Bananas, Porridge, and The Importance of Controlled Experiments

This was meant to be a story about how bad bananas are, and how natural isn’t always better. But it’s not. It’s a story about how bananas are probably ok, and control groups are important.


For a while now, I’ve been getting occasional symptoms of hypoglycemia (low blood sugar). Shakiness, clamminess, irritability, and a fast heartbeat. It’s no big deal, but it’s annoying when it happens in certain situations, like at work.

I noticed that it seemed to happen more often after I ate certain things. I started paying attention to my diet (see this post on a few things I did, like giving up soft drinks) and figured I was probably doing ok. Sugar crashes tend to be caused by overreaction to sharp sugar spikes, and I thought I was doing a pretty good job of avoiding these.

But I was still getting the symptoms.

So maybe I was still doing something wrong?

By the book

There’s only so much you can learn by reading. Despite trawling through tables on glycemic index (and, more to the point, glycemic load) values for all sorts of foods, I was still getting these sugar crashes. Where to go next?

In The Four Hour Body, I read that Tim Ferriss used a continuous glucose monitoring device to keep track of his sugar levels for a while. The one he recommended was ridiculously expensive (£1k+!), but after a bit of research I managed to find a disposable one that would last two weeks for £60.

So I bought one and, with some help, bravely implanted it in my arm. (thanks mum!)

Then for two weeks I kept track of what I ate and how it affected my sugar levels.


Here’s one thing I noticed: when I had my usual breakfast of porridge oats with banana, my blood sugar shot straight up and crashed down quickly afterwards. (for reference, non-diabetics tend to have blood sugar levels of 4–6mmol/l before meals, and 6-8mmol/l a while after eating)

Now I knew bananas weren’t low in sugar, but I didn’t think they’d have that much of an effect! All this time I’d been having that breakfast because I thought it would give me a good mix of quick and slow release energy to keep me going all morning!

I figured it was time to change my ways. But maybe I could do a few comparisons first.

I measured my blood sugar over a few other meals, and it was stable.

I decided to see how a banana compared to pure sugar. Here’s porridge oats with three teaspoons of sugar:

Almost identical to one banana! Crazy, I might as well have been having sugar with my porridge all this time. Right?


On the very last day my sensor was active, it occurred to me that I should do one last breakfast experiment: a control group. Just to see — what would happen if I had just porridge? No banana, no sugar, nothing else. Just porridge.

Two things:

  1. It’s disgusting. Seriously, don’t do it.
  2. Surprise! The effect on my blood sugar was the same.

Here’s pure porridge (oats + semi skimmed milk):

Spike, and crash! Like the other two cases. So my conclusions were wrong!


It turns out that the assumption I’d made at the beginning was wrong*.

I’d been reading too many food and nutrition blogs, and took them at their word when they told me that “oats are a source of slow-release energy”. It turns out they’re not**.

I’d somehow selectively ignored the data that said that oats are, actually, quite high GL. One serving of oats is about halfway between a banana and a can of coke, in terms of its impact on your blood sugar.

What did I learn?

Sometimes you need to trust the way you feel over what you’re reading. Oats definitely won’t be my go-to breakfast anymore.

I also learnt that it’s easy to make conclusions based on very little data. It’s important to conduct experiments designed to disprove your hypothesis, not just to support it!

And finally… if you’re one of the people I spoke to after my first two bowls of porridge, I take back everything I said about bananas! (probably*)

* As someone pointed out to me after reading this, technically I never controlled for the milk in my porridge, which also contains some sugar. My sensor has expired now, but if I had another chance I would do another test with just oats and water. And one where I just eat a banana, to see what that does.

** Someone else pointed out that there might be a difference between different types of oats. As I was eating Tesco’s cheapest oats, it might be worth re-doing this experiment to control for that. 

Eating to Live Forever: A Sustainable Healthy Eating Habit

Visionary technologist, writer, and current director of engineering at Google Ray Kurzweil believes that he’ll live forever. Within mere decades, he says, nanotechnology will allow us to halt and even reverse aging. His current mission is to stay alive until that happens. Much of the advice below is sourced from his book Fantastic Voyage: Live Long Enough To Live Forever.

Eating healthily is hard. It requires willpower and it’s hard to care about long-term benefits when there’s cake in front of you. But there’s an even harder problem — what does ‘healthy’ eating even mean?

Mmm… pop tart butter ball surprise.

I’ve never been visibly unhealthy but a lot of my meals were — picture Eric Cartman and Chief Wiggum in charge of the food for a five-year-old’s birthday picnic, but with more chocolate.

I never thought this was an issue as long as I stayed fit. Since then family illnesses, other people’s opinions, and some basic research convinced me that I should probably reconsider.

The beginning

A few years ago, after reading In Defense Of Food, I decided to give up soft drinks almost entirely. The evidence against soft drinks and refined sugar more generally is uncontroversial, and many think that in a few decades the soft drink industry will be viewed in the same way we view the tobacco industry today. But what about the other aspects of diet?

Is it enough to look at calorie count, or should you care about the balance of macro-nutrients (carbs, fat, protein, etc)? Does it matter more what you eat, where your food is sourced, or how it is prepared? Should you eat low-fat? Low-carb? Paleo? Atkins? Slow carb? Soylent?

As nutritionism is notoriously faddish, it’s important to look beyond what people around you are doing right now (juice cleanses, anyone?) and consider what matches up with the evidence we have and the understanding of how food is processed in our body.

Kurzweil’s approach

It’s hard not to believe Kurzweil — he’s more than just technically literate, has sufficient resources at his disposal, and has an enormous amount of self-interest in following the most effective diet possible. While his book contains a wealth of fascinating information on biological processes and chemical makeup of different types of food, Kurzweil’s main advice boils down to the following points:

  • Cut out sugar and simple carbs almost entirely
  • Eat mainly whole foods
  • Reduce fat intake, especially saturated fats
  • Eat a lot of vegetables of various colours
  • Drink lots of water and green tea, avoid excess alcohol and coffee
  • Take a variety of supplements

Does this make sense? Probably…mostly. Sugar and simple carbs cause glucose spikes, which cause insulin spikes, which might reduce insulin sensitivity, leading to diabetes and potentially other long term downsides. Fats, especially saturated fats, contribute to increased risks of heart disease. Many vegetables are low in both of the above while containing high levels of important vitamins and fibre. Water is important for almost every process in our bodies.

As for supplements… Kurzweil has recently cut down his daily dose of supplements to ‘only’ 150 pills. He believes that aggressive supplementation is a necessary part of a modern diet, as it allows us to make up for dietary deficits and ‘hack’ our bodies by exploiting our understanding of the chemical processes underlying disease and ageing. Though he may have a point, I think Nassim Nicholas Taleb has an interesting stance on this: our knowledge of supplements and their impact is still very limited, and while they may have some positive effects it’s not possible for us to know what negative effects supplements will have without further long-term research.

Further, the fact that Kurzweil has his own dietary supplements business makes this part of the advice less interesting and potentially more biased (though I don’t believe that this is necessarily true).

My approach? Write the above points down on a business-card sized piece of paper that I keep in my wallet and read before every meal, checking whether the meal complies. I’m hoping that this will guide me in the right direction.