Iodine is an essential mineral vital for the production of thyroid hormones, which regulate metabolism, growth, and development. The recommended daily intake (RDI) of iodine is 150 mcg per day for most adults, with higher requirements for pregnant or nursing women. Iodine deficiency can lead to various health issues, including goiter (swelling of the thyroid gland) and hypothyroidism, characterized by fatigue, muscle weakness, and weight gain. While many associate iodine-rich foods with animal products, several plant-based sources can help vegans and vegetarians maintain adequate iodine levels. This article explores these sources, providing a detailed guide to incorporating iodine into a vegan diet.
The Importance of Iodine
Iodine plays a crucial role in synthesizing thyroid hormones, specifically thyroxine (T4) and triiodothyronine (T3). These hormones are essential for regulating metabolism, influencing energy levels, and ensuring the proper development of the brain and nervous system, particularly during fetal development and infancy. Inadequate iodine intake can lead to iodine deficiency disorders (IDD), with cognitive impairment being a significant concern. Iodine deficiency during pregnancy can have severe consequences, affecting the neurological development of the child and potentially leading to miscarriages or stillbirths.
The Challenge for Vegans
The main sources of iodine in many countries are fish, eggs and dairy products. Since the primary sources of iodine in non-vegan diets are often sea fish, shellfish, and dairy products, vegans face a unique challenge in obtaining sufficient amounts of this mineral. Plant foods generally have lower iodine levels, and their iodine content can vary significantly depending on the iodine levels present in the soil where the plants are grown. It is not clear whether plant-based dietary patterns, such as the EAT-Lancet reference diet, would provide a sufficient intake of iodine. Those following a strict plant-based diet, such as vegans, cannot reach the recommended iodine intake from food alone and are reliant on iodine supplements.
Key Sources of Iodine for Vegans
Despite the challenges, several plant-based foods can contribute to meeting your daily iodine needs. Here's a detailed look at the best sources:
1. Seaweed
Seaweed stands out as one of the richest plant-based sources of iodine. These sea vegetables absorb iodine from seawater, making them an excellent addition to a vegan diet.
Read also: Tomatoes on Low Iodine Diet
Types of Seaweed and Their Iodine Content:
- Kombu Kelp: This brown seaweed has the highest iodine content. Kombu kelp can contain up to 2,984 mcg of iodine per seaweed sheet (1 gram), providing almost 2,000% of the recommended daily intake. Due to its high iodine content, kombu kelp should be consumed in moderation.
- Wakame: Another type of brown seaweed, wakame has a slightly sweet flavor and is commonly used in miso soup. The iodine content in wakame seaweed from various parts of the world averages 66 mcg per gram, or 44% of the daily recommended intake.
- Nori: This red seaweed is commonly used in sushi rolls and has a much lower iodine content than brown seaweeds. Nori contains between 16-43 mcg per gram, or about 11-29% of the daily value.
Incorporating Seaweed into Your Diet:
Seaweed can be easily added to soups, stews, salads, and pasta dishes. Small amounts of powdered or crumbled seaweed can be used as a condiment to enhance the flavor and boost iodine intake.
2. Iodized Salt
Iodized salt is table salt with added iodine, introduced in the US in the early 1920s to help decrease the occurrence of goiters. Currently, both iodized and uniodized salt are sold in the United States.
Iodine Content:
Approximately 1/4 teaspoon of iodized salt contains 71 mcg of iodine, which is 47% of the daily recommended intake.
Considerations:
While iodized salt is an effective way to increase iodine intake, it should be consumed in moderation due to its sodium content. Major health organizations often recommend restricting daily sodium intake to prevent or treat high blood pressure. However, salt only seems to raise blood pressure in salt-sensitive individuals, which is about 25% of the population.
3. Fortified Plant-Based Milk Alternatives
Plant-based milk alternatives, such as soy milk or almond milk, can be fortified with iodine.
Read also: Low Iodine Breakfast Ideas
Iodine Content:
The iodine concentration in plant-based milk alternatives varies, so it's essential to check the nutrition information on the label.
Choosing Fortified Milk Alternatives:
When selecting plant-based milk alternatives, look for products that contain around 25 mcg of iodine per 100 mL. Research in the UK, Norway, and the USA has shown that unless fortified with iodine, plant-based milk alternatives have very low iodine concentrations, just 2.1% of the value of UK cows’ milk.
4. Other Plant Foods
While fruits and vegetables generally contain lower levels of iodine, some can contribute small amounts to your daily intake.
Examples:
- Prunes: Five dried prunes provide 13 mcg of iodine, or about 9% of the daily value.
- Lima Beans: One cup of cooked lima beans contains 16 mcg of iodine, or 10% of the daily value.
- Strawberries: Adding 6-7 strawberries a day to your vegan diet will help cover 8% of your daily iodine intake.
- Potatoes: Potatoes have been noted to contain trace levels of iodine.
- Cranberries: Cranberries have been noted to contain trace levels of iodine.
Factors Affecting Iodine Content:
The iodine content of plant foods varies depending on the iodine levels present in the soil, irrigation water, and fertilizers used during cultivation.
5. Iodine Supplements
If dietary sources are insufficient, an iodine supplement may be necessary, particularly for those who are pregnant, breastfeeding, or have increased nutritional needs.
Read also: Easy Low Iodine Cooking
Considerations:
It’s essential to exercise caution with supplements, as excessive consumption may lead to toxicity. Consult with a healthcare provider before starting any iodine supplement regimen. Check that the source is not seaweed; the ingredients list should state potassium iodide or potassium iodate.
Dietary Recommendations and the EAT-Lancet Diet
The EAT-Lancet reference diet recommends a predominantly plant-based diet, rich in fruits, vegetables, wholegrains, legumes, nuts, and unsaturated oils, with a low-to-moderate amount of seafood and poultry, and a small quantity of red meat, milk, and dairy products. However, if milk is replaced with unfortified plant-based alternatives, total iodine provision would be just 54 μg/d (34 % and 22-27 % of the recommendations for adults and pregnancy, respectively). Plant-based dietary recommendations might place consumers at risk of iodine deficiency in countries without a fortification programme and where animal products provide the majority of iodine intake, such as the UK and Norway.
Factors Affecting Iodine Absorption
Certain foods, known as iodine antagonists, can inhibit iodine absorption. These include soy, flaxseed, and raw cruciferous vegetables. Vegans should be mindful of these foods and ensure they consume adequate iodine from other sources to counteract their effects.
The Risk of Iodine Deficiency in Plant-Based Diets
There is evidence that those following a strict plant-based diet, such as vegans, cannot reach the recommended iodine intake from food alone and are reliant on iodine supplements.
Potential Risks of Excessive Iodine Intake
Excessive iodine consumption can disrupt thyroid function, leading to weight gain, hypothyroidism, or hyperthyroidism. Some health bodies advise not eating seaweed more than once a week during pregnancy, as it may contain too much iodine that can disrupt thyroid function.
Symptoms of Iodine Deficiency
- Enlarged thyroid gland (goitre)
- Tiredness
- Weight gain
- Increased susceptibility to infections
- Depression
- Feeling cold at all times
- Dry and cracked skin
- Hair Loss