Protein Sources Compared
Animal and plant-based proteins ranked by protein content, completeness, cost, and digestibility.
TL;DR
- 01Animal proteins are generally complete (all nine essential amino acids) with high digestibility; most plant proteins are incomplete but can be combined.
- 02Chicken breast, Greek yogurt, eggs, and canned tuna offer the best protein-to-calorie ratios among animal sources.
- 03Lentils, edamame, and tofu are the most practical high-protein plant options for everyday eating.
Tips
- 01Vary protein sources throughout the week — different animals and cuts provide different micronutrient profiles. Salmon, eggs, and dairy complement each other's nutrient gaps.
- 02If you struggle to hit targets, replace a carbohydrate snack (crackers, fruit) with a protein-forward one (Greek yogurt, cottage cheese, hard-boiled eggs, edamame). This single swap often bridges a 20–30 g daily gap.
Warnings
- 01Soy-based proteins (tofu, tempeh, edamame) are the only plant proteins with a DIAAS score comparable to many animal proteins. For muscle building on a plant-based diet, these should be your primary protein anchor.
Why Protein Matters
Protein is the only macronutrient that provides nitrogen — the essential element in amino acids that build and repair every tissue in your body. Beyond muscle, protein is required for enzymes, hormones (including insulin and growth hormone), immune antibodies, and transport proteins like haemoglobin.
Adequate protein supports:
- Satiety: Protein stimulates PYY and GLP-1 hormones that reduce hunger — more effectively than fat or carbohydrates.
- Muscle protein synthesis (MPS): Stimulated most effectively by 20–40 g of protein containing at least 2–3 g of leucine per meal.
- Thermic effect: Protein requires 20–30% of its calories just to digest, compared to 5–10% for carbs and 0–3% for fat.
- Bone density: Contrary to older beliefs, higher protein intake is associated with better bone mineral density.
The minimum RDA is 0.8 g/kg/day. Most researchers now recommend 1.2–1.6 g/kg for active adults and up to 2.2 g/kg for those pursuing muscle growth.
Complete vs Incomplete Proteins
A complete protein contains all nine essential amino acids (EAAs) in adequate proportions. Most animal proteins and a handful of plant proteins meet this criterion. Incomplete proteins lack one or more EAAs in sufficient amounts but can be combined throughout the day to cover all requirements — the body pools amino acids over a 24-hour period.
| Source type | Complete? | Limiting amino acid (if incomplete) | Protein quality score (DIAAS) |
|---|---|---|---|
| Whey protein | Yes | — | 1.09 (excellent) |
| Egg (whole) | Yes | — | 1.13 (excellent) |
| Beef | Yes | — | 1.10 (excellent) |
| Chicken | Yes | — | ~1.08 (excellent) |
| Soy / edamame | Yes | — | 0.91 (high) |
| Lentils | No | Methionine | 0.59 (medium) |
| Black beans | No | Methionine | 0.62 (medium) |
| Wheat (bread) | No | Lysine | 0.45 (low) |
| Rice | No | Lysine | 0.59 (medium) |
The DIAAS (Digestible Indispensable Amino Acid Score) is the most rigorous protein quality metric. Scores above 1.0 indicate excellent quality; 0.75–1.0 is good; below 0.75 is adequate but lower quality.
Animal Protein Sources
Animal proteins deliver complete amino acid profiles with high bioavailability and are especially rich in B12, heme iron, zinc, and creatine — nutrients rarely found in meaningful amounts in plants.
| Food | Serving | Protein (g) | Calories | Protein kcal ratio | Notes |
|---|---|---|---|---|---|
| Chicken breast (cooked, skinless) | 100 g | 31 g | 165 kcal | 75% | Leanest common meat protein |
| Canned tuna (in water) | 100 g | 25 g | 116 kcal | 86% | Convenient, affordable |
| Greek yogurt (0%, plain) | 170 g | 17 g | 100 kcal | 68% | Also provides calcium and probiotics |
| Cottage cheese (1%) | 226 g (1 cup) | 28 g | 163 kcal | 69% | High in casein — slow digesting |
| Whole egg | 1 large (50 g) | 6 g | 72 kcal | 33% | Excellent leucine content |
| Salmon (cooked) | 100 g | 25 g | 208 kcal | 48% | Also provides ~2.2 g omega-3 |
| 93% lean ground beef (cooked) | 100 g | 26 g | 218 kcal | 48% | High in zinc and B12 |
| Shrimp (cooked) | 100 g | 24 g | 99 kcal | 97% | Highest protein-to-calorie ratio |
Plant Protein Sources
Plant proteins are valuable for their fibre, phytonutrients, and lower saturated fat content. To match the anabolic effect of animal protein, consume slightly larger portions or prioritise sources with higher leucine content.
| Food | Serving | Protein (g) | Calories | Complete? | Notes |
|---|---|---|---|---|---|
| Edamame (cooked) | 155 g (1 cup) | 17 g | 188 kcal | Yes | Best plant protein-to-calorie ratio |
| Tofu (firm) | 126 g (½ cup) | 10 g | 94 kcal | Yes | Versatile; absorbs flavour well |
| Tempeh | 85 g | 16 g | 160 kcal | Yes | Fermented soy; higher iron than tofu |
| Lentils (cooked) | 198 g (1 cup) | 18 g | 230 kcal | No | Combine with rice to complete profile |
| Black beans (cooked) | 172 g (1 cup) | 15 g | 227 kcal | No | High fibre; good iron source |
| Chickpeas (cooked) | 164 g (1 cup) | 15 g | 269 kcal | No | Excellent versatility |
| Hemp seeds | 28 g (3 tbsp) | 10 g | 166 kcal | Yes | Complete; high omega-3 ALA |
| Seitan (wheat gluten) | 85 g | 21 g | 104 kcal | No | Not suitable for gluten intolerance |
How to Hit Your Daily Protein Target
The most reliable method is to build each meal around a clear protein source and pre-plan the day's total. A simple rule: aim for 25–40 g of protein per main meal — easier to track than a running gram total.
| Target (g/day) | Sample day — animal-based | Sample day — plant-based |
|---|---|---|
| 120 g | 3 eggs + 2 egg whites (18g) + Greek yogurt (17g) + 150g chicken breast (46g) + 100g salmon (25g) + cottage cheese snack (14g) | Tofu scramble 20g + edamame 17g + lentil soup 18g + tempeh stir-fry 16g + hemp seeds + protein smoothie 20g |
- Protein powder (whey, casein, pea, rice) is a practical top-up — not a replacement for whole food. One scoop typically delivers 20–30 g protein for 100–130 kcal.
- Distribute protein across 3–4 meals rather than loading it at dinner — each meal should deliver at least 20 g to maximally stimulate muscle protein synthesis.
- Track for two weeks then rely on portion intuition — most people consistently underestimate protein intake before tracking.
FAQ
Most adults need 0.8–1.0g per kg of body weight, but active individuals and those building muscle benefit from 1.6–2.2g per kg. A 150lb (68kg) person aiming for muscle gain should target roughly 110–150g daily.
A complete protein contains all nine essential amino acids in adequate amounts, while an incomplete protein is deficient in at least one. Animal proteins are almost universally complete; most plant proteins are incomplete, but pairing sources like rice and beans across meals covers the gaps.
Labels show total protein, but your body can't fully absorb all of it equally — digestibility and amino acid balance both affect usability. A food with a DIAAS near or above 1.0 (like eggs or chicken) delivers nearly all its listed protein, whereas low-scoring sources like bread may provide far less usable protein than the number suggests.
Yes, but it takes more planning than an omnivore diet because most plant proteins score lower on digestibility and are often incomplete. Centering meals around soy, edamame, and tofu — the highest-quality plant options — and eating a variety of other protein sources throughout the day will cover all essential amino acids.
Chicken breast, canned tuna, egg whites, and non-fat Greek yogurt all deliver 20–30g of protein for around 100–150 calories, making them the most efficient options for hitting targets in a calorie deficit. Among plant sources, edamame and firm tofu offer the best protein-to-calorie ratio.