All About Carbohydrates

What are carbohydrates?
Carbohydrates are organic molecules typically classified according to their structure. And, structurally speaking, there are two types of carbohydrates – simple and complex.

Simple carbohydrates are smaller, more easily processed molecules and they’re named things like mono- and disaccharides since they contain either 1 sugar molecule or 2 sugar molecules linked together.

Complex carbohydrates, on the other hand, are called polysaccharides since they have more than 1 sugar group linked together.


Monosaccharides are the simplest form of carbohydrate and cannot be broken down any further since they contain only 1 sugar group. Oligosaccharides consist of short chains (di-, tri-, etc) of monosaccharide units all put together. And polysaccharides are long chains of monosaccharide units all put together.

Here’s a diagram showing what these structures look like:

As you might imagine, each subtype of carbohydrate has different effects in the human body due to its structure and what food it comes from. These effects are largely due to the following:

*How quickly and/or easily the carbohydrate molecule is digested and absorbed.

*Which other nutrients are provided along with the carbohydrate source (fat and protein slow down the digestion and/or absorption) of the carbohydrate source.

As you know, carbohydrates can vary greatly in texture, sweetness, rate of digestion, and degree of absorption.

Why is carbohydrate intake so important?
Carbohydrate consumption can alter energy dynamics and disease progression in the body. All carbohydrates we consume are digested into monosaccharides or simple sugars.

Yep, every single carb – even the high-fiber, low glycemic index, complex carbs you choose – become sugar molecules before they’re absorbed into the body. It’s just that the “healthier carbs” are digested and absorbed much slower while the “non-healthy” carbs are digested very quickly. And this digestion and absorption is influenced by the type of carbohydrate consumed, enzyme action in the mouth and gut, and other dietary factors.

Once absorbed, these monosaccharides/sugars go to the liver to fill energy stores. After that they enter the bloodstream and venture out to the other cells of the body. This is when insulin is released to handle this “sugar load” on the body.

See here for simple animation:

Carbohydrates are first and foremost a source of immediate energy for all of your body’s cells.

As previously mentioned, carbohydrates also cause a release of insulin. A larger insulin response can be beneficial at certain times (like after an intense workout) and not so beneficial at certain times (like before bed).

What you should know
There are differences between individuals and how they handle carbohydrates. Generally, carbohydrates that are digested and absorbed slowly can help to control insulin response, energy levels, and body composition. When the diet consists of added sugars and refined carbohydrates (which enter the body at a rapid pace), one may notice elevations in blood triglyceride levels, bad cholesterol, and insulin resistance.

When the dietary emphasis is placed on whole grains and unrefined carbohydrates (which enter the body in a controlled manner), a reduction in triglycerides can result (Jenkins et al 1987). Other benefits of a lower glycemic diet include increased vitamin & mineral intake, increased fibre intake, enhanced satiety, a higher thermic effect of feeding, and blood sugar control (Ludwig & Eckel 2002; Ludwig 2000).

The minimal recommended intake for carbohydrate is 130 grams per day for the general population. The amount of carbohydrates that should be consumed is associated with body size and activity levels. Intake is also dependent on dietary fat and protein intake.

The minimal recommended intake for fibre is 25 grams per day. The optimal amount is around 35 grams/day for women and 48 grams/day for men. Fibre comes in different forms (soluble/insoluble) and is important for satiety, blood fat levels, colon cancer, motility and gut health (Brown et al 1999; Wu et al 2003; Berkow & Barnard 2006; Wylie-Rosett et al 2004; Martinez et al 1997; Martinez et al 1996; Peters et al 2003; McKeown-Eyssen et al 1994; Macrae 1999; Park et al 2005; Tse et al 2000; Howard et al 2000; Griffenberg et al 1997). Fibre is found in vegetables, legumes, fruits, nuts, seeds, and whole grains.

For extra credit
While carbohydrate intake is a chief determinant of blood sugar levels, when consuming 3 whole grain foods per day, risk of developing type II diabetes is decreased by about 30% (Venn & Mann 2004).

Dextrose seems to be faster than fructose for post-exercise muscle glycogen re-synthesis (Blom 1987; Van Den Bergh et al 1996).

Summary and Recommendations
A minimum carbohydrate intake should be 130 grams per day with a majority coming from vegetables and fruits. Higher amounts of carbohydrates are needed with increased muscle mass and increased physical activity levels. However, be careful. Excessive carbohydrate consumption will be stored for future use (as fat or glycogen).

The rate at which the carbohydrate is digested and absorbed can influence body composition and health. Carbohydrate breakdown that is time-release from lower glycemic carbohydrates is better for satiety, blood sugar, and body composition. These carbohydrates are found in vegetables, fruits, legumes, and whole grains. Rapid digestion of carbohydrates is beneficial during the pre- and post-workout periods.

Consume at least 25 grams of fibre per day from vegetables, fruits, legumes, nuts, seeds, and whole grains to ensure optimal health and body composition.

DR JARROD D. MEERKIN PhD  AEP ESSAF

References
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Venn BJ, Mann JI. Cereal grains, legumes, and diabetes. Eur J Clin Nutr 2004;58:1443-1461.

Ludwig DS & Eckel RH. The glycemic index at 20y. Am J Clin Nutr 2002;76:264S-265S.

Ludwig DS. Dietary glycemic index and obesity. J Nutr 2000;130:280S-283S.

Blom PC, hostmark AT, Vaage O, Kardel KR, Maehlum S. Effect of different post-exercise sugar diets on the rate of muscle glycogen synthesis. Med Sci Sports Exerc 1987;19:491-496.

Van Den Bergh AJ, Houtman S, Heerschap A, Rehrer NJ, Van Den Boogert HJ, Oeseburg B, Hopman MT. Muscle glycogen recovery after exercise during glucose and fructose intake monitored by 13C-NMR. J Appl Physiol 1996;81:1495-1500.

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Martinez ME, McPherson RS, Levin B, Glober GA. A case-control study of dietary intake and other lifestyle risk factors for hyperplastic polyps. Gastroenterology 1997;113:423-429.

Martinez ME, McPherson RS, Annegers JF, Levin B. Association of diet and colorectal adenomatous polyps: dietary fiber, calcium, and total fat. Epidemiology 1996;7:264-268.

Peters U, Sinha R, Chatterjee N, et al. Dietary fibre and colorectal adenoma in a colorectal cancer early detection programme. Lancet 2003;361:1491-1495.

McKeown-Eyssen GE, Bright-See E, Bruce WR, et al. A randomized trial of a low fat high fibre diet in the recurrence of colorectal polyps. Toronto Polyp Prevention Group. J Clin Epidemiol 1994;47:525-536.

Macrae F. Wheat bran fiber and development of adenomatous polyps: evidence from randomized, controlled clinical trials. Am J Med 1999;106:38S-42S.

Park Y, Hunter DJ, Spiegelman D, et al. Dietary fiber intake and risk of colorectal cancer: a pooled analysis of prospective cohort studies. JAMA 2005;294:2849-2857.

Tse PW, Leung SS, Chan T, Sien A, Chan AK. Dietary fibra intake and constipation in children with severe developmental disabilities. J Paediatr Child Health 2000;36:236-239.

Howard LV, West D, Ossip-Klein DJ. Chronic constipation management for institutionalized older adults. Geriatr Nurs 2000;21:78-82.

Griffenberg L, Morris M, Atkinson N, Levenback C. The effect of dietary fiber on bowel function following radical hysterectomy: a randomized trial. Gynecol Oncol 1997;66:417-424.

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