Hospital patients get too much salt even when they're on a sodium-restricted diet, says a Canadian study.

On average, Canadians consume 3,400 milligrams of sodium a day, which is 1,100 milligrams over the recommended levels. At least three-quarters of that sodium comes from processed foods.

Restricting sodium is particularly important for certain hospital patients, such as those with heart failure.

Registered dietitian and postdoctoral researcher JoAnne Arcand of the University of Toronto and her colleagues and Mount Sinai Hospital analyzed 84 standard menus for regular, diabetic and sodium-restricted diets at three hospitals in Ontario between 2010 and 2011.

"We demonstrated that hospital patient menus contain excessive levels of sodium," the study's authors concluded in a letter published in Monday's online issue of the Archives of Internal Medicine.

Among the regular menus, 86 per cent exceeded the tolerable upper level of 2,300 milligrams per day, about a teaspoon of salt. All of the menus exceeded the adequate intake level of 1,500 milligrams per day for adults.

The hospital menus featured mainly outsourced, prepared foods. (Alex Brandon/Associated Press)

What's more, when patients on a sodium-restricted diet were able to choose foods, 47 per cent exceeded the 2,000 milligram limit prescribed for them. Arcand said that's likely because they selected larger quantities.

"I think the major solutions are just the government setting standards, hospitals implementing those standards and then the food industry certainly lowering sodium levels in the foods that they produce," Arcand said in an interview.

Setting a salt example

Earlier studies of sodium levels in long-term care facilities found those meals may contain up to 4,390 milligrams per day.

Hospitals and other public institutions increasingly serve prepared foods instead of making them from scratch.

All of the hospitals studied used rethermalization technologies and menus containing mostly outsourced prepared foods.

The findings likely reflect how we eat in general, but hospitals need to lead by example, said Dr. Beth Abramson, a cardiologist and spokesperson for the Heart and Stroke Foundation.

"Salt puts you at risk for high blood pressure and high blood pressure is a leading health threat to Canadians," Abramson said.

When Virginia Smith of Victoria was in hospital in 2002, she refused to eat the dry, white bread and acidic tea served for breakfast and the overboiled vegetables with canned beef gravy at lunch and dinner.

"I just couldn't understand why they would give food like that to people at their most vulnerable," Smith said.

A journal editorial accompanying the research said therapeutic and nutritional goals should match, particularly for salt-sensitive conditions such as heart, kidney and liver failure.

"A critical first step toward increasing the healthy choices for hospitalized patients may be to prepare all meals with low sodium content," wrote Dr. Kirsten Bibbins-Dominogo of the University of California, San Francisco’s division of general internal medicine.

"Through the simple act of serving food that meets national nutritional standards, our hospitals will act in the best health interest of their patients and their staff and will undoubtedly … be leaders in our ongoing dialogue on how to improve our food supply, which in turn will improve the health of us all."

In the study, the nutritional analysis was based on data from manufacturers. It included ordered salt, snacks and nutritional supplements. Combined diets such as sodium restricted and diabetic, meals modified for texture and kosher diets were excluded.

Most of the menus came from the general medical (27 per cent), surgical (24 per cent) and cardiology (20 per cent) wards.

With files from CBC's Melanie Nagy and Melanie Glanz