By Ananya Mariam Rajesh (Reuters) - Celsius Holdings said on Thursday it would buy health and wellness drinks brand Alani Nutrition in a $1.8 billion deal through a combination of cash and stock, boosting its portfolio to build on the growing demand for sports and energy beverages.

Celsius shares are up more than 30% after its quarterly results topped estimates and it announced plans to buy drink maker Alani Nu.

The purchase allows Celsius to add a fast-growing beverage popular with young women while better positioning it to compete against rivals Red Bull and Monster.