDL-C would be expected to decrease by 0.005 mmol/l, and this would be expected to increase the risk of CHD by 0.2% (-0.3% for LDL-C +0.5% for HDL-C) [4].  While it’s ideal to be able to judge the efficacy of the tax based on actual changes in population health rather than modelling, the estimated effect size here is probably too small to notice and would likely be drowned out by noise.  The Danish fat tax also had the issue where consumers could avoid the tax by purchasing heavily taxed foods in neighbouring countries without such a tax

SSB tax in Australia: a tax on SSBs hasn’t been implemented in Australia but one study in particular has estimated effect of a 20% tax on SSBs in Australia, and found the following [5]:


Males
Females
Consumption
141g/d to 124g/d
76g/d to 67g/d
Total energy intake
-16 kJ/d
-9 kJ/d
Change in BMI
-0.10
-0.06
Weight loss
0.32 kg
0.06 kg
Obesity prevalence
2.7% (0.7 percentage points)
1.2% (0.3 percentage points)
Health-adjusted life years
112,000 (4.54 d/per capita)
56,000 (2.27 d/per capita)

The estimated change in BMI as result of the tax is similar in magnitude to other studies in the US [6].  The tax is expected to cost 27.6 million AUD upfront, but generate 400 million each year and reduce healthcare costs by up to 29 million per year (savings are expected to increase over time and plateau at 29 million) [5].  This is a decrease of just ~0.024% in total healthcare expenditure (29 million/121.4 billion [7]) and is why it’s important to put those kinds of figures in context

Given that the revenue generated equates to about 0.329% of total healthcare expenditure, and that SSB consumption is likely responsible for at least a 1% of total healthcare expenditure (not aware of an estimation for this, but 1% seems like a reasonably conservative estimate), if the rationale for taxing SSBs is to internalise externalities then the tax would need to be substantially higher.  This is also true if the goal is to meaningfully improve population health

One of the problems with this model is that the health outcomes are based on BMI, which in turn are based on the very small estimated reduction in calorie intake, and doesn’t look at any effects of SSB intake independent of calorie intake and BMI.  And of course it looks at adults, whereas if it also included children the estimated effects would be greater because the analysis would include more people and because the expected health benefits are larger for younger people.  That being said, a modest (~20%) tax on SSBs in an affluent country like Australia (where the economic effect can be largely ignored by almost everyone) is certainly not going to be a silver bullet.  The food industry has a point when they say that SSBs only contribute about 3% on average to total energy intake.  ‘Extra’ foods contribute about 36% on average to total energy intake in Australia [8], so there’s a lot wrong with the average Australian diet.  Therefore, one could argue a lot of potential targets to tax, but also that there’s a lot more that needs to be changed by even a 10% reduction (~3 percentage points) in ‘extra’ foods as a result of a broad taxation policy

Other Objections

Some people argue that a tax on SSBs is a tax on the poor, as poorer people on average consume more SSB and are more motivated by changes in price, but there are a few issues with this objection.  (1) They are confusing intent with outcome.  This is a mistake many people make related to other issues where there is a race/sex/etc disparity.  The tax is not discriminatory (except against SSBs) as it’s not intended to disproportionately tax poorer people, but it’s simply that the people who consume more SSBs happen to be poorer.  It’s not like this is a tax on renting or living in apartments, which actually has more of a causal relationship with being poorer (2) People are free to purchase SSB or not.  There’s nothing forcing poorer people to consume more SSBs on average.  If they don’t want to pay the tax they can choose not to purchase them, after all SSBs are very discretionary food items.  (3) While the tax is estimated to cause large relative differences in total household expenditure (consumption multiplied by income differences), the actual increase in expenditure for low income earners is very modest (~0.2% household income, ~1% of food budget) [9] (4) A tax on SSBs is likely to disproportionately benefit the health of poorer people.  People in public health usually try to engage and improve the health of low SES people disproportionately.  After all, no one in public health is really advocating for a subsidy on salmon, avocado, blueberries and quinoa.  (5) Who do you suppose the tax revenue is likely to disproportionately benefit, almost regardless of what it’s used for?

Another objection is that a tax on SSBs will reduce sales and as a consequence some employees will have to be laid off (if the food industry objects to the tax for this reason, then you know they think it will work to some extent).  The goal isn’t (and shouldn’t be) to punish the food industry as they are reacting to consumer demand for the most part (but they should be punished when they distort science, and there are numerous examples of this).  But the food industry and their employees shouldn’t get upset that in countries with socialised healthcare, the government at some point may tax unhealthy food to improve health and/or internalise externalities, after all there is a rationale and incentive for it to do so.  While it’s unfortunate that a very small number of people may lose their jobs, it’s important to recognise that there are other jobs out there, and that changes in the world will always create winners and losers (the internet is a great example), and part of life is setting yourself up to manage such likely changes well

While I thought taxes/subsidies and bans fit nicely into the authoritarian left quadrant, a modest (~10-20%) tax on SSBs isn’t really that authoritarian.  However, a major concern, particularly from libertarians, is that a tax on SSBs sets up a precedent for governments to tax other things, where these other things may be quite inappropriate targets for improving population health, while also leading to a progressive loss in individual freedom.  This should also be of concern to people in ancestral health, low carbers and other, regardless of political opinion, as by adopting such dietary practices we acknowledge that the government and mainstream isn’t always right.  A good example of an inappropriate target is the Danish tax on saturated fat, as saturated fat is not associated with coronary heart disease in meta-analyses of observational studies [10], replacing saturated fat with polyunsaturated fat does not reduce coronary heart disease in adequately controlled randomised controlled trials [11], and reducing fat intake is hardly the best strategy for weight loss [12].  Similarly, total fat is a potential target, but increasingly less likely.  (Red) meat is another potential target for taxation for health or environmental reasons, despite evidence to the contrary [13] [14] [15].  Salt is another potential target because people in public health seem to have an almost pathological hatred of salt, despite the relationship between salt intake and mortality being on a U-shaped curve [16] and that reducing salt intake doesn’t affect blood pressure much but does have some undesirable side-effects [17].  Being in academia and around nutrition students hasn’t alleviated these concerns, it has strengthened them

This post is already quite long so I’ll simply list a few more papers if you’re interested:

  • Beverage purchases from stores in Mexico under the excise tax on sugar sweetened beverages: observational study [18]
  • Impact of the Berkeley Excise Tax on Sugar-Sweetened Beverage Consumption [19]
  • Using price policies to promote healthier diets [20]
  • Modelling the potential impact of a sugar-sweetened beverage tax on stroke mortality, costs and health-adjusted life years in South Africa [21]

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