Vitamins and Minerals: Overview
Proteins – including essential amino acids, Carbohydrate, Fiber, Essential FAs (omega 3 and omega 6), Water-soluble vitamins (C, thiamin, riboflavin, niacin, pantothenic acid, biotin, B6, B12, folate, choline), Fat-soluble vitamins (A, D, E, K), Macrominerals (calcium, magnesium, phosphorus, sodium, potassium, chloride), Trace minerals (iron, copper, iodine, fluoride, zinc, manganese, chromium, selenium, molybdenum)
Requirements are different between healthy people (age, sex, body size, pregnancy) and those with disease/illness/injury.
Recommended Dietary Allowances (RDA) – recommendations for levels of average daily intake of essential nutrients in healthy persons. Established by the Food and Nutrition Board of the Institute of Medicine, National Academy of Science.
Nutrient requirements determined by:
- New terms to be used in future RDA (RDA, AI, UL are for healthy populations only)
- (1) Adequate Intake (AI) – Used when there is not sufficient evidence to calculate an RDA. Like RDA, refers to a healthy population.
- (2) Tolerable Upper Intake Level (UL) – Maximal level of nutrient intake that is unlikely to pose risk of adverse health effects. Refers to total intake whether from food, fortified food and/or supplementals. Applies only to chronic daily use. Like RDA, refers to a healthy population.
- How is RDA for a particular nutrient determined?
- (1) Estimating avg or mean daily requirement (EAR) of a representative sample of a life-stage and gender group.
- (2) Estimating variability in the requirement of the nutrient for the target population.
- (3) Setting the RDA at 2 standard deviations above the avg requirement. This amt should be sufficient to satisfy the requirements of approximately 97.5% of the individuals in the life-stage and gender group.
- If the standard deviation (SD) of the EAR is available, the RDA is set at two SDs above the EAR:
- RDA = EAR + 2 SD EAR
- If data about variability in requirements are insufficient to calculate a SD, a coefficient of variation (CVEAR) of 10% is assumed:
- RDA = EAR + 2(EAR x 0.1) 1 CV = 1 SD
- RDA = EAR (1.2)
RDA for energy – Same as the estimated average requirement of a population group. May be used as a general guide for a population group but may be entirely inappropriate for a given individual since energy needs can vary greatly from person to person and are not easily predicated without detailed information about body size, body composition and physical activity.
RDA for nutrients – Set high enough so it meets the upper limit of variability.
- (1) Biochemical measure that assesses degree of tissue saturation or adequacy of enzyme function related to nutrient intake
- (2) Balance studies (for protein and minerals) - intakemineral – outputmineral = balance requirement for adult is smallest intake that maintains a zero balance for that mineral.
- (3) Amt necessary to prevent specific clinical signs/symptoms of nutrient deficiency state.
- (4) Amt necessary to support an optimal growth rate in infants and young kids.
- (5) Reduction of disease risk.
- (6) Nutrient intake provided by usual diets of apparently healthy people.
Þ depletion, disease
Excessive intake of essential nutrients Þ toxicity, or deficiency of another nutrient by interfering with absorption/utilization.
Can water soluble vitamins be toxic? Yes:
- Inadequate intake of essential nutrients
Ý B6 Þ ataxia, sensory nervous system dysfunctoin.
Can minerals be toxic? Yes, but not all are listed in RDA due to insufficient data.
Nutrition Labeling and Education Act of 1990 – Require "Daily Values" on labels
- (1) can have (or metabolite) a direct toxic effect.
- (2) Can lead to dependency states and withdrawal symptoms.
- (3) Can mask symptoms of a concurrent disease.
- (4) Can interact with other vitamins or drugs.
Unless FDA has direct evidence that a dietary of vitamin/mineral supplement is inherently dangerous or marked with an illegal claim, it will not and cannot regulate it. Therefore, Americans cannot rely on the federal government to protect them from supplement overuse or misuse or poor quality control.
Examples of Vitamin deficiency and overdose (more details later):
- population weighted average of the 1989 RDAs for adults and kids >4 y/o – % DV - percent of Daily Value
Þ Þ serotonin and glutamic acid Þ Þ GABA)
Vitamin A – Vitamin A toxicity results in bone resorption. There are two forms of Vitamin A:
- Vitamin B6 (pyridoxine) – B6 deficiency: weakness, difficulty walking, irritability, mental depression (could be due to the fact that B6 (in tranaminations) is a cofactor in the reactions: tryptophan
b -carotene plants – orange/yellow/dark green vegetables. b -carotene Þ Þ Vitamin A.
Selenium – toxicity Þ hair loss, swollen fingernails, nausea, vomiting, garlic breath. Some supplement companies prepare the supplement poorly and it contains much more selenium than advertised Þ toxicity.
Iron – toxicity Þ many kids seen at the poison control centers because they take too many "flinstones".
- Vitamin A (retinol) – whole milk, eggs, liver, fortified milk, margarine.
Enrichment and Fortification
Most foods are processed to improve preservative qualities
Enrichment – most (not all) of the original vitamins are added
- e.g., germ/bran removed from wheat, leaving endosperm
- this process removes most vitamins, also fiber
Fortified – more vitamins added than were in the original
- federal law: Fe, B1, B2, niacin – recently folic acid too
- no other vitamins or minerals (or fiber) are generally added