A health tax imposed to curb rising cases of obesity, diabetes and related diseases by reducing consumption of sugary beverages and ultra-processed food has started showing positive results in South Africa.

There was a 51-percent reduction in sugar, a 52-percent reduction in calorie intake and a 29-percent reduction in the volume of beverages purchased per person per day following the implementation of the tax, according to a study published in The Lancet Planetary Health.

The shrinking sales also prompted companies to adjust the amount of sugar in their beverages. "We also found that the relative reduction in the sugar content of taxable beverages was larger than that for volume, showing that industry reformulated products," said Nicholas Stacey, first author of the study.

Researchers also found that days before the new tax system was implemented, low-income households purchased more beverages in bulk compared to high-income ones. However, once the tax system came into force, the former curtailed their consumption of sugary drinks.

South Africa implemented the health promotion levy – commonly known as the sugar tax – in 2018. The tax amount is linked to the amount of sugar in the drink with the first teaspoon untaxed. Other countries, including Mexico and a few states in the U.S., have enforced similar taxes to reduce the consumption of beverages with high sugar and ultra-processed food.

"These results back up the impact we've seen from similar policies in other countries – that beverage taxes based on sugar content can help reduce excessive sugar and energy intake," said Professor Karen Hofman from South African Medical Research Council Center for Health Economics and Decision Science.

"Importantly, this shows that the lower-income households, which experience the greater burden of obesity, diabetes, hypertension and other nutrition-related non-communicable diseases, benefit greatly from this health promotion levy."

According to the World Health Organization (WHO), over-consumption of sugar has led to an exponential increase in obesity, diabetes and tooth decay globally. The population of obese adults and children has tripled since 1975, leading to a health crisis in many countries.

A single can of sugary drink contains about 40 grams of sugar, equivalent to around 10 teaspoons of sugar. Adults and children should reduce their consumption of free sugars to less than 10 percent of their daily energy intake for a healthy lifestyle, recommended the WHO guideline on sugar consumption.

(A boy sitting in a toy tricycle is pushed past shelves of bottled beverages at a supermarket in Nanjing, east China's Jiangsu Province. /Reuters)