Hong Kong’s Consumer Council has released a revealing analysis of six popular sugars—rock candy, red sugar, dark brown sugar, light brown sugar, raw slab sugar, and white sugar—finding that while none contain iron, darker varieties pack significantly more minerals, and all demand a caloric price that takes seven minutes of walking to burn off per teaspoon.
The study, conducted with insights from Dr. Luo Guiqing, a lecturer at the University of Hong Kong’s School of Chinese Medicine, examined both the nutritional composition and traditional medicinal properties of these everyday sweeteners. For countless Cantonese households that use these sugars in everything from home cooking to sweet soup (tong sui), the findings offer practical guidance.
Two Production Paths, Very Different Results
The six sugars fall into two broad categories. Traditional varieties—raw slab sugar, red sugar, dark brown sugar, and light brown sugar—begin as pressed sugarcane or sugar beet juice. The juice is filtered, boiled, and crystallized without the “centrifugation” step that separates sugar crystals from molasses. This omission preserves more of the plant’s natural minerals.
Modern manufacturers, however, often produce these same “traditional” sugars by coating refined white sugar with molasses and sometimes artificial color. Consumers can identify the difference by reading ingredient labels: if molasses or coloring appears on the list, the product was likely factory-assembled rather than traditionally milled.
What the Lab Results Showed
Testing revealed that mineral content tracks closely with color depth. Dark brown sugar and raw slab sugar contained the highest levels of calcium and potassium—minerals essential for bone health, blood pressure regulation, and nerve function. Slab sugar led with up to 944 milligrams of potassium per 100 grams, while rock candy contained only 2 milligrams, with some samples showing none at all.
Notably, none of the samples tested positive for iron, challenging popular belief that dark sugars “enrich the blood” in a nutritional sense.
Total sugar content ranged from 91 to 98 percent per 100 grams, with light brown sugar and white sugar showing the highest purity. Slab sugar contained the lowest sugar percentage due to higher moisture and molasses content.
A Spoonful of Reality
Dietitians warn that these mineral differences, while measurable, do not transform sugar into a health food. A single teaspoon delivers 24 kilocalories—enough that a 60-kilogram adult walking at 3 km/h would need roughly 7 minutes, or about 350 meters, to burn off.
Traditional Wisdom, Modern Application
Dr. Luo’s expertise adds a TCM dimension to the data. Red sugar and light brown sugar are traditionally recommended for individuals with cold extremities, pale complexions, and poor circulation, often brewed as ginger tea. Raw slab sugar is favored for strengthening the spleen and moistening the lungs, making it a staple in pear and snow fungus desserts. Rock candy is prized for its yin-nourishing, throat-soothing properties.
The takeaway? Choose sugars deliberately based on flavor and occasion, but consume all varieties sparingly—their mineral content complements, rather than replaces, a balanced diet.