Nutrient bioavailability refers to the extent to which nutrients from food are absorbed and utilized by the body. (Including vitamins and minerals, not necessarily just the "macros") In other words, it refers to the amount of a nutrient that can be digested, absorbed, and utilized by the body for its various functions. Bioavailability is influenced by many factors such as the chemical form of the nutrient, the presence of other substances in the food, and the individual's physiological state.
Nutrient bioavailability is not the same as nutrient content. Foods may contain high levels of certain nutrients, but if they are not bioavailable, they may not contribute significantly to the body's nutrient stores. So, it is important to consider both nutrient content and bioavailability when evaluating the nutritional value of foods and designing a healthy diet.
For example, some nutrients such as iron and calcium are more easily absorbed in their soluble forms, whereas others, like fiber, are not digested by the body and therefore have low bioavailability. Additionally, certain foods may contain substances that can inhibit or enhance the absorption of nutrients. For instance, some compounds in tea and coffee can interfere with the absorption of iron, while vitamin C can enhance the absorption of iron.
Bioavailability can also be influenced by an individual's physiological state. For instance, pregnant women have increased iron needs and are more efficient at absorbing iron. On the other hand, people with certain medical conditions, such as Crohn's disease or celiac disease, may have reduced nutrient bioavailability due to impaired digestion and absorption.
Some examples of foods with high nutrient bioavailability include:
- Meat, poultry, fish, and seafood, which are good sources of highly bioavailable iron, zinc, and vitamin B12
- Eggs, which are a good source of highly bioavailable protein and a range of important vitamins and minerals
- Some dairy products, such as whole fat milk and cheeses, which are a good source of highly bioavailable calcium and vitamin D
On the other hand, some healthy foods have lower bioavailability due to factors such as their chemical structure or the presence of compounds that can inhibit nutrient absorption. Examples of foods with lower nutrient bioavailability include:
- Plant-based sources of iron, such as spinach and lentils, which contain non-heme iron that is less easily absorbed than heme iron found in animal sources
- Whole grains and legumes, which contain phytic acid that can inhibit the absorption of certain minerals, such as zinc and iron
- Vegetables such as broccoli and cabbage, which contain compounds that can interfere with iodine absorption.
While these foods may have lower nutrient bioavailability, they still play an important role in a healthy diet and can be combined with other foods to increase nutrient absorption. For example, consuming vitamin C-rich foods, like citrus fruits or bell peppers, with plant-based sources of iron can increase the bioavailability of the iron. Cooking methods can also affect nutrient bioavailability, for example, soaking or sprouting grains and legumes can reduce phytic acid and improve mineral absorption.
For more in depth learning on bioavailability, watch/listen to this Podcast Episode.
Nutrient density is a term used to describe the amount of essential nutrients (such as vitamins, minerals, and fiber) in a given amount of food, relative to the number of calories it provides. In other words, it refers to how much nutritional value a food offers per unit of energy.
Foods that are high in nutrient density provide a lot of essential nutrients per calorie, while foods that are low in nutrient density provide relatively few essential nutrients per calorie. For example, leafy greens like spinach and kale are considered to be high in nutrient density, because they are low in calories but contain a wide variety of essential nutrients like iron, calcium, vitamin K, and vitamin C. In contrast, foods like candy or soda are low in nutrient density because they provide a lot of calories but contain few essential nutrients.
Nutrient density is not the same as calorie density, which refers to the number of calories in a given volume or weight of food. Some foods that are high in nutrient density, such as nuts and seeds, may also be high in calories, so it's important to eat them in moderation as part of a balanced diet.
Curious which foods are most nutrient dense (and which are least dense)? Open this research article and scroll down to Figures 1-6.
For more in depth discussion, read Chris Kresser's Blog Post: What is Nutrient Density and Why is It Important?