Or how much money you make on retail versus food service? So again, as this balances back out and goes more to food service, we're just loading up food service trucks instead of loading retail trucks, and we'll see a dip in volume from the services side and retail, and we'll see more throughput going to the food service distributors. So you're right, there was a lot of reports in the press about food shortages right after the spike of emptying out the grocery stores.
You had the early people that jumped in and were in panic mode right away. So we're not expecting any major moves in healthcare as we move throughout the year.Our next question is from Nate Crossett from Berenberg. And then just in terms of the margin improvement for the quarter, the up 130, can you have a sense as to how much of that was directly tied to COVID?Yes. Our incredibly diverse portfolio enables us to minimize volatility from these shifts.
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So that's one place in our supply chain where you can count on, because that space is dedicated to have fixed commitments. And one of the things, I think more of the news has been around the beef and pork sites that have seen higher instances to COVID. And then if I could just quickly ask about dairy. Now I'd like to take a moment to discuss our outlook for 2020. In the first quarter, our Global Warehouse same-store pool generated total revenue growth and NOI growth of 6.8% and 11.1%, respectively, on a constant currency basis. No, it was just -- it was a massive tug and the whole supply chain has to react overnight without warning to replenish the forward node. The events of the past few months have been unprecedented, and uncertainty remains high as major sectors of the economy remain significantly slowed down. We really are kind of agnostic as to whose truck we're putting it on. Or is there something else we should be thinking about in terms of where your guidance landed with the 2 items that you did point out in the release sort of going and get the other way?Yes. Major market distribution centers are supplied by production advantage sites, which are usually either attached or adjacent to food manufacturing facilities. As a result, throughput at our retail distribution centers increased significantly, resulting in higher services revenue at these sites.As I mentioned earlier, we also saw an increase in product through other nodes of the supply chain, mainly our major market distribution centers. But as you can see, with that volume going through our full boxes, we converted it.Okay.
This was partially offset by higher property taxes, property insurance, and increased sanitation costs from COVID-19.Same-store global warehouse services revenue for the first quarter grew 5.4% year over year or 7.5% on a constant-currency basis. On the service side, I'm not sure, but you really touched on labor. And they got the grocery stores replenished. Finally, we want to remind you that food manufacturers and retailers are still working hard to adjust to this unprecedented situation, and we will work diligently to continue to support them.Over the long term, barriers remain high for new development, while customer relationships and an integrated network remain more important than ever. Additionally, our churn rate was approximately 3.4% of total warehouse revenue. So that's put a little bit of headwind in the overall results. Today, we'll provide updates on our actual performance, as well as certain metrics on a constant currency basis. There might be specific items that run out, that run shorter, but there's a lot of inventory. We would like to thank you for joining us today for Americold Realty Trust first-quarter 2020 earnings conference call.
We are proud of our customer service during this COVID-19 pandemic.Corporate SG&A totaled $37 million for the first quarter of 2020 as compared to $31 million for the comparable prior year quarter. You had the early people that jumped in and were in panic mode right away. Our first quarter AFFO was $67 million or $0.33 per diluted share. And then just in terms of the margin improvement for the quarter, the up 130, can you have a sense as to how much of that was directly tied to COVID?Yes. Please proceed with your question.Just taking a couple of the topics that I've already been broached and maybe restating a little bit. During this call, we will discuss certain non-GAAP financial measures.More information about these non-GAAP financial measures and reconciliations to the comparable GAAP financial measures is contained in the supplemental information package available on the company's website.