I’ve tried googling this, but maybe I don’t use the right terms. But consider two cases:
1 - You generally have a healthy diet, but you just got back from vacation - 2 weeks of rich foods and lots of sweets. Will your cholesterol and glucose numbers shoot way up?
2 - You’re a junk food junkie and you’ve got a physical coming up - how long would you need to stick to salads and grilled chicken to give you better numbers?
My gut feeling is that if you normally have a healthy diet, a splurge won’t cause a worrisome spike. Also if you live on fast food and snacks, it’ll take more than a couple of weeks to clean your system up. Answers and links would be most appreciated.
I presume it shows in bloodwork right away, depending on the biological mechanism.
you glucose level, for example, is dependent on the last few hours. Your A1c accumulates over a period of 3 months, so will be a rough average of the last 3 months if I understand the process properly. To affect the numbers, you would have to reduce glucose (and limit starch which converts to glucose slowly) for several weeks.
Some tests measure levels after a fast - this presumes it shows what your default level is when temporary spikes have been processed. That standard fasting is 12 hours, suggests that most spikes as a result of recent meals are leveled out in that time.
medicalnewstoday says:
Some dietary changes may cause minor reductions in cholesterol in as little as 4 weeks . Most people can expect to see the difference in a few months by following a heart-healthy diet.
The inference is that a bad dietary change for a couple of weeks can make a minor difference but to really affect the numbers requires a longer term diet change.
OTOH, something like PSA is mainly unrelated to diet as far as I know.
I remember looking up the A1c process when someone asked a similar question. I had surmised that blood cells probably died off over time, so the test would be front-end-loaded for recent activity. But in fact, from one paper I ran across, blood cells do in fact last 3 months and then die consistently without a lot of variation. So yes, the most recent dietary habits will add the most weight to a test, but not as much as you might think. I presume the A1c is a simplistic number that assumes the same behaviour all 3 months.
I had a very high cholesterol reading the year my blood test was right after Halloween. I told my doctor that half my calories in the preceeding two days has been from milky way bars, and we agreed to ignore the result. The next year my blood work was done when my diet had been “normal for me”, and the numbers we back down to “normal for me”.
So i think cholesterol, at least, responds extremely quickly to dietary changes, and my doctor seemed to agreed.
When my doc has me get blood drawn, she orders a variety of tests, I believe to monitor kidney and liver function. Since everything has been OK so far, I’m going to guess that those are long-term markers, like A1c mentioned by md-2000. And if I’d thought about it, I’d have remembered that glucose is a more immediate change, especially with TV ads about the continuous monitoring devices.
This all came to mind because I do have some bloodwork ordered and while my dietary choices in the last few months have been less than sensible, I have been making the effort to do better of late - even before the office called and told me I was due. I guess I’ll find out in a couple of weeks what damage I may have done. OK, maybe damage is too harsh a word, but I’m guessing my really good numbers from the last test may not be matched this time.