Marion Nestle writes about the NEJM papers I’m losing my s#$t over:
(a) Does too much dietary sodium cause high blood pressure? Answer: an unambiguous yes (although not necessarily in everyone).
(b) Are public health recommendations to reduce salt intake warranted? I think so, but others disagree.
(c) If so, to what level? Although virtually all committees reviewing the evidence on salt and hypertension view public health recommendations as warranted, and advise an upper limit of about 2 grams of sodium (5 grams of salt, a bit more than a teaspoon (see table from the Wall Street Journal), these too are under debate.
These recommendations are strongly opposed by The Salt Institute, the trade association for the salt industry, its industry supporters, and some groups of investigators.
I’m not sure I would be as strident about (a) as she is, but fine. I agree that excessive salt intake is bad for people with hypertension. To support (b), though, you have to believe that the study I just talked about is wrong. You have to believe that the very low sodium recommendation is good for you. I totally disagree that this appears to be the case. In (c), she puts her money where her mouth is, saying 2 g is the sweet spot, even though that’s associated with a higher level of death and cardiovascular events than a diet with more salt. Why? I don’t know. She doesn’t provide evidence supporting that recommendation.
There are two other supporting assertions that she makes that I want to discuss.
The first is about conflict of interest. Nestle singles out Suzanne Oparil, who wrote the editorial in the NEJM, as being conflicted because she’s received grants and fees from companies making anti-hypertensive drugs and The Salt Institute. I’m of a number of minds about that. The first is that I don’t have any financial conflicts of interest here, and I interpreted the research the same way. I’m not in the pocket of Big Salt, and I don’t have any grants from such companies. I can judge the research without the editorial. It’s what I wrote earlier.
Additionally, you can’t cherry pick your “conflicts of interest”. For instance, Nestle appears to have a problem with this conflict of interest. She had a problem with the conflicts of interest in the study of “fruits and vegetables” I wrote about. But she had no problem with the funding or conflicts of interest in a study of the nutritional value of organic foods whose results she appears to agree with.
There are also conflicts of interest beyond financial ones. There are professional ones, where we favor results that support our own work. There are ideological ones, where we favor results that support our world view. These are just as important, but we only ever focus on the financial ones.
The second assertion I’d like to highlight is that it’s a “good idea for just about anyone” to cut down on salt. She believes that sodium is so pervasive in our food that we all need to reduce our consumption. I don’t think that’s clear. The average American sodium intake is 3.4 g per day. Given that there’s less room below that than above, it’s very likely that more Americans are consuming less than 3.4 g a day than are consuming more. And 3.4 g is at the low end of the 3-6 g that was the baseline in this study. Where is the evidence that most Americans need to cut back on their sodium?
I agree that people who are consuming excessive sodium need to consume less. I’m not convinced that anything lower than 3 g a day is warranted. It seems like most Americans are in a safe zone. Why are we pushing people en masse to eat less?
