By Jurriaan Plesman, BA (PSYCH), Post Grad Dip Clin Nutr
For more sources of information use Index to Specific Topics.
For many people it is difficult to believe that nutrition has anything to do with “mental illness”. Mood disorders may appear out of the blue, without any apparent cause. Often a stressful event may be a trigger, leaving a person with a lasting emotional turmoil, apparently quite unrelated to one’s diet. Mood disorders may be of many forms, from anxiety attacks, depression, Obsessive Compulsive Disorder (OCD), Post Traumatic Disorder (PTSD), to addiction. They all share the experience of sadness, without understanding its causes. But let us focus on depression as one example of the many mood disorders.
Nevertheless, both environmental and endogenous factors can operate in tandem, but in that case we need to treat the biological factors first, before considering “psychological” factors. We need a healthy body to be able to deal with stress.
The evidence is overwhelming that “endogenous” depression, sometimes called “clinical depression”, is nearly always due to some inner biochemical abnormality, although it may have psychological elements. Talk therapy and/or drug therapy often fails to bring permanent relief for the majority of patients. See studies.
I have said that one of the major factors triggering a depression or anxiety or a mood disorder is insulin resistance, a silent disease, and in particular pre-diabetic insulin resistance or hypoglycemia. See References. This can cause brain energy starvation triggering the release of excess adrenaline, a hormone that functions to convert glycogen (sugar stores) back into glucose, so as to feed the brain again. (See image) Insulin resistance interferes with the production of biological energy (ATP), necessary in the production of feel good neurotransmitters such as serotonin. Excess adrenaline production is a common feature of most, if not all, mood disorders.
Of course, this is not the only factor, there are many others. This can easily be established by carrying out a 4-hour glucose tolerance test as explained at our web site. We have found that most clients responded positively to this test, supporting the notion that a mood disorder is primarily a biochemical disorder. Other scientists have found the same:
Silent Diseases at the root of mood disorders
Abstracts from studies connecting mood disorders with nutrition here.
Anxiety, panic attack and depression may be associated with certain heart conditions such as mitral valve prolapse.
Medicine seems unable to predict and treat Syndrome X or the Metabolic Syndrome at its root. The reason could be that medical fraternity seem to be in denial about the existence of hypoglycemia following a statement made by the AMA in 1973. See: Marilyn Light. The test for hypoglycemia as mentioned above, would help doctors to diagnose it. Both Syndrome X and hypoglycemia (or pre-diabetic insulin resistance) are difficult to treat without drugs, hence conventional medicine centers around the use of drugs – practically the only form of “treatment”. Conventional medicine does not encourage to use non-drug treatments that are available. Allopathic medicine seldom solves the problem. In fact, orthodox medicine has been in denial about the existence of hypoglycemia for many years.(See also: Hypoglycemia: A forgotten disease by Dr George Samra –> page 6)
Biotin Deficiency, although rare disease, can cause various symptoms. The main cause may be the excess consumption of avidin in raw eggs. Symptoms: hair loss, brittle nail and a scaly red rash around the eyes, nose, mouth, and genital area. Neurologic symptoms in adults have included depression, lethargy, hallucination, and numbness and tingling of the extremities. Biotin may contribute to a lower blood sugar level. Linus Pauling Institute for sources of biotin.
Bisphenol A used in plastic can affect moods: “A 2008 study by the Yale School of Medicine demonstrated that adverse neurological effects occur in non-human primates regularly exposed to bisphenol A at levels equal to the United States Environmental Protection Agency‘s (EPA) maximum safe dose of 50 µg/kg/day. This research found a connection between BPA and interference with brain cell connections vital to memory, learning, and mood.” Wikepedia
- Glycogen Storage diseases
- Hereditary Fructose Intolerance
- Disorders of Pyruvate Metabolism
For an estimate of hypoglycemia incidence see Research Evidence for Hypoglycemia. Or look up Index.
Cobalt may be part of Vitamin B12. Cobalt has serious side effects both in deficiency and toxic stages. SYMPTOMS of deficiency are listed as Anemia, anorexia, bleeding gums, confusion, dementia, depression, difficulty maintaining balance, headache, nausea, numb and tingling extremities, pale gums, pale lips, pale tongue, poor memory, retarded growth, shortness of breath, sore tongue, weakness in the arms and legs, weight loss, yellow eyes and skin. However, if a normal diet is followed a deficiency is most unlikely.
“Salicylates can cause a reaction that both stimulates and depresses the nervous system. That is why you could experience depression, fatigue and hyperactivity all at once.” Source. For a full list of symptoms see Wikipedia. Discuss possible salicylate allergy with your doctor as it may affect other medications and diseases.
Other examples of a silent diseases are related to various illnesses of the the digestive system, that can affect the mind. A good illustration is the Leaky Gut Syndrome. When the bowel is inflamed, the gut lining becomes permeable and toxins are absorbed into the blood stream. This gives rise to many immunological reactions, among these symptoms of mood disorders. Partially digested molecules act as antigens – recognized as foreign substances by the body – that provoke an immune reaction. . RAS Hemat ,394,
COLITIS: Is a common factor in depression as it interferes with the absorption and metabolism of essential nutrients. An autoimmune reaction is ascribed to be the cause of ulcerative colitis, and hence it is even thought of as an autoimmune illness, diets low in fiber and high in sugar, and general incomplete diets, which are rich in a lot of other refined carbohydrates, like white flour, rice and pastas, are known to be linked to its onset, since these foods have largely been striped of essential fibers and nutrients. See: Herbs2000
There is strong evidence to support that depression is linked to the Leaky Gut Syndrome, Matthew Hogg, Maes M et als. 2008, Diseases associated with the Leaky Gut Syndrome are: inflammatory bowel syndrome or Irritable Bowel Syndrome(IBS), acne, eczema, psoriasis, AIDS, cystic fibrosis, liver disease, rheumatoid arthritis, asthma, celiac disease, lupus, fibromyalgia, Chronic Fatigue Syndrome (CFS), autism, food and chemical sensitivities. Louise Tenney, 14 and Elizabeth Lipski, 25 See also Altered Immunity & The Leaky Gut Syndrome by Dr Zoltan P Rona Volume 19 No 2, June 2003 Page 7. Further readings;
Addison’s Disease is an other illness, that can affect one’s moods. This condition is related to the adrenal glands, in particular te cortex (outer gland). which leads to a deficiency or complete lack of hormones. The cortex of the adrenal glands is responsible for he production of aldosterone, regulating salt in the blood. Levels of sodium are unbalanced leading to blood pressure problems. The cortex is also responsible for the production of testosterone. Symptoms of Addison’s disease are many and include mood swings, cravings for salty foods, irregulars periods in women, tremors. numbness in hands and feet. See Wisegeek.
Cushing’s Syndrome (excessive production of steroid hormones from adrenal glands) may cause mood swings, depression, panic attacks, anhedonia and other psychological problems. Wisegeek
Cushing’s Disease is a rare condition caused by excess cortisol production by adrenal glands. May be caused by taking glucocorticoid medication and other drugs containing steroids. It may also be the result of small non-tumourous tumours, called adenoma in the pituitary glands. This may trigger weight gain, and bloating about the face, increased amount of sweating, insomnia, hypertension, and dry, thin skin are also common symptoms.
Autism may be related to vaccines and immunisation programs. Natural Infectious Diseases decline preceding public immunization efforts by Raymond Obomsawin PhD
Allergies of the nervous system – that are closely related to gut diseases – can cause a diverse behavioural disturbances, including headaches and migraines, learning disabilities and depression. Hidden food allergies seem to be a common cause of attention deficit hyperactivity disorder (ADHD) and they may also be a causative factor in epilepsy, schizophrenia and depression.
Another silent disease affecting the mind is a food sensitivity to alpha-gliadin which is a component of gluten that can cause celiac disease, Rosalinda T Lagua, 92. Undiagnosed celiac disease is a common factor in the development of Alzheimer’s disease, Schizophrenia or Down’s syndrome and depression. Chris M Reading at al 2004 This applies to many other allergies and food sensitivities. Linda Knittel et al, 61,EW Cutler, 8, Gary Null, 116, Allergies: The Food and Disease Paradigm by Dr George Samra.
Lack of friendly bacteria and/or probiotics possibly due to over-prescription of antibiotics or any of the digestive illnesses may be responsible for depression. 2 studies on probiotics.
For a list of drugs and medications that may be responsible for depression see here —> Volume 10 No 2, June 1994 Page 7
Adrenal exhaustion is one of the silent diseases affecting the blood glucose supply to the brain. Insufficient glucose available to brain tissues contributes to many neurological symptoms of Adrenal Fatigue, including sleep disorder, brain fog, anxiety, and depression. Drlam.com May, 2009. It has been argued by some authors that adrenal exhaustion (AE) causes hypoglycemia (see here). But then the argument runs that AE is caused by “psychological” stress. This is like putting the cart before the horse, confusing symptoms for causes. A simpler explanation is that when the brain is deprived of its energy (ATP) from glucose, it will trigger the release of stress hormone (adrenaline and cortisol) from the adrenal glands, to replenish the brain with glucose. This may lead to Adrenal Exhaustion, which in turn may lead to depression. The most common illness that triggers excess stress hormones is hypoglycemia. This is easier to treat than “psychological” stress. Related to this topic see also: Chronic Fatigue Syndrome
Hyperhomocysteinemia: Abnormally high levels of homocysteine in the serum, above 15 µmol/L, are a medical condition called hyperhomocysteinemia. This has been claimed to be a significant risk factor for the development of a wide range of diseases, including thrombosis, neuropsychiatric illness, and fractures Wikipedia
Dyspareunia (painful sexual intercourse) mainly among women due to either medical or psychological factors can cause a variety of mood disorders as explained at Index.
And let us not forget hypothyroidism as a silent disease affecting the mind. It is shown as a flat curve sugar reaction in a four hour Oral Glucose Tolerance Test (Type 4 Hypoglycemia). This will naturally affect the conversion of sugar to biological energy called ATP, essential in the production of normal neurotransmitters. Hence this silent disease is associated with depression BJ Cohen , 92. Optimal iodine intake is essential for normal thyroid function and the prevention of ADHD and learning disabilities and academic underachievement. J. Gordon Millichap p.21. It is possible to test yourself at home for hypothyroidism with the Basal Temperature Test for Hypothyroidism. Symptoms of iodine deficiency:
“In areas where there is little iodine in the diet, typically remote inland areas and semi-arid equatorial climates where no marine foods are eaten, iodine deficiency gives rise to hypothyroidism, symptoms of which are extreme fatigue, goiter, mental slowing, depression, weight gain, and low basal body temperatures.” Wikepedia
Many people suffering from Post Natal Depression should be medically tested for hypothyroidism and/or hypoglycemia, which could be responsible for depression. For treatment see here. Imbalance in electrolytes as in hypoparathyroidism can cause psychiatric disorders. William L Webb et al Psychiatry on Line.
Alzheimer‘s Disease: Studies have shown that there is a significant association between insulin resistance (hypoglycemia) and Alzheimer’s disease. Pubmed studies. 5 JOM studies. For other missed medical conditions and nutritional aspects contributing to this disease see: Missed Medical conditions by Dr Chris Reading.
Fetal Alcohol Spectrum Disorder (FASD) also known as Fetal Alcohol Syndrome (FAS) is a term used as a general description of children affected by their mother’s use of alcohol while they were in the womb. One in 750 babies born are born with this syndrome. Because the placenta is permeable to alcohol, babies’ brains in the womb are exposed to toxic levels which will affect he cognitive functions in later life. Alcohol seems to be unique among many other drugs taken during pregnancy. FASD has facial physical features and cognitive symptoms, often difficult to define.
From a behavioural point of view the central nervous system damage can damage the brain across a continuum of gross to subtle impairments, which may affect learning ability, memory, moods, language, motor skills, attention, hyperactivity and impulse control. The latter can lead to violent outbursts that have led some people to confuse these symptoms with ADHD. Wisegeek, Wikipedia, See also: Index of Spec Topics
Hepatitis C Treatment with combination antiviral therapy pegylated interferon combined with ribavirin can cause one to feel fatigue, headache, nauseous, irritability, insomnia, confusion, depression. WebMD
Huntington’s Disease is an inherited disorder that causes deterioration of the brain, and will affect the personality of the patient. Huntington’s disease was named after doctor George Huntington in 1872. The disorder now affects around one in every 10,000 people. The major factor in Huntington’s disease is genetics. A child who has one parent afflicted with the disease has a 50% chance of developing the disease himself. Although it is usually an inherited disease, around 3% of sufferers have no trace of it within their family history.The first symptoms of Huntington’s disease usually appear around the age of 30 to 50 including changes in personality, from irritability and anger to depression, apathy and a loss of interest in things the person previously enjoyed. Wisegeek
“Depression is associated with an increased risk of dementia and AD in older men and women over 17 years of follow-up.” PMID: 20603483
Andropause is a collection of symptoms, including fatigue, decrease in libido, lack of concentration, mood swings, anxiety that is experienced by some middle-aged men. It has been attributed to a gradual decline in testosterone. Andropause correlates directly with depression, irritability, mood disorders and memory loss in mid-life crises. Google Scholar
Symptoms of the presence of Batten’s Disease mimic many other health issues. The symptoms usually begin to appear between the ages of four and ten. Some of the more common signs of the possible presence of Batten’s Disease are problems with vision, a change in learning ability and aptitude, personality changes, and a decrease in motor activity that leads to more frequent stumbling or falling. The child may also begin to experience seizures or episodes of feeling depersonalized. Wisegeek
GALLSTONES: Obesity, diabetes and Insulin resistance are a risk factor for developing gallstones hence may also be associated with mood disorders. See Index at Gallstones.
Gastric ulcers caused by Helicobacter pylori may contribute to postpandrial symptomatic hypoglycemia PMID: 10505722 and thereby may contribute to mood disorders.
People suffering from Glycogen Storage Disease may prove hypoglycaemic on a glucose tolerance test.
Helicobacter colonization and vitamin B12 deficiency may contribute to psychotic features. PMID: 340401
Megaloblastic Anemia, Pernicious Anemia or Iron Deficiency Anemia due to vitamin B12 and folate deficiency and/or iron deficiency affect red blood cells carrying hemoglobin (iron-containing pigment of red blood cells), that carry oxygen from the lungs to tissues. These can be responsible for psychological symptoms such as fatigue. Iron is needed to make optimal amounts of ATP. (WA Lishman,559). Iron deficiency is also related to ADHD. J Gordon Millichap p.20. They are examples of other silent diseases that could be responsible for depression, dementia and epilepsy. For a list of nutrients, deficiency of which can cause depression see RAS Hemat 165. See John Fry et al 208 on anaemia and how it contributes to depression and S Cembrowicz et al, 143 on various routine blood tests used in treating depression. Various studies on folate deficiency and depression and 23 JOM studies
It is interesting to note that most harmful heavy metals are in the same group 12 in the Periodic Table of heavy metals as zinc. Zinc is an essential co-enzyme in the metabolism of glucose. Rosalind S Gibson (2005) page 712. Copper and zinc levels should be in balance. If there is an excess of copper, this will lower zinc levels and will interfere with the ten step glycolysis of glucose to pyruvate. This will affect the production of biological energy called ATP and hence hinder the production of feel good neurotransmitters. This may explain the occurrence of hypoglycia which is characterised by having hypoglycemic symptoms, although blood sugar levels may be normal in a four hour Glucose Tolerance Test for hypoglycemia as designed by Dr George Samra (Kogarah). See also Notes on Hypoglycia
Infertility: In Australia there has been a 45% rise in the number of babies born through In Vitro Fertilisation (IVF) between 2004-8. In 2008. 10,509 babies were born through IVF. About 3.3% of Australians were born through fertility treatments. (source) and source.
People with rheumatoid arthritis, systemic lupus erythematosus, and ankylosing spondylitis, although strictly not silent diseases, are more likely to suffer from neuropsychiatric disorders Sundquist et als. 2008
A combination of potassium deficiency and ulcerative colitis can be responsible for severe emotional disturbance. Gastroenterology June 1956
Most inflammatory bowel disorders such as IBS, Crohn’s Disease and Celiac disease,are associated with psychiatric disorders. Roger Jones 5, ER Greig et al. 774, Cosimo Prantera et al 456 , TM Bayless et al 570 It is obvious that digestive disorders interfere with the absorption and metabolism of important and essential nutrients necessary in the production of the right hormones and neurotransmitters. Depression, anxiety, moodiness are also symptoms of many other “silent disease” Burton Goldberg et als., 621, Allen C Bowling, 66Stephen E Langer, 240. Hypoglycemic people are at risk of candidiasis and therefore may be a co-morbid condition among alcoholics. See notes on Candidiasis.
MEDICATIONS that can cause mood disorders. See here.
Lysine deficiency may lead to fatigue, dizziness and anemia
See how the microbiota can affect mood disorders
Multiple Sclerosis: “In fact, studies have suggested that clinical depression, the severest form of depression, is more frequent among people with MS than it is in the general population or in persons with other chronic, disabling conditions. ” National Multiple Sclerosis Society. “If you have another autoimmune disease, such as thyroid disease or Type 1 diabetes, your risk of developing MS is slightly higher. ” FamilyDoctor.org
Pellagra (From Wikipedia) is a vitamin deficiency disease most commonly caused by a chronic lack of niacin (vitamin B3) in the diet. It can be caused by decreased intake of niacin or tryptophan, and possibly by excessive intake of leucine. It may also result from alterations in protein metabolism in disorders such as carcinoid syndrome. A deficiency of the amino acid lysine can lead to a deficiency of niacin, as well. It’s symptoms can be described as the four D’s: diarrhoea, Dermatitis, Dementia an Death. A more comprehensive list among others is: Sensitivity to light, Aggression, alopecia (hair loss), glossitis (inflame tongue), insomnia, weakness, confusion, Ataxia, paralysis of extremities, peripheral neuritis, sensations of pain, irritability, emotional instability. When there is a niacin deficiency the body will convert tryptophan into niacin at the rate of 60 to 1, triggering a tryptophan deficiency and depression. See Research Evidence.
Liver Disorders & hypoglycemia: Severe illnesses of the liver, such as severe hepatitis, can cause hypoglycemia. Disorders of the kidney, which can keep your body from properly excreting medications, can affect glucose levels due to a buildup of those medications. Long-term starvation, as may occur in the eating disorder anorexia nervosa, can result in the depletion of substances your body needs in gluconeogenesis, causing hypoglycemia. Mayo Clinic
- There are countless other silent diseases, such as fibromyalgia (SR Pillemer et al, 48), hypercalcemia, or hypocholesterolemia due to statin drugs, leading to Coezyme Q10 deficiency, that may affect blood sugar levels and lead to mood disorders. There are a number of other diseases, that unwittingly may affect the mind. To explore these, please go to: Diseases associated with Emotional Disorders. See also: Medical tests of depression.
For more evidence how disease can affect the mind see Neurological Disorders at Wikipedia.
Many mind-altering silent diseases may be caused by between 50,000 – 100,000 chemicals released into the environment,(RE Hester et als.132) beginning with petrochemical fertilisers and pesticides used in soil by big pharma-dominated agriculture and food production. Heavy metals – by-products of he industrial society – can lead to a wide array of psychological problems.RAS Hemat 194. Most of these toxins find their way to rivers and the sea, where they contaminate fish we eat. This could easily be avoided if organic farming be universally adopted based on the science of soil biology that would render soils more productive. Dr Maarten Stapper. Videos by Dr Maarten Stapper about Biological Farming
Pyroluria: Carl Pfeiffer, believe that excessive excretion of pyrroles and Porphyria in the urine – as a result of improper hemoglobin synthesis – may be responsible for various mental disorders. It is claimed that kryptopyrrole increases the excretion of zinc, manganese and vitamin B6, (Carl C, Pfeiffer (JOM, 1983) thereby interfering with the synthesis of neurotransmitters and hormones. For more information see Journal of Orthomolecular Medicine 1974 Some studies has failed to find a connection between pyroluria and schizophrenia. Wikipedia  See also Index of Specific Topic at Porphyria
Temporomandibula joint (TMJ) disorder linked to depression: WEDNESDAY, Jan. 23 (HealthDay News) — There’s a link between depression and anxiety symptoms and temporomandibular joint (TMJ) disorder pain, a condition that affects the jaw, according to a new study. Jaw Pain Disorder tied to Depression
Prediabetes, other Metabolic syndromes could be linked to Neuropathy: “Components of the metabolic syndrome, including prediabetes, are potential risk factors for neuropathy, and studies are needed to establish whether they are casually related to neuropathy. These lines of enquiry will have direct implications for the development of new treatments for diabetic neuropathy,” the researchers said. Endocrinetoday, June 2012
Tourette’s Syndrome a condition, during which tics and involuntary muscular movements occur sometimes accompanied by inappropriate vocal exclamations, is due to a form of neurological dysfunction. The underlying cause is still a mystery, but seems to be biological, affecting the function of neurotransmitters in the brain. Although it may not be directly responsible for depression it can severely interfere with oneâ€™s social life, create a social stigma affecting oneâ€™s job opportunities and so on. Although symptoms do not appear during sleep, they are aggravated by stress, nervousness and anxiety. The psychological aspects and the syndrome itself can be greatly improved by nutritional therapy, with avoidance of a high refined carbohydrate diet (hypoglycemic diet) and supplementation of various vitamins (B complex, B6, B12, B3) and minerals (magnesium and potassium). See possible treatment & 3 JOM articles.
Wilson’s disease is an inherited disorder of copper accumulation. The basic defect is a failure of excretion of excess copper in the bile by the liver for loss in the stool. The accumulating copper causes damage primarily to the liver and the brain. Patients typically present in the second to the fourth decades of life with liver disease, a neurological disease of the movement disorder type, or a wide array of behavioural disturbances. Possible treatment with zinc and molybdenum PMID: 8521757, JOM articles
Chronic Pruritis (itching) can have a devastating effect on patients, causing health problems such as depression, anxiety and interruption of sleep. According to the research chronic pruritis can affect patients the same way as chronic pain. See Chronic pruritis report by Norman Swan, The HealthReport. Coming back to the problem of insulin resistance, the chicken-and-egg question is, which came first insulin resistance or obesity.
See also Chlorogenic Acid in raw coffee for treatment of obesity and hypertension.
The person who is suddenly struck with a mood disorder usually is not aware that what he believes triggered his “mental illness” is not so much an environmental stress situation, but rather an undiagnosed underlying biochemical disorder, reaching a breaking point. Mood disorders are often accompanied by delusions, just as in the more serious mental illnesses. We are genetically programmed to link our feelings and emotions to our immediate environment – present or past. In psychological jargon it is called Psychological Projection. Thus a negative self-image ” I am no good” soon becomes “people think I am no good”. If we have problem controlling our anger, it is always “the other person who makes me feel angry”.
False believes are usually triggered by stress hormones, as a result of some internal (endogenous) biochemical abnormality. A phobic reaction to a lift deludes the sufferer into thinking, that the elevator causes the anxiety reaction. It is often a delusion to think that a low self-esteem is the cause of depression, whereas in fact it may be simply one of the symptoms. We are often deluded into thinking that our anxieties and depressions are caused by stressful childhood experiences that has imprinted a “deeply” learned reaction patterns of learned behaviour stemming from the past. A “traumatic event” in PTSD is often mistaken to be the cause of the illness, instead of being a symptom. It is not difficult for an unscrupulous therapist to unwittingly reinforce these false beliefs and delusions to justify their “theory” of therapy.
In short, if you want to treat people for “mood disorders”;
One of the problems of nutritional therapy is that unlike drug therapy, the body needs time to adjust. People expect nutrients to work like drugs. Nutrients need to be taken over a long time. The length of time depends on the disorder being treated. Most illnesses respond to nutritional treatment within three months, but if drugs have been used it may take up to a year for receptors of neurotransmitters to repair themselves with a high protein diet. Nora Volkow
The consequence is that people with mood disorders are unable to consult government supported ‘alternative and complementary’ therapists who are trained and equipped to deal with “mental illness” in other than drug ways. Victims of the illness are left with the alternative to take more control over their own life by educating themselves about the nutritional aspects of mood disorders. Nutrients cannot be monopolized. It requires clients to become acquainted and read educational material about nutritional remedies, now widely available on the Internet. Happily, the Internet allows people to become educated. We will have to wait for the time when departments of psychology at universities around the world start training a new breed of psychotherapists with a knowledge and skills in psychology as well as human biochemistry. It is recommended that when treating yourself to discuss your findings with a professional health practitioner.
For further reading and research see:
Natural Mental Health Cures – Orthomolecular Psychiatry by Dr Vincent Bellonzi
Beat Depression w/out Psychiatric Antidepressant Drugs by Dr Vincent Bellonzi
Natural Cure for Depression by Dr Abraham Hoffer
The Truth about Mental Health Disorders by Professor John Breeding Ph.D, Psychologist
Depression, Fatigue, Thyroid & Drugs by Austin Nutrition