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In , Elmer McCollum and Marguerite Davis discovered the first vitamin, fat-soluble vitamin A , then water-soluble vitamin B in ; now known to be a complex of several water-soluble vitamins and named vitamin C as the then-unknown substance preventing scurvy. Trans fats are very rare in nature, and have been shown to be highly detrimental to human health, but have properties useful in the food processing industry, such as rancidity resistance. The first recorded nutritional experiment with human subjects is found in the Bible's Book of Daniel. The Cochrane Database of Systematic Reviews 4: Health and nutrition have been proven to have close links with overall educational success. It was ultimately decided that plaque was the cause of caries; thus, began a war on plaque that exists to this day.
Weston A. Price
Living organisms differ in the particular substances that they require as food, in the manner in which they synthesize food substances or obtain them from the surrounding environment , and in the functions that these substances carry out in their cells. Nevertheless, general patterns can be discerned in the nutritional process throughout the living world and in the types of nutrients that are required to sustain life.
These patterns are the subject of this article. For a full discussion of the nutritional requirements of humans in particular, see the article nutrition, human. Plant nutrition includes the nutrients necessary for the growth, maintenance, and reproduction of individual plants; the mechanisms by which plants acquire such nutrients; and the structural, physiological, and biochemical roles those nutrients play in metabolism.
Living organisms can be categorized by the way in which the functions of food are carried out in their bodies. Thus, organisms such as green plants and some bacteria that need only inorganic compounds for growth can be called autotrophic organisms; and organisms, including all animals , fungi , and most bacteria, that require both inorganic and organic compounds for growth are called heterotrophic. Other classifications have been used to include various other nutritional patterns.
In one scheme, organisms are classified according to the energy source they utilize. Phototrophic, or photosynthetic , organisms trap light energy and convert it to chemical energy , whereas chemoautotrophic , or chemosynthetic, organisms utilize inorganic or organic compounds to supply their energy requirements. If the electron -donor materials utilized to form reduced coenzymes consist of inorganic compounds, the organism is said to be lithotrophic ; if organic, the organism is organotrophic.
Combinations of these patterns may also be used to describe organisms. Higher plants, for example, are photolithotrophic; i. Certain photosynthetic bacteria that cannot utilize water as the electron donor and require organic compounds for this purpose are called photoorganotrophs. Animals, according to this classification, are chemoorganotrophs; i. Despite wide variations in the nature of the external energy source utilized by various organisms, all organisms form from their external energy source an immediate source of energy, the chemical compound adenosine triphosphate ATP.
This energy-rich compound is common to all cells. Through the breaking of its high-energy phosphate bonds and thus by its conversion to a less energy-rich compound, adenosine diphosphate ADP , ATP provides the energy for the chemical and mechanical work required by an organism. The energy requirements of organisms can be measured in either joules or calories. We welcome suggested improvements to any of our articles.
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Please note that our editors may make some formatting changes or correct spelling or grammatical errors, and may also contact you if any clarifications are needed. Stewart Truswell Kenneth Carpenter. Page 1 of 5. Next page Nutrition in plants. Learn More in these related Britannica articles: Regulation of fertility level and nutrient balance. Potash and nitrogen, and the balance between the two, may affect the incidence of certain bacterial, fungal, and viral diseases of corn, cotton, tobacco, and sugar beet.
A number of microelements, including…. Puppies need three basic things in order to thrive: Puppies need to eat three or four times a day from the time they are weaned until they are about six months old.
Thereafter they can be fed…. What we know is that a high level of circulating IGF-1 might increase the risk of one type of cancer in the prostate — not cancer in general. That high IGF-1 levels might promote a single type of cancer is a hypothesis, not a fact, and under all circumstances a growth factor as this one would most likely only play a part of an intricate confluence of factors. Most claims that IGF-1 is the primary cause of any cancer is based on cell studies, which can never be relied upon to establish cause and effect in the complex interactions inside the human body.
Cell studies can only give rise to hypotheses or help to explain the mechanisms behind and observed correlation that can be subsequently tested in further scientific studies. These scientific studies have been done and they show among other things that even when the contents of IGF-1 in the blood is raised a bit, the intake of low fat dairy milk is associated with a lower risk of colorectal cancer — in particular in people with a high level of circulating IGF-1 in the blood .
This is the exact opposite result of the hypothesis that milk consumption causes cancer in general and, in the context of the mentioned article, that this process is driven primarily by IGF In the end our primary concern is to know whether certain foods increase the risk of cancer — and not whether certain components of our food does so in isolation or in a petri dish.
Before describing what we actually know about the connection between milk and cancer, we have to first turn our eyes to the last group of milk hormones: A lot of the milk that we drink comes from pregnant cows and as with humans, this means that the levels of circulating estrogens are higher than normal.
Since that which happens in the blood is usually mirrored in the milk — in cows as in humans — the milk of cows pregnant in the third trimester contains as much as twenty times as much estrogen found in milk from non-pregnant cows. A new study in mice  tested whether the amount of estrogens found in regular dairy milk from pregnant cows had any effect on the circulating levels of estrogens and the genitals of the mice.
After that, the mice were given times as much estrogen as they had found in the milk samples with the highest amount of estrogen. Only when the amount of estrogen reached times the amount found in milk, it became possible to detect effects on the blood and genitals. This observation is really no mystery: Everything that we absorb across the gastrointestinal membrane is transported directly to the liver through the portal vein system before it enters the general circulation.
That the liver is so effective at metabolizing steroid hormones is also the primary reason that bodybuilders usually have to inject steroids instead of ingesting them. If they do ingest them it is because the steroids have been chemically modified to be able to resist the passage through the intestines and liver, which is also the reason why ingestible steroids can have a toxic effect on the liver .
And that is really the real question we want answered — not whether certain hormones could theoretically raise our risk of cancer. If there was any strong evidence that milk raised the risk of cancer in general, it would be listed at the top of every article on the internet trying to persuade you or scare from drinking milk.
You would see meta analyses of studies on milk that showed a clear connection between milk and cancer. Circumstantial evidence is ok to base our beliefs in when we have no other alternative. But we do have alternatives. Figuring out of there is a connection between a specific food and cancer is much harder than many people assume.
Even if we observe an association, it is not safe to assume that the one thing causes the other — it might as well be the other way around this is called reverse causality — which probably explains why artificially sweetened beverages and obesity are correlated  or it could be something else entirely that causes both the exposure and the outcome this is called a confounder.
Observe that an exposure and an outcome that seems connected, does not mean that one thing caused the other. When it comes to research into what raises the risk of cancer, we usually have nothing else than observations like these to go on.
We cannot make longitudinal controlled studies because it would be utterly unethical to try to actively provoke cancer in a group of people and if we did and saw even a small rise in cancer incidence, we would have to end the study immediately.
So how can we know whether something causes cancer or not? In Sir Austin Bradford Hill developed a set of criteria  that needs to be fulfilled for a causality between an assumed cause and effect to be established. The Bradford Hill-criteria in summary looks like this:. A good example of an association that fulfills the Bradford Hill-criteria is smoking and lung cancer. The observed period of time between first exposure and the appearance of diagnosable cancer is congruent with what we would expect.
There is a clear dose-response relationship more cigarettes lead to higher risk and there is a good explanation to what we observe, since cigarette smoke contains a long range of strong mutagens that is carcinogenic in both animal and cell studies. To the best of my knowledge there is not a single food that fulfills the Bradford Hill-criteria for causality. To be able to claim that milk increases the risk of cancer, it would take among other things that milk consumption was consistently correlated with a marked increased risk of cancer and that this effect was dose dependent.
Different studies point in different directions and with some types of cancers it seems like it is protecting against that specific type of cancer but seems to promote other types of cancer. At least that is the focal point of the articles that through blatantly selective presentation of the literature reveals themselves as anti-milk ideologues. Maybe the observed correlations are causal. Maybe milk plays a small part in both protecting against some cancers, and promoting others.
But it is factually wrong to hardheadedly claim that milk causes cancer. The criteria to claim causality simply are not there. A current systematic review and meta-analysis of observational studies on milk consumption and mortality showed, that milk neither lowers or raises the overall risk of death neither before time or by cardiovascular disease or cancer .
So milk in all likelihood is not relevant to worry about when it comes to cancer in humans. And that is perfectly fine because we have other things to worry about — such as smoking, alcohol and obesity — if we really are interested in lowering our risk of getting cancer. First of all, it is inflamed because there exists a plethora of truly horrifying untruths n articles, magazines and books.
These untruths about milk, hormones and cancer is convincing enough to fool even reasonable and rational people. I was myself once fooled by them. Therefore I would never dream of judging others for believing the same untruths nor for sharing them. Because if it was indeed true that milk was chock-full of hormones that gave us cancer it would be amoral to not shout this information from the rooftops and demand that health professionals took action.
It is perfectly fine to think that the production of milk is unethical or that the people responsible for the production of milk or the dairy lobbyists are exaggerating the health benefits of milk consumption. It is also perfectly fine to question the necessity of milk consumption and whether milk consumption is bad for the environment. As long as you remember to separate the different issues, because none of these attitudes changes what science tells us about milk, hormones or cancer.
Keep up the good work! You missed the most important and dangerous hormone, estrogen. Certain studies have shown a clear increase in estrogen in males after consuming milk. I especially like the last paragraphs in your usual aplomb. What a relaxed and still utmost precise piece of work! Have you done an article on Calcium or Vitamin E?