Date
14 November 2018
It is well-known that healthy foods can help maintain body health, but can our body absorb all the nutrients from the food we eat?  Photo: Reuters
It is well-known that healthy foods can help maintain body health, but can our body absorb all the nutrients from the food we eat? Photo: Reuters

Food and nutrition: The delicate relationship

Is it better for you to consume more nutritious food? Can our body absorb all the nutrients from the food we eat?

It is often said that spinach, coffee, and tea will affect our ability to absorb micronutrients such as calcium and iron; while vitamin D and C are able to enhance such ability. Are these sayings true?

Plant food is not only rich in dietary fiber, some also contain oxalate and phytate, which have chemical structures that strongly attract minerals such as calcium, iron, magnesium and zinc. When they combine in the intestine, the body’s absorption could be affected.

Phytate-rich food includes beans, and oxalate-rich food includes spinach, buckwheat and rice bran. Yet we do not need to worry too much as such situation would mostly occur only when the diet is unbalanced.

Some studies found that probiotics help change the chemical structure of phytate, thus reducing its effect on human body’s minerals absorption. For instance, phytic acid in natto is significantly lower.

Adequate Vitamin D, which can be synthesized when skins reacting to sunlight and also be absorbed from marine fish, egg yolk, fortified milk and other food, can help produce calcitriol (also known as active metabolite vitamin D) to help absorb calcium.

Tannic acid contained in caffeinated beverages, such as coffee and tea, can prevent the body from absorbing non-heme iron from plants. Excessive intake of tannic acid can also affect the absorption of other minerals.

That said, it is advised to drink these beverages about two hours after meals. Another method to increase iron absorption is to consume food rich in vitamin C. The properties of vitamin C can turn non-heme iron (from plant food) into easily digested heme iron (from meat). About 50 mg of vitamin C in an orange or a kiwi is capable of enhancing iron absorption by two to three times.

It is well-known that some of the healthiest foods such as beans, tomatoes, blueberries, sweet potatoes and almonds contain various antioxidants and phenolic compounds, which include lycopene, zeaxanthin, lutein, anthocyanins, carotene, vitamins A, C, E, and help protect human cells and tissues and maintain body health.

This article appeared in the Hong Kong Economic Journal on Jan 18

Translation by John Chui

[Chinese version 中文版]

– Contact us at [email protected]

JC/BN/RC

Lecturer at the Department of Applied Science of Hong Kong Institute of Vocational Education (Kwai Chung)

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