Kira Mei is a certified personal trainer and nutrition coach helping UK adults over 40 get fit, eat well, and build sustainable habits.
The supplement industry has spent decades convincing UK shoppers that protein is expensive, but a side-by-side comparison per 100g tells a different story. When you rank protein sources by pence per gram rather than by what the label shouts, the cheapest option in the country costs under 1p per gram — roughly a tenth of what a branded protein shake charges. Most people never run this comparison, so they buy a £2.50 shake for 30g of protein when a 49p tin of tuna delivers nearly the same. This is the full per-100g comparison of the cheapest protein sources in the UK, ranked from lowest to highest cost per gram, with realistic own-brand supermarket prices and the protein density of each. The conclusion is uncomfortable for anyone selling powder: the cheapest protein in Britain has been sitting in the tinned-fish aisle and the egg box all along.
The cheapest protein source in the UK per 100g is dry red lentils at roughly 0.5–1p per gram of protein, followed by tinned tuna (around 1.2p), eggs (around 1.5p) and own-brand Greek yoghurt (around 1.7p). All four beat branded whey (around 5–8p per gram) and protein bars (over 10p). Ranked by pence per gram, whole foods win decisively.
The Per-100g Protein Comparison, Ranked
Ranked by pence per gram of protein, dry red lentils are the cheapest protein source in the UK, followed by tinned tuna, eggs and own-brand Greek-style yoghurt — every one of them undercutting branded powders and bars.
The British Nutrition Foundation explains that protein quality and quantity both matter, which is why this comparison lists both the cost and the protein per 100g rather than price alone. A cheap source that delivers little protein per 100g is not actually cheap once you scale it to a daily target.
Plant tier — lowest pence per gram
Dry red lentils (own-brand, around 90p per 500g) carry roughly 24g of protein per 100g dry weight, which works out under 1p per gram. The caveat is bioavailability: plant protein is less efficiently used, so count lentils at around 70% effective and pair them with a small animal-protein hit. Dry chickpeas and split peas sit in the same tier. The dry-versus-tinned distinction matters here: a 500g bag of dry lentils cooks up to well over a kilo and costs a fraction of the equivalent tins, so buying dry and batch-cooking is what pushes the price to the bottom of the table. Tinned pulses are more convenient but cost two to three times more per gram of protein, so reserve them for the days you have not batched.
Tinned fish tier — best animal protein per penny
Tinned tuna in spring water (own-brand, around 49–75p per tin) delivers about 24g of protein per 100g drained, landing near 1.2p per gram. Tinned mackerel and sardines sit slightly higher per gram but add omega-3s, making them the best-value oily fish for hitting the NHS one-portion-a-week recommendation.
Egg and dairy tier — the complete-protein bargain
Eggs (own-brand, around £1.45 for six) carry about 13g of protein per 100g and land near 1.5p per gram, with the bonus of being a complete protein covering all nine essential amino acids. Own-brand Greek-style yoghurt (around £1.45/kg) and cottage cheese round out the dairy tier at 1.7–2.8p per gram.
How the Cheap Sources Compare to Supplements
Branded whey protein costs roughly 5–8p per gram and protein bars over 10p — five to ten times more than tinned tuna, eggs or lentils — so supplements are the most expensive protein per gram a UK shopper can buy.
Money Saving Expert's cheap supermarket food guide makes the broader point that own-brand basics undercut branded equivalents by 40–60%, and protein supplements are the sharpest example. The "high protein" label is a price multiplier applied to nutrition you can buy whole for a fraction.
Why whey still has a narrow use case
Whey is not useless — it is convenient and fast-digesting around training. But on pure cost per gram it loses to every whole-food source in this comparison. Treat it as an occasional convenience, not the base of your protein intake, and the weekly bill drops sharply.
The protein-bar trap
A typical branded protein bar offers 15–20g of protein for £1.50–£2.50, which is over 10p per gram before you account for the sugar and fat that come with it. Two boiled eggs deliver similar protein for under 30p. On the per-100g comparison, bars are the worst-value entry on the board.
How to read a protein label honestly
The number that matters on any pack is protein per 100g set against the price per 100g — everything else is marketing. A "high protein" pudding boasting "20g protein" on the front often hides a 200g serving and a price that works out at three or four times the cost per gram of plain yoghurt. Flip the pack, find the per-100g protein figure, divide the price by the grams, and the real value appears. Do this once in the supplement aisle and once in the dairy aisle and the gap is stark: the same money buys several times more protein from the whole-food shelf. The label is designed to stop you running that sum, which is exactly why running it is the single most useful budget-protein habit.
Applying the Comparison to a Real Weekly Shop
Anchoring a week around the three cheapest sources — lentils, tinned tuna and eggs — lets a UK shopper hit 130g of protein a day for under £4, with dairy and frozen chicken added for variety.
The NHS Eatwell Guide places beans, pulses, fish and eggs at the centre of a balanced plate, so building from the cheapest tier is also building to the national guideline rather than against it.
The three-source backbone
Lentils for batch-cooked lunches, tinned tuna for no-cook protein, and eggs for breakfast and snacks. These three cover roughly 60% of a daily target between them and cost pennies per portion, leaving budget for the variety that keeps the week interesting. The reason this trio works so well is that each one solves a different problem: lentils give cheap volume from a Sunday batch, tuna gives instant protein with no cooking at all, and eggs give a complete, portable protein that slots into any meal. Together they mean you are never more than a tin-opener or a fridge door away from 20–30g of protein, which is the practical difference between hitting a daily target and giving up on it by mid-afternoon.
Adding variety without losing the cost edge
Own-brand Greek yoghurt and frozen chicken bring the rotation the British Nutrition Foundation recommends, and both still land well under the supplement tier on pence per gram. The result is a varied, complete protein intake that costs a fraction of a supplement-led approach.
Why the cheapest source alone is not the answer
It would be easy to read this comparison and decide to live on red lentils, since they top the table. That misses the point. The cheapest source wins on pence per gram, but a diet built on a single ingredient fails on bioavailability, micronutrients and, frankly, willpower. The smart move is to anchor the bulk of your protein on the two or three cheapest sources and use the slightly pricier ones — dairy, chicken, the occasional oily fish — to fill the gaps the cheapest sources leave. That blend keeps the average cost per gram near the bottom of the table while covering the full amino-acid range and giving you a week of food you will actually eat. Cheapest on paper and cheapest in practice are not always the same thing.
Mistakes That Make Cheap Protein Expensive
Three mistakes erase the cost advantage of cheap protein — ignoring bioavailability, buying "high protein" labelled versions, and letting fresh protein spoil — and all three are avoidable with a list.
Mistake one — ignoring bioavailability
Counting lentil protein gram-for-gram against egg protein overstates what your body uses. Plant sources are less bioavailable, so pad the daily total slightly and pair pulses with an egg or dairy hit. Cheap protein still works; it just needs a small adjustment in the maths.
Mistake two — paying the protein-label tax
Buying the "high protein" version of a yoghurt or pudding costs two to three times the plain own-brand for the same or less actual protein. The comparison only holds if you buy the base ingredient, not the marketed upgrade.
Mistake three — letting protein spoil
Cheap protein wasted is expensive protein. NHS food safety guidance confirms cooked meals and chicken keep 3–4 days refrigerated and longer frozen, so batch, label and freeze rather than binning forgotten fresh packs. The cheapest entries in this comparison — lentils, tinned tuna, eggs — all share one quiet advantage: they barely spoil. Dry pulses and tins last for months or years, and eggs hold for weeks, so the per-gram cost on the page is also the cost in practice. That is part of why they sit at the top of the table and the perishable, pricier options sit below: low waste is its own form of value.
Kira Mei's Nutrition Blueprint is the systematic version of this comparison — a full calorie and macro education with a UK meal-prep system built around Aldi, Lidl and Tesco, so you can apply the cheapest-per-gram logic to any goal. One-time £49.99 at kiramei.co.uk, lifetime access, no subscription, no meal plan to follow forever. It's not a diet plan, it's a textbook.
How to Lock In the Lowest Protein Prices Across the Year
The biggest lever on protein cost is not which source you buy but when and how you store it: a freezer shelf of reduced meat and fish, bought at 30–75% off near closing time, beats any cheap-protein list bought at full price. Pence-per-gram only gives the headline rate; the shopper who freezes reductions and buys non-perishables in bulk pays well below it.
Time the yellow-sticker reductions
Most UK supermarkets discount short-dated fresh meat, fish and dairy in the early evening, with the deepest cuts close to closing. Money Saving Expert's supermarket guide tracks the rough markdown windows by chain. Reduced chicken thighs, mince and salmon freeze cleanly for up to three months, so one well-timed shop can stock a fortnight of animal protein at a fraction of the shelf price.
Use the freezer as a price hedge
Eggs, milk and hard cheese all freeze, and tinned and dried sources never spoil, so the freezer and the cupboard let you buy at the low point and eat at the high one. A multipack of frozen fish or a large bag of dried lentils spreads the unit cost across weeks and removes the mid-week top-up shop that quietly inflates every protein budget.
Always compare the unit price, not the pack price
The price-per-100g figure on the shelf-edge label is the only honest comparison between a small value pack and a large one. A bigger pack is usually — not always — cheaper per gram, and own-brand frozen or tinned protein routinely undercuts the branded fresh equivalent by half once you read the unit rate rather than the sticker.
Frequently Asked Questions
What is the cheapest protein source per 100g in the UK?
By cost per gram of protein, dry red lentils are the cheapest at roughly 0.5–1p per gram, carrying about 24g of protein per 100g dry weight. Tinned tuna follows at around 1.2p per gram, then eggs at 1.5p and own-brand Greek-style yoghurt near 1.7p. All four undercut branded whey (around 5–8p) and protein bars (over 10p), making whole foods the cheapest protein in the country by a wide margin.
Is cheap plant protein as good as meat protein?
Plant protein from lentils and beans is less bioavailable than animal protein, so your body uses slightly less of each gram. The British Nutrition Foundation recommends pairing or rotating sources to cover the full amino-acid range. In practice, count plant protein at around 70% effective and add a small egg or dairy hit. Done that way, cheap plant protein is a perfectly sound base for a high-protein diet on a budget.
How does tinned tuna compare to whey protein on cost?
Tinned tuna costs roughly 1.2p per gram of protein, while branded whey runs around 5–8p per gram — so tuna is four to six times cheaper per gram. A 49p tin delivers about 30g of protein with no powder, shaker or subscription required. Whey is convenient around training, but on pure cost per gram, tinned fish and other whole foods win the comparison decisively for UK budget shoppers.
How much protein do I actually need per day?
The NHS guideline is around 0.75g of protein per kilogram of body weight for a sedentary adult, rising for those who train regularly. For a 70kg adult that is roughly 55g as a minimum, though many active people target 100–140g. Whichever target you set, building it from the cheapest sources in this comparison — lentils, tuna and eggs — keeps the cost per day under £4 while still meeting the guideline.
Are protein bars ever worth it for budget shoppers?
Rarely on cost. A branded protein bar offers 15–20g of protein for £1.50–£2.50, over 10p per gram, making it the most expensive entry in the per-100g comparison. Two boiled eggs deliver similar protein for under 30p. Bars buy convenience, not value, so keep them for genuine on-the-go gaps and build the daily total from cheaper whole foods to protect the budget.
Disclaimer: This article is for informational purposes only and does not constitute medical, nutritional, or professional fitness advice. Always consult a qualified healthcare professional before making changes to your diet or exercise routine.