Nutrition Guidelines: DSHEA, DRI, EAR, RDA

Dietary Supplement Health and Education Act (DSHEA)

• Enacted in 1994 to govern dietary supplements
• It classifies vitamins, minerals, amino acids, and herbal remedies as foods, not drugs
• It prevents the FDA from regulating dietary supplements as pharmaceuticals
• Supplements do not require FDA approval prior to marketing
• The FDA bears the burden of proof to demonstrate a supplement's unsafety before restricting or banning it
• Manufacturers ensure supplement safety, without proving efficacy before sale

Dietary Reference Intakes (DRI)

• This provides the framework for nutrient intake recommendations for healthy populations

Estimated Average Requirement (EAR)

• Established for 17 nutrients
• The amount of a nutrient needed to meet the needs of 50% of individuals in a specific group
• Assesses nutrient intake at the population level
• Adequate Intake (AI) is used when an EAR is unavailable

Recommended Dietary Allowance (RDA)

• The daily nutrient intake sufficient for 97-98% of individuals in a given life stage and gender group
• RDA = EAR × 1.2 (or 2 standard deviations)
• Used as a goal for individuals, not populations
• It is set higher than the average human need to account for absorption and metabolism variations

Adequate Intake (AI)

• Used when there is insufficient data to establish an EAR
• Covers 97-98% of individuals in a specific life stage
• AI values are typically higher than RDA values

Tolerable Upper Intake Level (UL)

• It is the maximum daily intake unlikely to cause adverse health effects in 97-98% of individuals
• Not an intake goal, but a safety limit
• Helps prevent toxicity caused by excessive supplement consumption

Populations at Risk for Nutrient Deficiency

• Low-income individuals have limited access to nutritious foods
• Older adults experience reduced absorption and lower dietary intake
• Pregnant women have increased nutrient demands
• Individuals with GI disorders, such as Crohn’s disease and celiac disease are at risk
• Premature infants have underdeveloped nutrient stores
• Alcoholics experience nutrient depletion due to alcohol metabolism

Fat-Soluble Vitamins (A, D, E, K)

• Stored in adipose (fat) tissue and the liver
• Can accumulate to toxic levels if consumed in excess
• Require carrier proteins for transport
• Absorbed via the lymphatic system before entering the bloodstream

Water-Soluble Vitamins (B-complex and C)

• Not stored in the body, thus requiring daily intake
• Excess amounts are excreted in urine, which makes toxicity rare
• They play key roles in metabolism, energy production, and cellular function

Vitamin A

• Exists as retinoids (active form) and carotenoids (inactive form)
• Carotenoids are in plant-based foods and are converted to retinoids in the body
  • Lycopene is linked to a reduced risk of atherosclerosis
  • Lutein & Zeaxanthin support eye health and act as antioxidants

Vitamin A Sources

• Retinoids are found in liver, dairy, fish oils, eggs, and fortified milk
• β-Carotene (provitamin A) is found in carrots, mangoes, peaches, apricots, sweet potatoes, winter squash, cantaloupe, peas, broccoli, and dark leafy greens

Vitamin A Functions

• Cell differentiation and gene regulation
• Essential for vision (retina and rods) through the visual cycle
• Immune function, bone metabolism, and wound healing

Vitamin A Vision Cycle

• Rhodopsin (11-cis retinol + opsin) absorbs light
• 11-cis retinol converts to 11-trans retinol
• Opsin detaches and sends a signal to the brain
• 11-trans retinol reconverts to 11-cis retinol, rebinding with opsin to restart the cycle

Vitamin A Deficiency

• Night blindness is an early sign
• Keratinization of skin leads to rough, bumpy skin
• Pale nails and loss of color perception

Vitamin A Toxicity Risks

• Acute toxicity includes Gl upset, headaches, dizziness, and blurred vision
• Chronic toxicity (10× RDA) includes liver damage, bone weakness, hyperplasia, vascular sclerosis, and cirrhosis (irreversible liver damage)

Vitamin D Functions

• Regulates gene expression and cell differentiation
• Maintains calcium and phosphorus homeostasis
• Vitamin D functions as a hormone

Vitamin D Sources

• Sunlight: 15 min/day without sunscreen is sufficient
• Foods: Cod liver oil, liver, fortified dairy, and mushrooms

Vitamin D Metabolism & Activation

• Skin (or diet) converts Liver to calcidiol
• Calcidiol circulates in blood until needed
• Kidneys (stimulated by PTH) converts calcidiol to calcitriol (active form)
• Calcitriol acts in the intestines for increased calcium absorption
• Calcitriol acts in kidneys to enhance calcium reabsorption
• Calcitriol acts in bones to promote osteoclast activity for calcium release

Vitamin D Deficiency Risks

• Rickets in children leads to soft, deformed bones
• Osteomalacia in adults leads to bone softening and fractures

Vitamin E Functions

• Antioxidant that neutralizes free radicals
• Protects LDL from oxidation, reducing the risk of atherosclerosis

Vitamin E Sources

• Plant oils, wheat germ, avocado, nuts, nut butters, and leafy greens

Vitamin E Deficiency Risks

• Hemolysis (red blood cell bursting), can lead to anemia
• Weakened immune function

Vitamin E Toxicity Risks

• Interferes with vitamin K, increasing bleeding risk (hemorrhage)

Vitamin K Functions

• Blood clotting (coagulation)
• Bone health (supports calcium binding in bones)

Vitamin K Sources

• Leafy greens, vegetable oils, and margarine

Vitamin K Deficiency Risks

• Slow blood clotting leads to increased bleeding risk
• Prothrombin Time (PTT) is used to assess clotting function

Vitamin K Clinical Considerations

• Patients on blood thinners (e.g., Warfarin) must maintain a consistent Vitamin K intake to avoid fluctuations in clotting ability
• Excess Vitamin A can deplete Vitamin K