What food consists of: proteins, fats, carbohydrates, fiber and water

Food is more than just calories. It's a matrix of macronutrients, micronutrients, water, and hundreds of biologically active compounds that together determine metabolism, vascular health, immunity, and quality of life. Understanding the role of each component allows you to tailor your diet to provide energy, maintain body weight, and prevent disease. [1]

The three main sources of energy are carbohydrates, proteins, and fats. Each gram of carbohydrates and protein contains 4 kilocalories, while each gram of fat contains 9 kilocalories. Ethyl alcohol contains 7 kilocalories per gram, but it is not an essential nutrient and is associated with health risks, so it is not considered a useful energy source. [2]

In addition to energy, the body needs vitamins and minerals daily. These are dozens of substances that are not synthesized in sufficient quantities and must be obtained from food. Their "small" doses control "large" processes—from hormone synthesis and nervous system function to bone tissue renewal. Deficiencies in certain micronutrients increase the risk of anemia, osteoporosis, thyroid disorders, and other conditions. [3]

Finally, modern data highlight the importance of dietary fiber and plant phytonutrients, particularly polyphenols. While they provide virtually no calories directly, they regulate the gut microbiome, inflammation, and vascular risk. A diet high in fiber and polyphenols is associated with improved metabolic outcomes and reduced cardiovascular risk. [4]

Table 1. Energy value and recommended proportion of macronutrients

Component	Energy value per 1 g	Recommended percentage of total energy intake in adults	Key Features	Product examples
Carbohydrates	4 kcal	45-65%	Fuel for the brain and muscles, source of fiber	Whole grains, legumes, fruits, vegetables
Squirrels	4 kcal	10-35%	Building material, enzymes, immune proteins	Fish, eggs, dairy products, legumes, soy
Fats	9 kcal	20-35%	Hormones, absorption of fat-soluble vitamins, membranes	Olive oil, nuts, seeds, fatty fish
Ethanol	7 kcal	0%	Not necessary, increases risks	-

Source: National Academies of Sciences reports and macronutrient distribution standards. [5]

Carbohydrates: Quality over quantity

Carbohydrates come in different forms. Whole grains, legumes, vegetables, and fruits provide complex carbohydrates, fiber, vitamins, and minerals. Refined grains and added sugars provide mostly "empty" energy. International recommendations recommend that at least half of daily grain intake should be whole grains, equivalent to approximately 48 g of whole grains per day. [6]

Fiber is a key protective factor. The European Food Safety Authority recommends an adequate intake of 25 grams per day for adults, while practical guidelines recommend aiming for 28-34 grams, depending on the calorie content of the diet. Most people do not reach these levels. Increasing fiber intake should be gradual and accompanied by adequate fluid intake. [7]

Added sugars should be limited. The World Health Organization recommends keeping free sugars below 10% of daily energy intake, and if possible, below 5% for additional health benefits. This includes sugar in beverages, baked goods, sweet sauces, and syrups. [8]

The concept of the "glycemic index" is useful, but for population standards, recommendations are based primarily on the quality of carbohydrates and the proportion of whole foods. There is insufficient evidence to establish glycemic index standards, so we focus on whole grains, legumes, vegetables, and fruits as the primary sources of carbohydrates. [9]

Table 2. Fiber, whole grains, and sugars - practical guidelines

Indicator	A guide for adults	Where are they "hidden"?
Dietary fiber	≥25 g per day, optimally 28-34 g	Legumes, whole grains, berries, vegetables, nuts and seeds
Whole grains	≥48 g per day of at least half of all cereals	Oatmeal, whole grain bread and pasta, brown rice, quinoa
Free sugars	<10% energy, better <5%	Sweet drinks, desserts, sugar in coffee and tea, syrups

Sources: EFSA, DGA and World Health Organization recommendations. [10]

Proteins: Needs and Quality

The basic requirement for an adult is approximately 0.8 g of protein per kilogram of body weight per day. This is the minimum level to meet physiological needs. It is advisable to distribute protein sources among meals to ensure each meal contains a sufficient portion of amino acids.

Older adults have higher requirements. Consensus documents indicate that after age 65, 1.0-1.2 g per kilogram of body weight is appropriate, and in cases of illness and weight loss, up to 1.2-1.5 g per kilogram. In severe conditions, up to 2.0 g per kilogram is sometimes required under the supervision of a physician. Physical activity combined with adequate protein helps maintain muscle mass and strength. [12]

It's not just the "how much" but also the "what" protein that matters. The modern standard for assessing protein quality is the Digestible Essential Amino Acid Score (DIAAS), recommended by the Food and Agriculture Organization. It more accurately accounts for amino acid composition and digestibility. By combining plant sources—legumes and grains—a complete amino acid profile can be achieved. [13]

Sources for a daily plate: fish and seafood, eggs, dairy products, legumes, soy and its derivatives, nuts and seeds. A vegetarian diet, when properly combined, provides sufficient protein and essential amino acids, as well as dietary fiber and polyphenols. For accurate planning, it's convenient to consult the FoodData Central database. [14]

Table 3. Protein: Serving Guidelines and Examples

Category	Consumption benchmark	Examples of a serving size of 20-25g of protein
Adults	~0.8 g per kg of body weight per day	120-140 g cooked chicken fillet, 2-3 eggs, 200-250 g thick yogurt, 250-300 g stewed lentils, 250-300 g tofu
Elderly	1.0-1.2 g per kg of body weight per day	The same products, but with increased portions and even distribution over 3-4 meals

Sources: NASEM, PROT-AGE, ESPEN, food reference data - FoodData Central.

Fats: Which ones are necessary and which ones should be limited?

Fats are not the enemy. Polyunsaturated fatty acids, especially omega-3s, are essential for the heart, brain, and anti-inflammatory balance. European experts consider an adequate intake of alpha-linolenic acid (ALA) at approximately 0.5% of energy, and the target for docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) is at least 250 mg per day for adults. Eating fish twice a week, including fatty fish, helps meet these needs. [16]

It is recommended to limit saturated fats to less than 10% of total energy, replacing them with unsaturated sources such as extra-virgin vegetable oils, nuts, and seeds. This metabolism improves the lipid profile and reduces cardiovascular risks. [17]

The key rule is the complete exclusion of industrial trans fatty acids from partially hydrogenated oils. The World Health Organization's REPLACE initiative and national regulations aim to eliminate them from the food chain, as they increase the risk of heart attack and overall mortality. Choose products without "partially hydrogenated oils" in their ingredients. [18]

Remember that fats are energy-dense, and even "healthy" oils add a lot of calories. Use them as a quality ingredient, not as "fuel," and try to plan your omega-3 sources regularly. [19]

Table 4. Fats - what to choose and what to limit

Type of fats	What to do	Main sources
Polyunsaturated omega-3	Aim for regular consumption, target level for EPA and DHA at least 250 mg per day	Fatty fish, seafood, flaxseeds, chia, walnuts
Polyunsaturated omega-6	Maintain a moderate level of whole foods	Sunflower and corn oils, seeds
Monounsaturated	Use as a base cooking fat	Olive oil, almonds, avocado
Saturated	Limit to less than 10% of energy, replace with unsaturated	Fatty meat products, butter, palm oil
Trans fats	Exclude completely	Partially hydrogenated oils in baked goods and deep-frying

Sources: EFSA, World Health Organization. [20]

Water and Electrolytes: Hydration, Sodium and Potassium

Water is the main non-food component of the diet. European standards for adequate intake indicate a total water intake of approximately 2.0 liters per day for women and approximately 2.5 liters for men from all sources, including beverages and water in foods. Needs increase with heat, physical activity, and elevated body temperature. [21]

Sodium should be limited. The World Health Organization recommends less than 2 grams of sodium per day, which is equivalent to about 5 grams of table salt. This helps reduce blood pressure and the risk of stroke. The main contribution comes from prepared and processed foods, not from the salt shaker on the table. [22]

Potassium, on the other hand, should often be increased to approximately 3.5 g per day. Adequate potassium helps offset sodium-induced increases in blood pressure. The best sources are vegetables, fruits, legumes, dairy products, and fish. [23]

Caffeinated beverages and moderate amounts of unsweetened tea and coffee can contribute to hydration. It's best to minimize sugary drinks due to added sugar, and avoid using alcohol as a thirst quencher or energy source. [24]

Table 5. Sodium and potassium - guidelines and practical substitutions

Indicator	Landmark	Practical steps
Sodium	<2 g per day (≈5 g salt)	Limit prepared snacks, cold cuts, and salty sauces; choose low-sodium foods.
Potassium	≈3.5 g per day	Increase the proportion of vegetables and fruits, legumes, dairy products, and fish

Sources: World Health Organization and EFSA. [25]

Vitamins and minerals: what to pay attention to every day

Vitamin D and calcium are key to bone health. For most adults, the target values are 15 micrograms of vitamin D per day and 1,000 milligrams of calcium, with higher needs in older adults. If you don't get enough sun and your dietary intake is low, your doctor may recommend supplements. [26]

Iron is especially important for women of reproductive age. The recommended daily intake is approximately 18 milligrams for women and 8 milligrams for men. A deficiency leads to iron deficiency anemia, which can lead to weakness and decreased performance. Vitamin C enhances absorption, while coffee and tea after meals can reduce it.

Folate and vitamin B12 support hematopoiesis and the nervous system. For adults, the recommended daily intake is 400 micrograms of folate equivalents and 2.4 micrograms of vitamin B12. Pregnant women require higher levels of folate and iodine; discuss these needs with your doctor. [28]

Iodine is essential for thyroid hormone production. The recommended daily intake for adults is approximately 150 micrograms. This intake can be achieved through seafood, eggs, dairy products, and iodized salt. However, excess iodine is also undesirable, so a "golden mean" is advisable. [29]

Table 6. Key micronutrients: reference values and food sources

Nutrient	A guide for adults	Main functions	Rich sources
Vitamin D	15 mcg per day	Bone, immune regulation	Fatty fish, eggs, fortified foods
Calcium	~1,000 mg per day	Bone, muscle contractions	Dairy products, yogurt, cheese, green leafy vegetables
Iron	Men 8 mg, women 18 mg	Hematopoiesis, oxygen transport	Red meat, liver, legumes, whole grains
Folate	400 mcg equivalents	Hematopoiesis, cell division	Green leafy vegetables, legumes, citrus fruits, fortified cereals
Vitamin B12	2.4 mcg	Nervous system, hematopoiesis	Fish, meat, eggs, dairy products
Iodine	150 mcg	Thyroid hormones	Sea fish, iodized salt, dairy products
Potassium	~3,500 mg	Blood pressure, heart rate	Potatoes, beans, bananas, yogurt, fish

Sources: NIH ODS, EFSA, World Health Organization. [30]

Plant bioactive substances: polyphenols as health "moderators"

Polyphenols are a large group of phytonutrients found in berries, cocoa, tea, coffee, herbs, and spices. They are not vitamins, but they influence signaling pathways, vascular tone, and the microbiome. Reviews show that a polyphenol-rich diet is associated with reduced inflammatory markers and better cardiometabolic outcomes. [31]

The mechanism is largely mediated by the microbiome: large polyphenol molecules in the colon are converted by bacteria into metabolites, which are responsible for a significant portion of the effects. The composition of the microbiota also changes in response to diet. This is a two-way relationship between polyphenols and the microbiome. [32]

High levels of flavonoids in the diet have been associated with a lower risk of cardiovascular events in observational studies. This is not a reason to take supplements without medical advice, but it is a compelling argument for increasing the proportion of whole plant foods across a wide range of colors. [33]

The practice is simple: add berries or citrus fruits daily, dark green and red vegetables, use unsweetened green or black tea, unsweetened cocoa, herbs and spices in cooking. This will increase both fiber and polyphenols without excess sugar and calories. [34]

Table 7. Major classes of polyphenols and where to find them

Class	Products
Flavonoids	Berries, citrus fruits, onions, cabbage, tea
Phenolic acids	Coffee, whole grains, berries
Stilbenes	Grapes and grape products
Lignans	Flax seeds, whole grains
Proanthocyanidins	Cocoa, berries, peanuts

Summarized from modern reviews. [35]

Practical plate assembly and portion control

A general rule is to have half your plate consist of fruits and vegetables, a quarter of it whole grains or starchy vegetables, and a quarter of it protein. Add sources of "good" fats daily, especially olive oil, nuts and seeds, and fish several times a week. This plan is consistent with major nutrition guidelines. [36]

Try to plan for at least 25-30 grams of fiber per day. A good guideline is to include vegetables or fruits and a fiber source such as whole grains, legumes, nuts, or seeds in each meal. For a more controlled diet, choose foods with at least 1 gram of fiber for every 10 grams of carbohydrates. [37]

Drinks: Water as needed, and more during hot weather and intense exercise, unsweetened tea and coffee. Limit sweet drinks and juices due to added sugars and reduced satiety. Alcohol is unnecessary and increases cancer and cardiovascular risks. [38]

Eating foods with minimally processed ingredients automatically helps keep salt, sugar, and saturated fat levels within safe limits. When choosing packaged foods, check the ingredients and nutritional information: less sodium and added sugars, more fiber. [39]

Table 8. "Plate constructor" for the day - guidelines

Block	Minimum per day	Examples
Vegetables and fruits	≥400 g	Any seasonal ones, including frozen ones
Whole grains	≥48 g whole grains	Oatmeal, quinoa, brown rice, whole grain bread
Protein	1-3 servings	Fish, eggs, yogurt, beans, tofu
"Good" fats	Daily	Olive oil, nuts, seeds
Water	Based on thirst, the guideline is 2.0-2.5 liters in total.	Water, unsweetened tea and coffee

Sources: World Health Organization, EFSA, DGA. [40]

Common Mistakes and Myths

"All carbohydrates are bad." False. Excessive consumption of added sugars and refined grains is harmful. Whole grains, legumes, vegetables, and fruits are the foundation of a healthy diet. [41]

"Fats should be cut to a minimum." Dangerous. Saturated fats should be limited and industrial trans fats should be completely eliminated, while unsaturated fats are a healthy base for the diet. [42]

"Protein is only important for athletes." Incorrect. A lack of protein accelerates muscle loss in the elderly. Higher intakes are recommended for this group, especially when combined with strength training. [43]

"Alcohol is part of a healthy diet." No. It's a source of energy without benefits and has proven risks, including cancer. If alcohol is consumed, it should be in strict moderation and not for the "benefits." [44]

Table 9. Quick exchanges for every day

Task	Exchange
Less sugar	Soda → lemon water, sweet yogurt → natural yogurt with berries
Less sodium	Sausage → baked chicken breast, savory sauces → spices and herbs
More fiber	White rice → brown rice, whole wheat, pearl barley, quinoa; white bread → whole grain
More omega-3	Sausages for dinner → baked mackerel or salmon twice a week
Healthy fats	Margarine → extra virgin olive oil

Justification: recommendations of the World Health Organization, EFSA, DGA, Harvard Nutrition Source. [45]

Table 10. Fiber Sources: Serving Guidelines

Product	Sample serving	Fiber, approximately
Boiled lentils	1 glass	15-16 g
Boiled black beans	1 glass	15 g
Boiled oatmeal	1 glass	4-5 g
Berries	1 glass	6-8 g
Apple with skin	1 piece	4-5 g
Almond	30 g	3-4 g
Chia seeds	2 tablespoons	8-10 g
Boiled broccoli	1 glass	5 g

Sources: DGA Fiber Sources, Harvard Nutrition Source, USDA Reference Intakes. Values are average. [46]

Conclusions

1. The diet is based on whole foods: at least 400 g of vegetables and fruits per day, at least 48 g of whole grains, legumes, nuts, and seeds. This provides fiber, micronutrients, and phytonutrients. [47]
2. Maintain a macronutrient balance of 45-65% carbohydrates, 10-35% protein, and 20-35% fat, with an emphasis on unsaturated fats and regular sources of omega-3. Trans fats are prohibited. [48]
3. Key "limiters": free sugars less than 10% of energy, sodium less than 2 g per day, saturated fat less than 10% of energy. At the same time, increase potassium. [49]
4. Monitor your protein intake: adults need ~0.8 g per kilogram of body weight, the elderly need 1.0-1.2 g, and if you're ill, follow your doctor's individual recommendations. Distribute protein evenly throughout your meals.
5. Micronutrients every day: vitamin D, calcium, iron, folate, vitamin B12, iodine, potassium. Sources are a variety of foods, and supplements are prescribed by a doctor if needed. [51]