Sugar: The most misunderstood molecule in metabolism, By Mukaila Kareem

…next time you hear sugar being demonised, demand context. Sugar sitting on grocery shelves, in refrigerators, or in pantries doesn’t stimulate insulin — only its consumption does. And like anything in metabolism, the issue isn’t sugar itself, but chronic overconsumption over time. In all things, context matters.

Survival is fundamentally based on flexibility and adaptability in the face of limited resources. However, in social media pop health culture, metabolic facts are often replaced with buzzwords and catchphrases — sometimes due to ignorance, sometimes for profit, and sometimes due to a lack of real-world experience outside the Western world bubble. The goal is to create rigid dietary tribes — vegan, keto, carnivore — each convinced that their way is the only way. Yet, human survival has always relied on metabolic flexibility, shaped by geography, seasons, climate, and an omnivorous diet that allowed adaptation to changing environments.

Every year, millions of dollars are spent on low-carb conferences portraying sugar as the ultimate villain. The reality, however, is that sugar is life’s baseline energy source. The first stable product of photosynthesis is a simple three-carbon sugar, which serves as a metabolic crossroad: it can be broken down for ATP or used to build starch, cellulose, amino acids, proteins, fats, cholesterol, and even DNA. How, then, can sugar — the central intermediate molecule in metabolism — be considered toxic?

As I write this in the middle of winter, with temperatures frequently below freezing, trees stand bare, their leaves long shed in Fall season in preparation for hibernation. In tropical climates, this season would be the equivalent of the dry season — a period of scarcity, with anticipation for the rainy season’s bounty. If most households in the United States practiced subsistence farming, fresh fruits and vegetables would be rare this time of year. Yet, grocery stores are filled not only with fresh produce but also with aisles of sodas, juices, and other brightly coloured, sugar-laden beverages, often misleadingly marketed as “antioxidants.” In contrast to nature’s seasonal sugar availability, industrialised food production has made sugar omnipresent, detached from any natural cycle.

In natural environments, simple sugars are rare because they are not ideal for long-term storage. Plants produce large amounts of simple sugars, but these are quickly converted into starch and cellulose — the latter forming structural elements like stems and branches. Free glucose is uncommon in nature, but thousands of glucose molecules are linked together to form cellulose, the most abundant organic compound on earth. While sugars are chemically distinct from alcohol, their multiple hydroxyl groups, like alcohol, make them highly water-soluble, presenting a challenge for storage. This is why plants evolved to produce simple sugars in fruits, seasonally, to attract animals and humans for seed dispersal at the right time.

Today, we have the technological capability to strip fibre from starch, creating “pre-digested” processed foods engineered for maximal palatability, reaching what food scientists call the “bliss point.” Meanwhile, we blame our insatiable cravings on carbohydrates, often without context. We can even mimic fruits by enzymatically modified corn starch into high-fructose corn syrup — a cheap, fibreless, vitamin- and mineral-deficient sweetener — then blame sugar for our overconsumption, again without context. The truth remains: no plants, no sugar; no sugar, no life. Sugar — the scapegoat of the low-carb movement — is, in fact, the foundation of the food chain. Every calorie consumed, whether from meat, fat, or protein, ultimately derives from sugar through photosynthesis.

Plants, in many ways, are metabolic magicians. Unlike animals, they rely exclusively on sugar for ATP production. Their stored fats are not used for energy but for biosynthetic processes. In fact, oil-rich seeds must convert their fats into sugar (via the glyoxylate cycle) during germination because young seedlings lack functional leaves and cannot perform photosynthesis immediately. Obviously, plants don’t share the internet’s sugar paranoia. They make sugar, store sugar, burn sugar, and even convert fat into sugar — something animals cannot do.

So, next time you hear sugar being demonised, demand context. Sugar sitting on grocery shelves, in refrigerators, or in pantries doesn’t stimulate insulin — only its consumption does. And like anything in metabolism, the issue isn’t sugar itself, but chronic overconsumption over time. In all things, context matters.

Mukaila Kareem, a doctor of physiotherapy and physical activity advocate writes from the USA and can be reached via [email protected]