Many of us consciously eat a high-protein diet, with protein-rich products readily available, but how much protein do we really need? And does it actually help us lose weight?
In the early 20th Century, Arctic explorer Vilhjalmur Stefansson spent a collective five years eating just meat. This meant that his diet consisted of around 80% fat and 20% protein. Twenty years later, he did the same as part of a year-long experiment at the New York City’s Bellevue Hospital in 1928.
Stefansson wanted to disprove those who argued that humans cannot survive if they only eat meat. But unfortunately for him, in both settings he very quickly became ill when he was eating lean meats without any fat. He developed “protein poisoning”, nicknamed “rabbit starvation”. His symptoms disappeared after he lowered his protein intake and he raised his fat intake. In fact, after returning to New York City and to a typical US diet with more normal levels of protein, he reportedly found his health deteriorating and returned to a low-carb, high fat, and high protein diet until his death aged 83.
His early experiments are some of the few recorded cases of high protein intake having extreme adverse effects – but despite soaring sales of protein supplements, many of us are still unsure how much protein we need, how best to consume it, and if too much, or too little, is dangerous.
Despite obesity rates doubling over the past two decades, we’re becoming increasingly conscious of what we’re eating. In recent years many of us have swapped white bread for brown and wholemeal bread and full-fat milk for skimmed. Taking centre stage in our health kick is protein, with protein balls, bars and enhanced protein versions of staple products, from cereals to soup, dominating supermarket shelves. And with the global protein supplements market valued at $12.4bn (£9.2bn) in 2016, it’s clear we’re buying into the idea that we need as much protein as possible.
But some experts now argue that foods with inflated protein (and prices) are a waste of money.
Protein is essential for the body to grow and repair. Protein-rich food such as dairy, meat, eggs, fish and beans are broken down into amino acids in the stomach and absorbed in the small intestine, then the liver sorts out which amino acids the body needs. The rest is flushed out in our urine.
Adults who aren’t especially active are advised to eat roughly 0.75g of protein per day for each kilogram they weigh. On average, this is 55g for men and 45g for women – or two palm-sized portions of meat, fish, tofu, nuts or pulses.
Not getting enough protein can lead to hair loss, skin breakouts and weight loss as muscle mass decreases. But these side effects are very rare, and largely only occur in those with eating disorders.
Despite that, most of us have long associated protein with building muscle. This is accurate. Strength-based exercise causes a breakdown of protein in the muscle. For muscles to grow stronger, the proteins need to rebuild. A type of amino acid called leucine plays a particularly big part in triggering protein synthesis.
Some experts even argue that not consuming protein post-workout could cause the breakdown of muscle to be higher than the synthesis – meaning there’s no net gain in muscle mass. Supplement brands advise drinking protein shakes after a workout to help the growth and repair of muscle tissue, usually in the form of leucine-rich whey protein, a by-product of making cheese.