Rule 1 Casein Protein Powder

Recover stronger and sleep better with the best casein protein powder in New Zealand, designed to support your muscles while you rest. These slow-release proteins fuel overnight recovery and help maintain lean muscle mass between meals. Rich in essential amino acids and designed for sustained absorption, casein is ideal before bed or during extended periods without food.

Shop premium casein protein brands at the best prices — only at Sprint Fit.

Rule 1 is one of the fastest-growing sports nutrition brands worldwide, trusted by athletes for clean, effective, and great-tasting supplements. Their flagship R1 Protein features ultra-pure whey isolate for rapid absorption, while Whey Blend delivers a balanced mix of whey concentrate, isolate, and hydrolysate for everyday muscle growth and recovery. For those looking to gain mass, Clean Gainer provides high-quality calories from complex carbs and premium proteins.

Rule 1’s pre-workouts and pump formulas are designed to maximise energy, focus, and performance, while their BCAA and EAA blends support hydration, endurance, and muscle repair. Every supplement is crafted without unnecessary fillers, gluten, or banned substances, making Rule 1 a trusted choice for serious lifters and athletes alike.

At Sprint Fit New Zealand, we make it easy to shop the full Rule 1 range online. Enjoy fast nationwide shipping, exclusive discounts, and expert support when you buy Rule 1 supplements from us. Whether you’re new to fitness or pushing for elite performance, Rule 1 has the fuel you need to train harder, recover faster, and achieve your goals.

View All Rule 1

All Casein Protein Powder

From $69.95 $55.96

RULE 1
Casein
2LB

From $119.95 $95.96

RULE 1
Casein
4LB

Frequently Asked Questions

What is casein protein powder?

Casein protein powder is a slow-digesting dairy-based protein that provides a steady release of amino acids to the muscles over several hours. It’s ideal for use before bed or during long periods without food to support muscle recovery and prevent muscle breakdown.

When should I take casein protein?

The best time to take casein protein is before bedtime, as it fuels your muscles with protein throughout the night while you sleep. It’s also great between meals when you need long-lasting satiety and muscle support.

What’s the difference between casein and whey protein?

Whey protein digests quickly and is ideal for post-workout recovery, while casein digests slowly, making it perfect for overnight recovery. Both are effective, and many people use a combination of the two depending on specific training and nutrition needs.

Can I use casein protein if I’m lactose intolerant?

Some casein protein powders contain low levels of lactose, but not all are suitable for those with lactose intolerance. If you're sensitive to lactose, look for products labelled as lactose-free or choose non-dairy protein powders. We always recommend consulting with your healthcare provider before use.

Is casein protein powder good for building muscle?

Yes, casein protein supports muscle repair and growth by delivering a steady stream of amino acids over time. This helps reduce muscle breakdown and supports lean muscle maintenance, especially during sleep or fasting periods.