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Rule One R1 Plant Protein — 20g from Pea and Three Seed Proteins

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Rule One R1 Plant Protein20 grams of protein at 120 calories from four plant sources — pea, sunflower seed, pumpkin seed and watermelon seed. Stevia sweetened, soy free, and Informed Choice certified.The source blend is what makes this different from almost every other plant protein, and there is real thinking behind it.Why seeds rather than riceNearly every vegan protein on the market is pea and rice. R1 Plant Protein uses pea plus three seed proteins, and that choice solves the same problem by a better route.The problem with pea protein alone: it is excellent in lysine but relatively low in methionine, a sulphur-containing essential amino acid. On its own that leaves the amino acid profile incomplete.Rice protein is the usual fix, because rice is comparatively higher in methionine. But seed proteins — particularly sunflower and pumpkin — are richer in methionine still, which makes them a more efficient complement.There is a second reason to prefer seeds, and it is worth knowing. Rice plants take up inorganic arsenic from soil more readily than most crops, and testing of rice-based protein powders has found variable levels across products. It is not a reason to panic about rice protein, and reputable manufacturers test for it — but a blend built on seeds rather than rice does not raise the question at all.Watermelon seed protein has a nice piece of history behind itThis is the ingredient people skim past, and it connects to something you have probably taken.Citrulline — the pump ingredient in every pre-workout on our shelf — was originally isolated from watermelon. That is where the name comes from: watermelon's botanical name is Citrullus lanatus.Watermelon seed protein is naturally comparatively rich in arginine, the amino acid citrulline converts to in order to produce nitric oxide.The amount in a protein serving is nowhere near a pre-workout dose, so do not buy this expecting pumps. But it is a genuine and rather elegant piece of formulation rather than an ingredient chosen for the label.Informed Choice certification on a plant protein is unusualR1 Plant Protein is regularly tested for banned substances by LGC, one of the major sports anti-doping laboratories.Certification costs money to maintain, so it usually appears on flagship whey products rather than plant-based lines. Most vegan proteins carry none at all.If you compete in a tested federation and eat plant-based, this is a genuinely short list to choose from. Rule One also manufacture in their own GMP-certified facility rather than contracting production out.Specs Protein20g Calories120 Carbohydrate4g Fibre2g (including prebiotic inulin) Fat2g SourcesPea, sunflower seed, pumpkin seed, watermelon seed EAAsAll nine, naturally occurring SweetenerStevia leaf extract CertificationInformed Choice, tested by LGC Free fromDairy, lactose, soy, gluten, cholesterol, artificial flavours and colours Servings20Soy free is worth flagging — several proteins use soy lecithin as a mixing agent, so this suits anyone avoiding soy. R1 uses a gum blend of guar, acacia and xanthan instead.⚠ One note on the inulin. It is included as prebiotic fibre and it is a sensible addition for most people — but inulin is a fermentable fibre and a common FODMAP trigger. If you have IBS or follow a low-FODMAP diet, start with half a scoop.Honest note on 20g and 120 caloriesTwo things worth knowing rather than glossing over.20g is standard for a plant protein but 5g below a typical whey isolate. Plant proteins generally run lower, partly because the raw materials are less concentrated.Leucine is the number that matters more. Plant proteins are naturally lower in leucine — the amino acid that actually triggers muscle protein synthesis — than dairy proteins are. If this is your main post-training protein and maximising that response matters to you, a scoop and a half is a reasonable adjustment. If it is a top-up alongside meals, 20g is perfectly appropriate.Which vegan protein should you buy? ProteinDistinguishing feature R1 Plant Protein20g / 120 calInformed Choice certified. Seed-based, soy free Core VEGAN21g / ~120 calBest taste. Sucralose. Contains coconut PEScience Select Vegan20g / ~110 calStevia, simplest label 1st Phorm Vegan Power Pro19g / 100 calAdds greens, vitamins and enzymesThe honest guide: R1 if you are a tested athlete or avoiding soy. Core VEGAN if taste matters most. PEScience for the simplest stevia-sweetened option. Vegan Power Pro if you want greens and vitamins bundled in — though note it is made on shared equipment with milk and egg.How to mix it One heaping scoop in 8 to 10 ounces of water or plant milk. Plant proteins need more liquid than whey. Cold water genuinely matters with any plant protein — it mixes considerably better. The gum blend (guar, acacia, xanthan) improves texture, which is why this drinks better than a plain pea protein. Blend with fruit if you find plant proteins gritty. Frozen banana in particular transforms the texture. Post-workout, between meals, or at bedtime. Plant proteins digest at a moderate pace.Who this is for Tested athletes who eat plant-based — Informed Choice certification is rare here Anyone avoiding soy, which several proteins include as lecithin People who would rather avoid rice protein Anyone avoiding artificial sweeteners Vegans, vegetarians, and anyone dairy-free or lactose intolerant People following paleo or keto approaches — 4g carbs, 2g of that fibreWho this is not forIf you dislike stevia, Core VEGAN uses sucralose instead.If you have IBS or follow low-FODMAP, the inulin may not suit you. Start small.If you want maximum protein per serving, whey isolates deliver 25g. If you can tolerate dairy, whey remains stronger gram for gram — higher leucine, faster absorption, more research behind it. Choose plant for a reason.If you want a thick, creamy shake, plant proteins are thinner and grittier by nature.Stack it with: creatine — worth noting that the main dietary sources are meat and fish, so plant-based eaters start from a lower baseline and often respond more. See our creatine range.Frequently asked questionsHow much protein per serving?20g at 120 calories, from pea, sunflower seed, pumpkin seed and watermelon seed protein.Why seeds instead of rice?Pea protein is low in methionine and needs a complement. Sunflower and pumpkin seed proteins are richer in methionine than rice is, so they fill that gap more efficiently — and a seed blend avoids the arsenic question that rice-based proteins raise.Is it a complete protein?Yes — the blend provides all nine essential amino acids, naturally occurring rather than added.Why watermelon seed protein?It is comparatively rich in arginine. Citrulline, the pump ingredient in pre-workouts, was originally isolated from watermelon — hence the name Citrullus lanatus. The amount here is nowhere near a pre-workout dose.Is it tested for banned substances?Yes, Informed Choice certified by LGC — unusual for a plant protein, since most carry no certification at all.Does it contain soy?No. It uses a guar, acacia and xanthan gum blend rather than soy lecithin.What is the inulin for?Prebiotic fibre, which feeds the bacteria already in your gut. Note that inulin is a common FODMAP trigger — start with half a scoop if you have IBS.Is 20g enough?For a top-up alongside meals, yes. Plant proteins are naturally lower in leucine than dairy, so if this is your main post-training serving, a scoop and a half is a reasonable adjustment. Read more

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PRODUCT LABEL

Rule One R1 Plant Protein

20 grams of protein at 120 calories from four plant sources — pea, sunflower seed, pumpkin seed and watermelon seed. Stevia sweetened, soy free, and Informed Choice certified.

The source blend is what makes this different from almost every other plant protein, and there is real thinking behind it.

Why seeds rather than rice

Nearly every vegan protein on the market is pea and rice. R1 Plant Protein uses pea plus three seed proteins, and that choice solves the same problem by a better route.

The problem with pea protein alone: it is excellent in lysine but relatively low in methionine, a sulphur-containing essential amino acid. On its own that leaves the amino acid profile incomplete.

Rice protein is the usual fix, because rice is comparatively higher in methionine. But seed proteins — particularly sunflower and pumpkin — are richer in methionine still, which makes them a more efficient complement.

There is a second reason to prefer seeds, and it is worth knowing. Rice plants take up inorganic arsenic from soil more readily than most crops, and testing of rice-based protein powders has found variable levels across products. It is not a reason to panic about rice protein, and reputable manufacturers test for it — but a blend built on seeds rather than rice does not raise the question at all.

Watermelon seed protein has a nice piece of history behind it

This is the ingredient people skim past, and it connects to something you have probably taken.

Citrulline — the pump ingredient in every pre-workout on our shelf — was originally isolated from watermelon. That is where the name comes from: watermelon's botanical name is Citrullus lanatus.

Watermelon seed protein is naturally comparatively rich in arginine, the amino acid citrulline converts to in order to produce nitric oxide.

The amount in a protein serving is nowhere near a pre-workout dose, so do not buy this expecting pumps. But it is a genuine and rather elegant piece of formulation rather than an ingredient chosen for the label.

Informed Choice certification on a plant protein is unusual

R1 Plant Protein is regularly tested for banned substances by LGC, one of the major sports anti-doping laboratories.

Certification costs money to maintain, so it usually appears on flagship whey products rather than plant-based lines. Most vegan proteins carry none at all.

If you compete in a tested federation and eat plant-based, this is a genuinely short list to choose from. Rule One also manufacture in their own GMP-certified facility rather than contracting production out.

Specs

Protein	20g
Calories	120
Carbohydrate	4g
Fibre	2g (including prebiotic inulin)
Fat	2g
Sources	Pea, sunflower seed, pumpkin seed, watermelon seed
EAAs	All nine, naturally occurring
Sweetener	Stevia leaf extract
Certification	Informed Choice, tested by LGC
Free from	Dairy, lactose, soy, gluten, cholesterol, artificial flavours and colours
Servings	20

Soy free is worth flagging — several proteins use soy lecithin as a mixing agent, so this suits anyone avoiding soy. R1 uses a gum blend of guar, acacia and xanthan instead.

⚠ One note on the inulin. It is included as prebiotic fibre and it is a sensible addition for most people — but inulin is a fermentable fibre and a common FODMAP trigger. If you have IBS or follow a low-FODMAP diet, start with half a scoop.

Honest note on 20g and 120 calories

Two things worth knowing rather than glossing over.

20g is standard for a plant protein but 5g below a typical whey isolate. Plant proteins generally run lower, partly because the raw materials are less concentrated.

Leucine is the number that matters more. Plant proteins are naturally lower in leucine — the amino acid that actually triggers muscle protein synthesis — than dairy proteins are. If this is your main post-training protein and maximising that response matters to you, a scoop and a half is a reasonable adjustment. If it is a top-up alongside meals, 20g is perfectly appropriate.

Which vegan protein should you buy?

	Protein	Distinguishing feature
R1 Plant Protein	20g / 120 cal	Informed Choice certified. Seed-based, soy free
Core VEGAN	21g / ~120 cal	Best taste. Sucralose. Contains coconut
PEScience Select Vegan	20g / ~110 cal	Stevia, simplest label
1st Phorm Vegan Power Pro	19g / 100 cal	Adds greens, vitamins and enzymes

The honest guide: R1 if you are a tested athlete or avoiding soy. Core VEGAN if taste matters most. PEScience for the simplest stevia-sweetened option. Vegan Power Pro if you want greens and vitamins bundled in — though note it is made on shared equipment with milk and egg.

How to mix it

One heaping scoop in 8 to 10 ounces of water or plant milk. Plant proteins need more liquid than whey.
Cold water genuinely matters with any plant protein — it mixes considerably better.
The gum blend (guar, acacia, xanthan) improves texture, which is why this drinks better than a plain pea protein.
Blend with fruit if you find plant proteins gritty. Frozen banana in particular transforms the texture.
Post-workout, between meals, or at bedtime. Plant proteins digest at a moderate pace.

Who this is for

Tested athletes who eat plant-based — Informed Choice certification is rare here
Anyone avoiding soy, which several proteins include as lecithin
People who would rather avoid rice protein
Anyone avoiding artificial sweeteners
Vegans, vegetarians, and anyone dairy-free or lactose intolerant
People following paleo or keto approaches — 4g carbs, 2g of that fibre

Who this is not for

If you dislike stevia, Core VEGAN uses sucralose instead.

If you have IBS or follow low-FODMAP, the inulin may not suit you. Start small.

If you want maximum protein per serving, whey isolates deliver 25g. If you can tolerate dairy, whey remains stronger gram for gram — higher leucine, faster absorption, more research behind it. Choose plant for a reason.

If you want a thick, creamy shake, plant proteins are thinner and grittier by nature.

Stack it with: creatine — worth noting that the main dietary sources are meat and fish, so plant-based eaters start from a lower baseline and often respond more. See our creatine range.

Frequently asked questions

How much protein per serving?
20g at 120 calories, from pea, sunflower seed, pumpkin seed and watermelon seed protein.

Why seeds instead of rice?
Pea protein is low in methionine and needs a complement. Sunflower and pumpkin seed proteins are richer in methionine than rice is, so they fill that gap more efficiently — and a seed blend avoids the arsenic question that rice-based proteins raise.

Is it a complete protein?
Yes — the blend provides all nine essential amino acids, naturally occurring rather than added.

Why watermelon seed protein?
It is comparatively rich in arginine. Citrulline, the pump ingredient in pre-workouts, was originally isolated from watermelon — hence the name Citrullus lanatus. The amount here is nowhere near a pre-workout dose.

Is it tested for banned substances?
Yes, Informed Choice certified by LGC — unusual for a plant protein, since most carry no certification at all.

Does it contain soy?
No. It uses a guar, acacia and xanthan gum blend rather than soy lecithin.

What is the inulin for?
Prebiotic fibre, which feeds the bacteria already in your gut. Note that inulin is a common FODMAP trigger — start with half a scoop if you have IBS.

Is 20g enough?
For a top-up alongside meals, yes. Plant proteins are naturally lower in leucine than dairy, so if this is your main post-training serving, a scoop and a half is a reasonable adjustment.