What I've heard (and this seems to make sense) is that each time your cells divide (meaning old ones die off and new ones take their place), the new generation is greatly affected by the food we eat.
It's the old "garbage in - garbage out" philosophy. When feeding your body junk, new cells are more likely to be weak or malformed in some way, simply because they don't have the optimum building blocks. Think of it like building a house from clumps of dirt vs. bricks. You can still build it but it won't be nearly as solid or last as long.
Anyway, if that theory is correct than it follows that when eating food that supplies the optimum building blocks humans need, with each new generation our cells will get stronger and healthier until we reach optimum levels of health.
Here's where I get confused though. I'm not sure if this happens in one go-round or over several (or many) generations of new cells.
My intuition tells me that it's probably a multi-generational process. At the same time though I think that when making a major switch in lifestyle, the first few generations of new cells will probably be impacted the most (major healing and regeneration will take place), after which things will level out over time for the finishing touches. I can't substantiate this though, and even though I've spent quite a bit of time trying to research it on the internet I haven't been successful at finding conclusive results one way or the other.
Whether it happens quickly or slowly though, it's very exciting to realize that the food you eat can have such a positive impact on your health! No you don't have to take a pill to be healthy... simply eat a juicy, mouth-watering, grass fed burger!
While I'm on this subject, another point I want to address is this idea that our bodies completely regenerate themselves every 7 years or so (which I've seen posted all over the internet). I looked high and low for some confirmation of this and I'm sorry to say I didn't find any. What I did find however was this article which answers the question, "How old is my body if the cells keep renewing themselves?" You can find the article at: http://www.theregister.co.uk/2007/02/17/the_odd_body_cell_age/.
Another interesting reference I found was this list of life spans of common human cells, found on Answer.com:
Cell Type -- Lifespan
- Granulocytes (a type of white blood cells) -- 10 hours to 3 days
- Stomach lining cells -- 2 days
- Sperm cells -- 2-3 days
- Colon cells -- 3-4 days
- Epithelia of small intestine -- 1 week or less
- Platelets -- 10 days
- Skin epidermal cells -- 2 - 4 weeks
- Lymphocytes -- 2 months - a year
- Red blood cells -- 4 months
- Macrophages -- months - years
- Endothelial cells -- months - years
- Pancreas cells -- 1 year or more
- Bone Cells -- 25 - 30 years
According to this, since I converted to a paleo lifestyle about 6 weeks ago my granulocytes and stomach lining have replaced themselves 21 times or more, my colon and small intestine about 8 times, my platelets about 4 times, and my epidermis is into its second round.
It's interesting to me that the cells that replace themselves the fastest are the ones involved in digestion and absorption of nutrients. If my theory holds true, these cells have already undergone a vast metamorphosis from being inefficient and possibly compromised cells to healthy and happy cells. Also, because they've undergone several generations, I feel like at least these parts of my body are well on their way to optimum health!
By the way, I'm not an expert on paleo living or nutrition. So feel free to add to what I've laid out here, whether you concur or not. It's all good and I'm happy to learn more :)