Carbs: The good, the bad, and the sugary
I’m sure we’ve all spent some time checking out nutrition labels while grocery shopping, whether to make healthier food choices or to just to make a half-hearted attempt at doing so. “Hmm, these glazed, custard-filled donuts have 200% of my recommended daily intake of fat and sugar? Well they’re super yummy so I’m getting them.” Regardless, the ubiquitous nutrition label tries to convey basic information about the foods we eat, and while not comprehensive, it’s come a long way in the last fifty years.
Nutrition labels didn’t really exist until the late 60’s. Up until then labels were only used for food designed for specific dietary needs. For the most part, the food people ate was prepared at home from whole ingredients. The introduction of processed foods around that time prompted companies to provide labeling so people would know how their food was being modified. Initially these labels were left up to the manufacturer as far as what information to provide or whether to provide a label at all. In 1990 the FDA finally passed a law requiring nutrition labels, going into effect in 1994.
Still, these labels provided limited information and could be confusing to the general consumer, and often food producers would find clever ways to limit the disclosure of what was actually in their product. Over the years the FDA mandated changes that helped to make the information more useful and harder to manipulate. The latest iteration came out on January 1, 2020, and the most talked-about addition was the inclusion of “Added Sugars” in the carbohydrates category. And while I welcome the additional information, I believe a lot more could be done to make the carbohydrates in food more understandable.
We all know that some foods are considered “carbs,” or high in carbohydrates: sweets, bread, pasta, potatoes, rice, etc. But what exactly are carbs and how do they differ? At a molecular level, carbohydrates are composed of carbon atoms along with hydrogen/oxygen atoms in a 2:1 ratio, sometimes written as H2O. Thus, it is essentially ‘hydrated carbon,’ or carbohydrate. Linking carbon atoms together forms a chain, and the length of the chain is the main differentiator between types of carbohydrates.
Nutrition labels currently list ‘Total Carbohydrate,’ broken down into ‘Dietary Fiber’ and ‘Total Sugars’ along with grams of each and % Daily Value. According to the nutrition label, my breakfast granola has 11g total carbs, with 4g of fiber and 2g total sugars. This seemed odd to me, and after running some calculations, I concluded that since 4 + 2 does not equal 11, something had to be missing.
And in fact the missing component was starch. Starch is the most common carbohydrate in the human diet, so why it’s missing from nutrition labels is a bit of a mystery. Sugars are known as simple carbohydrates because they contain only one or two carbon atoms and they are readily converted to fuel by the body. Starches are known as complex carbohydrates because they contain longer carbon chains and they take longer for the body to convert them into fuel. Fiber is also a complex carbohydrate, but it contains chemical bonds that cannot be broken down by the human body, and therefore are considered nondigestible.
Sugars provide little to no nutrition and contribute to obesity, diabetes, tooth decay, and a host of other health problems. Fiber helps cleanse the colon and promotes regular bowel movements, among other benefits. So if sugar is the ‘ugly’ and fiber is the ‘good,’ is starch therefore the ‘bad?’ It depends.
Starch can be broken down into its own three categories: Rapidly Digestible Starch (RDS, or amylopectin), Slowly Digestible Starch (SDS, or amylose), and Resistant Starch (RS). In general, the longer it takes your body to break down the starch, the healthier it is. So lets call RDS ‘bad’ starch, and SDS and RS ‘good’ starch.
Bad starch is rapidly converted to sugar in the body, even in the mouth by enzymes in the saliva. This provides sugars for the bacteria in the mouth to process into acid which leads to tooth decay. Remember this the next time you’re munching on pretzels and thinking it’s harmless. Good starch takes longer for your body to convert into energy, which results in a longer ‘full’ feeling and steadier energy release.
Most whole foods contain roughly the same ratio of good starch and bad starch. What changes these ratios is when food is processed into a more ready-to-eat product. Processing involves modifying food through activities such as milling, boiling, steaming, adding acids, salt or oils, among others. These processes convert much of the good starch into bad starch. In a way, the food is being ‘pre-digested’ for you. Sound disgusting? Good!
Without the benefit of nutrition labels to tell us what kind of starch is inside, the best way to avoid the bad carbs is to choose foods that are higher in fiber and lower in sugars, and with minimal processing. A long list of unpronounceable ingredients usually means a food is highly processed. Buying whole foods and preparing them yourself is still the gold standard.
In the future I expect nutrition labels to include a breakdown of starch content, just like it did for fat several years ago. My guess is food processors are lobbying hard to prevent this. Once again, consumers are left stuck in the middle scratching their heads. Ugh, now I’m depressed. Where’s my donut?
Dr. McGann
