Tangles and Tau
This time they looked closely at the events that take place when nitric oxide is restricted. They discovered that a nitric oxide deficit puts the brake on a series of enzyme reactions that lead to tau proteins in brain cells becoming destabilized and breaking away from the cytoskeleton (“cell skeleton” or scaffolding) of neurons. Tau provides structure for the cytoskeleton and is not supposed to be free in the cell. When it becomes untethered, accumulation in the brain follows. This causes harmful changes that lead to cognitive decline and memory loss. Commenting on their findings, Dr. Faraco said, "Our study proposes a new mechanism by which salt mediates cognitive impairment and also provides further evidence of a link between dietary habits and cognitive function." His colleague Dr. Iadecola added, "[T]he stuff that is bad for us doesn't come from a saltshaker, it comes from processed food and restaurant food. We've got to keep salt in check. It can alter the blood vessels of the brain and do so in a vicious way." The message is clear, but it's important to get things in perspective.No Need to Panic
For the study the mice were given more than eight times their normal daily salt intake. This would be the equivalent of humans ingesting 7.5 grams of sodium - more than double the average American consumption of 3.4 grams of sodium a day – which itself is quite high. An individual would have to be living on processed foods and restaurant meals to get anywhere near the equivalent of what the mice were forced to endure. Dr. Evangeline Mantzioris, program director of nutrition and food sciences at the University of South Australia, praised the research, but cautioned the salt intake of the mice was incredibly high and "we cannot with certainty say the same effect would happen in humans." Her fellow Australian, Professor John Funder, a leading neuroscientist at the University of Melbourne, went much further, saying, "Any extrapolation from mice on a salt intake of eight percent to the human situation...is grossly irresponsible in terms of science." The study is important, being the first to demonstrate a link between what the researchers called "excessive salt intake" and tau pathology, but it does no more than point to the possible impact of salt in humans.My Take
So, as often happens, more study is needed. I’m most concerned about salt’s potential impact on nitric oxide to the brain. I’d be interested to learn more, including some studies involving humans. But a mouse study with a mega-intake of salt doesn’t tell me much. I’ve always been a skeptic of the medical profession’s scary warnings about salt. For years, people with high blood pressure were told to give up salt. This was not an effective approach. I looked into this years ago, and only about ten percent of hypertension patients had a salt problem. For the other nine out of ten, giving up salt was useless (and very hard to do.) There are also one or two famous anticancer diets that demand a no-salt regimen, but this was not backed by studies. The diets came from respectable alternative doctors, but after fifteen years of writing about alternative cancer treatments, I’ve learned that opinions and theories far outnumber provable facts. Now we have a weakly supported claim that salt – really massive amounts of it – might contribute to dementia. At this point, I’m not going to change my habits, which are pretty moderate anyway. And as for salt-heavy processed, packaged and fast foods – it’s always good advice not to eat them. I don’t.