Netflix’s ‘You Are What You Eat’ uses a twin study. Why studying twins is so important for science

A brand new Netflix documentary, “You Are What You Eat,” showcases units of similar twins as they undertake totally different diets. For eight weeks one twin follows a vegan weight loss plan whereas the opposite one follows an omnivorous weight loss plan. The experiment is compelling as a result of, being genetically similar, the well being of every twin could be very comparable earlier than the trial.

I will not spoil the ending for many who have not seen it, however should you want the drab writings of lecturers over the glitz and glamor of Netflix, you possibly can learn the revealed paper in the journal JAMA Network Open.

The documentary underscores the extraordinary contribution twin research make to advancing our understanding of the world. However this goes effectively past evaluating totally different diets.

British polymath Sir Francis Galton first documented the placing similarities of twins in 1875, arguing this proved “nature” was an vital contributor to our inclinations and well being. Since then, twins have been used extensively in analysis. What’s it then that makes twins so particular, and the way do researchers harness the facility of twins?

Twins as comparisons for one another

The Netflix documentary highlights one vital characteristic of twins—they’re good for making comparisons. An identical twins share practically all of their genes, and normally develop up in the identical family, which means they expertise the identical parenting, education and so forth.

The documentary is an instance of a randomized controlled trial, the place individuals are chosen at random for some intervention (like a brand new drug) and people not chosen function controls (in drug trials they could get a placebo). Randomized trials are usually seen because the gold customary in evaluating what works.

We do not really want identical twins for such trials. In reality, relatively few trials use twins. However twins will help to make sure the therapy and management teams are as comparable as doable. That is particularly vital when there are few individuals. Within the Netflix research, there have been solely 44. With out twins, their outcomes would have been extra unsure.

For moral causes or simply sheer practicality, we will not at all times run randomized trials. That is the place twins will help us out. Say we need to know the impact of education on earnings, or the impact of smoking on developing lung cancer.

These questions, and plenty of extra, have been tackled by evaluating the variations inside units of similar twins (for instance, the place one twin smokes and the opposite would not).

By specializing in variations between twins, we remove genetic and customary household components, and may be extra assured about causality. Utilizing twins would not totally remedy the issue of omitted components, however it helps to cut back it.

Twins and heritability

Galton’s fascination with twins stemmed from desirous to know why we’re the way in which we’re. Is it our genes (nature), or is it our upbringing and private experiences (nurture)? His early observations had been casual, however finally researchers developed refined strategies to disentangle genes and atmosphere.

The primary strategy is basically to see whether or not similar twins, who’re genetically the identical, are extra comparable than fraternal twins, who on common share solely 50% of the gene variants that make us distinctive. If the similar twins are extra comparable, that signifies genes matter.

For instance, twin research have proven that round 40% of individual differences in personality may be defined by genes, together with as a lot as 80–90% of differences in height and weight on the finish of childhood.

Limitations and misuse of dual analysis

One disadvantage to twin research is that twins are a choose group, and findings could not at all times generalize to the broader inhabitants. Solely about 1.4% of births in Australia are twins.

Twin heritability research additionally depend on strong assumptions, like that the widespread household atmosphere issues to the identical extent for similar and fraternal twins. This may be overcome by specializing in identical twins reared apart, however these research are uncommon.

There has additionally been some misunderstanding and misuse of findings from twin research. Galton’s perception within the energy of nature led him to advertise eugenics, the thought of selective breeding to attain “genetic superiority”, which had devastating consequences within the twentieth century.

However our genes usually are not our future. Whereas a sure mixture of genes could increase the probability you are extraverted, who we develop as much as be is a sophisticated interaction between genes, upbringing and private experiences. Even issues with a genetic basis, like Alzheimer’s, are hardly ever sure to happen, and we will take actions to cut back our danger.

The way forward for twin analysis

Twin research have been carried out for many years, with more than 60 twin registries working world wide. In Australia, the biggest registry is Twins Research Australia, who’ve round 75,000 members.

With extra alternatives to hyperlink information, genome mapping, and advances in machine learning, what we will be taught from twins will solely improve sooner or later. And we will count on twins to proceed to play a key position in advancing our understanding of the world for a few years to return.

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