Nutrients: macro/micro/phyto

When we consider the nutritional needs of the body in order to survive and function, we can broadly divide the dietary nutrients into macro, micro, and phyto.

  • Macronutrients: dietary components required in large amounts in the diet. For example carbohydrates, proteins, and fats.
  • Micronutrients: chemical elements or substances required in trace amounts for the normal growth and development of living organisms. For example vitamins & minerals.
  • Phytonutrients (phytochemicals): bioactive plant-derived compounds associated with positive health effects. Such as antioxidants.


The three macronutrients carbohydrates, proteins, and fats all have their own specific roles and functions in the body, and all supply us with calories or energy. For this reason, the body requires these nutrients in relatively large amounts to grow, develop and continually thrive.

Macronutrient absorption

In the gut, food is broken down or digested into component macronutrients and absorbed. Absorbed nutrients then follow one of two pathways: they will either be oxidised to provide energy immediately or they will be stored so that they can provide energy at some time in the future. Some macronutrients are more readily oxidised than others. There appears to be a hierarchy: carbohydrate and protein are oxidised first while fat is oxidised later. This seems to be because the body does not store protein (protein only accumulates where it is being actively used – which is why you lose muscle if you are not using it) and the body has only a very limited storage capacity for carbohydrate. In comparison to these macronutrients, fat can very easily be stored in almost unlimited amounts all around the body. Due to the body’s selection of carbohydrate and protein as first targets for oxidation, carbohydrate oxidation and protein closely track with carbohydrate intake and protein intake, respectively. In contrast, fat intake does not immediately stimulate fat oxidation but instead can be readily diverted to be stored.

Macronutrients and appetite

We eat more food when we are hungry as we respond to our appetite. Different macronutrients seem to differ in their impact on our appetite sensations. Protein quickly settles our appetite and promotes greater satiety or feelings of fullness than carbohydrate and fat. High protein meals therefore have more ability to reduce energy intake from a meal, as well as intake from the next meal than do meals that are low in protein.

The reason for this difference is that macronutrients are not all equally able to stimulate the release of the hormones from the gut that are required to stimulate appetite. Ghrelin (a gut hormone that stimulates hunger) appears to be suppressed more effectively by carbohydrates or proteins than it is by fat. In addition, protein and carbohydrates are more effective at stimulating GLP-1 (a gut hormone that promotes fullness) than is fat. Protein also induces the strongest release of PYY (another gut hormone that promotes sensations of fullness).


These nutrients include minerals and vitamins. Together, they are extremely important for the normal functioning of the body. Their main function is to enable the many chemical reactions to occur in the body. Nevertheless, micronutrients do not function for the provision of energy.


Vitaminsare essential for normal metabolism, growth and development, and regulation of cell function. They work together with enzymes and other substances that are necessary for a healthy life. Vitamins are either fat-soluble or water-soluble.
– Fat soluble vitamins are Vitamin A, D, E and K. Fat soluble Vitamins can be stored in the fatty tissues in the body when in excess, and so are not excreted easily. This means that you do not need to eat them as often as Water soluble vitamins. Green leafy vegetables, milk and dairy products and plant oils provide these vitamins.
– Water soluble vitamins include the Vitamin B group and Vitamin C. Water soluble vitamins are excreted in urine when in excess and so need to be taken daily. Green leafy vegetables are rich in Vitamin B, whereas Vitamin C is found abundantly in citrus fruits.


Minerals are found in ionized form in the body. Approximately 4% of the body’s mass consists of minerals. They are further classified into macrominerals and microminerals (or trace minerals).
– Macrominerals present in the body include Calcium, Potassium, Iron, Sodium and Magnesium to name a few. Iron is a constituent of Hemoglobin which is present in blood. Hence macrominerals constitute a larger percent of the body and are needed in more amounts, as compared to micro minerals.
– Microminerals include Copper, Zinc, Cobalt, Chromium and Fluoride. They are mostly co-factors, and are necessary for the function of enzymes in the body, but are needed only in minor quantities.


Phytonutrient-rich foods include colorful fruits and vegetables, legumes, nuts, tea, whole grains and many spices. They affect human health but are not considered nutrients that are essential for life, like carbohydrates, protein, fats, vitamins and minerals.

Among the benefits of phytonutrients are antioxidant and anti-inflammatory activities. Phytonutrients may also enhance immunity and intercellular communication, repair DNA damage from exposure to toxins, detoxify carcinogens and alter estrogen metabolism. The U.S. Department of Agriculture (USDA) notes that consuming a phytonutrient-rich diet seems to be an “effective strategy” for reducing cancer and heart disease risks.

There are more than 25,000 types of phytonutrients.



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