Bioavailability of Nutrients
Balanced Diet - bioavailability of nutrients
A balanced diet is the key to a happier, healthier life, so the mantra goes.
Experts advise us to eat more fruit and vegetables; boost protein and fiber intake; make sure we get the optimum levels of vitamins and minerals.
But what actually happens to these nutrients once they are inside the body?
Food scientists, working in an area called bioavailability, are trying to answer this question in a bid to discover how people can get the very best out of what they eat. Many nutritionists now believe that we do not absorb everything we eat. The current view is that while there is a certain amount of a given nutrient within a food, what is actually absorbed may be quite a bit less.
Bioavailability means how much of a specific nutrient within a food is usefully absorbed by the body. However, bioavailability is not set in stone, and researchers are working to find ways of manipulating the levels of nutrients that can be absorbed by the body. If people are meeting dietary requirements, all of the nutrients they need are probably being absorbed, but for people who suffer vitamin or mineral deficiencies, or for those in developing countries where nutrition is poor, research into bioavailability can be very useful.
Iron availability
Take iron - a lot of people are just not getting enough of it, and too little can lead to anemia and increased susceptibility to infections. But how we get our iron can impact on the amount we absorb. While red meat contains the type of iron - haem-iron - that is most readily absorbed by the body, vegetarians are pointed towards iron-rich foods such as spinach.
However, this vegetable contains the mineral in a form that is not so readily absorbed - non-haem iron.
But, a glass of orange juice alongside your plate of spinach can make all the difference.
Vitamin C in orange juice changes the iron to its non-oxidized state (haem iron) - which is much more readily absorbed than the oxidized iron (non-haem iron).
You can manipulate to some extent the gastric and small intestinal chemistry by what you eat and combine. Conversely, tea and coffee contain compounds called phenols that inhibit iron absorption - so they shouldn't be consumed alongside iron-rich foods.
Raw versus cooked
Whether your food is raw or cooked can also make a difference.
Tomatoes contain lycopene, a form of antioxidant. Antioxidants have been hailed for their ability to neutralize free radicals, which are linked to ageing, stroke and heart disease.
Fresh tomatoes have a reasonably high antioxidant potential but if you boil or can them the antioxidant potential goes up fix or six-fold.
This happens because the lycopene in the raw tomato has been transformed to trans-lycopene in the cooked version, and trans-lycopene is much more readily absorbed. It is worth noting that cooking will reduce the level of Vitamin C in tomatoes, but this outweighed by the positive of raising the lycopene levels.
Likewise, cooking carrots makes the beta-carotene, another form of antioxidant, more available because you break down the cell wall with the cooking process.
Fat-loving
A nutrient's relationship with water and oil can also alter bioavailability.
To absorb fat-soluble nutrients, you have to get them out of the cellular structure, and then they have to be transferred into lipophilic - or fat-loving - carriers in the gut to be absorbed.
Lutein is one such nutrient. Present in spinach and other green vegetables such as kale, broccoli and peas, some evidence suggests it can protect or slow age-related macular degeneration, a leading cause of blindness.
Dressing some raw vegetables with oil helps nutrient absorption. Lutein is actually absorbed more efficiently if it is eaten with a little bit of fat. The oil helps lutein to hop onto to the fatty acids in the gut and to be absorbed.
Bioavailability is a growing area, and something that has the potential to impact on the health-food industry: Once you begin to understand and can manipulate how nutrients are delivered into the body, it can help you to tailor a product that can deliver certain attributes. However, this is still a very a complex field, especially because different nutrients interact in different ways.
For a long time breakfast cereals have been fortified with added iron. But they also contain phytates - a form of energy store - which are present in whole-grain cereals, and these actually inhibit the absorption of iron. Furthermore, calcium in dairy products can also inhibit iron absorption. So pouring milk over your cereal will complicate matters, contributing to inhibition of the absorption of iron.
Jigsaw puzzle
According to researchers, there are pros and cons of combining food in this way.
By cooking tomatoes to gain antioxidants, vitamin C is degraded. By adding fats to green vegetables, your caloric intake is boosted, but you do raise the bioavailability of fat-soluble nutrients. Now, experts add, more is not always best. High intake of some vitamins and minerals has been associated with risks. Thus, the more we understand about how the body absorbs nutrients, the better the dietary choices we can make.
It is all about understanding how these nutrients are absorbed in the body, and how much of them we need to reduce or even prevent certain diseases while avoiding any adverse symptoms. It is really part of the jigsaw of understanding optimum nutrition.
A balanced diet is the key to a happier, healthier life, so the mantra goes.
Experts advise us to eat more fruit and vegetables; boost protein and fiber intake; make sure we get the optimum levels of vitamins and minerals.
But what actually happens to these nutrients once they are inside the body?
Food scientists, working in an area called bioavailability, are trying to answer this question in a bid to discover how people can get the very best out of what they eat. Many nutritionists now believe that we do not absorb everything we eat. The current view is that while there is a certain amount of a given nutrient within a food, what is actually absorbed may be quite a bit less.
Bioavailability means how much of a specific nutrient within a food is usefully absorbed by the body. However, bioavailability is not set in stone, and researchers are working to find ways of manipulating the levels of nutrients that can be absorbed by the body. If people are meeting dietary requirements, all of the nutrients they need are probably being absorbed, but for people who suffer vitamin or mineral deficiencies, or for those in developing countries where nutrition is poor, research into bioavailability can be very useful.
Iron availability
Take iron - a lot of people are just not getting enough of it, and too little can lead to anemia and increased susceptibility to infections. But how we get our iron can impact on the amount we absorb. While red meat contains the type of iron - haem-iron - that is most readily absorbed by the body, vegetarians are pointed towards iron-rich foods such as spinach.
However, this vegetable contains the mineral in a form that is not so readily absorbed - non-haem iron.
But, a glass of orange juice alongside your plate of spinach can make all the difference.
Vitamin C in orange juice changes the iron to its non-oxidized state (haem iron) - which is much more readily absorbed than the oxidized iron (non-haem iron).
You can manipulate to some extent the gastric and small intestinal chemistry by what you eat and combine. Conversely, tea and coffee contain compounds called phenols that inhibit iron absorption - so they shouldn't be consumed alongside iron-rich foods.
Raw versus cooked
Whether your food is raw or cooked can also make a difference.
Tomatoes contain lycopene, a form of antioxidant. Antioxidants have been hailed for their ability to neutralize free radicals, which are linked to ageing, stroke and heart disease.
Fresh tomatoes have a reasonably high antioxidant potential but if you boil or can them the antioxidant potential goes up fix or six-fold.
This happens because the lycopene in the raw tomato has been transformed to trans-lycopene in the cooked version, and trans-lycopene is much more readily absorbed. It is worth noting that cooking will reduce the level of Vitamin C in tomatoes, but this outweighed by the positive of raising the lycopene levels.
Likewise, cooking carrots makes the beta-carotene, another form of antioxidant, more available because you break down the cell wall with the cooking process.
Fat-loving
A nutrient's relationship with water and oil can also alter bioavailability.
To absorb fat-soluble nutrients, you have to get them out of the cellular structure, and then they have to be transferred into lipophilic - or fat-loving - carriers in the gut to be absorbed.
Lutein is one such nutrient. Present in spinach and other green vegetables such as kale, broccoli and peas, some evidence suggests it can protect or slow age-related macular degeneration, a leading cause of blindness.
Dressing some raw vegetables with oil helps nutrient absorption. Lutein is actually absorbed more efficiently if it is eaten with a little bit of fat. The oil helps lutein to hop onto to the fatty acids in the gut and to be absorbed.
Bioavailability is a growing area, and something that has the potential to impact on the health-food industry: Once you begin to understand and can manipulate how nutrients are delivered into the body, it can help you to tailor a product that can deliver certain attributes. However, this is still a very a complex field, especially because different nutrients interact in different ways.
For a long time breakfast cereals have been fortified with added iron. But they also contain phytates - a form of energy store - which are present in whole-grain cereals, and these actually inhibit the absorption of iron. Furthermore, calcium in dairy products can also inhibit iron absorption. So pouring milk over your cereal will complicate matters, contributing to inhibition of the absorption of iron.
Jigsaw puzzle
According to researchers, there are pros and cons of combining food in this way.
By cooking tomatoes to gain antioxidants, vitamin C is degraded. By adding fats to green vegetables, your caloric intake is boosted, but you do raise the bioavailability of fat-soluble nutrients. Now, experts add, more is not always best. High intake of some vitamins and minerals has been associated with risks. Thus, the more we understand about how the body absorbs nutrients, the better the dietary choices we can make.
It is all about understanding how these nutrients are absorbed in the body, and how much of them we need to reduce or even prevent certain diseases while avoiding any adverse symptoms. It is really part of the jigsaw of understanding optimum nutrition.
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