The primary reason people eat plant-based food is because of their nutritional content, and the many health benefits associated with it. For example, consuming them reduces the risk of developing heart diseases, diabetes, cancer, slows down aging, prevents cancer, helps to manage weight, and so on. Surveys have shown that vegans and vegetarians are at higher risk of developing certain deficiency diseases. This is because of the low bioavailability of some plant nutrients, and this makes it harder for our bodies to absorb them. Read on to know more about bioavailability and absorption of plant nutrients.
Bioavailability is the amount of nutrients absorbed from the food that you consume. It varies for different types of nutrients found in plant-based food. For example, the bioavailability of macronutrients like fats, carbohydrates, and proteins is 90%, whereas it varies very much for micronutrients like minerals and vitamins. Most of the plant-based diet deficiencies are due to the low bioavailability of certain minerals and vitamins. This is because their absorption in the digestive system is hindered by certain enzymes and compounds found in plant food.
The nutrients contained in food are released and absorbed when they are broken down in the digestive system. There are two cases to be considered, i.e. when there is excess, as well as lack of certain nutrients. In the former case, the excess nutrients will be either stored or excreted, whereas in the latter case our body efficiently absorbs them. But when we have adequate levels of nutrients, they are absorbed less efficiently by our bodies due to their lower need. Besides, the nutritional requirements vary from person to person, and there is no one size fits all. Listed below are the other main factors that affect nutritional bioavailability.
- Composition of body
- Status of health
- Stage of life, i.e. childhood, adulthood, pregnancy, etc.
- Nutrient levels of the body
- Processing and cooking of food
- The chemistry of the nutrient
- The presence of inhibitors that decreases the bioavailability of the nutrient
- The presence of catalysts or enhancers that increases the bioavailability of the nutrient.
According to many health experts like doctors and dieticians, the best way to avoid nutritional deficiencies due to a plant-based diet is to eat a balanced diet consisting of a wide variety of plant-based food. This ensures that your body gets adequate amounts of micronutrients.
Plant Nutrients Of Special Concern
Iron is an important micronutrient that is required for vital body functions like red blood cell production. According to the WHO, iron deficiency is the most common nutritional deficiency in the world. This is more common in developing countries where people eat predominantly plant-based food.
Iron is found in two forms, and they are haem iron and non-haem iron. Haem iron is found abundantly in red meat and other animal-derived foods, whereas non-haem iron is found predominantly in plant-based foods like leafy greens, legumes, nuts, grains, and seeds. Haem iron is readily absorbed by our body, and its rate of absorption depends on the iron levels in our body. Non-haem iron absorption depends on various dietary factors. For example, phylates found in certain vegetables, whole grains, and legumes, polyphenols found in coffee and tea, and high amounts of dietary calcium act as inhibitors to the absorption of non-haem iron.
It has been found that haem iron found in animal food products increases the absorption of non-haem iron. Also, studies have shown that consuming vitamin C increased the absorption of non-haem iron. So, it is important to include sources of vitamin C like citruses as part of your plant-based meal.
Calcium is an important dietary nutrient required for marinating good bone health, and animal food products like dairy, eggs, and fish are a rich source of it. The bioavailability of calcium in plant-based food like kale, spinach, broccoli, etc., is limited, and this is mainly due to certain types of pf inhibitors. Oxalic acid which is found in many leafy greens attaches to calcium to form oxalate, and it is not easily absorbed in the gut. Likewise, phylates found in legumes, whole grains, and vegetables like beets binds to calcium and inhibits its absorption. Also, fiber and tannins reduce the bioavailability of calcium.
The levels of vitamin D also affects calcium absorption in our body. Calcium absorption from plant-based food can be increased by reducing the levels of inhibitors. This can be done by cooking the food, as well as processing foods like legumes and whole grains by dehulling and germinating them.
Cooking And Processing Plant-Based Food
Cooking reduces the nutrient content of certain plant-based foods like fruits. But it improves the bioavailability of nutrients like beta-carotene in carrots and iron in spinach. Likewise, cooking makes the nutrient lycopene found in tomatoes more bioavailable. Milling, soaking, fermentation, and germinating reduces the phylate levels in legumes and whole grains.
So, proper cooking of a plant-based meal ensures that the nutrients contained in it are easily absorbed by our body.