Plant-based and vegetarian diets have grown popularity over the last decade with Vegan Australia estimating 400 to 500 thousand Australians following a strict plant-based lifestyle. Plant-based eating patterns are associated with several beneficial health outcomes. In particular, emerging evidence continues to favour a plant-based diet in conferring multiple health benefits. However, despite several health benefits of going meat-free, a purely plant-based diet is far more likely to leave people deficient in important nutrients like zinc, vitamin D, B12 and iron which are more readily available in fish, poultry, red meat and dairy foods.
Vitamin B12 in particular is almost exclusively sourced from meat, which also contains more readily bioavailable iron in the form of haem iron. Levels of iron in the blood, as well as iron stores (in the form of ferritin) have been shown to be lower in vegetarians and vegans, than in people who consume meat. This is in part due to the absorption characteristics of iron derived from haem being significantly more efficient than the non-haem iron found in plant foods. Complementing iron intake from non-animal sources with vitamin C can help overcome its poor absorption characteristics. This is why it is important to take vitamin C in conjunction with dietary iron supplements.
Similar to iron, absorption of zinc is not as effective from plant sources as it is from animal sources. Supplementation with these nutrients may assist vegans and vegetarians to attain healthy intakes of these essential vitamins and minerals, while making the most of the health benefits conferred by a predominantly plant-based diet.
The team at IMUNI Health has reviewed the literature to unveil which nutrients are most at risk of insufficient intake when following a plant-based diet. For individuals who don’t meet dietary intake requirements, supplementation with the following nutrients, vitamins and minerals is likely to be beneficial for human health.
Selenium is a nutritionally essential mineral for humans, that plays critical roles in thyroid hormone metabolism, reproduction, and DNA synthesis. Selenium plays a role in immune system regulation and is a co-factor for glutathione peroxidase, an important antioxidant enzyme within the immune system.
Besides Brazil nuts, which are relatively rich in selenium, the major sources of dietary selenium include seafood and meat, especially organ meats.
In general, plant-based foods tend to have lower levels of selenium compared to animal products, and the amount of selenium contained in plant sources tends to vary widely depending on the selenium content of the soil the plants are grown in. Several other factors affect the selenium concentrations in plant-based foods, including soil pH, whether the form of selenium in the soil is amenable to plant uptake, and the amount of organic matter contained in the soil. Research suggests that people at highest risk of deficiency are vegetarians who consume their diets in regions with selenium deficient soil. For instance, the lowest selenium intakes in the world exist in certain regions of China, where large proportions of the population consume primarily vegetarian diets and selenium content of soil is very low.
In addition, average selenium intakes are low in some European countries, especially among those consuming vegan diets. Historically, New Zealand had relatively low intakes of selenium, until the country increased importation of foreign wheat with higher levels of selenium. In terms of bioavailability, studies have demonstrated that selenomethionine tends to have the best absorption characteristics with more than 90% selenomethionine absorbed by the human body, compared to only 50% selenium absorbed from selenite.
Australian foods have been found to contain lower levels of this mineral, suggesting that the average Australian diet is likely to be lower than the minimum suggested adequate daily intake for chromium of 50 mcg/day. One study assessed the chromium content in Australian foods from 150 different foods selected from across the five main food groups and found that most fruits and vegetables, fats and oils, and refined grains contained low amounts of chromium. Chromium has been shown to play an important role in glycemic control and regulation of blood glucose levels as well as having secondary benefits for antioxidant systems.
Importantly, given the lower levels of chromium found in many plant-based foods, there might be a role in supplementing the diet with chromium in people who follow plant-based diets, especially given that dietary supplements tend to have similar bioavailability to food-sources of chromium, making them similarly effective at replenishing chromium levels.
Coenzyme Q10 (aka. ubidecarenone or ‘CoQ10’) and the importance of B vitamins
Coenzyme Q10 or ‘CoQ10’ is a vitamin-like compound that acts as a cofactor in many critical metabolic pathways, including the production of adenosine triphosphate (ATP) in oxidative respiration, which is responsible for the production of 95% of the body’s energy. It also serves important roles as an antioxidant and cell membrane stabiliser. As the body is capable of synthesising coenzyme Q10, it is not technically considered a vitamin, despite functioning in a similar way to typical vitamins obtained from dietary sources. CoQ10 is ingested in small amounts in dietary sources – most notably meat and seafood, with lower amounts consumed from fruits and vegetables.
Absorption of coenzyme Q10 from food sources appears to be equivalent to absorption of coenzyme Q10 from supplements. However, the majority of the body’s daily CoQ10 requirement is normally derived via biosynthesis within the body. The biosynthesis of CoQ10 is dependent on a 17-step process involving a myriad of vitamins and trace elements, including vitamins B2 (riboflavin), B3 (niacinamide), B5 (pantothenic acid), B6 (pyridoxine), B9 (folate), B12 (cobalamin) and vitamin C. Because its biosynthesis is dependent on these nutrients, it is important that sufficient quantities are consumed in the human diet, as deficiencies in any of these cofactors can result in suboptimal CoQ10 biosynthesis.
Vitamin B12 in particular is almost exclusively sourced from animal food products, and B12 deficiency is therefore more common in those who consume strict plant-based diets without adequate supplementation. Some vegetarians and vegans are at risk of other B vitamin deficiencies. For example, vegetarian athletes are more susceptible to vitamin B2 (riboflavin) deficiency due to increased demands and insufficient intake due to avoidance of B2-rich animal sources. B vitamin deficiencies uncommonly occur in isolation, with B12 deficiency for example often associated with deficiencies in other B vitamins including vitamin B6.
Due to plant-based diets having lower quantities of CoQ10 than animal products, and its biosynthesis being dependent on several cofactors which are more prevalent in animal foods, we have incorporated a significant dose of CoQ10 in IMUNI Vegan Complete, to ensure adequate intake of this important energy-producing powerhouse and antioxidant.
Humans obtain almost all of their daily vitamin B12 requirement from animal foods, which can leave vegans and vegetarians particularly vulnerable to vitamin B12 deficiency. Adequate B12 intake is vital for red blood cell production and normal neurological function. It is required for synthesising the fatty acids in myelin which is an important component of normal nerve conduction. In conjunction with folate, it is also necessary for DNA synthesis.
Some randomised controlled trials have demonstrated that high dose oral B12 might have similar efficacy to intramuscular injection. IMUNI Vegan Complete contains co-methylcobalamin which is one of the active forms of vitamin B12. Interestingly, the bioavailability of vitamin B12 obtained from dietary supplements is about 50% higher than that obtained via food sources.
Iron and Vitamin C
Almost two-thirds of the body’s iron is found in haemoglobin - the oxygen carrying component of the red blood cell. The synthesis of haemoglobin is dependent on adequate intake of dietary iron from food. The Recommended Dietary Intake (RDI) ranges from 8mg for men, to 18mg for menstruating females (due to increased blood loss from regular menstruation). Higher amounts may be required during pregnancy.
Dietary sources of iron come in one of two forms: haem iron, and non-haem iron. Haem iron is exclusively sourced from animal products such as meat, fish and poultry, and is more highly bioavailable than non-haem iron obtained from plants. Due to the poorer absorption characteristics of non-haem iron, iron deficiency occurs more commonly in vegetarians and vegans, then in omnivores. Taking vitamin C alongside iron supplements is important, as vitamin C has been shown to assist in optimising absorption of non-haem iron.
The RDI for zinc ranges from 8 to 14mg per day for adult women and men, respectively. However, strict vegetarians and vegans may require intakes 50% higher than the RDI, corresponding to 12mg per day for women, and 21mg per day for men. This is because zinc absorption is largely dependent on dietary intake of animal protein and bioavailability of zinc from animal sources is therefore superior to zinc derived from plant sources. Implementation of effective dietary planning can assist vegans and vegetarians in obtaining sufficient intake of zinc from plant sources. Supplementation is beneficial when dietary planning is inadequate.
Iodine (potassium iodide)
Iodine was one of the first trace elements recognised as being essential for human health. Iodine plays an integral role in the synthesis of thyroid hormone which is required for normal human growth and metabolism. Certain groups are at higher risk of iodine deficiency, including those who avoid the food groups with highest levels of iodine (bread, eggs, milk, fish and iodised salt). As eggs, milk, and fish make up a substantial portion of dietary intake, strict vegetarians may require more careful dietary planning to achieve adequate consumption of iodine-rich foods. Adequate dietary planning incorporating iodine-rich foods such as seaweed can help to ensure vegans and vegetarians meet their dietary requirements. However, supplementation can be beneficial if dietary planning is inadequate.
Mushrooms are the richest natural plant source of vitamin D. In fact, they are the only non-animal food product that contains a considerable amount of bioavailable vitamin D, making them the primary source of dietary vitamin D for vegans and vegetarians. However, if mushrooms are grown indoors and not exposed to the sun or UV light they will not contain any vitamin D. Most fresh mushrooms sold in grocery stores in Australia, New Zealand, North America and the UK are grown in atmospherically controlled growing rooms in complete darkness leaving them with little to no vitamin D.
Despite Australia’s sunny climate vitamin D insufficiency remains highly prevalent. Many factors contribute to vitamin D insufficiency, including:
- Inadequate dietary intake and plant-based diets
- Advancing age - efficiency of vitamin D synthesis in the skin declines with age
- Darker skin – higher melanin content of skin reduces vitamin D synthesis
- More time spent working indoors
- Improved adherence to sun protection measures – SPF15+ sunscreen blocks >99% of vitamin D synthesis
- Obesity – vitamin D retained in fat is not bioavailable
Due to the lack of vitamin D in most vegetarian foods, sunlight remains the primary source of vitamin D for vegans and vegetarians. However, too much sunlight exposure can increase the risk of skin cancer and several factors (including those described above) can limit vitamin D availability from sunlight alone. In these circumstances where sunlight exposure is insufficient to meet vitamin D requirement supplementation with vitamin D might be beneficial.
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