Plant protein vs whey protein is a fair question to ask before buying a tub. The answer involves your training and the rest of the day's food as much as the powder. Whey comes from milk. It is the liquid that drains off when milk is split for cheese or paneer, and ICMR-NIN's Dietary Guidelines for Indians, 2024, call it a by-product of that process. The same guidelines list soybeans, peas and rice as the usual plant sources of protein powder.1
What makes a protein complete
A complete protein carries all nine essential amino acids, the ones the body cannot make for itself. ICMR-NIN notes that animal proteins, including the protein in milk, contain all nine, and whey is a milk protein.1 Among plant proteins, Harvard's Nutrition Source describes soy as a complete protein, and it lists tofu and soy milk among everyday soy foods.2
Many other plant proteins fall short. Hoffman and Falvo's review of protein sources says proteins from vegetable sources generally lack one or two essential amino acids.3 So a complete protein comparison puts whey and soy on the same side, with most other single plant sources needing a partner.
That partner is usually another food on the plate. ICMR-NIN recommends combining cereals with pulses, at about 3 parts cereal to 1 part pulse by raw weight. It calls this the most efficient way to get all nine essential amino acids from a vegan diet.1 Dal with rice or roti already follows that pattern, and at 3 to 1, 90 g of raw atta pairs with about 30 g of raw dal.
ICMR-NIN's Indian Food Composition Tables put numbers on that plate. Whole-wheat atta has 10.57 g of protein in 100 g, and chana dal has 21.55 g.4 Ninety grams of atta gives about 9.5 g of protein. Thirty grams of chana dal adds about 6.5 g, and together they make about 16 g from one plain meal.
Training and protein for muscle gain
ICMR-NIN's guidelines put the order of things plainly. Protein is used to build muscle only when you are physically active and doing strength exercise.1 That holds for protein for muscle gain from any source, plant or dairy.
In its position stand on protein and exercise, the International Society of Sports Nutrition (ISSN) lists whey and soy among proteins that can trigger muscle protein building.5 For other plant sources such as pea, rice and hemp, it says research on their effect on training results is still limited.5
So neither powder builds muscle on its own. Training does the building, the protein supplies the material, and anyone relying on plant protein needs to cover all nine essential amino acids across the day.
Plant vs whey protein in a day's food
Whichever you choose, it counts toward the same daily total. ICMR-NIN's figure of 0.83 g of protein per kg works out to about 54 g a day for someone who weighs 65 kg.1 A scoop that lists 20 g brings 20 g of that, whether the protein came from peas, soy or whey. The plain meal above adds about 16 g more, and the rest comes from other meals.
For vegetarians who eat dairy, milk and curd bring complete protein of their own. ICMR-NIN also notes that eating cereals with milk improves the protein quality of a meal, so a glass of milk with that roti does more than add its grams.1
Horlicks Protein uses a third source
Horlicks Protein takes a different route from both. Its Chocolate and Coffee sachets list fermented yeast protein, and Unflavoured pairs fermented yeast protein with whey protein concentrate. A 36 g sachet in 200 ml of cold water or milk adds 24 g of protein to the same 54 g day. Fermented yeast protein is neither a plant protein nor a dairy one, so it sits outside the plant vs whey question altogether.
For anyone who prefers a bottle, the Horlicks Protein milkshake holds 20 g of ultra-filtered milk protein per 240 ml.
Summing this up, whey comes from milk, and plant protein powders usually come from soybeans, peas or rice. Whey and soy both carry all nine essential amino acids, while many other plant proteins need combining, which ICMR-NIN suggests doing with cereals and pulses at about 3 to 1. Neither type builds muscle without training, which ICMR-NIN makes a condition for protein to be used that way. The ISSN lists both whey and soy among proteins that can support it, with less research so far on pea, rice and hemp. Horlicks Protein uses fermented yeast protein, with whey protein concentrate also in Unflavoured, and each sachet gives 24 g of protein.
Sources
1. ICMR-National Institute of Nutrition. Dietary Guidelines for Indians, 2024. https://nin.res.in/dietaryguidelines/pdfjs/locale/DGI_2024.pdf
2. Harvard T.H. Chan School of Public Health. The Nutrition Source, Soy. https://nutritionsource.hsph.harvard.edu/soy/
3. Hoffman JR, Falvo MJ. Protein, which is best? Journal of Sports Science and Medicine, 2004. PubMed 24482589. https://pmc.ncbi.nlm.nih.gov/articles/PMC3905294/
4. ICMR-National Institute of Nutrition. Indian Food Composition Tables, 2017. https://www.nin.res.in/ebooks/IFCT2017.pdf
5. Jäger R, et al. International Society of Sports Nutrition position stand: protein and exercise, 2017. PubMed 28642676. https://pmc.ncbi.nlm.nih.gov/articles/PMC5477153/