php - How to fix memory leaks in Magento related to load() method?

I'm importing data(products, customers, and orders) from a Magento store to another Magento store.

For example, when I try to import the products, I need to load the product to check if it already exists and use some attributes of the loaded product. I'm using the method Mage::getModel('catalog/product')->load($sku) and I run the script using command line.

Something like: $ php -f shell/mymodule.php

The problem is that Magento doesn't stop to increase the memory usage when I use the load() method in a loop.

foreach ($result['items'] as $item) {
     echo $index . ' - Memory: ' . memory_get_usage() . "\n";

     /** @var Mage_Catalog_Model_Product $product */
     $product = Mage::getModel('catalog/product');
     $product->load($product->getIdBySku($item['sku']));

     $product->getOptionInstance()->unsetOptions()->clearInstance();
     unset($product);
     gc_collect_cycles();

     $index++;
}
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• 1 - Memory: 28147376
• 2 - Memory: 34600320
• 3 - Memory: 34661976
• 4 - Memory: 34721128
• 5 - Memory: 34776600
• ...
• 10 - Memory: 35051216
• ...
• 100 - Memory: 40148904

In some cases I need to import thousands of products, which causes a memory overflow. As you can see in the script above, I also tried to run some optimization functions within the foreach but that isn't enough in performance to prevent memory overflow.

$product->getOptionInstance()->unsetOptions()->clearInstance();
unset($product);
gc_collect_cycles();
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I found a kind of solution that changes the Magento core, but it was made for Magento 1.4 and doesn't work for Magento 1.9 that I am using.

https://ringsdorff.net/2009/07/23/guest-post-fix-for-memory-leaks-in-magento/

Is there any effective solution to prevent the increase of memory usage in Magento 1.9?