How Much Protein Do You Really Need?

The nutrient builds and repairs muscle after your workout, but studies are now linking too much protein to health dangers like heart disease. So, now what? Shape investigates.

It’s no big secret that protein is crucial for fit women.“It contains essential amino acids that help create muscle, maintain bone health and keep blood pressure in check,” says registered dietitian Nancy Rodriguez, a professor of nutritional sciences at the University of Connecticut in the US. The nutrient can also help keep you slim. Protein is slower to digest than carbohydrate, so a relatively small amount will keep you full for hours. Plus your body actually burns calories in order to digest and use it.

There seems to be a clear-cut case for the benefits of protein, but here’s where things get complicated: A growing body of evidence indicates that you can have too much of a good thing.

“High amounts of protein can increase your level of growth hormone, insulin and Tor, an enzyme that accelerates ageing, all of which may promote tumour growth,” says Valter Longo, a professor of gerontology and biological sciences at the University of Southern California.

His research found that adults who get more than 20 per cent of their total calories from animal protein have a four times greater risk of dying of cancer than those who get less. Loading up on the nutrient can also increase your chance of heart disease, according to a study in the Journal of Internal Medicine.

The key words in this research are animal protein, however. Scientists are finding that the type of protein you eat can make all the difference.

In a study in the Archives of Internal Medicine, for instance, a higher intake of red meat, especially the processed type, was associated with cancer and cardiovascular death. (Meat lovers were also less likely to be physically active and more apt to have a poor diet overall.) Eating less-processed types of protein was linked to a lower risk of mortality.