Is cod liver oil a good source of vitamin D for older adults or individuals at risk of vitamin D deficiency?

Is Cod Liver Oil a Good Source of Vitamin D?

Yes, cod liver oil is a good source of vitamin D, containing approximately 10 µg (400 IU) per 5 mL serving, and can effectively raise serum 25-hydroxyvitamin D levels, though it should not be the sole strategy for preventing vitamin D deficiency in older adults who require 800 IU daily. 1, 2

Vitamin D Content and Effectiveness

• Cod liver oil is classified among the richest natural dietary sources of vitamin D, containing 5-25 µg per 100g, making it comparable to fatty fish like salmon and sardines 1
• A single 5 mL daily serving of cod liver oil provides approximately 10 µg (400 IU) of vitamin D, which is half the recommended daily intake for adults over 70 years 3, 1
• Current intake of cod liver oil is positively associated with serum 25(OH)D concentrations, with daily users achieving levels around 60 nmol/l compared to 40 nmol/l in non-users 4
• Consumption of cod liver oil as part of traditional meals can acutely raise plasma 25(OH)D levels, demonstrating its bioavailability 5

Limitations for Older Adults

• Natural food sources alone, including cod liver oil, are insufficient to meet daily vitamin D requirements, making fortified foods and supplementation essential for most people, especially older adults and those with limited sun exposure 1
• Adults over 70 years require 20 µg (800 IU) daily, meaning cod liver oil alone provides only 50% of the recommended intake 1, 2
• A large randomized controlled trial of 34,601 adults found that daily cod liver oil supplementation (10 µg vitamin D) during winter did not reduce the incidence of acute respiratory infections compared to placebo, suggesting the dose may be suboptimal for immune benefits 3

Important Safety Considerations

• Historical formulations of cod liver oil contained very high concentrations of vitamin A, which has been associated with negative effects on bone mineral density when consumed during childhood 6
• The vitamin A content of commercial cod liver oil was reduced by 75% in Norway due to concerns about excessive vitamin A intake and its potential negative impact on bone health 6
• Women who consumed cod liver oil throughout childhood had significantly higher odds of low bone mineral density in later life (OR 2.3,95% CI: 1.4-3.9), likely due to the previously high vitamin A content 6

Practical Recommendations

• For older adults at risk of vitamin D deficiency, cod liver oil can be part of a comprehensive strategy but should be combined with additional vitamin D supplementation to reach the recommended 800 IU daily intake 1, 2
• Older adults living independently require 15 µg (600 IU) daily supplement all year round, not just winter, which exceeds what cod liver oil alone provides 1
• Individuals with dark skin pigmentation, those living in Northern latitudes, people with indoor lifestyles, and patients with gastrointestinal disorders affecting fat absorption require particular attention to supplementation beyond dietary sources 1
• Consuming vitamin D with dietary fat improves absorption since it is fat-soluble, making cod liver oil's fat content advantageous for vitamin D bioavailability 1

Monitoring Approach

• Annual serum 25-hydroxyvitamin D monitoring is recommended, with repeat testing 3-6 months after dosage changes, targeting minimum levels of 50 nmol/L (20 ng/mL) 1
• A common mistake is relying solely on dietary sources including cod liver oil without supplementation, even with optimal food choices including fatty fish and fortified products 1