Observational Study July 29, 2026

Vegan, Vegetarian, and Omnivore Diets Compared for Omega-3, Vitamin D, and Iodine Status

General Wellness Heart Health Omega 3 Index (O3i)

Researchers in Taiwan compared blood and urine markers of nutritional status among 45 omnivores, 46 lacto-ovo vegetarians, and 24 vegans. They measured fatty acid profiles in red blood cells, vitamin D levels in plasma, and iodine levels in urine.

Vegans had the lowest levels of saturated fat, trans fat, and omega-3 fatty acids (including EPA and DHA), but the highest levels of omega-6 fatty acids. Using the ‘omega-3 index,’ a measure of long-term omega-3 status, vegans scored lowest (2.6), followed by vegetarians (3.7), and omnivores had the highest score (5.8).

Vitamin D deficiency was most common among vegans (75%), compared to omnivores (36%) and vegetarians (24%). Iodine insufficiency followed a similar pattern, affecting 76% of vegans versus roughly half of the other two groups.

What this means for you

This study suggests that fully plant-based diets, while lower in saturated and trans fats, may come with a higher chance of running low on omega-3s, vitamin D, and iodine unless these nutrients are deliberately addressed through fortified foods, targeted food choices, or supplementation.

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Source

Tzu Chi Medical Journal

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This summary is for educational purposes only and is not medical advice. Always talk to your healthcare provider before making changes to your supplement routine.