Added sugars are not chemically different from naturally-occurring sugars. In other words, the molecular structure of sugar is not different for the sugar added to your food products, versus the sugar inherent (naturally-occurring) in plants… plants like fruit!
In this case, by "added sugars," I mean "nutritive sweeteners" (sweeteners that contribute calories) as opposed to "non-nutritive sweeteners" (alternative sweeteners providing little to no energy, like sugar alcohols and artificial sweeteners).
Wait, wait. You mean sugar from fruit is just as “bad” as added sugar?
To best answer that question, “sugar is sugar.” However, sugar derived from fruit is packaged with other essential nutrients outside of solely carbohydrates. Fruits supply the gamut of macro- and micronutrients – fats, protein, dietary fiber, vitamins, and minerals.
Unlike sugar derived from fruits, added sugar offers nothing other than carbohydrates in the form of mono- and disaccharides. Added sugar does not contain fats, protein, nor dietary fiber. While it may contain vitamins and minerals, the amounts are insignificant and in some cases, the result of manufacturing processes (not naturally-occurring). For this reason, added sugar has earned the descriptor, “empty calories" .
It is for this reason that many food scientists cannot resist the temptations of a proper eye roll with the “Added Sugars” portion of the new Nutrition Facts label. More specifically, in regards to a Daily Reference Value unique to only “Added Sugars,” and not total sugar content (including the inherent sources) .
In many ways, the label is progress and a step in the right direction… perhaps I’m expecting jumps, leaps, and bounds. It’s no secret that if I ruled the world, a Daily Reference Value would apply to the total sugar content of a food product.
What’s so bad about this "sugar" – the added and the inherent kind?
By now, I'm sure you've read a top 10 list somewhere attempting to answer this question. Further, I'm sure 8 of those 10 "reasons" were associations with various, serious diseases ranging from obesity, to fatty liver disease, inflammation, and cancer. While these associations may be founded on legitimate scientific research, the two below reasons are keystones (fundamentals) that can certainly snowball into bigger problems (like those just mentioned). After all, it's the dose that makes the poison.
1. Sugar causes tooth decay.
Bacteria responsible for tooth decay thrive on sugar. Thriving bacteria produce acids which in turn, eat away at tooth enamel and eventually, can cause cavities and gum disease.
2. High sugar intake can result in unhealthful levels of blood lipids.
Higher intakes of sugars are associated with increases in low-density lipoproteins (LDL, commonly referred to as “bad cholesterol”) and triglycerides. Higher intakes of sugars appears to decrease high-density lipoproteins (HDL, commonly referred to as “good cholesterol”). Increased levels of triglycerides and LDL, in combination with decreased levels of HDL, are risk factors for heart disease . For this reason, the American Heart Association has long recommended (before the FDA’s labeling changes) the below Daily Added Sugar Limit (25g for women, 36g for men) .
Sugar is sugar. #biology
Recall, there are four single sugar molecules (collectively referred to as monosaccharides). They are glucose, fructose, galactose, and ribose. These monosaccharides are the building blocks of disaccharides and polysaccharides. Additionally, they are found in all nutritive sweeteners - your added and your inherent sugars. The below is a step-by-step account of how these molecules are processed in one's body.
Step 1. Salivary amylase
Digestion breaks down carbohydrates into monosaccharides, meaning di- and polysaccharides are broken down into monosaccharides. This process begins with salivary amylase (when food enters the mouth). Starch, a component of carbohydrates, is broken into smaller particles (via the salivary enzyme, amylase) and eventually into the disaccharide, maltose (glucose molecule + glucose molecule).
Step 2. Pancreatic amylase
In fact, disaccharides (sugars) are not digested in the mouth. Once departing the mouth, food travels to the stomach. As it pertains to the digestion of carbohydrates, stomach acid inactivates the amylase enzyme, halting digestion. It’s when the pancreas secretes pancreatic amylase into the small intestine that the action happens all over again.
Step 3. Small intestine (maltase, sucrase, lactase)
The bulk of carbohydrate digestion (specifically sugars) actually occurs in the small intestine. Enzymes in the microvilli of the small intestine continue disaccharide digestion, breaking these two-unit molecules into monosaccharides. The below enzymes are responsible for breaking down the following disaccharides into their monosaccharide units:
Table 1. Disaccharides to Monosaccharides: The disaccharide, maltose encounters the enzyme, maltase and breaks it into two units, glucose and glucose.
Step 4. Bloodstream
Carbohydrate digestion is complete when all monosaccharides are absorbed into the mucosal cells lining the small intestine. From there, they (monosaccharides) pass through the cell lining and into the bloodstream.
Once entering the bloodstream, the non-glucose monosaccharide units (fructose, galactose, and ribose) are converted into glucose via the liver.
The body then utilizes glucose as follows:
(1) If energy is needed immediately:
Glucose is released into the bloodstream where it can travel to cells and provide energy.
(2) If energy is not immediately needed:
Glucose is stored as glycogen in either the liver or muscles.
(A) Stored in liver:
Glycogen stored in the liver is later utilized to maintain blood glucose levels between meals.
(B) Stored in muscle:
Glycogen in muscle is later utilized for immediate energy needs, such as exercise.
Step 5. Cells
Hormones also play a critical role in utilization of sugar by the body. In order to provide adequate levels of glucose to cells throughout the body (tissue, muscle, nerve, & brain cells), a number of hormones are involved in regulating blood glucose levels - including insulin, glucagon, epinephrine, norepinephrine, cortisol, and growth hormone.
In order for glucose to help the various cells function optimally, it must be transported across the cell membrane. The insulin hormone is essential in accomplishing this transport. Further, insulin is released from the pancreas, and stimulates the liver and muscles to take up glucose, storing it as glycogen. As mentioned, glycogen is later utilized to (A) maintain blood glucose level between meals, and (B) for immediate energy needs, such as exercise .