With nutrient intake, one should look at the food and what is in it, as well as what nutrients can that food product efficiently deliver to one’s body. Nutrients in food products are usually lost throughout the all of the processing stages in the body. The science of bioavailability deals with the concept of knowing how much of the nutrients can be absorbed by one’s body. One’s body does not simply absorb and utilize all of the nutrients that are present in a food product, because there are many stages at which the food product will loose nutrients. One can measure the bioavailability of a food product by observing plasma values when one has ingested the food product in comparison to when one has been injected with the food product. When one has been injected with the food product, no nutrients are lost, so this is the base line for comparison. The implications of bioavailability are that food structure lowers nutritional status. Structure can substantially reduce the bioavailability of the food components. Sometimes food products are left intact in one’s stool, which means none of that food’s nutrients were absorbed by one’s body. There are many mechanisms by which nutrients can be taken out of food products. With processing food products, there are aways nutrient losses. There are also a number of factors that affect the bioavailability of nutrients. Nutrients can become connected to other materials in the body, such as proteins or sugars. If the material that the nutrient is attached to is digestible then one is able to digest the nutrient along with the attached material. If the nutrient is attached to a material that is indigestible then one cannot digest the nutrient as well as the other material. Nutrients can be in liquid, solid, or crystalline form; therefore form could also affect how much one’s body is able to absorb the nutrients. The absorption of nutrients and rate of which food is passed through the intestine depends on each person’s different intestinal patterns. The intestine moves food through it by pulsile contractions. The rate by which one can pass foods through their body depends on the food matrix as well as it is highly individualized. For example, elderly people have impaired transit dynamics due to their bodies not being as good of quality as when they were in the prime of their lives. Since there are such a variety of food structures, the rate by which the stomach empties can range from 1-8 hours. The goal of everyone is to maximize the bioavailability of nutrients to our bodies. The food processing companies therefore strive to loose as little of nutrients as possible in the processing stage. If too much of the nutrient is lost in a food product, then that could be considered adulteration of the food product. It is considered adulteration of the food product because people expect to gain a certain amount of nutrients from certain foods, and if these nutrients are lost this may lead to poor health in those individuals. Blanching a food product can cause loss of water-soluble nutrients, considering the food is cooked in water, hence leaching the nutrients out of the food product. When fruits and vegetables are flumed, or moved through the processing lines floating in water, they loose water-soluble nutrients again. Cooking obviously causes the loss of nutrients for the same reason. Clotting causes some compounds to concentrate while eliminating other nutrients. For example, in the cheese making process the whey is expelled when the fat and protein of the cheese is concentrated. Solubility of a nutrient in whatever you are cooking it in may lead to less or more leaching. Much of the losses occur early in processing of fruits and vegetables. There are also processes that increase the bioavailability of a nutrient, such as milling. Milling is a process by which whole grains are crushed and the different parts, endosperm, germ, bran, are separated. This increased the bioavailability of the nutrients in whole grains because before humans could not digest whole grains due to the rigid structure. Milling can be a disruptive process to the final nutrient quality, despite increasing the bioavailability of the nutrients. One wants to maximize disassembly while minimizing nutrient losses. Chemical stability is also very important for processing and storing foods with minimizing nutrient losses. For example, ascorbic acid (Vitamin C) readily breaks down into non Vitamin C derivatives. The oxidative processes rate increases when the partial pressure of oxygen increases. Therefore, one would want to store foods containing ascorbic acid in a low oxygen atmosphere. Metals also increase the rate of oxidation of this nutrient; hence one should keep foods containing ascorbic acid away from metal. The rate of oxidation also depends on water activity and temperature, as well as pH and a number of other environmental factors. Low temperatures and low water activities stabilize Vitamin C’s rate of oxidation. A low water activity means that there is not much water available to undergo reactions with other compounds in the food product. Vitamin C can be especially altered in vegetables in the processing and cooking phases. For example, in England people traditionally consumed mashed potatoes to obtain their requirement for Vitamin C. It was quite a long process of cutting up and peeling the potatoes to boil and mash them, thus someone invented dried mashed potatoes. Then a problem arose considering exposing the mashed potatoes to air for a long period of time as well as removing the water from the potatoes leached the ascorbic acid from the potatoes. Taking into account how popular these dried mashed potatoes became due to the convenience in cooking them, this caused on outbreak of scurvy in their population. They eventually figured out what happened and now they simply just add ascorbic acid back into the final dried mash potato product. Thiamine is also susceptible to degradation in food products. Many preservatives, such as sulfites, can act as a nucleophiles, therefore breaking thiamine into two halves. Once thiamine is broken into two parts, it is no longer thiamine. Riboflavin is also readily lost in food products. Riboflavin has an aromatic ring structure; therefore it absorbs UV light and energy, which breaks down the molecule. The oxidation of riboflavin is associated with a rancid smell, especially in milk. Scientists solved the problem of photooxidation by placing products that contain riboflavin in opaque containers, rather than glass containers.
Folates are also lost in the processing stage. The bioavailability of folate varies with age, considering as you get older one’s digestibility of folates decreases. In elderly that are not digesting enough folate can develop neurological degeneration. Some people are simply genetically predisposed to not being able to absorb folate readily. These people have a deficiency in MTHFR (methyltetrahydrofolate reductase). This is the reason why the scientists working for the government want to fortify cereal grains with folate. Since a subset of the population has a genetic mutation that makes them absorb folate slower, these individuals who can have children can pass this onto their children. If a woman has a folate deficiency during pregnancy, so will her child, which results in neurological disorders and sometimes failure of pregnancy. These were the engines to drive the FDA to make sure they fortify the food supply. Although we can no longer treat the population as a homogenous population with all nutrients because we are all different in that some people are predisposed to having different bioavailabilities for particular nutrients. This is the case with folate because there is a certain subset of the population that can be put at risk of having an overdose of folate with supplementation because they have an increased bioavailability of folate. A high folate status can result in an increased progression of some cancers, and a low folate status can increase the initiation of cancer. Pantothenic acid is also a water soluble vitamin, therefore can be lost in processing. A pantothenic acid deficiency is unheard of in humans. No one has seen this deficiency up to this point in time, although it is still possible that it could occur sometime in the future. Niacin is another water-soluble vitamin that can be lost in the processing stage. Niacin is not very available in corn, since the structure of corn is very rigid. Corn is a core staple food of Mesoamericans, whom should be niacin deficient. The Mesoamericans are not niacin deficient since they alkylated their corn through a process of adding fire ashes to the corn. This process makes the niacin more bioavailable. Carotenoids are also water-soluble nutrients; therefore they can be lost in processing.
The nutrient quality of carotenoids depends on what isomer is present in the food product. The bioavailability of carotenoids depends on the amount of fat in the diet, considering with an increased amount of fat in the diet one can get an increased bioavailability of carotenoids. Sometimes carotenoids are present in a food product in the crystalline form, and one has to heat and cook the food to be able to increase the bioavailability of the carotenoids. Cooking makes carotenoids more bioavailable because the isomers change and it causes the carotenoids to transition from the crystalline to liquid state. Vitamin E is a lipid-soluble nutrient that is present in food products. Vitamin E acts as a chain breaking antioxidant in biological membranes that contain unsaturated fatty acids, in which it stops free radical catalyzed oxidation reactions from taking place. In the year 2000, scientists realized that there is only one isomer of Vitamin E present in our food products. Before 2000, scientists thought alpha, beta, and gamma tocopherols make up Vitamin E in our foods, but this was proven wrong. The reason why Vitamin E is an antioxidant is because it is oxidized before anything else in a membrane; therefore it inhibits the oxidation of other compounds present in membranes, such as unsaturated fatty acids. Since Vitamin E is a lipid-soluble nutrient, it has to be transported around the body in chylomicrons, which are simply transporters for lipid-soluble compounds that one ingests in their diet. The bioavailability of amino acids is crucial to the well being of the person who is consuming them, especially when speaking about essential amino acids. Essential amino acids are those that the body cannot make, or cannot make in sufficient quantities that are required by the body. Therefore, to maintain function and life, one must consume the correct amount of amino acids in their diet. Lysine is an essential amino acid that degrades and becomes oxidized the quickest, therefore lysine is the most vulnerable to oxidation out of all the amino acids. Lysine is lost in many processing steps, such as when food in undergoing the Maillard reaction, lysine is completely lost from the food product. With food reactions, there is a transition state or activation state that needs to be overcome to change the substrates to products. The thermal energy that is released or consumed tells us how much energy was put out or required to turn the substrates into products. Catalysts lower how much energy is needed to complete the reaction that was taking place. This rate of change in the energy can be describes with an Arrhenius equation. We can develop an Arrhenius relationship for all of the essential nutrients. Therefore, we can predict how long that nutrient will last at particular temperatures. Hence, the effects of food processing can be modeled and predicted. In food processing, we are gradually loosing nutrients, so we compute time and temperature required to maximize destruction of bacteria and minimize nutrient losses. Humans are very lucky that nutrients are the most stable in comparison to bacteria in terms of thermal resistance. If this were not true, then food would be nutritionally inadequate before it would be safe to eat. Whole-wheat kernels contain phytic acid, which binds to its nutrients, making them unavailable for absorption. Once a mineral is bound to phytic acid, you cannot absorb it; you simply just excrete it out as waste. This is why we grind up wheat to get around this hurdle. In the process of dough making there is a phytase enzyme that comes about and breaks down phytic acid so all the minerals can be released. The process of dough making makes wheat an effective nutrient. Cooking is also an excellent way to break down cell walls. Fermentation improves the bioavailability of nutrients and makes food products more safe, stable, and delicious.