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Monday, June 23, 2014

Nutrition: Back to the Basics


Nutrition is a confusing subject. One day fat is bad, the next it is good for you. Then you turn around the next day and the media is telling us that carbs are the root of all evil. And don’t even get me started on this whole gluten-free panic.With all of these mixed messages in the media, is it any wonder that our society is heavily confused with how to properly nourish themselves? Before looking at any of these trends (which I would like to eventually discuss individually on some of these Mondays), I think it is of utmost importance to go back to the basics.
I pulled out my old notes from my Human Nutrition course and other textbooks I have accumulated
to draft this post. 

Before we dive in, I want you to understand that nutrients (chemical substances that contribute to health), are classified into two categories: macronutrients and micronutrients. The macronutrients include: carbohydrates, lipids, and protein. The micronutrients include vitamins and minerals. A simple way to differentiate the two is by remembering that you need a relatively large amount of macronutrients (grams), whereas you need a relatively small amount of micronutrients (milligrams). In this particular post, I want to keep our focus on the macronutrients.


What are they?
Carbohydrates (or carbs, as we commonly refer to them) are the primary source of energy for the body.1 Carbohydrates are composed of the elements carbon, hydrogen, and oxygen in the ratio of C:O:H2.2 The carbons are hydrated by the two hydrogens and one oxygen per carbon, hence the name.2 Carbohydrates might also be referred to as “sugars,” ie. glucose. The important dietary carbohydrates include the categories of monosaccharides, disaccharides and oligosaccharides, and polysaccharides.2 In this post, I won’t go into much further detail other than to explain that those categories are essentially just different lengths and branching of carbohydrates.    
What do they do?
As previously mentioned, carbohydrates are the major fuel of the body.1 When metabolized, your body converts these into glucose (or blood sugar).1 Once in the blood stream, the glucose is utilized by cells, tissues, and organs. In fact, your central nervous system and red blood cells cannot use any other source of energy other than glucose. (Therefore, we don’t want to eliminate carbohydrates from the diet). If the glucose is not used, then it is stored in the liver as glycogen and used later.3
Subcategories:
Carbohydrates are divided into simple and complex carbs.2 Simple carbs include both the naturals sugars found in fruits, vegetables, and dairy products, but also the sugars added during processing foods.2 Complex carbs, on the other hand, include whole grain products, legumes and starchy vegetables.2 The complex carbohydrates are the foods with the dietary fiber. As a rule of thumb, strive to choose the foods that are complex carbs over those that are refined.
How much do I need?
The Recommended Daily Allowance (RDA) for carbohydrate intake is 130 grams per day.4


What are they? Lipids are also comprised of carbon, hydrogen and oxygen.2 We commonly refer to the lipid group as fats, though technically, fats only include those products that are a solid at room temperature and oils are the liquids. (However, for this post, I will use the terms lipids and fats interchangeably.) Triglycerides (a glycerol plus three fatty acid molecules) are the major form of fats in foods and are also the major form of energy storage in the body.2
What do they do? Dietary fat gives you energy, helps absorb certain vitamins, and is important within the body’s membrane functions.5
Subcategories: To best examine the types of fat, I thought a chart would be the most beneficial:6

Overall, limit the saturated fat in your diet as studies have shown their effect in raising the total blood cholesterol levels. In addition, limit Trans fatty acids. A good rule of thumb for Trans fatty acids: if the ingredients list uses the words “hydrogenated,” then it contains some level of Trans fats. Opt for the polyunsaturated and monounsaturated fats. And if you are needing to choose between margarine and butter for baking, I recommend butter.
How much do I need? There is no RDA set for fats like there is for carbohydrates. However, the American Heart Association Recommends that you limit your saturated fat intake to 5-6% of your total calories, minimize trans fat intake, and limit the cholesterol intake to less than 300 mg. Overall, fat should comprise about 25-35 percent of a person’s total daily calories. Try and keep most of your fats in the monounsaturated and polyunsaturated family.7


What are they? Protein is different from the other macronutrients in that it also contains the element Nitrogen.2 Protein is comprised of chains of amino acids and are the main structural material in the body. Protein is commonly found in meat, poultry, fish, milk/milk products, legumes and nuts.2
What does it do? Along with being the main structural material in the body, protein has many functional roles as enzymes, immune factors, a contributor to the acid/base balance, and the maintenance of fluid balance.2
How much do I need? The RDA for adults is 0.8 g/kg of body weight. For example, a 140 lb female would need about 51 grams of protein each day (140lb/2.2=63.6kg*0.8kg).4


The take home message: All macronutrients are important! Each serve their purpose in your body and you need a healthy balance. The main challenge is to choose the healthier option of each. I hope this guide has helped give you a basic background of the three macronutrients. 

What topic are you curious about for next Monday?



References:
1)    MedlinePlus [Internet]. Bethesda (MD): National Library of Medicine (US); [updated 2014 Jun 2]. Carbohydrates; [updated 2014 Jun 2; reviewed 2014 May 27; cited 2005 Aug 12]; [about 2 p.]. Available from: http://www.nlm.nih.gov/medlineplus/carbohydrates.html
2)    Mahan, L. Kathleen., Escott-Stump, Sylvia., Raymond, Janice L.Krause, Marie V. (Eds. 12) (2008)Krause's food & the nutrition care process /St. Louis, Mo. : Elsevier/Saunders.
3)    MedlinePlus [Internet]. Bethesda (MD): National Library of Medicine (US); [updated 2014 Jun 2]. Complex Carbohydrates; [updated 2014 May 16]; [about 1 p.]. Available from: http://www.nlm.nih.gov/medlineplus/ency/imagepages/19529.htm
4)    Dietary Reference Intakes for Energy, Carbohydrates, Fiber, Fat, Fatty Acids, Cholesterol, and Amino Acids (2002/2005). This report may be accessed via www.nap.edu.
5)     MedlinePlus [Internet]. Bethesda (MD): National Library of Medicine (US); [updated 2014 Jun 2]. Dietary Fats; [updated 2014 Jun 17]; [about 1 p.]. Available from: http://www.nlm.nih.gov/medlineplus/dietaryfats.html.
6)    Huntsville Hospital Wellness Center Nutrition Services, 2007. Available from: http://www.hhsys.org/services/wellness/weightloss/monthly/pdfs/0212_TypesOfFat.pdf
7)    American Heart Association. Fats and Oils: AHA Recommendation. 2014 May 9. Available from http://www.heart.org/HEARTORG/GettingHealthy/FatsAndOils/Fats101/Fats-and-Oils-AHA-Recommendation_UCM_316375_Article.jsp

Disclaimer: All photos (with the exception of the first two and the last one) are not my own.

1 comment:

  1. I really enjoyed reading the science behind this! I used to be really good friends with a dietitian (before she moved away) and she and I would talk about this very thing.

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