Which should I be avoiding, sugar or saturated fat?

The idea that saturated fat is good and that sugar is bad is very fashionable at the moment. I want to have a bit of a wander through the evidence surrounding this, specifically the effects of saturated fat and sugar on the incidence of heart disease.

When you’re looking at health interventions in human beings, the place to start is a meta-analysis, where the results of lots of studies are pooled together to try to find the big picture of what’s happening. When it comes to saturated fat and heart disease, there are a plethora of these analyses. One that has been reported upon a great deal is this “meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease”, which reports no correlation between saturated fat and heart disease. Significantly, this study makes no differentiation between patients who replaced saturated fat in their diets with poly- and mono-unsaturated fats, and those who replaced it with carbohydrates, meaning that it is difficult to separate the role of saturated fat in these cases from the role of sugars: if decreasing saturated fat intake also increased sugar intake, then the effect on cardiovascular disease could be due to either of these factors (or lots of other factors), so this doesn’t help us answer the question.

A meta-analysis which does look at the difference is this one from the Cochrane collaboration, which found that replacing saturated fats with unsaturated fats decreased risk of heart disease, while replacing saturated fats with carbohydrates did not decrease the risk.

I couldn’t find a meta-analysis of studies on the link between sugar and heart disease – perhaps because interest in this idea is quite new. I’ve found a recent study that showed a link between consumption of added sugar (i.e. sugar not from fruit, milk, or other intrinsic sources, but from sugary drinks and processed foods) and heart disease. It seems like far more studies on this are needed. It would have been surprising to find out that sugary drinks are good for you, but it’s not necessarily obvious that they would correlate with heart disease. The current theory seems to be that sugar, like saturated fat, increases the level of “bad” cholesterol in the bloodstream.

There’s quite a good meta-metaanalysis, where scientists pick over the evidence for dietary advice regarding heart disease risk. The conclusion basically encapsulates my favourite systems biology maxim: “it’s a bit more complicated than that”. In general, replacing saturated fats with poly-unsaturated fats reduces heart disease risk, but some saturated fats may have different effects than others, and other things present in foods high in saturated fats might change its effects. In general, replacing saturated fats with carbohydrates doesn’t reduce heart disease risk, but if the carbohydrates are unrefined (e.g. wholegrains) then perhaps it does reduce heart disease risk.

The multifactorial nature of heart disease probably goes some way to explaining the “French paradox” – the fact that the French diet has more saturated fat than the UK diet, and yet they have lower levels of heart disease (incidentally, there are yearly stats published on heart disease in Europe that make for fascinating reading). There are multiple differences between the diets of our countries, and between other lifestyle factors such as activity levels, smoking, drinking, and weight.

The change in advice regarding cholesterol is brought up a great deal to discredit the link between saturated fat and heart disease (even though the levels of cholesterol in your blood are linked to your risk of heart disease, the levels of cholesterol that you eat aren’t something you need to worry about, so you can be like Gaston and eat five dozen eggs in the morning to help you get large).

Advice on this, and on other things, has changed over the years – trans fats, previously thought to be a healthy alternative to saturated fats, are actually way worse, and high fructose corn syrup is probably far less healthy than sugar (although please note that in the UK we don’t really eat much of either, and that fructose is no reason to avoid eating fruit). There is a lot of controversy over the link between saturated fat and heart disease, and I think it’s fairly clear that it’s not the sole culprit – in human biology, there is rarely ever a single reason for a phenomenon. Broadly, the answer to the question “Which should I be avoiding?” is “both” (to a certain extent – obviously, you need a little of everything in your diet).

From searching through the studies, I can’t find a lot of compelling evidence for increasing saturated fat in one’s diet, so arguing that we’ve been misled about saturated fat entirely feels like rather a leap. I’m looking specifically at heart disease here, not necessarily weight loss (there’s a whole other blog post on that, I think). It’s very possible to reduce saturated fat without increasing your intake of refined carbohydrates, and the evidence supports the idea that replacing saturated with poly-unsaturated fats either decreases one’s risk of heart disease or, at worst, doesn’t have any ill effects on one’s health. Reducing sugar intake is a good idea for multiple other reasons anyway (your teeth and your risk of diabetes, for example), so if it also reduces your risk of heart disease then that’s a bonus.

I think arguments like this come about from attempts to create a healthy diet that looks completely identical to an unhealthy diet, with certain nutrients replaced with others, when the easiest path is to encourage what we know to be healthy – a diet much, much higher in fruits and vegetables than is currently the norm in the UK. Things seem to be slowly moving in that direction, especially with the rise of more convenient ways of getting one’s “five a day”. We have to change the world to either make people’s lives easier, giving them more time to cook and more money for buying lovely fresh ingredients, or make it easier to get healthy food cheaply, by heavily subsidising healthy options or opening heavily-subsidised healthy cafeterias where people can get good food quickly and cheaply.

tl;dr: Eat some salad. Or don’t, it’s your body, not mine.

Simon Jenkins’ aversion to maths doesn’t add up

When an article begins by bemoaning the giving of a prestigious prize to an amazing maths teacher whose videos have helped a lot of people to understand complicated concepts, you know you’re in for a treat.

Simon Jenkins has argued that teaching mathematics to children is pointless, and that we should instead be teaching them about science, and in so doing has displayed a shocking level of ignorance about what science actually is.

Having trained as a biochemist and a computational biologist, I’m in a particularly privileged position to see the centrality of maths to much of modern life, especially in the life sciences.

Jenkins praises “…a radical new GCSE syllabus [that] dragged school science away from test tubes and Bunsen burners towards everyday life, to pollution, global warming, additives, health and diet.”

I would like to point out that without the aforementioned test tubes and Bunsen burners, we would have no understanding of “additives”, “health”, or “diet”. The way you find, for example, the amount of fat inside a foodstuff, is to take it into a lab and perform experiments on it.

“But that does not mean every primary pupil must spend hours, indeed years, trying to learn equations and πr2, which they soon forget through disuse.”

The fundamental mathematics that he decries in this article, such as solving equations or finding the area of a circle, are completely essential in a lab and in interpreting the results of an experiment. Much of my undergraduate degree was spent solving the simple equations that give the concentrations of reagents in serial dilutions.

Even the much-dreaded calculus has a role here, in describing rates of change.

Just a cursory glance at the researcher profiles on the Maths Department website here at my university shows the dazzling array of practical areas that mathematical research is pivotal to: tumour growth, solar cells, flocking behaviour, glacier flow, cardiovascular disease, wound healing, and antibiotic resistance. This research uses cutting-edge mathematics, drawing from the furthest recesses of number theory and calculus.

“There is no “need” for more mathematicians. The nation needs, and therefore pays most for, more executives, accountants, salesmen, designers and creative thinkers.

Even if you agreed which this sentiment (which I do not), I defy you to find an accountant or designer without a grasp of basic mathematics.

The rise of the computer age has made mathematics even more pivotal in modern life. Video games and computer animation are now booming creative industries, attracting many young artists. Both of these fields rely heavily on physics engines that cause a character’s body to move realistically or a projectile to hit its target, meaning that these creative thinkers use complex mathematics on a day-to-day basis.

The computer on which you typed this under-researched and ill-thought-out article runs on hardware and software created by people who benefited from years of mathematical education. In the source code of the Guardian website where your article is displayed, you can see how many times the word “radius” comes up in the code behind the rounded corners that make the page seem so cuddly and user-friendly. There are complicated algorithms behind resizing content for smaller screens, making the text accessible for people using screen readers, and in the way that the hyperlinks direct you through the internet, across networks of disparate servers, to their destination.

I’m not for a second going to argue that the British education system’s over-reliance on league tables, constant assessment, and the setting of targets is a good thing. There’s a reason that teachers are leaving the profession in droves, and it’s because they’re overworked, micromanaged, and underpaid.

The answer, however, is not to throw away a key part of the curriculum and refuse to teach students how to do simple geometry. You’d have to make use of pi if you wanted to do something as simple as make a circle skirt, and you’d have to understand basic logic if you wanted to write a computer script to automate a task. The idea that the world could still function if a generation of children grew up without an adequate mathematical education is laughable.

“In maths, roughly a third of those surveyed had no idea how to calculate a mode, a median, a “line of best fit” or the area of a circle. I seriously doubt this poll, since it implies that two-thirds did know the answers.”

As someone helpfully pointed out in the comments, this poll actually implies that two-thirds know one or more of the answers, not all of them. Mathematics is also essential to interpreting poll results so that you can write coherent news articles. Perhaps you should give it another chance.

Edit: an entertaining update.

“Diet Coke Exposed”, or: “How not to make an infographic”.

I happened to stumble upon this infographic about Diet Coke this morning – it’s trending on Facebook and has been repeated, unquestioned, in The Metro, The Mirror, and some other reputable news sources.

Here is the picture (click for a larger version):

Diet coke infographic

The graphic, and its accompanying article, falls short on a lot of the things you might expect from a piece of scientific writing. I’m going to give some advice to the “Renegade Pharmacist” author, so that his articles can be better in the future.

You need a consistent list of references.

I understand that it is difficult to add references to such a small graphic, but I would highly recommend doing so. You don’t have to give the URL, just some information to let people find the paper, like:

Swithers SE. Trends Endocrinol Metab. 2013, 24(9):431-41.

This tells you the author’s name, the journal name, the issue number, and the page. At scientific conferences, information is often shared in the form of posters, and it is expected that posters will have a reference list.

In the longer article, you have some explanatory sections beneath each point, but then the references are all in a jumble at the bottom. Some of them have URLs, some of them have article titles, and some of them have author names. You can list them in the order that you use them, or in alphabetical order, but it’s important that they be consistent. There are several different referencing formats you could use. If you collect your sources together using a reference manager like Mendeley, it will even generate the reference list for you.

Every claim must be backed up with a reference.

Your graphic makes eight main claims:

  1. Phosphoric acid is bad for your teeth.
  2. Aspartame tricks your body into thinking you have eaten sugar.
  3. Within 20 minutes,  drinking Diet Coke causes insulin release.
  4. Within 20 minutes, Diet Coke increases the risk of diabetes and metabolic syndrome.
  5. Within 40 minutes, the combination of caffeine and aspartame causes addiction.
  6. After 60 minutes, drinking Diet Coke makes you want sugar.
  7. After 60 minutes, Diet Coke depletes your body of essential minerals.
  8. After 60 minutes, Diet Coke dehydrates you.

After you make each statement, you must immediately cite the source it came from. You can do this by putting a little number next to the statement that corresponds to the numbering in your reference list (just like Wikipedia does), or you can give the author’s name and the date of the paper (e.g. Nettleton et al. 2009) afterwards in brackets. I’m sure many of those claims are backed up by items in your reference list, but it takes effort to go through and find that out, whereas what you want is for people to be able to quickly assess the evidence you’re basing your argument on.

References must be from reputable sources.

Papers that are published in scientific journals are first scrutinised by experts in the field. Lots of papers don’t get through this reviewing process, as it involves going through the paper with a fine-toothed comb looking for problems in the science.  This peer review process is not perfect, and not every paper that is published turns out to be correct, but peer reviewed journals are still the best possible source of scientific information.

Some of your citations are from scientific journals, but many are from news articles or blogs. It’s important that your evidence is from the primary scientific literature.

You mustn’t extrapolate from unrelated studies.

One of your links to support the claim that Diet Coke causes addiction was to this paper from 2013, which looked at the effects of diet soda on rat brains. The final paragraph of its abstract reads:

“These results suggest that diet soda has adverse effect on the cerebellum of adult female albino Wistar rats.”

The scientists here have chosen their words carefully so that they do not overstate the implications of their work. This is a study that was performed on this very specific subset of rats, and gives information about this very specific subset of rats.

Generalising from animal studies to human studies is a really important area of biology, but it can’t be done on the basis of one study. The absolute best source of information is a study that looks at lots and lots of other studies, across a broad range of animals and in humans, like this one from 2007. These are called meta-analyses, and it is always worth trying to find one when you’re investigating a topic. For health information, the Cochrane library is very useful.

The credentials of the person you are referencing aren’t as important as the fact that the information is from a paper in a peer-reviewed journal.

There were a few sentences about the sources of your information that gave me pause.

“Susan E. Swithers, a professor of psychological sciences and a behavioural neuroscientist.”

“Marisa has over 20+ years as a weight loss therapist with her method proven to be the only one to work by the famous UK TV series Super Size Super Skinny”

On subjects like this, the professional qualifications of the person giving the information aren’t as important as the strength of the evidence that they’re basing their arguments on. This is why it’s important to look for peer-reviewed papers, because they (hopefully) demonstrate good evidence.

You depend too heavily on one source of information.

The paper “Artificial sweeteners produce the counterintuitive effect of inducing metabolic derangements” forms the crux of many of your arguments – in some cases, you quote the paper and its accompanying article verbatim. If you were merely providing a summary of this particular paper, this would be fine, but your article draws in evidence from lots of places, meaning that it needs to be more balanced than this.

You did some things correctly.

It is a very good idea to take a company’s claims about their product with a pinch of salt, and you rightly point out that these arguments apply to lots of different drinks, including Diet Pepsi, and off-brand versions of diet sodas.

You’ll note that I haven’t actually commented on the science put forward in the infographic. This is for a simple reason: I haven’t investigated the topic, and as such wouldn’t dream of holding forth on it.

Animal testing, Norman Baker and new possibilities: some numbers and thoughts

A total of 4,121,582 animal experiments were carried out in the UK last year. To put that in perspective, the UK consumes an estimated 2.5 billion animals a year as food. That means that for every one animal used for scientific research, 606 animals are killed for meat.

Similarly, the Dog’s Trust calculated that in 2013 there were 111,986 stray dogs in the UK, 8,903 of whom were put to sleep. According to Home Office statistics, 4,779 scientific procedures were carried out on dogs in the same. This means that, for every one dog used in an experiment, approximately 23 dogs wandered the streets alone, and two dogs were put down because they didn’t have a home to go to.

I think it’s reasonable, given those figures, to suggest that animal testing is not the most pressing cause of preventable animal suffering in the UK (not to mention the way we treat foxes and badgers). But is it justified on scientific grounds?

It has been argued by various animal rights organisations (with some notable exceptions) that animal testing is unhelpful and misleading, and as such is of no use in human medicine. However, medical advances from areas as disparate as blood transfusions, vaccines and MRI scanning would have been impossible without animal experimentation, and animal research has taught us innumerable things about living systems.

Animal experiments by field, 2013 UK

These were: toxicology (375,010), immunology (578,400), cancer research (501,400), physiology (472,200), anatomy (458,000), genetics (449,900), molecular biology (197,094), pharmaceutical R&D (239,730), and other, including psychology, pathology, nutrition and zoology (848,266). (source)

We’ve got a lot of big challenges in medical science at the moment: cancer, AIDS, antibiotic resistance, neurodegenerative disorders, and a host of other things that we haven’t cured yet. Without animal testing, we’re not going to solve any of them very soon.

So rather than a question of practicality, the debate should solely rest upon fundamental morality: how many animals can be sacrificed to save one human life? The possible answers range from “none” to “an infinite number”, with “five rabbits and a marmoset” somewhere in between. I leave this as an exercise for the reader.

Those caveats in place, I’m very excited by Norman Baker’s announcement last week that he has a particular interest in developing non-animal alternatives, and I want to have a look at what those alternatives might be.

Animals used in toxicology in 2013

Mice (189,000), rats (99,200), other rodents (8,200), fish (42,500), birds (16,700), rabbits (10,100), and other animals (9,300, including 2,100 monkeys). (source)

Toxicology is a big area of animal research, because if you want to sell something that people will eat, rub on themselves, or just touch all day, you need to make sure that it’s not going to kill them. Non-animal toxicology tests are generally done in combination with animal tests, and act as early screening methods so that animal resources aren’t wasted on substances that are likely to be toxic.

The Ames test for carcinogenicity is one of my favourites. One of the ways that a substance can cause cancers is by directly causing mutations in the DNA of cells. The Ames test takes bacteria that have small mutations that make them unable to live without histidine, and mixes them with the compound under investigation, and then leaves them somewhere without any histidine for a while. If any of them survive, it’s likely that the substance helped them regain their ability to live without histidine by mutating their DNA.

Using human cells to test drugs on is a great idea as well, but what we really need is some idea of how the cells would act in the body. Usually, human cells live inside complex structures, as part of tissues and surrounded by an extracellular matrix. They are affected by blood vessels, nearby organs, and the other cells around them. One way to start to model this is by creating an organ-on-a-chip, where cells are grown on a tiny, microfabricated chip designed to mimic their natural environment, and connected by fluid to other groups of cells from the same organ. Researchers have been working on models of the lung, liver, kidneys and heart using this technology, but they haven’t yet been proven to be useful.

It can be difficult to get hold of human cells to use, and it’s even harder to keep them alive, so working out how to transform human stem cells into realistic versions of adult cells will be a huge step forwards in this field.

Finally, in silico approaches, in which we combine all the information we know about a bodily system into a mathematical model, and use it to predict results. My group in Oxford have done some interesting things predicting cardiac side-effects of drugs, and the Virtual Physiological Human project aims to collect together models of the entire body. We’re still a long way away from having computational models that are as refined as animal systems, but as we learn more about humans we can build better and better models.

It’s not just human models we need, either. For agricultural chemicals and ecology screens, we need to know the effects of new compounds on wildlife and farm animals, so we need excellent models of these systems as well.

When we can finally replace animal testing with equally effective alternatives, it will represent an enormous amount of effort, research and knowledge, and will amount to nothing less than the total, systematic understanding of the human body. Contrary to Mr. Baker’s pleas to industry to work on alternatives, the best place for this research is in universities and other non-profit organisations that are able to publish their results without losing a competitive advantage.

If you’re interested in reading more, the National Centre for the Replacement, Refinement and Reduction of animals in research (NC3RS) is an organisation in the UK that funds and co-ordinates research into animal alternatives, and Altex is a journal specifically dedicated to the 3 Rs.

Aside: cosmetics testing has been illegal in the UK for a number of years, but a lot of imported products (including those from P&G, Unilever and Estée Lauder) are tested on animals. It is essential to test products for safety; it isn’t essential to invent a new kind of shampoo twice a year. I think that human civilisation has probably created the best lipstick it’s ever going to, and despite the fact that anti-ageing creams have never been shown to work on a living creature, they still seem to sell fairly well anyway. To end animal screening for cosmetics that don’t fill a useful need like providing for people with allergies or eczema, we need to put pressure on the organisations that create them.

Elliot Rodgers, pickup artistry and losing your virginity.

I’ve read a lot in the last few days about Elliot Rodgers’ gender-motivated killing spree. I’ve had a brief skim of the manifesto he released, and it made me think about the lives of young men.

This pervasive idea that sex is something that women withhold from men, that sex is a reward that is freely given for good behaviour, or that sex is a measure of your intrinsic worth as a human being, has got to be a god-awful thing to grow up with.

The pick-up artistry forums and meeting-places on the internet like The Red Pill all add to this myth – that there are a particular set of behaviours and attributes that will reliably lead to you being given the opportunity to sleep with attractive women. Allegedly, women are interested in only a small subset of things in a partner – attractiveness, social standing, and traits which speak to her innate psychology or memories from her childhood. Basically, every woman has one of these inside her:

Attractiveness-o-meter

If you can meet all of these needs, then you will be given sex.

Attractiveness-o-meter

I can see why, if you believed this, you’d be really hurt and angry when you tried the techniques you’ve heard about and they didn’t work. Imagine if you took your driving test and, despite doing everything perfectly, you still weren’t awarded a license at the end of it. “Stupid examiner!” you’d think. “Can’t you see what a good driver I am?”

The problem is, sexual relationships don’t work that way. When you decide to sleep with someone, you don’t just weigh up their good and bad points and decide whether or not they pass. You think about what you want at that moment, what your relationship status is, how the conversation is going, what you’re attracted to, and a load of other factors, none of which are a judgement on the worth of the other person. It’s about both of you, not just about you.

Everyone’s attractiveness-o-meter is different, and there’s no way to find out how different unless you get to know the person. Being attractive is about, in the words of Dr. Seuss, finding “mutual weirdness” with another person.

Matching attractiveness-o-meters

Do you know how unlikely it is that a person who has all of the traits that you like also likes all of your traits, and is in a position to enter into a sexual relationship with you at any given time? People who have a large number of sexual partners tend to have one thing in common: they’ve asked lots of people to be their sexual partners.

People are virgins until they’re not any more. You’ve never had sex? I’ve never been skydiving – but that doesn’t tell you anything about me. It’s just an experience I’m yet to have.

It's not embarrassing to be a virgin. It's simply one state of being.

Young men: your worth as a human being is not dependent on the attention and opinion of other people. Women are just like you, but with boobs, and nobody owes you sex. Don’t pay attention to The Red Pill, or the pickup artist community, or the rest of the misogynists you can find on the internet. All they do is spawn hatred and anger and self-loathing, and legitimise the actions of people like Elliot Rodgers.