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By Matthew Magno

When doing so much work out at sea, it’s only necessary that sailors garner enough nutrients to survive at the end of the day! A thorough analysis using archaeological data to convert to modern-day units revealed the amount of each mineral the sailors consumed per week.

With the task of interpreting iron and magnesium, it was concluded that sailors had an excessive intake of both minerals in their diet. But first, how in the ship biscuit and salted beef do iron and magnesium contribute and function in the body?! 


When consumed, magnesium is absorbed in the gut, particularly the small intestine, and is stored in the bone. Excess magnesium is excreted by the kidneys through the form of urine. Of the total consumed, 24-76% is actually absorbed in the gut and the rest is removed through fecal matter! It can be found within the cell where it acts as a counter-ion for ATP and nucleic acids, stabilizing many enzymes including ATP-generating reactions. Magnesium is significant in the synthesis of fat, proteins, nucleic acids, and muscle contractions. 

Iron is usually absorbed in the gut as well, specifically in the duodenum and jejunum. From absorption, around 70% of iron in the body is found in hemoglobin and myoglobin. The main role of iron in the body is in the red blood cells where it carries oxygen to the body’s cells and tissues. Contrary to magnesium, only small amounts of iron are lost in urine, feces, and skin. The recommended dose of iron for males 19-50 years old is 8 mg/day. 


It was determined that sailors received more than twice the dosage at 19.7 mg/day. To be heavily affected by iron overdose it would have to be taken at acute occurrences, gradual consumption is more than often not harmful. Only taking more than 20 mg/kg in the form of supplements is harmful. Though, because supplements did not exist in the 17th century, there is little risk of iron overdose on dietary sources with normal intestinal function.

The weekly total for magnesium stands is 2940 mg/week for males 30+ or 420 mg/day, but more than three times the amount is consumed by sailors in the 17th century. This is usually fine because magnesium can be excreted through urine if there is too much. Though, if the individual’s kidneys are failing there could be an inability to process magnesium meaning hypermagnesemia can occur. Symptoms can include weakness, confusion, slowed breathing rate, and decreased reflexes. It is often uncommon for this to occur.

A numerous amount of the minerals were consumed in excess of the daily recommended value. Though, that is not necessarily a bad thing! The amount of work required to perform tasks daily as a 17th-century sailor would more than likely require enormous amounts of energy. Of course, more research must be done to exactly pinpoint how sailors fared in grueling conditions out at sea.

With that in mind, stay tuned for the latest updates in all things Ship Biscuit and Salted Beef research!