The company said its Gold Investor Index fell to 53 in May, an eight-month low, versus 58.6 in April.

In April, the gauge jumped to 58.6, its highest level in 16 months as investors took advantage of bargain prices after bullion's historic sell-off.

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A number above 50 indicates more buyers than sellers. While net buying by the firm's mostly buy-and-hold type customers is seen as bullish, net selling might suggest individual retail investors are exiting the gold trade. BullionVault says it has 47,500 users worldwide.

"Private investors remained positive on gold, although the bearish sentiment really accelerated in May," said Miguel Perez-Santalla, Vice President at BullionVault in New York.

However, retail investors are likely to reenter the market as they have been keeping their cash in their accounts for future opportunities, said Perez-Santalla.

BullionVault's data showed cash holdings in its customers' accounts rose 6 percent in May.

In the weeks after bullion $225-per-ounce-drop between April 12 and 16, individual investors could not get enough gold coins and bars at bargain prices as they flew off the shelves of physical dealers.

In May, however, demand from physical gold buyers started to show signs of slowing as premiums of gold and silver coins and bars began to come off their peaks.

Spot gold rose around 2 percent to $1,410 an ounce on Monday. Bullion was still nearly $150 below its level prior to its mid-April drop.

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