Amazon-Whole foods $13.7 billion deal rocks the stock market on Friday  

Amazon is spending $13.7 billion to buy Whole Foods, but its damage to the stock market has already been in the tens of billions.

Just among the biggest losers in the retail and food categories in the S&P 500, the market cap destruction for just 20 stocks was $37.7 billion Friday.

Amazon has been an unparalleled disruptor for the retail industry, and the fact it is now turning its focus to groceries has sent a chill through a whole new category. Even the food companies supplying the stores have been slammed.

Cowen analysts say the grocery business breaks down into three categories and Amazon is attacking all three. Perishable food, like meat and milk; non-perishables, like cereal, cereal and pasta, and consumer products, like baby products, dish detergent and shampoo.