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Ancestry? Health? What do you want to use your DNA for?

Squirrel scientist looking at direct-to-consumer genetic test results

What Can 23andMe, AncestryDNA or other genetic test tell me?

Direct-to-consumer genetic tests can tell you all sorts of interesting information about who you are: your ethnicity and physical characteristics (‘traits’), where you come from (your family tree and geographical origins), and your health (disease risk, lactose tolerance, and more). They can also be used to help you find and connect with your living relatives. What you might learn about yourself depends on which provider you choose. 

Three of the most popular providers are Ancestry, 23andMe, and FamilyTreeDNA:

Ancestry.com is the largest provider with over 14 million customers. Their ‘AncestryDNA’ service is focused almost exclusively on helping you learn about your ethnicity, learn about your ancestors’ relatively recent geographical origins and migration, and helping you find your living relatives. Unfortunately, they limit their analysis to ‘autosomal’ DNA, and do not currently offer analysis of ‘mitochondrial’ DNA or ‘Y-chromosome’ DNA (if you are male). Mitochondrial and Y-chromosome DNA is passed much more faithfully from parent to child than autosomal DNA, allowing for a much deeper tracing of your maternal and paternal ancestral roots tens of thousands of years into the past. Lately Ancestry has begun introducing some information about your physical traits in their tests, such as predicted facial features and taste in food. 

If your priority is finding your living relatives and/or learning detailed information about your relatively recent family history (reaching back maybe 4-7 generations), Ancestry is likely the best option for you. In addition to having the largest customer genetic database, they also have a massive database of genealogical records (such as marriage and death certificates). If these aren’t your priorities, 23andMe may be a better choice.

23andMe.com is the second largest provider with over 10 million customers. It is also the most innovative. They offer the most comprehensive (and scientifically-validated) health-related reporting available, including disease risk and carrier status for various inherited genetic diseases, as well as the broadest menu of physical traits. Accordingly, they are also the only provider that is FDA regulated. They also offer ethnicity and ancestral information similar but not identical, to Ancestry.

Ancestry’s strengths lie in predicting your ethnic composition and recent ancestral origins, and in finding your living relatives. Although 23andMe offers ethnicity estimates and a family-member finding service, they lack the genealogical records database and larger size of Ancestry’s customer genetic database. However, 23andMe is better suited to helping you learn more about your much deeper ancestral origins and geographical migrations. This is because in addition to ‘autosomal’ DNA which can be helpful for tracing ancestry back as far as 7 generations, they also test your ‘mitochondrial’ DNA and ‘Y-chromosome’ DNA (if you’re a male) which can be traced tens of thousands of years into the past.

FamilyTreeDNA.com is another relatively popular direct-to-consumer genetic test provider, but its customer database is the smallest of the three (somewhere in the low millions). They claim to have the world’s largest Y-chromosome DNA database (which is useful if you are a male and wish to trace your paternal ancestral migration pattern back tens of thousands of years), and the most specialized Y-chromosome testing.

Like 23andMe this company offers ethnicity estimates, relative finding capabilities, and deeper ancestral tracing through Y-chromosome and mitochondrial DNA analyses, but they have a smaller customer database and don’t offer any health or physical trait insights. Like Ancestry this company offers family-tree building tools, but they lack their much larger genetic and genealogical databases.

Although 23andMe is the only provider to offer health insights to their customers, they are not the only ones able to do so. Each of the above providers collect an enormous amount of raw genetic data on their customers. This data can reveal much more about you and your health than any of these companies currently report, including genetic insights that have yet to be uncoveredthis poses a significant privacy risk.

Why don't providers offer identical tests? or produce identical results?

If you sent your DNA sample in to each of these companies you would receive different reports back, and where those reports overlap, they will likely draw slightly different conclusions. This is a consequence of four significant differences between these providers:

All providers use the same underlying genetic sequencing technology to run their primary analyses (a technology developed and provided by Illumina). But each examine a different collection of genetic markers (common variations in your DNA) known as “single nucleotide polymorphisms” or SNPs. While there is some overlap in the roughly 700,000 markers that each test evaluates, there are also significant differences, including the presence of tens of thousands of company-proprietary SNPs. Each SNP offers its own unique piece of information about you. 

When it comes to ancestry, use of mitochondrial DNA and Y-chromosome DNA allows for tracing your maternal (mother-to-mother) and paternal (father-to-father) lineages back tens of thousands of years. But it is not very useful for finding living relatives. In contrast, autosomal DNA analysis is the best means of finding relatives and building a family tree, but it is limited to roughly seven generations of ancestral tracing. This is because you are likely to share no more than 1% of your autosomal DNA with any given ancestor at seven generations back.

The size and composition of customer databases differ, and therefore so will their results – and this doesn’t just apply to finding family members. Existing customer data is also used to help develop and continuously refine their genetic analysis algorithms, so your ethnicity and other test results depend in part on who else is included in their database. For example, if you happen to be part of an underrepresented ethnic group, your ethnicity results will be less accurate than they would be otherwise and are more likely to vary between providers.

As opposed to offering ancestry or physical trait information, providing test results of a medical nature requires stringent validation and FDA approval – a very expensive and time-consuming process. Even though the raw data of Ancestry and FamilyTreeDNA does contain some of the health-related SNPs used by 23andMe to generate their customer reports, these companies choose not to report on them.

In addition to capitalizing on a massive and expanding body of publicly available genetics research, each provider also pursues their own in-house research agenda to improve their existing algorithms, to find new insights to report to their customers, and to find new ways to monetize their customer databases.

Can any of these tests offer me practical advice on my health?

The ultimate promise of consumer genetic testing is to empower consumers to make better health and wellness decisions through truly personalized lifestyle, diet and medical choices. We’re not quite there yet, but 23andMe is starting to accumulate an impressive array of tests that could offer real-world value to some customers. Being FDA regulated they are also under the most scrutiny. You can find their current test menu here.

You should be skeptical of the results you get back

There is an abundance of research that connects or associates specific genetic variations (SNPs) in DNA with all sorts of traits: eye color, disease predisposition, sexual orientation, behavior, longevity, body-weight, drug addiction, and on and on. Some of these associations are scientifically well-validated (large studies that have been independently verified), and some of them are not. Some of these associations have been studied in diverse populations (that include people similar to you – which is important), and some of them have not.

Associating a genetic variation (or more often a collection of variations) with, say, an enhanced risk of diabetes doesn’t mean that the genetic variation helps cause diabetes. While it could mean that, more likely it means that this variation just tends to be inherited by people who also tend to get diabetes for some other reason.

You should be very skeptical of any lifestyle advice that you receive

Even 23andMe offers some dubious health recommendations in their reports, or perhaps more precisely, offers information in a way that might be easily misunderstood by their customers. For example, they offer customized dietary advice according to your ‘genetic weight’ (your predicted body weight based on your genetic ‘peer group’ for whom they know height and weight). You can find a sample report here.

Putting aside the fact that this form of dietary advice is hardly personalized, is it even sound? For example, is it rational to expect that reducing your consumption of red meat would result in an X% decrease in your body weight? Their sample report appears to say so (“These habits made the biggest difference in people with your genetics”). But, this is only an association. Could the reduced body weight of your red meat-avoiding genetic peers be explained by something else instead? Perhaps these people tend to be more health conscious or physically active, or perhaps they are more likely to count calories and avoid fast food. What if you took this advice and substituted the red meat calories in your diet for something else, would your body weight decrease as they imply – or might it increase? It would depend on what you decided to eat in its place.

Where can I get more information about my test results? Or re-analyze my raw data?

If you want to dig in a bit deeper into your data you might use the open source SNPedia resource to learn more about some of the specific SNPs that appear in your results. But this resource is not comprehensive (it contains information on only 110,000 SNPs), nor is it necessarily well vetted or up-to-date since it is maintained by a small community of volunteers.

Alternatively, you could upload your raw data to one of the many websites that offer to re-analyze it for you to tease out some of the many other insights that remain buried within your genetic code. But buyer-beware! It’s not clear which of these secondary providers have the expertise to re-analyze your data. There is also no regulatory oversight of these companies, nor any way for consumers to verify the information they get back. Uploading your raw data to these third-party companies could also constitute a major genetic privacy risk.

If you are eager to use your raw data to learn more, you might consider the bare-bones Promethease service which dutifully applies the SNPedia database to your data set. However, it’s not very user friendly and obviously suffers from the same limitations as SNPedia. We do like how conscious they are about safeguarding their customers’ genetic privacy (you can find their privacy statement here). Nevertheless, if you decide to proceed you should consider taking steps to anonymize your interaction.

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