Another cry of wolf on autism

The road to medical understanding is pitted with confounding news headlines. Take one last week warning that women exposed to too much of the ubiquitous vitamins folate and B-12 during pregnancy face an increased risk of having an autistic child.
The research, out of Johns Hopkins University, is part of a quest to unravel the causes of autism. The provocative folate finding is a valuable clue, but the way the university publicised it was not useful and potentially dangerous.
For years, doctors have been urging women who are even thinking about getting pregnant to take folate in the form of folic acid supplements. In the United States, flour and other foods are fortified with folic acid as well. Getting too little is associated with serious and sometimes fatal birth defects. Furthermore, earlier studies showed that too little folate increased the risk for autism.
Making matters more complicated, blood levels of folate depend on genes that influence folate metabolism.
Columbia University epidemiologist Ian Lipkin, who is an author of a study connecting too little folate to autism, said it’s possible that there’s a risk at either extreme, but scientists won’t know without more data. His finding, announced in 2013, was part of a study of more than 100,000 Norwegian women and their children. Lipkin and his colleagues are gathering data on genes, drugs taken during pregnancy, supplements, evidence of infections and other variable that might be connected to autism risk.
A number of studies have shown that genes have something to do with autism, but Lipkin says that doesn’t mean that autism is inevitable even in people who are genetically predisposed. Sometimes there’s what he calls a gene-environment interaction -- a situation where genes pose more or less risk depending on diet or other conditions. That’s the case in several other diseases, such as phenylketonuria, which can lead to severe brain damage, but only if affected children are exposed to phenylalanine, an amino acid present in many foods.
Lipkin’s results linking autism to low folate come from Norway, where flour isn’t routinely fortified with the nutrient. Those who took supplements were 40 percent less likely to have an autistic child. (Estimates of the rate of autism vary, but some consensus has formed around a rate of 1 in 68 people.)
The more recent study, suggesting a risk from too much folate, was carried out on 1,391 women and their children in Boston. The researchers examined blood levels of folate and asked about supplement use. They found that about 10 per cent of the subjects had unusually high levels of folate right before giving birth – about four times the level considered adequate. Those women were more than twice as likely as the others in the study to have autistic children. A few women had very high levels of vitamin B-12 and they, too, had a higher risk. Those with unusually high levels of both B-12 and folate had a huge risk – 17.6 times the average rate.
Those findings weren’t presented in a peer-reviewed scientific paper, but were discussed at an autism meeting last week and publicised in a press release titled, “Too much folate in pregnant women increases risk for autism, study suggests.” Despite the alarming headline, lead author Danielle Fallin said the news shouldn’t have been taken to mean that people should stop using the recommended supplements.
It’s not clear whether the women at the high end were getting too much folate by way of supplements or fortified foods. Fallin said she thinks genetic differences are likely to play a bigger role. She said the results don’t tell them whether the high folate levels or high vitamin B-12 caused the autism risk, or whether certain genes led to the high folate levels and increased autism risk through some other mechanism.
Lipkin said he hopes to get more than just statistics from his project. If the data show a drug or gene or supplement is associated with autism, he wants to know how it works. That’s important, given how much health advice is based on statistics without an understanding of how foods or extra vitamins or even exercise affect the human body.
It will be fascinating to see how genes, folate and B-12 interact to influence brain development, but until the scientists figure it out, they need to exercise more caution in their publicity campaigns. History tells why.
Lipkin was among those who helped debunk the 1998 claim that autism was tied to childhood vaccines. Subsequent investigation revealed that the original vaccine paper was based on fraudulent science. But to his continued frustration, he said, many people still avoid getting their children vaccinated. Health myths, once established, are nearly impossible to dislodge. - Bloomberg View