Densidad Nutricional por Caloría: Qué Significa y Cómo lo Calcula FoodAlt

What Is Nutrient Density?

Nutrient density describes how much useful nutrition a food provides relative to a chosen reference. That reference can be food weight (per 100 g), energy (per 100 kcal), a typical serving size, or another standardized basis.

A food with high nutrient density provides a relatively large amount of vitamins, minerals or other nutrients for the amount of weight or energy it contains. A food with low nutrient density provides fewer nutrients relative to its weight or energy content.

Nutrient density is not a single fixed number. It depends on which nutrients you measure, which reference you use, and what comparison basis you choose. Different measurement bases can produce different rankings for the same set of foods. The FoodAlt methodology explains how these comparison bases work in practice.

What Is Nutrient Density Per Calorie?

Nutrient density per calorie measures how much of a specific nutrient a food provides for a fixed amount of food energy. Instead of asking "how much nutrient is in 100 g of this food?", it asks: "how much nutrient does this food deliver per 100 kilocalories?"

This is useful because foods differ greatly in their energy content. A 100 g comparison gives every food the same weight, but not the same amount of energy. A calorie-normalized comparison asks a different question: how much nutrient is delivered for a fixed amount of food energy?

For example, if two foods contain different amounts of water, fat or carbohydrate, comparing them only by weight can produce a different result from comparing them at the same energy intake. Neither comparison is wrong; they answer different questions.

Nutrient Density Per 100 g vs Per 100 kcal vs Per Serving

There are several valid ways to compare nutrient density. Each answers a different question. FoodAlt's methodology uses four comparison modes:

No single comparison basis is always superior. Per 100 g is the international scientific baseline for food composition data. Per serving reflects how much you might actually eat. Per 100 kcal reveals how efficiently a food delivers nutrients relative to its energy content. FoodAlt shows multiple comparison bases so you can choose the one that matches your question.

Why Compare Foods Per 100 Calories?

Foods differ greatly in water content and energy density. Raw spinach contains 23 kcal per 100 g, while avocado contains 160 kcal per 100 g. A per-100-g comparison gives both foods the same weight, but spinach provides roughly one-seventh the energy of avocado in that same weight.

Calorie normalization asks a different question: "If I allocate 100 kcal of my daily energy intake to this food, how much of a given nutrient do I get?" This can be useful when:

• Comparing foods with very different water content (leafy greens vs nuts)
• Comparing foods with very different fat content (vegetables vs oils)
• Evaluating which food delivers more of a nutrient for a fixed energy budget
• Understanding how calorie density affects nutrient delivery

Calories provide energy, and energy needs vary by person and goal. Nutrient density per calorie is a comparison tool, not a rule that lower-calorie foods are always better. Some foods are intentionally energy-dense; for example, nuts and seeds provide calories, protein, healthy fats and minerals together. A person who needs more energy may benefit from calorie-dense foods. A person managing calorie intake may prefer foods that deliver more nutrients per calorie.

How FoodAlt Calculates Nutrient Density

FoodAlt's per-100-kcal calculation uses a straightforward formula documented in the FoodAlt methodology:

Step 1: Start With Food Composition Data

Every food record in FoodAlt is mapped to an authoritative food composition database. The primary source is USDA FoodData Central (Foundation Foods, SR Legacy and Survey databases). Each food page displays its source record and unique identifier (such as a USDA FDC ID) with a direct link to the underlying data.

All nutrient amounts start as values per 100 g edible portion, which is the international scientific standard for food composition reporting.

Step 2: Normalize to 100 kcal

To convert a nutrient amount from a per-100-g basis to a per-100-kcal basis, FoodAlt applies this formula:

Nutrient per 100 kcal = Nutrient per 100 g × (100 ÷ Calories per 100 g)

This scales the nutrient amount up or down depending on the food's calorie density. Low-calorie foods (such as leafy greens) are scaled up because 100 kcal requires more than 100 g of the food. High-calorie foods (such as nuts and seeds) are scaled down because 100 kcal requires less than 100 g.

Step 3: Compare Nutrients With Reference Values

To evaluate how meaningful a nutrient amount is, FoodAlt compares it with Dietary Reference Intakes (DRI), which are the daily values established by the National Academies of Sciences, Engineering, and Medicine. The DRI values used in FoodAlt are listed in the FoodAlt nutrient directory.

For example, if a food provides 28.1 mg of vitamin C per 100 g and the daily value for vitamin C is 90 mg, that food provides about 31% of the daily value per 100 g. On a per-100-kcal basis, the percentage changes depending on the food's calorie content.

What Nutrients Does FoodAlt Track?

The FoodAlt nutrient directory tracks the following vitamins and minerals alongside macronutrients. The daily values shown are the standard adult reference values used for comparison:

FoodAlt also tracks macronutrients (protein, carbohydrates, fiber, fat, saturated fat, sugar) and sodium. The nutrient directory contains 12 vitamins and 6 minerals (excluding sodium). The full list is available on the Explore Nutrients page.

What Is the FoodAlt NDI?

The FoodAlt Nutrient Density Index (NDI) is an analytical score that summarizes how much of multiple vitamins and minerals a food provides relative to their dietary reference values on a per-calorie basis.

NDI combines individual nutrient-to-DRI ratios into a composite score. A higher NDI indicates that a food delivers a larger proportion of reference nutrient intakes per unit of energy. However, a composite score can summarize several nutrients at once, which means it can also hide individual nutrient strengths and weaknesses.

FoodAlt encourages users to inspect individual nutrients alongside any composite score. Look at the NDI to get a general sense of nutrient density, then examine the specific nutrients behind it to understand what a food actually provides.

NDI is a FoodAlt analytical model designed to make food comparisons easier. It is not a clinical nutrition assessment, a medical score, or an official dietary quality index. Different nutrient density scoring systems exist in nutrition research (such as the Nutrient Rich Foods Index and the Naturally Nutrient Rich score), and they use different nutrients, weights and methods. NDI is FoodAlt's approach to this problem.

Worked Example: Nutrient Density Per 100 kcal

Here is how the per-100-kcal calculation works using a real food from the FoodAlt database.

Food: Raw spinach (Spinacia oleracea)

From USDA FoodData Central:

• Calories: 23 kcal per 100 g
• Vitamin C: 28.1 mg per 100 g

Calculation:

Vitamin C per 100 kcal = 28.1 mg × (100 ÷ 23) = 28.1 × 4.35 = 122.2 mg per 100 kcal

Raw spinach provides 28.1 mg of vitamin C per 100 g. Because spinach has only 23 kcal per 100 g, you would need about 435 g of spinach to reach 100 kcal. At that amount, you would consume approximately 122.2 mg of vitamin C, well above the 90 mg daily value.

This does not mean you should eat 435 g of spinach at a time. It means that for every 100 kcal of energy you allocate to spinach, you receive a substantial amount of vitamin C relative to other foods.

How Two Foods Can Rank Differently

The same two foods can rank differently depending on whether you compare by weight or by calorie. This is one of the most important concepts in nutrient density comparison.

Example: Potassium in avocado vs spinach

Per 100 g, spinach provides 558 mg of potassium and avocado provides 485 mg; spinach is higher, but the difference is moderate. Per 100 kcal, spinach provides 2,426 mg and avocado provides 303 mg, an 8-fold difference. Avocado is calorie-dense (160 kcal per 100 g) because of its fat content, so 100 kcal of avocado is only about 63 g. Spinach is very low in calories (23 kcal per 100 g), so 100 kcal of spinach is about 435 g.

Both facts are true. Avocado is a useful potassium source that also provides healthy fats, fiber and vitamin E. Spinach delivers far more potassium per calorie. The better choice depends on whether your goal is potassium per calorie, potassium per serving, or a food that also provides fats and energy. For a broader comparison of potassium-rich foods, see Potassium-Rich Foods: 5 Foods With More Potassium Than Bananas.

How Preparation State Changes Comparisons

Cooking changes the water content, weight and nutrient concentration of a food. Raw spinach and cooked spinach have different nutrient values per 100 g because cooking reduces water content and may degrade heat-sensitive vitamins such as vitamin C and folate.

Comparing raw spinach with cooked spinach, or raw spinach with baked sweet potato, without noting the preparation state can produce misleading results. FoodAlt explicitly labels the preparation state of every food record (Raw, Cooked, Boiled, Roasted, Baked or Dried) and displays a mismatch notice when comparing foods with different preparation states.

When evaluating nutrient density, always check whether the comparison uses the same or clearly identified preparation states. The FoodAlt methodology explains how preparation state is handled across all comparisons.

What the NDI Score Can Tell You

• Relative micronutrient delivery: Which food provides more vitamins and minerals per calorie in a given comparison
• Calorie-normalized nutrient value: How efficiently a food delivers nutrients relative to its energy content
• Comparison between food records: How two or more foods differ in overall nutrient density
• A starting point for food exploration: Identifying foods worth investigating for specific nutrient goals

What the NDI Score Cannot Tell You

• Whether a food is universally healthy for all people
• Whether a person should eat a specific food
• Whether nutrients are fully absorbed (bioavailability varies by food, preparation and individual)
• Whether a food fits someone's calorie, protein or macronutrient needs
• Whether a food fits an allergy, intolerance or medical dietary restriction
• Whether a food tastes good or is culturally appropriate
• Whether a food is affordable or accessible in a given location

NDI is one lens for understanding food composition. It is not a complete assessment of food quality, healthfulness or dietary suitability.

Does Higher Nutrient Density Mean a Food Is Healthier?

Not necessarily. Health depends on overall dietary pattern, not on any single food or score. A food with a high NDI provides substantial micronutrients per calorie, but that does not mean it is the only food a person should eat, or that it is appropriate for every individual.

• Individual needs differ: A person with high energy needs (such as an athlete) may benefit from calorie-dense foods that would score lower on a per-calorie nutrient density measure.
• Macronutrients matter: Protein, fat and carbohydrate have important roles beyond micronutrient delivery. A food low in micronutrients but high in protein may still be valuable for muscle maintenance.
• Energy requirements matter: Calories provide energy, and the body needs energy to function. Nutrient density per calorie is a comparison tool, not a rule that lower-calorie foods are always better.
• Dietary preferences and restrictions matter: Allergies, intolerances, cultural preferences and medical conditions all influence which foods are appropriate for a given person.

Choosing foods that provide more micronutrients relative to their energy content can be one useful part of a nutrient-adequate dietary pattern. But nutrient density is only one dimension of food quality.

Limitations of Nutrient Density Scores

Any nutrient density scoring system has limitations. Understanding these makes comparisons more useful:

• Nutrient density is only one dimension of food quality. Taste, cost, availability, cultural importance and environmental impact also matter.
• Calories are not inherently bad. Energy-dense foods serve important purposes. Nuts, seeds and oils provide essential fatty acids and fat-soluble vitamins alongside their calories.
• Protein quality may not be fully captured. Amino acid profiles and digestibility vary between foods. A composite micronutrient score does not reflect protein quality.
• Bioavailability is not always represented. The amount of a nutrient in a food is not the same as the amount your body absorbs. For example, iron from plant foods (non-heme iron) is generally less bioavailable than iron from animal foods (heme iron).
• Nutrient interactions are complex. Some nutrients enhance the absorption of others (vitamin C enhances iron absorption). Some inhibit it (phytates reduce zinc absorption). A score cannot capture all interactions.
• Food processing and preparation change nutrient composition. Cooking can reduce heat-sensitive vitamins. Drying concentrates nutrients per gram. Scores based on one preparation state may not apply to another.
• Missing data can affect comparisons. If a nutrient was not measured in a food's source record, the score may underrepresent that food's actual nutrient content.
• Different DRI references can affect scores. Daily values vary by age, sex and life stage. A score based on adult male DRI values may not apply equally to children or pregnant women.
• A composite score can hide individual strengths and weaknesses. A food might score well overall but be low in a specific nutrient you need, or score poorly overall but be an excellent source of one important nutrient.

Nutrient Density Is Not the Only Goal

People choose foods for many reasons. Someone may want:

• More protein (see High-Protein Plant Foods)
• More dietary fiber (see Dietary Fiber and Gut Health)
• More potassium (see Potassium Beyond Bananas)
• More vitamin C (see Guava vs Orange)
• More calcium or iron
• Fewer calories
• More energy from calorie-dense foods
• A different balance of macronutrients

Therefore, "better" depends on the user's goal. FoodAlt does not simply ask which food has more nutrients. It helps you understand how much nutrition a food provides relative to its energy, preparation and comparison basis, so you can find a better food for what you need.

FoodAlt's Four Food Comparison Modes

FoodAlt provides four ways to compare foods, as documented in the FoodAlt methodology:

A. Per 100 g edible portion: The international scientific baseline for food chemistry. Compares nutrient concentration by weight.

B. Per typical serving size: Reference portions based on dietary guidelines or common consumption (such as 1 medium fruit, 1 cup cooked, or 1 tablespoon). Reflects what you might actually eat.

C. Per 100 kcal: Calculated as Amount × (100 ÷ Calories per 100 g). Shows how much nutrient you get per unit of food energy.

D. Per 300 kcal: Normalizes two foods to the same total caloric intake (300 kcal) for direct comparison.

300 kcal is a mathematical comparison basis, not a recommended dietary serving. It provides a larger scale for comparison that can make differences between foods easier to see.

You can switch between these modes when you compare foods on FoodAlt.

What Happens When Nutrient Data Is Missing?

Not all nutrients have been measured in every food record. When a nutrient was not analyzed in the underlying source data, FoodAlt distinguishes between two cases:

• 0 / 0.0: The nutrient was analyzed and found to be absent or below detection thresholds. This is a verified zero.
• Not available: The specific laboratory assay did not measure this nutrient in that source record. FoodAlt never defaults missing data to zero.

This distinction matters for nutrient density scoring. If a nutrient is missing (not measured), treating it as zero would unfairly penalize the food. FoodAlt's methodology explicitly handles this case. If you believe a nutrient value is incorrect or missing, you can report it on the data corrections page.

FoodAlt Nutrient Density Methodology

FoodAlt is an educational food decision tool built on transparent, reproducible nutritional mathematics. Here is a summary of how nutrient density comparisons work:

• Data source: Food composition data comes primarily from USDA FoodData Central (Foundation Foods, SR Legacy and Survey databases). Each food record links to its source with a unique record ID.
• Comparison bases: FoodAlt supports per 100 g, per serving, per 100 kcal and per 300 kcal comparisons.
• Per-100-kcal formula: Nutrient per 100 g × (100 ÷ Calories per 100 g).
• Reference values: Nutrient amounts are compared against Dietary Reference Intakes established by the National Academies. The specific daily values used are listed in the FoodAlt nutrient directory.
• Preparation state: Every food record identifies its preparation state (Raw, Cooked, Boiled, Roasted, Baked or Dried). Comparisons between foods with different preparation states display an explicit mismatch notice.
• Missing data: Missing nutrient values are not treated as zero. FoodAlt distinguishes verified zero from not-available.
• Limitations: Nutrient density scores do not capture bioavailability, nutrient interactions, protein quality, or individual dietary needs. NDI is an analytical model, not a clinical assessment.

For the complete methodology, see the FoodAlt Methodology & Data Principles page.

Find a Better Food for What You Need

FoodAlt helps you compare foods and explore useful alternatives based on what you need, whether that is more protein, more fiber, more potassium, more vitamin C, fewer calories, or a different nutrient profile.

• Compare foods side by side by nutrient density, weight or serving
• Find food alternatives based on specific nutrients
• Explore nutrients tracked by FoodAlt
• Browse the food database