Why we can’t ever be sure

The main problem with so many medical studies – nearly all of them, in fact – is that no matter how hard the investigators try to even out differences among study participants- that’s the part where they always say, “We controlled for differences in income, smoking, diet, type of vehicle, favourite sports team, middle initial, primary school teachers, and all the other things the investigators thought might contribute to different outcomes for the study participants – they can never be sure they accounted for everything that might matter.

So many factors that we haven’t studied much (and which are very hard to control for – gender, early experience, later experience, income, stress levels, personality, and a host of others – can make a huge difference in health outcomes, with perhaps the most important one being genes.

How much, for example, do genetic differences account for a relatively simple thing to measure such as cholesterol levels?

Well, it’s not as simple as it seems because we are all genetic mongrels.

So, for example, according to MyHeritage.com, I am 6 % Sardinian, which is a wonder, of course, because as far as anyone in my family can account for, I am a totally eastern European (Ashkenazi) Jew , although maybe that does account somewhat for my love of cheese and olives and other Mediterranean dietary specialties.

But this small amount of non-Ashkenazi genetic influence may matter a lot when it comes to figuring out my genetic response to cholesterol-lowering medication, or how my HDL levels (high) might interact with my LDL levels (also high).

It would be a very rare study, however, that would try to pare out my genetic difference from say another Ashkenazi Jewish gorgeous brilliant man similar to myself in every way except, hey, not even slightly Sardinian.

And there are of course dozens, probably hundreds, of genes that interact with each other and influence cholesterol metabolism.

But it’s probably even more complicated when it comes to cancer risk and cancer prevention because there are thousands of genes that have some role to play in cancer risk, all of which co-exist and interact in the soup that is our chemical make-up.

So it should be no surprise at all that in a recent study published in The Journal of the National Cancer Institute looking at how Vitamin E supplements might influence cancer risk, the researchers concluded that variation in one gene – one lonely gene – determined something very important if you had bought into the hype about vitamin E and were taking it as a supplement, namely, that depending on which variant of that gene you had (there are 3 variants, apparently), you either had a heightened or a lowered risk of getting cancer as a result of consuming more vitamin E.

That’s right: according to this study, if you take vitamin E supplements, one variant of a single gene can raise your risk of getting cancer as a consequence, while if you happened to inherit its close cousin, vitamin E would help you lower your risk of cancer.

Bottom line is that all we know about preventing most illnesses – but especially cancer and cardiovascular diseases – is that not smoking, eating a good diet, staying active, drinking moderately, and a couple of other lifestyle habits can lower – but not eliminate – the risk of getting those conditions.

When we try to tip the scales by adopting one or two easy tricks – usually something digestible, of course, because it’s easy to eat and drink, not so easy to do something more active – we are as likely to make things worse as we are to make them better.