Protein Powder with Water or Milk: What Changes in Your Shake?

By Dr Nillie Teymouri and Tina Hirst

Choose the mixing liquid for what it adds to your drink. Water adds no protein or energy; milk and plant drinks change the finished shake’s nutrient amounts. The useful choice depends on your meals, preferences and suitability, as well as the powder’s directions.^{1, 2}

The powder is ready. Now comes the small decision: water from the tap, milk from the fridge or the oat drink you use in coffee?

Start with what you want from the glass. A lighter texture? Additional protein? A drink made without dairy ingredients? Those are different questions, and the mixing liquid answers only part of them.

Commercial disclosure: Amaris Mint® sells BioBoost Balance+ Protein™, discussed below.

Water, dairy milk and plant drinks at a glance

With water: the powder’s contribution stays the same

If you use the same amount of powder and drink the whole serving, mixing it with more water does not remove protein. It spreads the powder through a larger volume. That changes the concentration and texture, not the total amount of protein from the powder.

Water can be convenient when you want a simple drink alongside food. Start with the volume in the preparation instructions. If the label gives a range, you can choose within it to find a consistency you enjoy.

A shake made with water still contains the energy, ingredients and allergens of its powder. “Mixed with water” does not mean calorie-free or dairy-free.

With milk: count what the carton contributes

Cow’s milk adds protein and calcium as well as energy. Whole, semi-skimmed and skimmed versions differ in fat content, so use the information for the one you actually pour. NHS guidance recommends choosing lower-fat milks for adults.¹

Whether that addition is useful depends on the rest of your food. You might enjoy milk with your breakfast shake; on another day, water might suit the meal you already have planned. Our guide to how much protein women need per day helps put the extra protein into context.

Adding milk does not automatically turn a protein supplement into lunch. If that is the job you need it to do, read protein shakes versus meal replacements before relying on the drink as your meal.

With plant drinks: read beyond “oat” or “almond”

A 2025 assessment by the UK’s Scientific Advisory Committee on Nutrition and Committee on Toxicity compared cow’s milk with almond, oat and soya drinks. Protein content and fortification varied. Its modelling used product data through January 2022 and assumed no compensating changes elsewhere in the diet. It was not a trial comparing finished protein shakes.²

Check the current carton for protein and for added calcium, vitamin B12, vitamin D and iodine. One added nutrient does not guarantee the others. Unsweetened, fortified plant drinks can be a useful starting point for adults.^{1, 2}

Choose a flavour you enjoy, then ask what it contributes. A creamy texture alone cannot tell you the protein content. If your usual carton changes, give its label another look.

Work out the finished drink once

Before adding figures together, check whether the powder’s nutrition information describes it as sold or as prepared with a specified liquid. Government guidance explains that prepared values depend on the accompanying preparation instructions.³

If milk is already included in the stated serving, do not add it again. If the figures are for powder alone, use the liquid’s label and the volume you add.

For example, imagine a drink labelled with 3 g of protein per 100 ml. A 250 ml portion contributes:

3 × 250 ÷ 100 = 7.5 g of protein from the liquid.

This is a fictional liquid-only example, not a BioBoost value. To calculate the whole shake, you also need the verified protein amount in the powder serving. The protein powder label checklist explains the serving basis in more detail.

Lactose intolerance and milk allergy need different checks

Lactose intolerance concerns the digestion of lactose, a sugar in dairy foods. Milk allergy is a different condition. Lactose-free cow’s milk is still dairy and is not suitable for a milk allergy.^{4, 6}

Changing the liquid cannot remove lactose or milk proteins already present in the powder. A whey powder mixed with oat drink still contains milk protein. Check both products’ ingredients and allergy advice; a vegan label alone does not guarantee that unintended milk traces are absent.^{4, 5}

If digestive symptoms keep returning, speak to a GP rather than assuming the liquid is the cause.⁴ This guide cannot establish whether a particular powder is suitable for you.

Where BioBoost Balance+ Protein™ fits

BioBoost Balance+ Protein™ is a daily nutrition protein designed to make daily protein and nutrition simpler alongside food. The Vanilla product directions allow 200–300 ml of water, dairy milk or a plant-based alternative per recommended serving. Follow your pack’s preparation instructions and daily amount.⁷

Suitability: Contains milk. Not suitable for people with a milk allergy. The product page states that it may contain traces of gluten, egg, soy and shellfish/crustaceans. Contains bovine collagen; not suitable for vegetarians or vegans. Not recommended during pregnancy or breastfeeding, or for under-16s. If you take medication or are under medical supervision, seek advice before use. Always check your pack.⁷

Food supplements should complement a varied, balanced diet and healthy lifestyle and should not be used as a substitute for either.

Make your next shake an easy choice

Choose a suitable liquid, check what it adds and prepare the recommended serving. Let the finished drink fit the food you are having and the texture you enjoy.

References

1) NHS. Dairy and alternatives in your diet.

2) Scientific Advisory Committee on Nutrition and Committee on Toxicity. Assessment of the health benefits and risks of consuming plant-based drinks: summary. 2025.

3) Department of Health. Technical guidance on nutrition labelling. 2017.

4) NHS. Lactose intolerance.

5) Food Standards Agency. Food allergy and intolerance advice for consumers. GOV.UK.

6) North Bristol NHS Trust. Dietary advice for avoiding lactose. 2025.

7) Amaris Mint®. BioBoost Balance+ Protein™: Vanilla. Commercial product information.