Is high-sodium bread a silent killer?

NORTHERN CARIBBEAN UNIVERSITY (NCU) professor, Mark Harris, has raised alarm about the excessive level of salt in bread, a staple for households in Jamaica, which is likely contributing to the high incidence of hypertension and stroke among the island’s population.

He has warned further that many processed foods contain relatively high levels of salt which are masked and undetectable by human taste cells.

Writing against the background of the findings of a live experiment conducted at the recently held NCU Science Symposium 2024, Harris argues that if salt intake were reduced by a factor of 24 per cent, the rate of untimely deaths in the world would drop precipitously.

With bread being a major source of energy and nutrition, many Jamaicans consume four or more slices each day. But he noted that the current market domination of one type: high-sodium bread, could add to the total proportion of cardio-vascular-related diseases and, indirectly, to death among Jamaicans.

According to Harris, as far back as 1989, the United States-based National Research Council stated that “(in) non-westernised populations, diets are low in sodium, the prevalence of hypertension is very low, and blood pressure does not increase with age…” Moreover, the American Heart Association recommends no more than 1,500 milligram of sodium daily for hypertensive individuals. Furthermore, a United Kingdom Government body recommends a limit of 1,130 milligram of salt per 100 gram in foods. As salt consists of 40 per cent sodium, this equates to 222 milligrams of sodium per 50 grams of food as ideal for human consumption.

Yet, the NCU academician pointed out, a 50-gram bread slice from two of the major breadmaking companies in Jamaica contain 270 and 280 milligrams of sodium respectively, the latter being above the above-mentioned limit by 24 per cent. It gets worse: the flagship loaf (FS) of one of the above-mentioned bakeries contains 370 milligrams of sodium per slice: a whopping 15 per cent of the recommended daily allowance (RDA) of no more than 1,500 milligrams per day for hypertensive adults.

Hence, for hypertensive individuals (a high proportion of Jamaica’s population), fewer than five slices per day of the above-mentioned flagship high-sodium bread, excluding sodium from added food items, exceeds the RDA.

Taste-perception experiment

The situation is further aggravated with many processed foods containing relatively high levels of salt being undetectable by human taste cells. During the Science Symposium held March 13, Harris, lecturer in environmental geoscience, along with environmental science lecturer Dwight Rose, led a double-blind real-time perception experiment involving 10 senior students as subjects. As neither the subjects (students) nor the designated administrator (Dwight Rose) knew beforehand why they were doing the experiment, it was a “double blind”, the highest category of validity and bias avoidance.

Earlier, Harris measured (by drying and weighing) and subtracted the water (approximately 29 per cent) in each of the above-mentioned high-sodium breads. The dried remains contained the equivalent of 434 and 450 milligrams of salt, respectively, in a “50-gram” slice, that is, more than the equivalent of two third of a teaspoonful (600 milligrams) of table salt per slice weighing approximately 40 grams excluding water. But in the dried FS bread, it is 594 milligrams of salt per 50 grams, the equivalent of almost one teaspoon of table salt per slice.

After rinsing their mouths with distilled water, 10 students ate a portion of a slice of the water density, thereby preserving a low-to-average viscosity because a higher water

viscosity could have reduced effective rinsing. The same test was done on “water cracker”.

Three-fold higher salt detected

The results of the experiment show that, on a scale of 1-10, with granular sugar or salt as the reference “10”, students detected sugar taste in the FS bread at an average perceived strength of “3.7”, and salt at “6.1”. For a local brand of water crackers, students scored “2” for salt and “0.1” for sugar. This is a three-fold higher salt detected in the bread compared to salt detected in the water crackers.

Yet, the packages listed RDA salt at four per cent for crackers and 15 per cent for the bread, almost four times the salt in the crackers. Why did the students detect only 12 per cent and not the full 15 per cent RDA salt in the bread?

Sugar partially masks the perception of salt in foods. The high levels of sugar apparently removed 3/15 (= 20 per cent) of the sensation of salt in the bread (the taste test suggested the bread had over 30 times the sugar concentration in the crackers).

In analysing the results, Harris says they reveal two dangers of high-sodium bread containing sugar for hypertensive individuals:

(a) intrinsically high salt levels, and

(b) the tendency to eat more foods which erroneously seem to contain less salt. Unknowingly, this practice could easily push salt consumption over the RDA, he points out.

Yet, intolerably, 24 per cent (33 per cent for the FS bread) excess of sodium in some major breads continues in Jamaica, a country leading much of the world in stroke deaths. Unfortunately, sodium, being an element, resists metabolism (breakdown) in the body. Therefore high-sodium bread is an insidious agent of excess dietary sodium.

Harris offers the following recommendations:

· As masking of salt by sugar in foods puts at risk a population of hypertensive individuals which often does not read labels, all in all, such vulnerable individuals should expeditiously reevaluate their intake of high-sodium bread.

· Pre-packaged food manufacturers failing to list the salt content may be (unwittingly or wittingly) masking it with sugar and this should be a red flag for hypertensive individuals.