After about 5 months of paleo, my wife has finally decided to take the plunge and give it a try to join me. She's coming from a very SAD diet (as did I). She's got a strong sugar addiction, has always loved Mountain Dew, etc...
So today (day 5 for her) she's experiencing a strange pain in her lower back and down through the back of her legs. She describes it as "it feels like my nerves are shrinking, they are too short - it pulls all the way down from my back to my heels".
I'm bringing this question here because I experienced something very similar about 1 week into my paleo transition. At the time I attributed it to the extra exercise I was doing. However, her description of the pain is almost identical to what I felt, and she's not doing any extra exercise right now - she's only really changed how she eats/drinks. My pain lasted about 3 days. It was VERY uncomfortable. I'd find myself curling into a fetal position at night to try to stretch my lower back and back of my legs. Laying flat or standing up just hurt.
Any ideas how a paleo transition could cause this kind of thing? I haven't seen any other questions or reports of this...
The first time (!) I transitioned, I felt major flu-like symptoms including achy muscles. Also, because I went from regular coffee to decaf (cold-turkey), all my little caffeine-related aches and pains screamed for more caffeine until they were flushed away - joints and tendon-like places.
I would guess that you're experiencing some sort of withdrawal from some food or chemical that was a regular part of both your diets. If you experienced the same pain and it went away, it's likely that hers will too.
That said, I hope that someone with more medical knowledge answers this question!
P.S. This might be a good question to ask Robb Wolf.
This could be indicative of an electrolyte imbalance as this sounds like musculoskeletal cramping. She may be mobilizing water and losing sodium and potassium along with it. I would suggest increasing water intake and keeping a food log (such as Fitday or Nutrition Data) for a few weeks/until eating patterns are well established. Compensating for electrolyte losses is important. It might also help to include offal and higher sodium/potassium foods in the diet in the short term.