Vitamin A (Retinol, Beta-Carotene)

Overview

Vitamin A is a fat-soluble vitamin essential for normal vision, immune function, reproduction, and cell communication. It exists in two main forms: preformed vitamin A (retinol and retinyl esters) found in animal products, and provitamin A carotenoids (like beta-carotene) found in plant foods.

Key Functions in the Body

• Maintains healthy vision (especially night vision)
• Supports immune system function
• Promotes normal growth and development
• Helps maintain skin and mucous membrane health
• Acts as an antioxidant (beta-carotene form)

Daily Recommended Intake (NIH Guidelines)

RAE = Retinol Activity Equivalents

Best Food Sources

• Beef liver – 6,582 µg RAE per 3 oz (730% DV)
• Sweet potato (baked) – 1,403 µg RAE per 1 medium (156% DV)
• Carrots – 1,069 µg RAE per 1 cup raw (119% DV)
• Spinach – 573 µg RAE per 1 cup cooked (64% DV)
• Mango – 181 µg RAE per 1 cup sliced (20% DV)

Health Benefits (Evidence-Based)

• Vision health – Prevents night blindness and supports retina function
• Immune defense – Enhances white blood cell function
• Skin health – Supports epithelial cell repair and growth
• Reproductive health – Essential for sperm production and fetal development

Deficiency Symptoms & Causes

Symptoms:

• Night blindness
• Dry eyes (xerophthalmia)
• Increased infection risk
• Dry skin

Causes:

• Poor diet lacking in animal and colorful plant foods
• Malabsorption disorders (celiac, Crohn’s)
• Chronic alcohol use

Toxicity & Safe Upper Limits

UL: 3,000 µg RAE/day (adults)

Toxicity symptoms:

• Nausea, dizziness, headaches
• Liver damage
• Birth defects (if excess during pregnancy)

Scientific References

• National Institutes of Health (NIH): Vitamin A Fact Sheet
• World Health Organization (WHO): Micronutrient Facts

Vitamin D (Calciferol)

Overview

Vitamin D is a fat-soluble vitamin important for calcium absorption, bone health, and immune function. It can be made in the skin when exposed to sunlight.

Key Functions in the Body

• Enhances calcium and phosphorus absorption
• Maintains bone density
• Supports immune system
• Plays a role in muscle function

Daily Recommended Intake (NIH Guidelines)

Best Food Sources

• Salmon – 447 IU per 3 oz (75% DV)
• Fortified milk – 120 IU per cup (20% DV)
• Egg yolk – 44 IU per egg (7% DV)
• Mushrooms (UV-exposed) – 366 IU per cup (61% DV)

Health Benefits (Evidence-Based)

• Supports strong bones and teeth
• Boosts immune function
• May reduce risk of osteoporosis

Deficiency Symptoms & Causes

Symptoms:

• Bone pain
• Muscle weakness
• Increased fracture risk

Causes:

• Lack of sunlight exposure
• Poor diet
• Kidney or liver disorders

Toxicity & Safe Upper Limits

UL: 4,000 IU/day (adults)
Excess may cause hypercalcemia, kidney damage

Scientific References

• NIH: Vitamin D Fact Sheet

Vitamin E (Tocopherol)

Overview

Vitamin E is a fat-soluble antioxidant that helps protect cells from oxidative damage. It also supports immune function and skin health.

Key Functions in the Body

• Protects cell membranes from free radical damage
• Supports immune defense
• Helps widen blood vessels and prevent clotting

Daily Recommended Intake (NIH Guidelines)

Best Food Sources

• Sunflower seeds – 7.4 mg per 1 oz (49% DV)
• Almonds – 7.3 mg per 1 oz (49% DV)
• Spinach – 3.7 mg per cup cooked (25% DV)
• Avocado – 2.1 mg per fruit (14% DV)

Health Benefits (Evidence-Based)

• Antioxidant defense against cell damage
• Supports healthy skin
• May reduce risk of heart disease

Deficiency Symptoms & Causes

Symptoms:

• Muscle weakness
• Vision problems
• Immune system issues

Causes:

• Fat malabsorption disorders
• Very low-fat diet

Toxicity & Safe Upper Limits

UL: 1,000 mg/day from supplements
Excess may increase bleeding risk

Scientific References

• NIH: Vitamin E Fact Sheet

Vitamin K (Phylloquinone & Menaquinone)

Overview

Vitamin K is a fat-soluble vitamin essential for blood clotting and bone health. It exists mainly as K1 (from plants) and K2 (from animal products and fermented foods).

Key Functions in the Body

• Activates proteins for blood clotting
• Supports bone mineralization
• Helps prevent arterial calcification

Daily Recommended Intake (NIH Guidelines)

Best Food Sources

• Kale – 531 µg per cup cooked (442% DV)
• Spinach – 444 µg per cup cooked (370% DV)
• Broccoli – 220 µg per cup cooked (183% DV)
• Natto (fermented soybeans) – 850 µg per 3 oz (over 700% DV)

Health Benefits (Evidence-Based)

• Blood clot regulation
• Bone health – reduces fracture risk
• Heart health – may prevent arterial stiffness

Deficiency Symptoms & Causes

Symptoms:

• Easy bruising
• Excessive bleeding
• Slow wound healing

Causes:

• Long-term antibiotic use
• Fat malabsorption disorders

Toxicity & Safe Upper Limits

• No UL established for K1 or K2
• High doses from supplements may interfere with anticoagulants

Scientific References

• NIH: Vitamin K Fact Sheet