What is protein good for? 7 functions of protein in your body (2026)

Protein is good for far more than just muscle building. It’s the building block of your muscles, organs, skin, hormones and immune system. Without enough protein your body can’t repair or maintain itself properly. Adults need around 0.8 grams of protein per kilogram of body weight per day; athletes sit higher. In this article you’ll read exactly what protein does, how much you need and where to get it from.

What is protein and why does your body need it?

In Dutch, “proteïne” and “eiwit” are two words for the same thing. The English “protein” and the Dutch “eiwit” both refer to the same macronutrient. Proteins are large molecules built from amino acids — the building blocks your body uses for virtually every biological process, from repairing muscle fibres to producing hormones.

Protein, amino acids and essential amino acids

There are twenty different amino acids. Nine of them are essential: your body can’t make them itself and you need to get them through food. The remaining eleven are non-essential, meaning your body produces them itself, provided you get enough calories and other nutrients.

Animal protein sources like chicken, eggs and quark contain all nine essential amino acids and are therefore called “complete proteins”. Plant sources sometimes lack one or more essential amino acids, but by combining smartly — like rice with lentils — you can hit a full amino acid profile as a vegan too.

Difference between “proteïne” and “eiwit”

In Dutch practice you mostly see “proteïne” on packaging of protein shakes, sports nutrition and fitness bars. “Eiwit” you’ll find on the official nutritional value tables and in advice from the Voedingscentrum. There’s no substantive difference: both terms describe exactly the same macronutrient.

Protein delivers 4 kilocalories per gram, just like carbs, but it works differently in your body. It’s more satiating, costs more energy to digest and has a direct structural function that fats and carbs simply don’t have.

What is protein good for? 7 main functions

Protein plays a role in your body that goes far beyond growing muscles. Below are the seven most important functions, from tissue repair to the production of haemoglobin in your blood.

1. Building and repairing muscles

After training, small tears form in your muscle fibres. Protein delivers the amino acids needed to repair those tears and let the muscle grow back stronger and thicker. Without enough protein you’ll stagnate, no matter how hard you train at the gym.

2. Maintaining organs, skin and hair

Your skin, nails and hair are largely made up of proteins like collagen and keratin. Your liver, kidneys and gut continuously renew their cells. Protein delivers the raw material for all that maintenance. You’ll often notice a deficit first in your skin and hair: dull, more brittle, less resilient.

3. Producing enzymes and hormones

Enzymes are proteins that speed up chemical reactions in your body — think digesting food or repairing DNA. Hormones like insulin and growth hormone are also built from amino acids. Without enough protein these processes go out of balance, with consequences for your energy, blood sugar and recovery.

4. Stronger immune system

Antibodies, the proteins that fight infections, are entirely built from amino acids. A chronically low protein intake noticeably weakens your immune system. That applies even more in periods of stress, illness or intensive training — exactly the moments when your body asks more of you.

5. Longer satiety and weight management

Of the three macronutrients, protein is the most satiating. It stimulates the production of satiety hormones like PYY and GLP-1 and suppresses the hunger hormone ghrelin. Anyone eating more protein generally eats fewer calories across the entire day. On top of that, digesting protein costs more energy than digesting fat or carbs — the so-called thermic effect of food.

6. Stronger bones

Bones consist of about a third proteins, primarily collagen. Protein helps with calcium uptake and supports the production of bone tissue. Research shows that people who eat enough protein have higher bone density and are less likely to develop osteoporosis later in life WHO (official).

7. Transport of oxygen and nutrients

Haemoglobin, the molecule in your red blood cells that transports oxygen, is a protein. Albumin transports fatty acids, hormones and medication through your blood. Without enough protein these transport mechanisms work less efficiently, directly affecting your endurance and recovery capacity.

How much protein per day do you need?

The official guideline from the Voedingscentrum is a handy starting point, but exact need depends strongly on your age, activity level and life stage.

Non-athletes

For healthy adults the Voedingscentrum recommends 0.8 grams of protein per kilogram of body weight per day. For someone of 70 kilograms that’s 56 grams per day. Concretely: a 150-gram portion of chicken fillet delivers roughly 35 grams of protein, two eggs together provide 12 grams and a tub of low-fat quark adds another 10 grams. With that you’re already well above the recommended daily amount.

Strength athletes and endurance athletes

Anyone who trains regularly needs more. Sports nutrition research typically uses a range of 1.2 to 1.6 grams per kilogram for endurance athletes and 1.6 to 2.0 grams per kilogram for strength athletes. For that same 70-kilo person it means between 112 and 140 grams per day. Spread that across four to five protein-rich meals for the best result.

65-plus and pregnant women

Older adults break down muscle tissue faster and need more protein to maintain muscle mass: at least 1.0 to 1.2 grams per kilogram per day. Pregnant women have an extra need of around 10 grams per day on top of the normal recommendation, rising in the third trimester. When in doubt, always consult a dietitian or GP.

Best protein sources from the Dutch supermarket

You don’t need to buy expensive supplements to get enough protein. Albert Heijn, Jumbo and Lidl offer more than enough affordable and nutritious options, both animal and plant-based.

Animal sources: chicken, quark, eggs, fish

Chicken fillet is one of the most efficient protein sources: 150 grams delivers around 35 grams of protein for about €1.50. Greek quark in 500-gram own-brand tubs at Lidl or AH delivers around 50 grams of protein for less than €1.80. A box of six eggs at Jumbo costs around €1.00 and together delivers 42 grams of protein. Tinned mackerel gets you to 20 grams of protein per tin for under €1.50.

Plant sources: legumes, tofu, tempeh, nuts

Lentils and chickpeas, dry or tinned, deliver 8 to 9 grams of protein per 100 grams cooked, for less than €1 per tin at Lidl. Tofu in 200-gram packs costs about €1.50 at AH and delivers 16 grams of protein. Tempeh scores even higher: around 20 grams of protein per 100 grams. Nuts and nut butters are less efficient as a protein source due to their high fat content, but they combine well as a supplement to a meal that already contains other protein sources.

Protein shakes and bars: when yes or no

Protein shakes aren’t a necessity, but they can be useful as a supplement on days when it’s hard to hit your protein target through regular food. Think busy work days or periods of intensive training. A good rule of thumb: use shakes and bars only once your daily meals are already protein-rich. They never replace a varied eating pattern.

Protein and sports: what really works?

Training without enough protein is like building without cement. The muscle growth you want to achieve depends largely on how much and when you eat protein. Want to learn more about the basics of strength training?

Timing and distribution across the day

Research shows your body optimally handles 20 to 40 grams of protein per meal for muscle protein synthesis. Eating more in one go doesn’t work proportionally better. So spread your daily protein intake across three to five meals. A day with 140 grams of protein spread across four meals is more effective than stuffing it all into one big evening meal.

Whey, casein or plant-based?

Whey is absorbed quickly and is popular right after training because of its high leucine content, an amino acid that triggers muscle growth. Casein digests more slowly and is suitable as an evening snack because it gradually releases amino acids overnight. Plant-based proteins like pea or soy protein are fine alternatives.

Protein before or after training

The so-called “anabolic window” of 30 minutes right after training is less strict than long thought. Protein intake within two hours after training has a positive effect, but the total daily intake weighs more than the exact moment. Eat a light meal with protein and carbs before training if you’re going intensively for an hour or longer.

What we saw at 250+ Dutch gyms

Gymsearch analyses gyms across the Netherlands, from gyms Amsterdam and gyms in Rotterdam to smaller cities like Zwolle and Tilburg. What stands out when you look at the offering around nutrition and protein.

Gyms with nutritional coaching

Of the more than 250 gyms in our database, roughly 60 percent offer some form of nutritional coaching. That ranges from a one-off introductory chat to a fully customised nutrition plan. Pure Gym and Anytime Fitness sit in between: they refer to external dietitians or offer online nutrition modules.

What does coaching with protein advice cost?

A single nutrition consultation at a gym averages €50 to €80. A full personal training programme including nutrition plan runs from €150 to €350 per month, depending on the number of sessions and the location. For an up-to-date overview, check our page on comparing prices. Gyms in Amsterdam and gyms in Utrecht tend to be 15 to 20 percent more expensive than comparable gyms in Eindhoven or Groningen.

Can too much protein be harmful?

The fear of too much protein is larger than necessary, but it isn’t entirely unfounded. In healthy people, a higher protein intake is generally safe, but there are limits to take into account.

Myth: protein bad for your kidneys

Healthy kidneys have no trouble with a higher protein intake. The myth comes from research in people with existing kidney diseases, for whom a lower-protein diet is indeed recommended. For healthy adults there is no strong evidence that an intake up to 2.0 grams per kilo damages kidney function. A consistent intake of more than 3.0 grams per kilo per day is unnecessary and offers no extra benefits.

When to see a GP or dietitian?

Consult a GP or dietitian if you have or suspect kidney problems, if you’re pregnant and unsure about your protein intake, or if you want to eat substantially more than the guidelines advise. A dietitian draws up a personal nutrition plan that matches your specific situation and goals.

Conclusion: how do you get enough protein?

Spread your protein intake across the day, vary between animal and plant sources and use protein shakes only as a supplement to an already protein-rich eating pattern. Anyone who moves regularly and eats enough protein gives their body the best base for recovery, muscle growth and long-term health.