Eating like a caveman is getting costlier.
That's dour news for the growing number of Americans adopting diets that mimic the eating habits of their hunter-gatherer ancestors.
The Bloomberg Protein Index, which tracks the prices of beef, beans, bacon and nine other protein sources, has jumped 28 per cent in the five years through May. The measure has increased 5 per cent this year, twice as fast as the gain for all food prices, as beef and pork got more expensive.
While more than half of American consumers are looking to eat more protein and millions are adhering to the Paleolithic, or Paleo, diet, the higher cost of the muscle-building amino acids threatens to curb their enthusiasm and send them in search of cheaper alternatives.
That reversal may hurt foodmakers and restaurant chains 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 researcher NPD Group, said in an interview. Consumers may switch to smaller sizes or substitute cheaper options such as chicken for higher-priced sources like beef, he said.
The idea of high protein consumption as a key to staying fit was popularised in the 1960s with Irwin Stillman's book The Doctor's Quick Weight Loss Diet. Robert Atkins followed in the 1970s and 1980s with diets designed to boost energy and drop pounds by limiting carbohydrates.
More recently in vogue is the Paleo diet, which encourages people to eat only whole, unprocessed foods like those available to humans in the Stone Age. About 1 million to 3 million Americans may have adopted the diet, according to an online study conducted by Hamilton Stapell, a professor at State University of New York at New Paltz.
Now, prices for some of the most common types of meat are surging this year. Pork has climbed as a virus killed as many as 8 million hogs, reducing supplies. Beef prices are up after years of drought shrank cattle herds to the smallest since 1951. Prices for eggs and dairy products also have gained in the past 12 months as export demand grows.
More than half of adults want more protein in their diets, according to a March study from Port Washington, New York-based NPD. The per cent of adults who look for "protein" on nutrition labels rose to 24.9 per cent in 2013, the highest since at least 2004, the study shows.
Consumers are experimenting more with non-meat protein, as well, in part to find cheaper sources of the nutrient, according to the study. Along with obvious choices such as yoghurt, nuts and seeds, more are flocking to pea powders, quinoa and lentils.
The Bloomberg Protein Index includes prices for ground beef, eggs, whole milk, pork chops, whole chicken, sliced bacon, dried beans, cheddar cheese, sirloin steak, whole turkey, creamy peanut butter and ham from the US Bureau of Labor Statistics. Beef, pork and ham have gained the most this year, while turkey, eggs and peanut butter prices have fallen.
An adult weighing 180 pounds needs about 54 grams of protein a day, while a 130-pound person should have 39 grams, according to the US Department of Agriculture.
Eating more protein and fat can aid weight loss by making people feel better satiated and helping them avoid snacks, said Domingo Pinero, professor of nutrition and food studies at New York University. Dieters should proceed with caution as some can develop kidney or cardiovascular complications from too much protein, he said.
Almost all Americans, as long as they're eating sufficient calories, are probably getting enough protein, Pinero said. About 35 per cent of adults in the US are considered obese, according to the Centers for Disease Control and Prevention.
"There's no such thing as protein deficiency in this country," he said.