Plant-based diets are becoming popular because of their health benefits and ability to prevent the development of chronic diseases. Also, compared to animal-based food like meat, fruits and vegetables have better nutritional content. That said, some of the nutrients in plant-based food are not easily absorbed by the body; they are absorbed better from animal-based foods. This is called nutrient bioavailability, and you must consider it when choosing food items to add to your plant-based diet. In this article, we will explore about intake and management of nutrient bioavailability in a plant-based diet, and shared below are details about this.
What Is Nutrient Bioavailability?
Bioavailability is the proportion of a nutrient in the food that is available for the body. The food we eat is digested, and the nutrients are absorbed in the intestines. This process is affected by other compounds present in the food. For example, the presence of compounds called antinutrients inhibits or reduces the absorption of certain nutrients from plant-based food. Sometimes, this can be avoided or reduced by processing the food. Some of the methods for processing food are applying heat, cutting, mincing, crushing, pounding, and so on. Listed below are the nutrients in plant-based food whose bioavailability is reduced.
The bioavailability of calcium in plant-based food is limited due to the presence of antinutrients called oxalates. Legumes, kale, broccoli, bok choy, and figs are some of the commonly recommended sources of this essential nutrient. Oxalates or oxalic acid is present in plant-based food like leafy green vegetables, and it reduces the bioavailability of calcium; oxalic acid binds to calcium to form oxalate, which is difficult to be absorbed in the gut.
Another antinutrient that decreases the absorption of calcium is phytates, which are present in legumes, grains, and pulses. Calcium absorption can be increased by reducing phytate levels. This can be done by germinating or de-hulling legumes, grains, and pulses. Above all, calcium absorption can be increased by maintaining healthy vitamin D levels in the body.
One of the major reasons for the misconception that plant-based food is low in protein is because plant proteins are not complete proteins. On the contrary, animal proteins are complete proteins, and hence healthier. Plant proteins do not have some of the essential amino acids, while animal proteins contain all the essential amino acids. So, to get all the essential amino acids, you should eat a wide variety of foods.
You can overcome the drawback of incomplete protein in plant-based foods by the method of protein complementation. Here, you combine different foods in your plant-based meal to meet your protein needs.
- Grains like wheat, brown rice, and oats lack the amino acids lysine and threonine. You can complement them with legumes like soy, lentils, pea, and beans as they are good sources of amino acids absent in grains.
- Nuts and seeds lack the amino acid lysine. Consuming pea, beans, and lentils will complement lysine.
- Legumes like soy, beans, and pea lack the amino acid methionine. This can be complemented by consuming brown rice, wheat, and potato as they are good sources of methionine.
- Corn lacks the amino acid tryptophan, and this can be complemented by consuming legumes like pea, beans, and lentils.
Finally, the presence of tannins, fiber, and phytates in plant-based food reduces the digestibility of proteins; this makes the absorption of amino acids difficult.
Zinc deficiency is prevalent globally, and this is particularly common in low-income countries where most of the population depends on plant-based food sources for nutrition. This is mainly due to the low bioavailability of zinc in plant-based food. A study has shown that the average intake of this micronutrient for vegans is 20% lower than that of non-vegetarians. Furthermore, the high fiber content in legumes and whole grains reduces the absorption of zinc.
Legumes and grains are good sources of zinc, and its absorption is inhibited by the presence of the antinutrient phytic acid. Processing plant-based food by methods like heating, soaking, germination, and fermentation reduces the phytate content. As a result of this, zinc bioavailability is increased; at optimum pH, the activity of phytate degrading enzymes increases. The phytate degrading is effective at acidic pH for cereals, and alkaline or neutral for legumes. Finally, processes like pressure cooking, de-hulling, and fermentation enhance the absorption of zinc because these methods break down the fiber in grains and legumes.
Vegans are more susceptible to vitamin B12 deficiency because this nutrient is absent in most plant-based food. A study has shown that when compared to meat-eaters, an average vegan consumed approximately 93% less vitamin B12. This is a widely acknowledged fact, and it is advised that those who follow a vegan diet take vitamin B12 supplements or consume foods fortified with this vitamin.
The absorption of vitamin B12 depends on gastric acid and a protein called intrinsic factor (IF); they are produced by the stomach. As you age, the ability of your stomach to produce these compounds decreases. Because of this, your ability to absorb vitamin B12 decreases.
Remembering these important points will help you to follow a healthy and balanced plant-based diet.