Protein 101: A Guide to the Building Block of Life 2025
Proteins are essential macronutrients crucial in the body's structure, function, and regulation of tissues and organs. They are the building blocks of cells, making them essential for the growth, maintenance, and repair of muscles, skin, bones, and other tissues.
These days, protein-boosted foods and supplements are commonplace. From shakes to powders to food packaging – it seems like everyone wants you to consume it. But what is protein, and just how important is it for your diet, really?
Along with fats and carbs, proteins make up the trio of macronutrients needed to keep you healthy and happy. In fact, there are several famous dietary programs that focus on proteins (like Keto, Paleo, or Whole 30).
Together with our in-house nutritionist, I’ve done a deep dive on protein. I’ll walk you through everything from the best sources of protein to the best ways to incorporate it into your diet.
Why Do We Need Protein?
Proteins are a fundamental structural part of every cell in your body. Therefore, to grow, develop, and live a healthy life, you must maintain and replenish these literal blocks of life. You do this through the food and supplements you consume.
Every part of the human body, including skin, hair, bones, muscles, and other tissues, contains protein. Overall, there are over 10,000 types of protein in your body, which are hard at work to keep you alive and functioning1.
Growth & Repair
Adequate protein intake is crucial for muscle health, wound healing, and overall body function. I’m not just talking about building up your muscle in the gym – proteins are with you from birth, helping your muscles and tissues go through every growth stage.
On the other hand, a high-protein diet will help you if your main goal is to build up your body and increase muscle mass. Protein is essential in both growth and repair, so a diet high in protein will help you advance faster2.
Bone health is also a factor to consider, especially if you are a woman heading toward menopause. Recent studies show that a diet rich in protein can protect you against osteoporosis and fractures as you get older3.
Enzymes & Hormones
Enzymes (which are a type of protein) catalyze biochemical reactions essential for metabolism, digestion, and cellular processes4.
Proteins also serve as structural components of hormones, such as insulin, which regulate various physiological functions5. They’re also in charge of producing dopamine and serotonin (mood-regulating neurotransmitters), which have a powerful influence on mental health and brain function6.
Additionally, proteins act as receptors and transport molecules, facilitating hormone action and distribution throughout the body.
Immune Function
Did you know antibodies are protective proteins that recognize and neutralize foreign invaders like bacteria and viruses7?
Proteins also contribute to the formation of immune cells and support the production of cytokines, which are signaling molecules that coordinate the immune response. Therefore, you need adequate protein intake to maintain a strong immune system and protect your body from infections and diseases.
In fact, it was proven that an overall diet low in protein can weaken your immune system and make you more susceptible to getting sick. After all, if your body doesn’t have enough protein to build antibodies, it won’t be able to fight off invaders8.
Energy Source
Although protein is not a main energy source (carbs and fats are), your body can break it down and use it for energy when there’s no alternative. This process is called gluconeogenesis and usually occurs during prolonged fasting or long periods of high-intensity physical activity9.
Other Functions
Luscious hair, strong nails, and clear, glowing skin are all due to the work of proteins. Keratin (a key component of hair, skin, and nails) is a type of protein that contributes to their strength and integrity10.
Adequate protein intake also supports the production of collagen, which helps maintain skin elasticity and hydration11.
Additionally, proteins are crucial for transporting molecules. Hemoglobin, for example, carries oxygen from the lungs to the rest of the body. Other transport proteins include albumin, which helps distribute nutrients and hormones through the bloodstream, and lipoproteins, which transport fats and cholesterol.
Main Sources of Protein
There are 2 main natural sources of protein: animal- and plant-based foods. Animal proteins contain all essential amino acids, while most plant proteins are lacking in 1 or more areas.
Only a few plant-based proteins, like quinoa and tofu, are “complete” with all amino acids. Most combinations of grains and legumes have complementary amino acids and therefore also form a complete protein.
Common sources of daily protein include eggs, dairy (yogurt, milk, and cheese), meat, legumes, nuts, and whole grains. Here is a list of some of the most high-protein healthy foods you can enjoy12:
Animal-based sources | Plant-based sources | ||
Food | Protein /100g | Food | Protein /100g |
Chicken Breast (cooked) | 32.1g | Hemp Seeds | 31.6g |
Beef Loin (cooked) | 27.7g | Pumpkin Seeds | 30.2g |
Pork Loin (cooked) | 26.4g | Peanuts (raw) | 26.2g |
Duck Breast (cooked) | 23.5g | Tempeh | 20.3g |
Tuna (canned) | 29.1g | Chia Seeds | 16.5g |
Cod (cooked) | 20.4g | Cashew Nuts (roasted) | 15.3g |
Salmon (smoked) | 18.3g | Lentils (cooked) | 9.0g |
Eggs (boiled) | 12.6g | Chickpeas (canned) | 7.5g |
Greek Yogurt (Whole Milk) | 9.0g | Tofu (firm) | 6.9g |
Whole Milk | 3.15g | Quinoa (cooked) | 4.4g |
Protein Supplements
If you associate protein supplements with big, bulky muscles, you’re not entirely wrong. Many bodybuilders and fitness-focused people use them to enhance muscle growth and help with recovery after strenuous exercises.
However, protein powders are also used for weight loss since they help you feel full without consuming too many calories. This is why you see protein powders and shakes marketed as meal replacements or snacks. Despite the marketing, it is not recommended to rely on these products as your only sustenance.
Of course, there’s the convenience factor (easy to prepare and consume on the go). Supplements also help you meet your daily protein needs without stressing too much about your diet. If you’re on a restrictive diet (like low-calorie or low-carb), a protein supplement is a good way to meet your goals.
The decision of whether to include protein supplements in your diet or not rests entirely with you and your healthcare provider or dietician/nutritionist. If you decide in favor, here are some of the most common supplements on the market:
Whey – Derived from cow's milk, it contains all essential amino acids and is easily digested
Casein – Also obtained from milk, it releases more slowly than whey, making it ideal for sustained protein intake throughout the day.
Soy – Suitable for vegetarians and those with lactose intolerance.
Pea – Hypoallergenic, easy to digest, and supports muscle growth similar to whey protein.
Hemp – Contains all essential amino acids and is rich in omega-3 and omega-6 fatty acids.
Rice – Hypoallergenic, easy to digest, and supports muscle growth.
How Much Protein Do We Need?
The amount of protein your body needs depends on your age, sex, health state, and level of physical activity. Also, recommendations differ from one region to another. In the US, for instance, the recommended daily intake (RDI) is 0.8 grams of protein per kilogram (0.36 grams per pound) of body weight (BW) per day13. In the EU, the RDA is 0.83 grams per BW14. In the UK, the recommendation is 0.75 grams per BW15.
In fairness, the recommended dosage doesn’t differ that much between the three regions. Still, it’s important to know that this is the minimum amount to maintain nitrogen balance and support basic bodily functions. To reap all the benefits, you may need to go higher.
Protein needs for specific groups of healthy individuals | g of protein/kg BW | Value in g/day for a 75kg person |
Children (<13 years) | 0.95 | - |
Children16 (13 - 18 years) | 0.85 | - |
Sedentary adults (18 - 65 years) | 0.8 | 60 |
Seniors17 (65+ years) | 1 - 1.3 | 75 - 97.5 |
Pregnancy18 (check with your doctor) | 0.8 - 1.119 | 60 - 82.5+ |
Endurance Athletes | 1 - 1.6 | 75 - 120 |
Strength & Power Athletes20 | 1.6 - 2 | 120 - 150 |
Author’s Tip: Based on my observations and our nutritionist’s recommendations, as long as you maintain a healthy diet that fits your lifestyle, you don’t have to worry about your daily protein intake too much. Most people get the necessary amount of protein from their regular diet.
What Happens Without Enough Protein?
The symptoms of protein deficiency are quite difficult to ignore since they significantly impact your health and lifestyle. The most common symptoms are swelling (edema), a weak immune system, brittle hair and nails, stunted growth, fatigue, and weakness throughout the day21.
Protein deficiency can affect blood sugar levels, leading to fluctuations and potential issues with glucose regulation in the body. You’ll also crave sugary foods more as the body seeks quick energy sources. Since protein plays a significant role in neurotransmitter production, you may also suffer mood swings, irritability, and difficulty concentrating.
However, protein deficiency is rare in the developed world. It more often appears in tandem with energy deficiency as a result of a lack of food in developing countries.
Too Much Protein: Is It Possible?
Believe it or not, there are risks to consuming too much protein. Popular high-protein diets (like Atkins, Keto, or Paleo) and various marketing campaigns that promote protein powders and bars may have you believing that more protein is always better. This isn’t actually the case.
Most healthy people can easily consume and process between 0.8 and 2 grams of protein per body weight daily. Very active people need more protein for growth and recovery.
On a regular diet that includes whole foods and healthy animal-based products, it’s not easy to over-consume protein. However, if you follow a high-protein diet and top it up with supplements, you may be able to go over the threshold without knowing it.
So what happens then?
The most common symptoms are22:
Intestinal discomfort
Nausea
Fatigue
Dehydration
Headaches
Diarrhea
Slow heart rate
Others
Chronic overconsumption of protein may lead to kidney damage, cardiovascular disease, increased cancer risk, and other highly problematic health issues23.
Protein & Special Diets
When you’re on a special diet, your protein sources may not be as diverse as they should be. This makes it a bit more complicated to ensure your overall nutrition doesn’t suffer. But it’s not impossible; it just takes some planning.
Protein for Vegans & Vegetarians
Animal-based protein sources contain all 9 essential amino acids the body needs but can’t produce. This is why they’re referred to as complete proteins. Most plant-based sources are incomplete since they don’t provide all essential amino acids needed for protein production. Some exceptions include quinoa, edamame, and soy products like tofu and tempeh. This is why it can be difficult for vegetarians – and especially vegans – to ensure they get the full range of amino acids.
This doesn’t mean you have to give up on your dietary preferences and choices, but you should pay more attention to your meal planning. It’s important to make sure you get your protein from a variety of sources to get all the essential amino acids. Check out my colleague's well-detailed tips for vegetarian meal planning if you need a bit of inspiration.
Protein in Weight Loss & Muscle-Building Diets
High protein diets can be beneficial for several purposes, especially if you’re trying to trim fat and build muscle. However, it’s important to remember that there’s more to dieting than simply eating as much protein as possible. Besides a balanced nutrient intake, you also have to incorporate an exercise regimen to see results.
But even if your goal isn’t bigger muscles, when you consume more protein, it’s easier to get a lean physique. Protein-rich foods optimize muscle growth and recovery, and they also keep you fuller longer, so it’s easier to keep hunger and cravings under control24.
However, remember that foods high in protein still have calories, so make good choices. This includes using healthier cooking methods, such as baking and using less oil. Here are some good protein sources for weight loss:
Lean meats
Seafood
Beans and legumes
Soybeans and soy products
Low-fat dairy
Eggs
Nuts and seeds (better eaten in moderation as they’re quite high in fat and calories)
Tips for Optimizing Protein Intake
Protein optimization involves balancing protein sources, distributing intake evenly throughout the day, and aligning it with activity levels and goals. Also, remember that many factors like age and fitness level influence optimal intake, so make decisions accordingly and ask an expert for support if you need extra guidance.
FAQs
Can you get enough protein from plants alone?
You can get enough protein from plants alone. Many plant sources, such as beans, nuts, seeds, and grains provide protein. By consuming a variety of these foods, you can meet your daily protein needs without relying on animal products.
Is protein timing important for workouts?
Fitness enthusiasts suggest that consuming protein shortly after a workout (in a 15 to 60 minute window) can enhance muscle protein synthesis. However, recent research indicates that the overall amount of protein consumed throughout the day is more important than the specific timing25.
How do protein needs change as you age?
Protein needs tend to increase with age due to age-related muscle loss and reduced efficiency in protein utilization. Older adults may need more protein to maintain muscle mass and overall health. Adequate protein intake can help mitigate age-related declines in muscle function and support immune health26.
Is it true the body can only use 30 grams of protein at once?
Most people don’t need more than 25-30 g per meal. Researchers have found that muscle synthesis is better when your protein intake is spread throughout the day. This appears to be more efficient than if you tried to eat your entire daily protein requirement in a single sitting27.
Will more protein help me build muscle faster?
If you are physically active, consuming more protein can help build muscle. However, it is not recommended to consume more than 30-35% of daily calories from protein since the rest of the energy should come from a good ratio of other macronutrients.
What's the best protein source?
Complete proteins, found in animal sources like meat, fish, milk, eggs, and poultry, are highly bioavailable and contain all essential amino acids. While most plant-based sources lack one or more essential amino acids, a well-planned diet can provide adequate protein through the right pairings.
References
1. https://nutritionsource.hsph.harvard.edu/what-should-you-eat/protein/
2. https://www.mdpi.com/1660-4601/16/24/4897
3. https://www.csbj.org/article/S2001-0370(19)30144-8/fulltext
4. https://www.ncbi.nlm.nih.gov/books/NBK554481
5. https://pmc.ncbi.nlm.nih.gov/articles/PMC9875820/
6. https://pmc.ncbi.nlm.nih.gov/articles/PMC1863555/
7. https://www.genome.gov/genetics-glossary/Antibody
8. https://www.mdpi.com/2072-6643/12/6/1562
9. https://www.ncbi.nlm.nih.gov/books/NBK541119/
10. https://pmc.ncbi.nlm.nih.gov/articles/PMC2736122/
11. https://nutritionsource.hsph.harvard.edu/collagen/
12. https://fdc.nal.usda.gov/food-search
13. https://www.health.harvard.edu/blog/how-much-protein-do-you-need-every-day-201506188096
14. https://www.efsa.europa.eu/en/press/news/120209
15. https://www.nutrition.org.uk/nutritional-information/protein/
16. https://pmc.ncbi.nlm.nih.gov/articles/PMC8147948/
17. https://pmc.ncbi.nlm.nih.gov/articles/PMC4555150/
18. https://pmc.ncbi.nlm.nih.gov/articles/PMC7997328/
19. https://www.sciencedirect.com/science/article/pii/S2161831322007712
20. https://pmc.ncbi.nlm.nih.gov/articles/PMC2117006/
21. https://www.ncbi.nlm.nih.gov/books/NBK234922/
22. https://www.healthline.com/health/protein-poisoning#symptoms
23. https://www.ahajournals.org/doi/10.1161/hc4001.096152
24. https://pmc.ncbi.nlm.nih.gov/articles/PMC7539343/
25. https://pubmed.ncbi.nlm.nih.gov/23459753/
26. https://medlineplus.gov/nutritionforolderadults.html
27. https://jissn.biomedcentral.com/articles/10.1186/s12970-018-0215-1
