To answer and clarify some general questions from the comments: (Sleeper Agent Get Burned)
I'm not expecting to rain on anyone's parade. There is an inevitable pull to the side of quasi-scientific posturing in the paleosphere. Sometimes I just like to yank back. The even-tempered bloggers (Paul Jaminet and Stephan Guyenet) have large blogrolls. I do not. Like Kurt Harris, I'm a bit more on the cranky side, and I consider my blogroll to be something of an endorsement, meaning I often find valuable information and interesting ideas on those blogs without a huge amount of garbage. Of course nearly all of those on the blogroll have published something I vehemently disagreed with. That's pretty cool, of course. Differing opinions open the mind. When it goes too far into the land of obvious pseudoscience and woo or dangerous advice or the endorsement of that, it is no longer my cup of tea, and I drop the blog. I've dropped several blogs in the past but I just haven't mentioned it. Sometimes, though, not mentioning or pointing out something is taken as tacit approval.
As to Gary Taubes' petition, I merely have a problem with the very specific nature of the treatise. He basically asks us to sign a petition endorsing his particular theory of obesity, which involves insulin and the adipose tissue as the main regulating mechanism. It should be obvious to anyone reading my blog that I don't agree with that theory and feel it has been disproven. That doesn't mean I don't think insulin is involved, or that low carb diets aren't helpful, or that I'm eating a 90% carb diet of unsalted potatoes. I just wish Gary had been a tad less specific - more of a "let's study low carb diets and not be afraid of fat" petition, and "let's not give up on obesity just because most people fail at diets." I'm 100% in favor of not giving up on obesity.
As to supplements, I take some myself and have written extensively about them. However, I don't think they are the be-all, cure-all, and used pharmacologically, a risk-benefit analysis ought to be taken, though the full data will never be known. In addition, supplements won't cure a crappy diet, crappy sleep hygiene, and complete other lack of self-care or stress reduction. I like Stumptuous' rant for that reason. It's a step back. Let's evaluate as best we can the safety and efficacy, and more often than not the shiny new supplement with the promising data becomes the harmful supplement when more data is gathered. The same is true for prescription pharmaceuticals.
Speaking of supplements, vitamin D is a tricky one. It was the paleosphere darling for a while. The unheralded sunshine vitamin the dermatologists wanted to take from us with their creams and sun hats. And while getting a certain amount of D to keep from being deficient is clearly helpful, and it seems there is decent data to show that "deficient" for the IOM may be too low when one considers cancer data and being prudent, it is also clearly problematic to go for the gold and have the highest vitamin D level around (not that anyone recommends that). In the past year or so, the promising pro-Vitamin D papers have been followed by some disappointing findings. Some very thoughtful editorials have been written in JAMA and Nature on the subject (not even by dermatologists).
I've posted on vitamin D and depression before (here and here). It seemed very promising when I read the articles at the Vitamin D Council. But when I looked up the actual scientific studies, there wasn't much at all. I could honestly pull together a sober recommendation that there are plausible reasons to think D levels would effect mood, and since it also plausibly could prevent cancer and help bones, seems reasonable to stay in a nice healthy range.
But of course, I keep an eye out. And this week on twitter a new paper came to my attention from my own alma mater (1). This paper is a population study of vitamin D levels and depression scores. 5 previous population studies have been done, with 3 showing correlations between low levels and depression, and two showing no correlation.
As I've explained before, the brain needs vitamin D for neuronal repair. As depressive disorders can be progressively neurodegenerative, in a similar way but with far less global neuron damage as dementia, it is very plausible that low vitamin D levels could hasten or worsen an existing depression, or perhaps even cause depressive symptoms. Indeed, low levels of vitamin D have been associated with increased inflammatory markers, and inflammation is associated with depression.
The current study is the largest population-based study to date, of 12,600 some odd relatively healthy patients at the Cooper Clinic in sunny Dallas, Texas between 2006 and 2010. The sample was 68% men with a mean age of 52. All participants had baseline 25 (OH) vitamin D (actually D2+D3, though D2 levels are typically negligible in my experience unless someone is taking a prescribed D2 supplement) and had level of depression tested with a standard 10 item questionnaire.
Patients with a history of depression were analyzed separately. There were significantly more women in that group, as well as a significantly higher number of people with history of diabetes, cardiovascular disease, and cancer. Those with a history of depression had a lower education level, were less likely to exercise, and had a higher BMI. Age, smoking history, and vitamin D levels were not significantly different in the patients with a history of depression compared to those without.
Among these 12,600 folks, low vitamin D (less than 20 ng/ml) was very common - 50.7% of the sample was affected. Those who exercised regularly were much more likely to have normal vitamin D levels than those who did not. Those with high levels of vitamin D were significantly less likely to have current depression symptoms than those who had deficient vitamin D. The effect was stronger in the group with prior history of depression, and was also stronger in October to March than in the sunnier times of the year.
The study was limited by the observational nature and the relatively brief screening tool used to diagnose depressive symptoms. But the findings are interesting, and certainly it is still reasonable not to be deficient in Vitamin D, whether you are depressed or not.
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