An article published in July’s issue of the Harvard Health Letter provides a selection of nutrients that “work in pairs”, in an effort to “inform some food choices - and give just a taste of the cruel complexity of the nutrition lurking behind guidelines and easy-to-read labels”.
“Nutrition guidelines and labels sometimes seem to have been written one nutrient at a time. But good nutrition – and the way in which our bodies absorb and process nutrients – is a much bigger puzzle than a nutrient-by-nutrient tally sheet suggests,” states the article.
“Most nutrients don't fly solo: They interact, join forces, cancel each other, jockey for position on metabolic pathways. One reason food is so often nutritionally preferable to pills or supplements is that food contains a mixture of nutrients, so we benefit from their interactions with each mouthful.”
The article provides examples of five pairs of nutrients that interact, which it says is “far from a complete catalog”.
Vitamin D – calcium
The article stresses the importance of vitamin D for the absorption of calcium by the body. The vitamin, which also aids in the absorption of other minerals such as phosphorus, has been linked to benefits including protection against heart disease and some forms of cancer.
“Some of these benefits may be the result of the vitamin's absorption-related duties, but it may have a more direct effect on disease processes and the immune system than previously believed,” states the article.
Current recommendations suggest that adults should have an intake of 1,000mg of calcium and 400 international units (IU) of vitamin D daily. This figure increases with age: Adults over 50 should receive 1,200 mg of calcium, and adults over 70 should receive 600 IU of vitamin D.
Vitamin B12 – folate
Folate, which is one of the eight B vitamins, depends on vitamin B12 to be absorbed, stored and metabolized.
Recommended amounts in the US are 2.4 micrograms of B12 and 400 micrograms of folate.
Deficiencies in these vitamins can cause macrocytic anemia. The US requires cereal grains to be fortified with folate, and many breakfast cereals are fortified with added B12.
Zinc – copper
Copper and zinc compete for absorption sites in the small intestine. If too much zinc is present copper absorption is diminished and a deficiency may occur.
Daily zinc recommendations are 11mg for men and 8mg for women. Recommended copper intake is 900 micrograms per day for all adults.
Niacin – tryptophan
Tryptophan is one of nine amino acids required by the human body for their function as protein building blocks. One importance of tryptophan is its role as a supplier of niacin, which is one of the B vitamins (B3).
Daily niacin requirements are 16mg for men and 14mg for women.
Sodium – potassium
Salt – or sodium chloride – accounts for around 90 percent of the American consumer’s sodium intake. Although an essential nutrient, the average American consumes thousands of milligrams more sodium than required on a daily basis, leading to high blood pressure and an increased risk of stroke and heart attack.
Potassium can help counterbalance this by encouraging kidneys to excrete sodium.
Current guidelines recommend 4,700mg potassium per day, and 1,200 to 1,500mg sodium. The average American intake is around 2,500mg potassium and 2,500 to 7,500mg sodium per day.