Genewize http://www.genewize.com/ is a new company offering "100% Product Personalization from Your Personal DNA Assessment." They analyze your DNA to identify certain selected SNPs (single nucleotide polymorphisms) and use the data to tweak the ingredients of the nutritional products they want to sell you (containing everything from vitamins to spinach powder).

They previous offered a therapeutic skin health regimen linked to DNA-based skin health assessment. "First introduced in 2005, the Dermagenetics Skin Care System is the first comprehensive system of personalized (mass customized) skin care product manufacturing based on genetic testing that measures single nucleotide polymorphisms (pronounced "snips") in DNA."

Even if you don't know anything about the underlying science, it's easy to see some red flags on the website. Genewize sells direct to public. It is a multilevel marketing system where your own purchases are free if you enroll enough other people. The website offers the usual testimonials, which are rather vague - people claim to feel better, sleep better, have more energy, harder nails. They offer no scientific studies showing that people have better health outcomes when using their supplements. The fine print at the bottom has the usual FDA disclaimer: the products are not approved to diagnose, treat, cure, or prevent disease.

I picked one Genewize finding at random to analyze:

• Because people with SNPs on the ApoB gene have higher ApoB levels, they experience moderate increases in total cholesterol, LDL cholesterol, and triglycerides.

What they really mean is that on average, other people with the same SNPs are statistically more likely to have these increases. What good does it do to know that? We still need to do blood tests to find out what the individual patient's levels actually are. We do that anyway, without any need for genetic testing. And even if an individual has high cholesterol, there is no evidence that taking these supplements does any good.

Knowing a SNP is really not very informative. Genes don't operate in isolation. There may be other genes whose effects interact with this one. The expression of this gene may be affected by other regulatory genes that turn this gene on and off. Epigenetic factors and environmental influences alter gene expression. We don't know enough yet for SNP testing to be of any real clinical benefit. And the evidence for any benefit from nutritional supplements is shaky at best. If you don't need any supplements in the first place, genetic analysis to improve the mix of ingredients is pointless.

Genewize is just another in a long line of companies trying to make a profit off a scientific concept that is promising but is not yet ready for prime time. Stephen Barrett and I wrote about dubious genetic testing for Quackwatch several years ago and nothing has really changed.