Protein Requirments while Dieting

Proteins are broken down in the stomach during digestion by enzymes known as proteases into smaller polypeptides to provide amino acids for the organism, including the essential amino acids that the organism cannot biosynthesize itself. Aside from their role in protein synthesis, amino acids are also important nutritional sources of nitrogen.

Proteins, like carbohydrates, contain 4 kilocalories per gram as opposed to lipids which contain 9 kilocalories and alcohols which contain 7 kilocalories. The liver and to a much lesser extent the kidneys, can convert amino acids used by cells in protein biosynthesis into glucose by a process known as gluconeogenesis. The amino acids leucine and lysine are exceptions.

Sources of proteins

Dietary sources of protein include meats, eggs, grains, legumes, and dairy products such as milk and cheese. Of the over 20 amino acids used by humans, 12 nonessential amino acids can be synthesized by the body, and are not required in the diet (though there are exceptions for some in special cases). The 9 essential amino acids, however, cannot be created by the body and must come from dietary sources.

Most animal sources and certain vegetable sources have the complete complement of all 9 essential amino acids. However, it is not necessary to consume a single food source that contains all the essential amino acids, as long as all the essential amino acids are eventually present in the diet: see complete protein and protein combining.

 Protein quality

Different proteins have different levels of biological availability to the human body. Many methods have been introduced to measure protein utilization and retention rates in humans. They include biological value, Net Protein Utilization or NPU, and PDCAAS (Protein Digestibility Corrected Amino Acids Score) which was developed by the FDA as an improvement over the Protein Efficiency Ratio (PER) method. These methods examine which proteins are most efficiently used by the body. In general they conclude that animal complete proteins that contain all the essential amino acids such as milk, eggs, and meat, and the complete vegetable protein soy are of most value to the body.

Egg whites have been determined to have the standard biological value of 100 (though some sources may have biological values higher), which means that most of the absorbed nitrogen from egg white protein can be retained and used by the body. Since the amino acids found in plants are biologically different from those found in humans and animals, the biological value of plant protein sources is considerably lower. For example, corn has a BA of 70 while peanuts have a relatively low BA of 40.

 Digestion of protein

Digestion typically begins in the stomach when pepsinogen is converted to pepsin by the action of hydrochloric acid, and continued by trypsin and chymotrypsin in the intestine. The amino acids and their derivatives into which dietary protein is degraded are then absorbed by the gastrointestinal tract. The absorption rates of individual amino acids are highly dependent on the protein source; for example, the digestibility of many amino acids in humans differs between soy and milk proteins and between individual milk proteins, beta-lactoglobulin and casein. For milk proteins, about 50% of the ingested protein is absorbed between the stomach and the jejunum and 90% is absorbed by the time the digested food reaches the ileum. Biological value (BV) is a measure of the proportion of absorbed protein from a food which becomes incorporated into the proteins of the organism’s body.

 Dietary requirements

According to the recently updated Dietary Reference Intake guidelines, women aged 19–70 need to consume 46 grams of protein per day, while men aged 19–70 need to consume 56 grams of protein per day to avoid a deficiency. The difference is because men’s bodies generally have more muscle mass than those of women, or this may be attributed to weight difference by taking 0.8 g(of protein)/kg of body weight.

Because the body is continually breaking down protein from tissues, even adults who do not fall into the above categories need to include adequate protein in their diet every day. If enough energy is not taken in through diet, as in the process of starvation, the body will use protein from the muscle mass to meet its energy needs, leading to muscle wasting over time. If the body does not consume adequate protein in nutrition, then muscle will also waste as more vital cellular processes (e.g. respiration enzymes, blood cells) recycle muscle protein for their own requirements.

Other recommendations suggest 0.8 gram of protein per kilogram of bodyweight per day while other sources suggest that higher intakes of 1-1.4 grams of protein per kilogram of bodyweight for enhanced athletes or those with a large muscle mass.

How much protein needed in a person’s daily diet is determined in large part by overall energy intake, as well as by the body’s need for nitrogen and essential amino acids. Physical activity and exertion as well as enhanced muscular mass increase the need for protein. Requirements are also greater during childhood for growth and development, during pregnancy or when breast-feeding in order to nourish a baby, or when the body needs to recover from malnutrition or trauma or after an operation.

 Protein deficiency

 Protein deficiency in developing countries

Protein deficiency is a serious cause of ill health and death in developing countries. Protein deficiency plays a part in the disease kwashiorkor. War, famine, overpopulation and other factors can increase rates of malnutrition and protein deficiency. Protein deficiency can lead to reduced intelligence or mental retardation; see deficiency in proteins, fats, carbohydrates.

In countries that suffer from widespread protein deficiency, food is generally full of plant fibers, which makes adequate energy and protein consumption very difficult. Symptoms of kwashiorkor include apathy, diarrhea, inactivity, failure to grow, flaky skin, fatty liver, and edema of the belly and legs. This edema is explained by the normal functioning of proteins in fluid balance and lipoprotein transport.

Dr. Latham, director of the Program in International Nutrition at Cornell University claims that malnutrition is a frequent cause of death and disease in third world countries. Protein-energy malnutrition (PEM) affects 500 million people and kills 10 million annually. In severe cases white blood cell numbers decline and the ability of leukocytes to fight infection decreases.

 Protein deficiency in developed countries

Protein deficiency is rare in developed countries but small numbers of people have difficulty getting sufficient protein due to poverty. Protein deficiency can also occur in developed countries in people who are dieting or crash dieting to lose weight, or in older adults, who may have a poor diet. Convalescent people recovering from surgery, trauma, or illness may become protein deficient if they do not increase their intake to support their increased needs. A deficiency can also occur if the protein a person eats is incomplete and fails to supply all the essential amino acids.

 Excess protein consumption

Because the body is unable to store in the form of protein, excess consumed protein is broken down and converted into sugars or fatty acids. The liver removes nitrogen from the amino acids, so that they can be burned as fuel, and the nitrogen is incorporated into urea, the substance that is excreted by the kidneys. These organs can normally cope with any extra workload but if kidney disease occurs, a decrease in protein will often be prescribed.

Many researchers think excessive intake of protein forces increased calcium excretion. If there is to be excessive intake of protein, it is thought that a regular intake of calcium would be able to stabilize, or even increase the uptake of calcium by the small intestine, which would be more beneficial in older women.

Proteins are often progenitors in allergies and allergic reactions to certain foods. This is because the structure of each form of protein is slightly different; some may trigger a response from the immune system while others remain perfectly safe. Many people are allergic to casein, the protein in milk; gluten, the protein in wheat and other grains; the particular proteins found in peanuts; or those in shellfish or other seafood.

 Testing for protein in foods

The classic assay for protein concentration in food is the Kjeldahl method. This test determines the total nitrogen in a sample. The only major component of most food which contains nitrogen is protein (fat, carbohydrate and dietary fiber do not contain nitrogen). If the amount of nitrogen is multiplied by a factor depending on the kinds of protein expected in the food the total protein can be determined. On food labels the protein is given by the nitrogen multiplied by 6.25, because the average nitrogen content of proteins is about 16%. The Kjeldahl test is used because it is the method the AOAC International has adopted and is therefore used by many food standards agencies around the world.

Essential Amino Acids and Dieting

Essential Amino Acids

 

An essential amino acid or indispensable amino acid is an amino acid that cannot be synthesized de novo by the organism (usually referring to humans), and therefore must be supplied in the diet.

 

Essentiality vs. conditional essentiality in humans

Nine amino acids are generally regarded as essential for humans: phenylalanine, valine, threonine, tryptophan, isoleucine, methionine, histidine, leucine, and lysine. Arginine is required by infants and growing kids. They are called essential not because they are more important to life than the others, but because the body does not synthesize them, making it essential to include them in one’s diet in order to obtain them. In addition, the amino acids arginine, cysteine, glycine, glutamine and tyrosine are considered conditionally essential, meaning they are not normally required in the diet, but must be supplied exogenously to specific populations that do not synthesize it in adequate amounts. An example would be with the disease phenylketonuria (PKU). Individuals living with PKU must keep their intake of phenylalanine extremely low to prevent mental retardation and other metabolic complications. However, phenylalanine is the precursor for tyrosine synthesis. Without phenylalanine, tyrosine cannot be made and so tyrosine becomes essential in the diet of PKU patients.

Which amino acids are essential varies from species to species, as different metabolisms are able to synthesize different substances. For instance, taurine (which is not, by strict definition, an amino acid) is essential for cats, but not for dogs. Thus, dog food is not nutritionally sufficient for cats, and taurine is added to commercial cat food when the base ingredients do not meet the requirements of the cat, but not to dog food.

The distinction between essential and non-essential amino acids is somewhat unclear, as some amino acids can be produced from others. The sulfur-containing amino acids, methionine and homocysteine, can be converted into each other but neither can be synthesized de novo in humans. Likewise, cysteine can be made from homocysteine but cannot be synthesized on its own. So, for convenience, sulfur-containing amino acids are sometimes considered a single pool of nutritionally-equivalent amino acids. Likewise arginine, ornithine, and citrulline, which are interconvertible by the urea cycle, are considered a single group.

 Recommended daily amounts

The following table lists the recommended daily amounts for essential amino acids in humans, together with their standard one-letter abbreviations. In some cases, humans can use either of two amino acids, so only the total matters.

Amino acid

WHO-recommended daily intake for

human adults, mg per kg body weight

mg per 70 kg

F Phenylalanine

+ Y Tyrosin

14 (total)

980

L Leucine

14

980

M Methionine

+ C Cysteine

13 (total)

910

K Lysine

12

840

I Isoleucine

10

700

V Valine

10

700

T Threonine

7

490

W Tryptophan

3

245

H Histidine

unknown, 28 in infants (? sum with arginine)

(? 1960)

R Arginine

unknown, required for infants, maybe seniors

(?)

Taurine may be necessary to preserve arterial and collagen pliability at 2 mg/kg/day, small but needed (142 mg/day per 70 kg human).

 Use of essential amino acids

Foodstuffs that lack essential amino acids are poor sources of protein equivalents, as the body tends to deaminate the amino acids obtained, converting proteins into fats and carbohydrates. Therefore, a balance of essential amino acids is necessary for a high degree of net protein utilization, which is the mass ratio of amino acids converted to proteins to amino acids supplied.

All essential amino acids may be obtained from plant sources, and even strict vegetarian diets can provide all dietary requirements, provided they are based on a variety of whole plant foods. Some believe that careful monitoring of nutrient levels is important in strict vegetarian diets, but there are virtually no cases of protein-deficiency among populations consuming adequate calories. The only common cases of protein-deficiency occur among populations that are chronically undernourished.

Complete proteins contain a balanced set of essential amino acids for humans. Animal sources such as meat, poultry, eggs, fish, milk, and cheese provide all of the essential amino acids. Complete proteins are also found in some plant sources such as spirulina, quinoa, soy, buckwheat, hempseed, and amaranth, among others.

The net protein utilization is profoundly affected by the limiting amino acid content (the essential amino acid found in the smallest quantity in the foodstuff), and somewhat affected by salvage of essential amino acids in the body. It is therefore a good idea to mix foodstuffs that have different weaknesses in their essential amino acid distributions. This limits the loss of nitrogen through deamination and increases overall net protein utilization.

Protein source

Limiting amino acid

Wheat

lysine

Rice

lysine

Legumes

tryptophan

Maize

lysine and tryptophan

Pulses

methionine (or cysteine)

Beef

 

phenylalanine (or tyrosine)

Egg, chicken

none; the reference for absorbable protein

Milk or Whey, bovine

methionine (or cysteine)

 Mnemonics

Using the one letter designation shown above, mnemonic devices have been developed for students wanting or needing to memorize the essential amino acids. Previous devices have utilized the first letter of the amino acids name, and in general did not include arginine which is not always essential. One mnemonic device that has been used in the past is PVT TIM HALL.

Another method uses the first letter of each essential amino acid to begin each word in a phrase, such as: “Any Help in Learning These Little Molecules Proves Truly Valuable.” This method begins with the two amino acids that need some qualifications as to their requirements.

Note that these devices work by using the first letter of the actual amino acids name. Due to repetition of letters, several amino acids have one letter abbreviations that are different than their first letter (e.g. lysine is K). Thus the complete list of essential amino acids utilizing one-letter codes is MILKVWTHFR.

A mnemonic that involves only the true one-letter codes for each amino acid is: “I Have Received Much Kudos for Learning These Very Well,” for IHRMKFLTVW.

Vitamins Supplements in Diets

Dietary supplements, often containing vitamins, are used to ensure that adequate amounts of nutrients are obtained on a daily basis, if optimal amounts of the nutrients cannot be obtained through a varied diet. Scientific evidence supporting the benefits of some dietary supplements is well established for certain health conditions, but others need further study. A meta-analysis in 2006 suggested that Vitamin A and E supplements not only provide no tangible health benefits for generally healthy individuals, but may actually increase mortality, although two large studies included in the analysis involved smokers, for which it was already known that beta-carotene supplements can be harmful.

 

In the United States, advertising for dietary supplements is required to include a disclaimer that the product is not intended to treat, diagnose, mitigate, prevent, or cure disease, and that any health claims have not been evaluated by the Food and Drug Administration. In some cases, dietary supplements may have unwanted effects, especially if taken before surgery, with other dietary supplements or medicines, or if the person taking them has certain health conditions. Vitamin supplements may also contain levels of vitamins many times higher, and in different forms, than one may ingest through food.

 

Intake of excessive quantities can cause vitamin poisoning, often due to overdose of Vitamin A and Vitamin D (The most common poisoning with multinutrient supplement pills does not involve a vitamin, but is rather due to the mineral iron). Due to toxicity, most common vitamins have recommended upper daily intake amounts.

 

Since 2005, suppliers have distinguished their products as either Medical Grade or Pharmaceutical Grade products. Both of these classifications indicate products that are manufactured to be easily absorbed by the body. Normal vitamin manufacturing is not regulated in the United States to the same standards as are medicinal pharmaceuticals, although U.S. vitamins which are manufactured for food consumption by humans or animals must be manufactured to Food Chemicals Codex (FCC), grade, commonly called “food grade”.

 

 Governmental regulation of vitamin supplements

 

Most countries place dietary supplements in a special category under the general umbrella of foods, not drugs. This necessitates that the manufacturer, and not the government, be responsible for ensuring that its dietary supplement products are safe before they are marketed. Unlike drug products, that must explicitly be proven safe and effective for their intended use before marketing, there are often no provisions to “approve” dietary supplements for safety or effectiveness before they reach the consumer. Also unlike drug products, manufacturers and distributors of dietary supplements are not generally required to report any claims of injuries or illnesses that may be related to the use of their products.

 

 Names in current and previous nomenclatures

 

The reason the set of vitamins seems to skip directly from E to K is that the vitamins corresponding to “letters” F-J were either reclassified over time, discarded as false leads, or renamed because of their relationship to “vitamin B”, which became a “complex” of vitamins. The German-speaking scientists who isolated and described vitamin K (in addition to naming it as such) did so because the vitamin is intimately involved in the Koagulation of blood following wounding. At the time, most (but not all) of the letters from F through J were already designated, so the use of the letter K was considered quite reasonable.

 

The following table lists chemicals that had previously been classified as vitamins, as well as the earlier names of vitamins that later became part of the B-complex:

Previous name Chemical name             Reason for name change

Vitamin B4                       Adenine                                       DNA metabolite

Vitamin B8                 Adenylic acid                                     DNA metabolite

Vitamin F         Essential fatty acids             Needed in large quantities (does

not fit the definition of a vitamin).

Vitamin G                     Riboflavin                        Reclassified as Vitamin B2

Vitamin H                      Biotin                Reclassified as Vitamin B7

Vitamin J                Catechol, Flavin                                Protein metabolite

Vitamin L1           Anthranilic acid                       Protein metabolite

Vitamin L2          Adenylthiomethylpentose             RNA metabolite

Vitamin M                    Folic acid                          Reclassified as Vitamin B9

Vitamin O                        Carnitine                                     Protein metabolite

Vitamin P                       Flavonoids                  No longer classified as a vitamin

Vitamin PP                        Niacin                           Reclassified as Vitamin B3

Vitamin U                  S-Methylmethionine                              Protein metabolite

 

Niacin in Your Diet

Niacin, also known as nicotinic acid and vitamin B3, is the organic compound with the formula HO2CC5H4N. This water-soluble, colorless solid is a derivative of pyridine, featuring a carboxylic acid functional group at the 3-position. The designation vitamin B3 also includes the corresponding amide nicotinamide (”niacinamide”), wherein the CO2H group has been replaced by a CONH2 group. Niacin is converted to niacinamide in vivo, and though the two are identical in their vitamin functions, niacinamide does not have the same pharmacologic and toxic effects of niacin, which occur incidental to niacin’s conversion. Thus niacinamide does not reduce cholesterol or cause flushing, although nicotinamide may be toxic to the liver at doses exceeding 3 g/day for adults. Niacin is a precursor to NADH, NAD, NAD+, and NADP, which play essential metabolic roles in living cells. DNA repair, and the production of steroid hormones in the adrenal gland.

 

History

 

Niacin was first described by Weidel in 1873 in his studies of nicotine. The original preparation remains useful: the oxidation of nicotine using nitric acid. Niacin was extracted from livers by Conrad Elvehjem who later identified the active ingredient, then referred to as the “pellagra-preventing factor” and the “anti-blacktongue factor.” When the biological significance of nicotinic acid was realized, it was thought appropriate to choose a name to dissociate it from nicotine, in order to avoid the perception that vitamins or niacin-rich food contains nicotine. The resulting name ‘niacin’ was derived from nicotinic acid + vitamin.

 

Niacin is referred to as Vitamin B3 because it was the third of the B vitamins to be discovered. It has historically been referred to as “vitamin PP.”

 

 Dietary needs

 

Severe deficiency of niacin in the diet causes the disease pellagra, whereas mild deficiency slows the metabolism, causing decreased tolerance to cold. Dietary niacin deficiency tends to occur only in areas where people eat corn (maize), the only grain low in niacin, as a staple food, and that do not use lime during meal/flour production. Alkali lime releases the tryptophan from the corn in a process called nixtamalization so that it can be absorbed in the intestine, and converted to niacin.

 

The recommended daily allowance of niacin is 2-12 mg/day for children, 14 mg/day for women, 16 mg/day for men and 18 mg/day for pregnant or breast-feeding women.

 

Note: Niacin synthesis is deficient in carcinoid syndrome because of metabolic diversion of its precursor, tryptophan, to form serotonin.

 

 Pharmacological uses

 

Niacin, when taken in large doses, blocks the breakdown of fats in adipose tissue, thus altering blood lipid levels. Niacin is used in the treatment of hyperlipidemia because it reduces very-low-density lipoprotein (VLDL), a precursor of low-density lipoprotein (LDL) or “bad” cholesterol. Because niacin blocks breakdown of fats, it causes a decrease in free fatty acids in the blood and, as a consequence, decreased secretion of VLDL and cholesterol by the liver.

 

By lowering VLDL levels, niacin also increases the level of high-density lipoprotein (HDL) or “good” cholesterol in blood, and therefore it is sometimes prescribed for patients with low HDL, who are also at high risk of a heart attack.

 

Niacin is sometimes consumed in large quantities by people who wish to fool drug screening tests, particularly for lipid soluble drugs such as marijuana. It is believed to “promote metabolism” of the drug and cause it to be “flushed out.” Scientific studies have shown it does not affect drug screenings, but can pose a risk of overdose, causing arrhythmias, metabolic acidosis, hyperglycemia, and other serious problems.

 

 Toxicity

 

People taking pharmacological doses of niacin (1.5 - 6 g per day) often experience a syndrome of side-effects that can include one or more of the following:

 

    * Dermatological complaints

          o facial flushing and itching

          o dry skin

          o skin rashes including acanthosis nigricans

    * Gastrointestinal complaints

          o dyspepsia (indigestion)

    * Liver toxicity

          o fulminant hepatic failure

    * Hyperglycemia

    * Cardiac arrhythmias

    * Birth defects

 

Facial flushing is the most commonly-reported side-effect. It lasts for about 15 to 30 minutes, and is sometimes accompanied by a prickly or itching sensation, particularly in areas covered by clothing. This effect is mediated by prostaglandin and can be blocked by taking 300 mg of aspirin half an hour before taking niacin, or by taking one tablet of ibuprofen per day. Taking the niacin with meals also helps reduce this side-effect. After 1 to 2 weeks of a stable dose, most patients no longer flush. Slow- or “sustained”-release forms of niacin have been developed to lessen these side-effects. One study showed the incidence of flushing was significantly lower with a sustained release formulation though doses above 2 g per day have been associated with liver damage, particularly with slow-release formulations.

 

High-dose niacin may also elevate blood sugar, thereby worsening diabetes mellitus. Hyperuricemia is another side-effect of taking high-dose niacin, and may exacerbate gout. Niacin at doses used in lowering cholesterol has been associated with birth defects in laboratory animals, with possible consequences for infant development in pregnant women.

 

Niacin at extremely high doses can have life-threatening acute toxic reactions. Extremely high doses of niacin can also cause niacin maculopathy, a thickening of the macula and retina which leads to blurred vision and blindness.

 

 Inositol hexanicotinate

 

One popular form of dietary supplement is inositol hexanicotinate, usually sold as “flush-free” or “no-flush” niacin (although those terms are also used for regular sustained-release.) While this form of niacin does not cause the flushing associated with the nicotinic acid form, it is not clear whether it is pharmacologically equivalent in its positive effect.

 

 

Health and Essential Fatty Acids

Essential Fatty Acids, or EFAs, are fatty acids that cannot be constructed within an organism from other components (generally all references are to humans) by any known chemical pathways; and therefore must be obtained from the diet. The term refers to those involved in biological processes, and not fatty acids which may just play a role as fuel. As many of the compounds created from essential fatty acids can be taken directly in the diet, it is possible that the amounts required in the diet (if any) are overestimated. It is also possible they can be underestimated as organisms can still survive in less than ideal, malnourished conditions.

There are two families of EFAs: ω-3 (or omega-3 or n-3) and ω-6 (omega-6, n-6.) Fats from each of these families are essential, as the body can convert one omega-3 to another omega-3, for example, but cannot create an omega-3 from scratch. They were originally designated as Vitamin F when they were discovered as essential nutrients in 1923. In 1930, work by Burr, Burr and Miller showed that they are better classified with the fats than with the vitamins.

Functions

In the body, essential fatty acids serve multiple functions. In each of these, the balance between dietary ω-3 and ω-6 strongly affects function.

  • They are modified to make
    • the classic eicosanoids (affecting inflammation and many other cellular functions)
    • the endocannabinoids (affecting mood, behavior and inflammation)
    • the lipoxins from ω-6 EFAs and resolvins from ω-3 (in the presence of aspirin, down regulating inflammation.)
    • the isofurans, neurofurans, isoprostanes, hepoxilins, epoxyeicosatrienoin acids (EETs) and Neuroprotectin D
  • They form lipid rafts (affecting cellular signaling)
  • They act on DNA (activating or inhibiting transcription factors such as NFκB, which is linked to pro-inflammatory cytokine production)

 Nomenclature and terminology

Fatty acids are straight chain hydrocarbons possessing a carboxyl (COOH) group at one end. The carbon next to the carboxylate is known as α, the next carbon β, and so forth. Since biological fatty acids can be of different lengths, the last position is labeled ω, the last letter in the Greek alphabet. Since the physiological properties of unsaturated fatty acids largely depend on the position of the first unsaturation relative to the end position and not the carboxylate, the position is signified by (ω minus n). For example, the term ω-3 signifies that the first double bond exists as the third carbon-carbon bond from the terminal CH3 end (ω) of the carbon chain. The number of carbons and the number of double bonds is also listed. ω-3 18:4 (stearidonic acid) or 18:4 ω-3 or 18:4 n-3 indicates an 18-carbon chain with 4 double bonds, and with the first double bond in the third position from the CH3 end. Double bonds are cis and separated by a single methylene (CH2) group unless otherwise noted. So in free fatty acid form, the chemical structure of stearidonic acid is:

 

 The essential fatty acids start with the short chain polyunsaturated fatty acids (SC-PUFA):

  • ω-3 fatty acids:
    • α-Linolenic acid or ALA (18:3)
  • ω-6 fatty acids:
    • Linoleic acid or LA (18:2)

These two fatty acids cannot be synthesized by humans, as humans lack the desaturase enzymes required for their production.

They form the starting point for the creation of longer and more desaturated fatty acids, which are also referred to as long-chain polyunsaturated fatty acids (LC-PUFA):

  • ω-3 fatty acids:
    • eicosapentaenoic acid or EPA (20:5)
    • docosahexaenoic acid or DHA (22:6)
  • ω-6 fatty acids:
    • gamma-linolenic acid or GLA (18:3)
    • dihomo-gamma-linolenic acid or DGLA (20:3)
    • arachidonic acid or AA (20:4)

ω-9 fatty acids are not essential in humans, because humans generally possess all the enzymes required for their synthesis. Exceptions do occur in older people or people with a liver problem that do not completely produce a sufficient amount, and hence many supplement companies market Omega 3-6-9 blends.

 Essentiality

Between 1930 and 1950, arachidonic acid and linolenic acid were termed ‘essential’ because each was more or less able to meet the growth requirements of rats given fat-free diets. Further research has shown that human metabolism requires both ω-3 and ω-6 fatty acids. To some extent, any ω-3 and any ω-6 can relieve the worst symptoms of fatty acid deficiency. Particular fatty acids are still needed at critical life stages (e.g. lactation) and in some disease states. In nonscientific writing, common usage is that the term essential fatty acid comprises all the ω-3 or -6 fatty acids. Authoritative sources include the whole families, without qualification. The human body can make some long-chain PUFA (arachidonic acid, EPA and DHA) from lineolate or lineolinate.

Traditionally speaking the LC-PUFA are not essential. See (Cunnane 2003) for a discussion of the current status of the term ‘essential’. Because the LC-PUFA are sometimes required, they may be considered “conditionally essential”, or not essential to healthy adults.

Mary G. Enig has pointed out numerous studies showing the need for omega-3 and omega-6 essential fatty acids in mammalians A 2005 study has shown evidence that gamma-linolenic acid, GLA, a product of omega-6, has been shown to inhibit the breast cancer promoting gene of Her2/neu.

Biologist Ray Peat has pointed out flaws in the studies purportedly showing the need for n-3 and n-6 fats. He notes that so-called EFA deficiencies have sometimes been reversed by adding B vitamins or a fat-free liver extract to the diet. In his view, ‘the optional dietary level of the “essential fatty acids” might be close to zero, if other dietary factors were also optimized.’

Essential fatty acids should not be confused with essential oils, which are “essential” in the sense of being a concentrated essence.

 Food sources

Almost all the polyunsaturated fat in the human diet is from EFA. Some of the food sources of ω-3 and ω-6 fatty acids are fish and shellfish, flaxseed (linseed), hemp oil, soy oil, canola (rapeseed) oil, chia seeds, pumpkin seeds, sunflower seeds, leafy vegetables, and walnuts.

Essential fatty acids play a part in many metabolic processes, and there is evidence to suggest that low levels of essential fatty acids, or the wrong balance of types among the essential fatty acids, may be a factor in a number of illnesses, including osteoporosis.

Plant sources of ω-3 contain neither eicosapentaenoic acid (EPA) nor docosahexaenoic acid (DHA). The human body can (and in case of a purely vegetarian diet often must, unless certain algae or supplements derived from them are consumed) convert α-linolenic acid (ALA) to EPA and subsequently DHA. This however requires more metabolic work, which is thought to be the reason that the absorption of essential fatty acids is much greater from animal rather than plant sources (see Fish and plants as a source of Omega-3 for more).

The IUPAC Lipid Handbook  provides a very large and detailed listing of fat contents of animal and vegetable fats, including ω-3 and -6 oils. The National Institutes of Health’s EFA Education group publishes ‘Essential Fats in Food Oils.’ This lists 40 common oils, more tightly focused on EFAs and sorted by n-6:3 ratio. Stuchlik and Zak, ‘Vegetable Lipids as Components of Functional Food  list notable vegetable sources of EFAs as well as commentary and an overview of the biosynthetic pathways involved. Users can interactively search at Nutrition Data for the richest food sources of particular EFAs or other nutrients. Careful readers will note that these sources are not in excellent agreement. EFA content of vegetable sources varies with cultivation conditions. Animal sources vary widely, both with the animal’s feed and that the EFA makeup varies markedly with fats from different body parts.

 Human health

Almost all the polyunsaturated fats in the human diet are EFAs. Essential fatty acids play an important role in the life and death of cardiac cells.

 

Benefits of Whey Protein in Dieting

Benefits of Whey Protein for Maintaining Lean Muscle Mass and Increased Metabolism 

 

 The Arizona Diet Products plan is a nutritionally complete weight loss program that contains a scientifically designed balance of protein, carbohydrates, and essential vitamins and minerals. Unlike fad diets that restrict a specific macronutrient, such as protein or carbohydrates, the Arizona Diet Products plan is nutritionally balanced — allowing for optimum weight loss results. One key component of the Arizona Diet products is the utilization of whey and casein protein. Since the amount of lean muscle a person has is the main determinant of their metabolic rate, utilizing whey and casein protein allows the body to maintain lean muscle, while still losing weight. As a result, as the body loses weight, it is able to maintain lean muscle mass, and also a higher metabolic rate throughout the diet. As a result of this, the body also maintains a higher metabolic rate after reaching its goal weight. 

 

 Third Party Study: Consumption of fluid skim milk promotes greater muscle protein accretion after resistance exercise than does consumption of an isonitrogenous and isoenergetic soy-protein beverage. 

 

 BACKGROUND: Resistance exercise leads to net muscle protein accretion through a synergistic interaction of exercise and feeding. Proteins from different sources may differ in their ability to support muscle protein accretion because of different patterns of postprandial hyperaminoacidemia. 

 

 OBJECTIVE: We examined the effect of consuming isonitrogenous, isoenergetic, and macronutrient-matched soy or milk beverages (18 g protein, 750 kJ) on protein kinetics and net muscle protein balance after resistance exercise in healthy young men. Our hypothesis was that soy ingestion would result in larger but transient hyperaminoacidemia compared with milk and that milk would promote a greater net balance because of lower but prolonged hyperaminoacidemia. 

 

 DESIGN: Arterial-venous amino acid balance and muscle fractional synthesis rates were measured in young men who consumed fluid milk or a soy-protein beverage in a crossover design after a bout of resistance exercise. 

 

 RESULTS: Ingestion of both soy and milk resulted in a positive net protein balance. Analysis of area under the net balance curves indicated an overall greater net balance after milk ingestion (P < 0.05). The fractional synthesis rate in muscle was also greater after milk consumption (0.10 +/- 0.01%/h) than after soy consumption (0.07 +/- 0.01%/h; P = 0.05). 

 

 CONCLUSION: Milk-based proteins (such as New Lifestyle Diet products) promote muscle protein accretion to a greater extent than do soy-based proteins when consumed after resistance exercise. The consumption of either milk or soy protein with resistance training promotes muscle mass maintenance and gains, but chronic consumption of milk proteins after resistance exercise likely supports a more rapid lean mass accrual. 

 

 American Journal of Clinical Nutrition. 2007 Apr; 85(4):1031-40.

What if I don’t lose weight each day?

First of all, it is completely normal to gain a pound or so from one day to the next when you are dieting. We do not recommend that you weigh each day. Abrupt changes from one day to the next are almost always caused by water, so don’t worry.

Occasionally, during a long period of weight loss, the body will hold onto its fat for a week or two and weight loss will slow or stop. This is what we call a plateau. During a plateau phase, do not stop taking your supplements. Stopping your supplements will cause the body to go into a starvation phase and it will be even harder to begin losing weight again. We recommend that you increase exercise moderately during a plateau and not worry. Your body will stop holding onto the fat after a short time, and you will start losing weight again rapidly and safely.

Can I drink alcohol?

You should not drink alcohol while on a diet. Alcohol will slow your weight loss down dramatically. Alcohol is high in calories and these calories are absolutely the worst kind you can get while dieting. If you are dieting and on a low carb diet, and low fat diet, then the last thing you want to do is erase all your effort by drinking hollow calories.

How much coffee can I drink?

We recommend that you limit your coffee intake to two or three cups per day. Caffeine causes a release of adrenaline in your body and may cause changes in your blood sugar levels. You can use low-fat milk or half-and-half in your coffee, and we recommend no-calorie sweeteners.

What is ketosis?

Ketosis is a natural metabolic state your body attains when faced with a low caloric intake and with an adequate protein supply. The body metabolizes fat for gluconeogenisis (energy) and the byproducts of the fat metabolism are ketones. Ketones are not harmful to your body. In fact, the brain works well on ketones.