​NEW YORK – Move over, Irwin Stillman   and Robert Atkins — eating like a caveman is way more vogue.

The Bloomberg Protein Index, which tracks the prices of beef, beans, bacon and nine other protein sources, jumped 28% in five years through May and so far has increased 5% this year, “twice as fast as the gain for all food prices, as beef and pork got more expensive,” notes the news source.

With beef prices already high, consumers who are looking to add more protein to their diets by following the Paleolithic, or Paleo, diet, higher costs may “send them in search of cheaper alternatives,” writes Bloomberg, a reversal that may “hurt foodmakers such as Kraft Foods Group Inc. and restaurant chains like Taco Bell that are advertising more protein-heavy fare.”

“For people who wanted to add protein just because it’s healthy, if they start to get sticker shock, they might pull back a little bit,” Darren Seifer, an analyst at NPD Group, told Bloomberg, noting that consumers may substitute beef for cheaper options such as chicken.

Bloomberg notes that pork prices are climbing due to reduced supplies (a virus has killed as many as 8 million hogs) and beef prices are up after years of drought. Prices for eggs and dairy products are also increasing alongside export demand.

Higher meat costs make it “a challenge to do more with protein today,” said Panera Bread Co. COO Scott Davis, who came up with the chain’s protein-rich egg-and-ham breakfast sandwich while dabbling in the Paleo diet, notes Bloomberg.

Foodmakers are also jumping on the high-protein bandwagon. Kraft’s Oscar Mayer introduced P3 Portable Protein Packs with meat, cheese and nuts earlier this year. Marketing Vice President Joe Fragnito told Bloomberg that the company experimented with other high-protein foods such as salads, but most people think of meat, cheese and nuts as “the original sources of protein.”

Kellogg Co. is also planning to introduce new products that point out the protein value of milk and cereals. “Consumers are seeking protein,” said CEO John Bryant. “We’re talking about the benefits of protein that comes with cereal and milk, which is very much on track with the consumer today.”