Vegans, Are Your Diets Nutritionally Complete?

Vegan diets are often deficient in vitamin B12, vitamin D, calcium, zinc, iron, omega-3 fatty acids, and iodine.

Vitamin B12 is found in animal products such as meat, eggs, and dairy, with only trace amounts in plant foods. Vitamin D is obtained from sun exposure, but this may not be sufficient, especially in winter or in certain climates. Omega-3 fatty acids are found in fish and eggs, but vegans can obtain them from chia seeds, flaxseeds, walnuts, and hemp seeds. Zinc is found in beans, legumes, and whole grains, but phytic acid in these foods can hinder its absorption. Iron is abundant in plant foods like leafy greens, whole grains, and dried fruits, but it is not as easily absorbed as iron from animal products. Iodine is found in seaweed, but vegans may need to supplement it as it is not present in many plant foods.

Vitamin B12

The deficiency of vitamin B12 is more common among vegans due to their limited consumption of animal products. For vegetarians, supplementation is an efficient means of treating and preventing deficiency; a daily dose of 50 to 100 micrograms is advised.

There are still significant gaps in the research on this topic, such as the absence of randomised controlled trials evaluating various forms or dosages of vitamin B12 among vegetarians. Additionally, there is a need for more information and awareness about the significance of this vitamin in vegan diets.

Vitamin D

Signs of Deficiency and Toxicity

Omega-3 fatty acids

There are three main types of omega-3 fatty acids: alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). While ALA is present in plant oils, DHA and EPA are found in fish, krill, and algae. The body can convert ALA to EPA and DHA, but the conversion rate is less than 15%, so it is important to consume all three types of omega-3s.

Vegan diets are often deficient in omega-3 fatty acids, particularly EPA and DHA, as these are mostly found in animal products. However, vegans can ensure they are getting enough omega-3s by including plenty of ALA-rich foods in their diet, such as:

• Chia seeds
• Flaxseeds (linseeds)
• Hemp seeds
• Walnuts
• Perilla seeds
• Seaweed and algae
• Edamame beans
• Kidney beans
• Soybeans
• Wheat germ

Some experts suggest that, in addition to consuming plenty of ALA-rich foods, vegans should also consider taking a microalgae supplement to increase their EPA and DHA intake. This is particularly important during pregnancy, breastfeeding, and childhood due to the role of omega-3 fats in brain, nerve, and eye development.

Zinc

The main inhibitor of dietary zinc absorption is phytic acid, found in legumes, unrefined cereals, seeds, and nuts. Phytate forms an insoluble complex by chelating with zinc, inhibiting its absorption. The inhibitory effect can be overcome by food-processing techniques that use enzymes or thermal processing to hydrolyze phytic acid. Modern processing methods such as leavening and fermentation often achieve a molar ratio of phytate to zinc of below 12, so bioavailability is less of an issue.

Vegetarians appear to adapt to lower zinc intakes by increasing absorption and retention of zinc. Studies show that vegetarians have similar serum zinc concentrations to, and no greater risk of zinc deficiency than, non-vegetarians, despite differences in zinc intake. However, the World Health Organization recommends only 14 mg/day of zinc for vegan men, which is significantly lower than the Australian recommendation for vegetarian men of 21 mg/day.

Vegan food options that are high in zinc include beans, lentils, tofu, tempeh, oats, wholemeal bread, whole wheat pasta, quinoa, brown rice, pumpkin seeds, hemp seeds, other nuts and seeds, and tahini.

Iron

The average amount of iron a vegan needs is 32 milligrams per day for women and 14 milligrams per day for men. Vegans need up to 1.8 times more iron than people who eat meat because their bodies do not absorb iron from plant-based sources as readily as they do from meat.

However, vegans are no more likely to develop iron deficiency anaemia than the general population because their diet is typically high in vitamin C, which improves the absorption of non-heme iron.

Good sources of vegan-friendly iron include blackstrap molasses, lentils, tofu, tempeh, spinach, beans, and Swiss chard.

Frequently asked questions