Nutrition 101: Understanding Macro and Micronutrients and What They Do for Your Body

With the amount we hear in the news/media about nutrition, we should all be about half way to a degree in Nutrition, right?  Every celebrity who has ever lost 5 pounds has something to say about their achievement and how they got there. Celebrity chefs are everywhere (some better than others) telling you what and what not to eat, ‘health food’ stores have a miracle cure for everything (at a cost), and everyone has that friend/family member who can ruin any meal by telling you exactly what is wrong with what you are eating ;)

So, we are going to start off with some of the basics of nutrition just to filter out some of the noise you have inevitably been exposed to.

Nutrition is about how food nourishes the body and ultimately influences health. I believe this is something people often forget, particularly if trying to lose weight. It’s easy to view food as the enemy when in fact, a proper diet is a key influencer in preventing a number of illnesses from scurvy (vitamin C deficiency) to cancer. But a diet needs BALANCE in order to maximize all the benefits of food.

Food is made up of 6 groups of nutrients; chemical substances which are needed for our growth and function. These are carbohydrates, fats and oils, proteins, vitamins, minerals, and water.


Carbohydrates, fats and oils, and protein are called macronutrients and are the components of food which provide energy. The energy in food is responsible for maintaining body function and performing physical activity. The energy content in food is measured in kilocalories (kcal) but we tend to call them calories in everyday life. Note: food labels may say either calories or kcal but they are talking about the same thing.

So, lets run through each of the macronutrients and what the body needs to function at its best.

Carbohydrates: Firstly, the dreaded and feared carbs! Carbohydrates have been unjustly vilified lately in the media. They are the primary source of energy for our body (particularly during exercise) and most importantly, they are essential to brain function. Carbohydrates provide 4 kcal per gram of carbohydrate and between 45-65% of the kcal in our diet should come from carbohydrates. Where the confusion lies is in the type of carbohydrate you should be eating. You should be getting your carbs from fruit, vegetables, whole grains, dairy, seeds and nuts, not added sugar.

The new Dietary Guidelines for Americans (2015-2020) has recently been published and suggests no more than 10% of your total daily kcal from added sugar. If you live in the UK you are in even more trouble (if you have a sweet tooth). Guidelines there suggest no more than 5% of total kcal be from added sugars. That is about one can of soda! I will do a follow-up blog on sugar in the near future but in the meantime, try to keep consumption to a minimum! Fruit juices, soda, candy, cookies, and processed foods are a big source of added sugars. Read food labels (again, another blog) and you can tally up exactly how much sugar you are eating.

Fats and oils: Next we have fats and oils which were equally vilified in the 90’s ‘low-fat’ era! They are an important source of energy particularly at rest and during low intensity exercise as well as a source for the fat soluble vitamins (A, D, E and K). Our body can store large (sometimes too large) quantities of fats in adipose tissue which can be mobilized and used for energy at times when we are not eating. Fats are very energy dense and contain 9 kcal per gram so are much easier to overconsume. It is recommended that fats take up 20-35% of the kcal in our diet but again, it’s important to eat the RIGHT fats. Dietary fats should be mono and polyunsaturated fats (think olive oil, avocados, nuts, and seeds). Less than 10% should be saturated fats (the type found in dairy and red meats) and trans fat (as found in processed foods) should be kept as low as possible. Again, I will do a follow-up blog discussing the role of dietary fats in health and disease.

Protein: Finally, we have protein, the building blocks of our body. Protein is composed of amino acids which are broken down when we eat protein and reassembled in our bodies for tissue growth, repair, and maintenance.  Proteins, which contain 4 kcal/g, are found in many foods but meat, dairy, nuts, legumes, and seeds are the primary sources. We should be getting about 10-35% of the kcal in our diet from protein.


Aside from the energy producing macronutrients, food is also composed of micronutrients. Micronutrients (vitamins and minerals) are needed at a relatively small amount in order to support normal health and body functions. They are generally absorbed through the gut (except vitamin D which is synthesized in the skin with sunlight!) and transported where they need to go in the body.

Vitamins: Vitamins are essential to energy metabolism (the process of breaking down macronutrients for energy) but do not contain any energy themselves. They also are important for bone, muscle and blood health, immune function, and vision (among other things!). There are two types of vitamins, fat soluble (A,D,E and K) and water soluble (vitamin C, thiamine, riboflavin, niacin, vitamin B6, vitamin B12, pantothenic acid and folate).

Minerals: Minerals (such as sodium, potassium, calcium, magnesium, and iron) are needed for the health of bones and blood, fluid regulation, energy production, as well as needed for the elimination of harmful waste. Minerals are classified into major and trace minerals based on the quantity needed in our diet and how much is found in our body.

Water: The last nutrient found in food is water. Water is needed for fluid balance, regulation of nerve impulses and body temperature, muscle contractions, nutrient transport and excretion of waste.

Prior to taking my first nutrition course, I thought I knew lots about nutrition. I knew what was healthy, what was unhealthy; and to eat the good stuff. One of the first exercises you do in an undergraduate nutrition course is a food diary. I diligently wrote down everything I ate for 3 days and calculated my total daily kcal, vitamin and mineral intake (before the days of apps which do it all for you!). I thought I was doing pretty good. I have always been a relatively healthy eater and certainly didn’t eat any ‘junk’ on those 3 days. My professor singled me out and asked to use my diary as an example in class. Of course I said yes (beaming with pride – I definitely had this nutrition thing nailed). I was mortified to discover I was being used as a BAD EXAMPLE! Why?  Because over half of my caloric intake for the day was from skim milk. One food. I had enough calcium to cover the entire class but was severely lacking many other nutrients (macro and micro). In addition, seems it wasn’t the dryer in my dorm shrinking my clothes- I was definitely on an upward course for weight gain. All from skim milk (okay, maybe the 25 cent draft also contributed to the weight gain).

The take home message from this (potential overload of) information is that nutrition is NOT just about calories or weight regulation— it’s about balance and nourishing your body and ensuring it is receiving everything it needs to work its best. The push for low sugar and reducing fat is not all about weight regulation, it’s about ensuring you get adequate nutrients to support your bodily functions. Sugar, for example, brings ‘nothing to the table’ except calories (and carbohydrates) however if you substitute sugar for a sweet potato, you suddenly have an abundance of vitamins and minerals alongside the carbs.

It doesn’t matter if you are trying to lose weight, gain weight, or stay where you are, you should be cognizant about WHAT you are putting into your body.  Try new recipes, explore new tastes, jump on the ‘superfood’ (i.e. nutrient dense) band wagon, and eliminate processed foods. Try to focus less on calories in and calories out and more on maximizing your fight against disease.




Topics: Nutrition, Food, Education

Dr. Tara Coletta, PhD

Written by Dr. Tara Coletta, PhD

Tara's research focused on obesity and metabolism. She studied exercise science (MS, UMass Amherst) before earning a PhD in nutritional biochemistry (Tufts University). Wellness remains an integral part of Tara’s life as she works to balance being a mother of three.