Evidence Based Nutrition

So, it is January a new year, a new start, a time in which people use to change something in their lives to introduce or try something new. A campaign was introduced to help reduce meat intake and encourage diets higher in plant-based foods promoting more of a vegan diet, this is known as Veganuary. Veganuary is where people try vegan diets for a month so they can discover what it would be like to go vegan and decide if they would like to continue as going vegan can be a major life-changing choice. There are multiple reasons to switch to a vegan diet such as health and animal treatment however there is a big incentive to go more plant-based to cut down the impact on the environment as meat-based diets use more resources than plant-based (13). For example, the production of 1 kg of beans requires 3.8m² of land, 2.5 m³ of water, 39 g of fertilizer, and 2.2 g of pesticide on the other hand the same amount of beef uses 52 m² of land, 20.2 m³ of water, 360 g of fertilizer and 17.2 g of pesticide 8-14 times more resources needed to produce beef (6). 

Plant-based diets are not only more sustainable and healthier for the planet but also healthier for humans, those on plant-based diets have typically been found to have lower risks of cardiovascular disease (CVD), obesity, type 2 diabetes and some cancers (2). They also have been found to have lower BMI, lower LDL cholesterol and lower blood pressure (2). A vegan diet can improve human health and has been recognised that a well-planned plant-based diet can be nutritionally adequate appropriate for human health and development throughout the lifespan inclusive of infancy and pregnancy (6, 3). Although it should be noted that during pregnancy an increase in vitamins and minerals are required than the general recommended daily allowance (RDA). 

A poorly planned plant-based diet can cause problems due to struggling to get the right amount of certain macro and micronutrients that would be gained through meat intake. Carbohydrates are not an issue in plant-based diets however vegans are at risk of becoming deficient in protein and omega 3 fatty acids, the micronutrients at risk of being deficient in include vitamin B₁₂, vitamin D, iron, zinc, calcium, and iodine (13). 

Fat (n-3) and Protein

The best source of Omega 3 fatty acids (n-3) are fish however, vegans do not consume fish either therefore are likely to become deficient in this nutrient. Consumption of n-3 fats are associated with reduced risks of heart disease, stroke and is important for cardiovascular health eye and brain function and health (15). The n-3 fatty acids are separated into three, there is EPA, DHA and ALA. EPA and DHA are mainly found in fish ALA is the plant-based n-3 fatty acid, this can be converted into EPA and DHA in the body although conversion has a very low efficiency (1). However, vegans can reach n-3 fatty acid requirements as long as they are getting a regular intake of ALA and DHA, good plant-based sources of n-3 ALA fatty acids include flax seeds/oil, walnuts, chia seeds, rapeseed oil, sunflower oil and soybeans (12). Also, sea vegetables such as seaweed and microalgae are great sources for vegans, brown algae were found to be a good source of DHA and EPA (2, 12). However, the UK diet is typically low in sea vegetables therefore microalgae supplements can be taken instead, or foods fortified with DHA it should be noted that too much DHA can raise LDL cholesterol, cause impair immune responses and prolonged bleeding times (4). 

Plant-based diets can provide a sufficient amount of protein however, plant-based protein is not as easily digested as animal protein and has been suggested that vegans should consume more protein due to this factor (11). The typical recommendation for protein intake is 0.8 grams per kg of bodyweight however vegans should consider 1-1.4 grams and even up to 2 grams per kg of body weight for athletes on a plant-based diet (8). There are essential amino acids and non-essential amino acids the essential just means these need to be acquired through the diet whereas the non-essential our bodies can produce. Essential amino acids are found in meat products and food that has all 8 of these essential amino acids are known as complete proteins. Achieving a meal with complete proteins in a plant-based diet can be done as long as you combine a variety of ingredients, for example, blended seeds and nuts such as cashews or almonds and sesame seeds with hemp milk for a cream sauce over steamed kale and bok choy creates a complete protein dish (7). Chia seeds, hemp seeds, quinoa and soybeans are plant-based complete proteins. Green vegetables are high in protein such as kale, and collards also seeds, nuts, grains and legumes are good sources of protein for vegans (7). Mixing these can provide enough protein for the vegan diet therefore should not have any deficiency issues. 

Vitamin D and Calcium

Vitamin D and calcium work together in supporting bone health. Vitamin D is a deficiency common in the general population not just vegans therefore it is recommended to take vitamin D supplements throughout the year especially in the winter months in colder and darker countries as sunlight decreases in the winter months. The RDA of vitamin D is 10ug per day for adults and 8.5-10ug for babies aged 1 and over however, it is thought for adults the intake should be higher as 4000IU (100ug) or even more can be tolerated without toxic effects but I will go more into this in a vitamin D blog. There are plant-based sources of vitamin D such as mushrooms however these are less bioavailable but due to the fortification of foods getting vitamin D may not be as much of an issue for vegans as it used to be, as long as they consume fortified cereal, soy milk, oat milk etc. and use D₂ supplements (which is the vegan acceptable form of vitamin D) then vitamin D levels should be sufficient. 

Calcium intake can be adequate in a plant-based diet however if the diet is not carefully planned this can lead to impaired bone mineralisation and fractures (15). The RDA of calcium for adults is 700mg a day, this is less for children, but teenagers may require more up to 1000mg a day and even higher for those that are breast feeding. Calcium can again be found in fortified foods as well as kale, spinach, and tofu however plant sources of calcium also contain oxalate and phytate which inhibit calcium absorption (17). Vitamin D increases the amount of calcium absorbed therefore can be ingested either from food in the meal or taken as a supplement after the meal. As long as enough intake of vitamin D and calcium is adequate, and the diet is balanced and contains a variety of foods then bone health should not be an issue for vegans as vitamin K, potassium and magnesium should be supplied enough through the diet as these also play roles in bone health (2). 

Iron

Iron intake is a concern for those following a plant-based diet, iron is important for the production of red blood cells. There are two major forms of iron in food heme iron and non-heme iron, heme iron is found in animal products only and non-heme can be found in both animal and plant-based products (9). Non-heme iron is not as well absorbed (2-20%) as heme iron (13-35%) this is most likely due to phytate in plants which inhibits iron absorption (9, 7). To increase absorption of iron vitamin C with the meal which is contained in most fruits and vegetables can help enhance absorption. Good sources of iron include seeds, nuts, legumes, beans, kale and fortified foods (15). Also, a good way to increase iron intake is by using Lucky Iron Fish (look it up) in your cooking. RDA of Iron for men is 8-9mg a day, women aged 19-50 need 15mg and women over 50 require 9mg per day. 

Zinc

Zinc is an essential trace element that is important for cell growth and repair, gene expression and cell signalling (12, 5). Zinc is mostly found in animal products however the vegan alternative sources of zinc can be found in seeds, beans, nuts and grains, also fortified milk and cereal. Phytates found in vegetables along with calcium and insoluble fibre can inhibit zinc absorption which is why vegans may be at risk of deficiency (18). Zinc absorption can be increased by the amount of protein in the meal as well as organic acid citrate (Citric acid) (5). RDA of Zinc differs with age as well but in adult in men it is 9.5mg and 7mg for women. 

Iodine

Iodine is also a trace element which means it may be essential but is only required in smaller amounts. Iodine is vital for the synthesis of thyroid hormones which are used for the regulation of metabolism, growth and neurological development (3). Iodine is found mostly in fish and dairy products with vegetables being low in iodine and not as bioavailable therefore absorption is not as effective (10). Adults require 140ug of Iodine a day, sources of iodine for vegans include fortified foods such as some loaves of bread and sea vegetables such as seaweed however again this is rarely consumed in the common western diet, iodised salt may also be an alternate source (3). Some fruits and vegetables can contain iodine e.g., strawberries, cranberries, green beans, corn and potato.  

Vitamin B₁₂

Vegans are found to have lower plasma B₁₂ levels and are at higher risk of vitamin B₁₂ deficiency (2). Vitamin B₁₂ is needed for blood formation and cell division with a deficiency in B₁₂ can lead to macrocytic anaemia and irreversible nerve damage along with abnormal neurologic and psychiatric symptoms (15, 2). Vitamin B₁₂ is only found in animal-based products therefore supplementing with B₁₂ may be required although foods can be fortified with B₁₂ it is still recommended to supplement. Adults require 2.4ug of vitamin B₁₂ a day. There have been studies on nori (purple laver), which is what is used to wrap around rice in sushi, finding that this sea vegetable contains vitamin B₁₂ as well as iron and n-3 fatty acids (16). Shiitake mushrooms also have been found to contain B₁₂ although the content varied between 1.3-12.7 ug/100g, this was significantly lower than nori – purple laver (16). 

Conclusion

A well-planned plant-based diet can provide all nutrients required, can be better for human health and for the health of the planet. However, it is recommended to take supplements of vitamin B₁₂, vitamin D₂, and possibly n-3 (depending on the diet) to avoid deficiencies in these nutrients. B₁₂ and vitamin D especially are harder to gain through the diet alone, although, the fortification of foods has made it a lot easier to achieve adequate amounts on a plant-based diet. Including sea vegetables can be a great addition to a vegan diet however I am aware these are not popular or regularly consumed in the UK. As long as the variety and quality of food are not restricted then a plant-based diet is nutritionally adequate (14). 

Micronutrient	Men RDA	Women RDA	Children RDA	Teenagers RDA	Older Adults RDA	Pregnancy RDA
Vitamin B12	2.4ug	2.4ug	0.9ug-1.2ug	1.8-2.4ug	2-2.4ug	2.6ug-2.8ug (BF)
Vitamin D	10ug	10ug	8.5ug	10ug	20ug
Calcium	700-1,000mg	700-1,000mg	200-700mg	1,300mg	1,000-1,200mg	1,300mg
Iodine	140ug	140ug	90-130ug	140-150ug		220-290ug
Zinc	9.5-11ug	7-8ug	2-5ug	8-11ug (M) 8-9ug (F)		11-13ug
Iron	8-9mg	15-18mg	0.27mg-11mg	11-18mg	8mg	27mg 10mg (BF)

*key*

• M= Male
• F= Female
• BF= Breast feeding
• mg= milligrams
• ug= micrograms

• Instagram
• LinkedIn

• Everything You Need to Know About Vitamin C
• Vitamin D and the Winter Months
• Everything You Need to Know About Vitamin K
• The Mediterranean Diet
• Everything You Need To Know About Vitamin E

References

1. Burdge GC, Finnegan YE, Minihane ME, Williams CM, Wootton SA.( 2003) ‘Effect of altered dietary n-3 fatty acid intake upon plasma lipid fatty acid composition, conversion of [13C]alpha-linolenic acid to longer-chain fatty acids and partitioning towards beta-oxidation in older men.’ Br J Nutr; 90: 311–21.
2. Craig, W. (2009) ‘Health effects of vegan diets’. The American Journal of Clinical Nutrition, 89(5) pp.1627S-1633S.
3. Eveleigh, E., Coneyworth, L., Avery, A. and Welham, S. (2020) ‘Vegans, Vegetarians, and Omnivores: How Does Dietary Choice Influence Iodine Intake? A Systematic Review’. Nutrients, 12(6) p.1606.
4. Food and Nutrition Board, Institute of Medicine of the National Academies. (2005) ‘Dietary fats: total fats and fatty acids. Dietary Reference Intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids (macronutrients).’ Washington, DC: National Academy Press,: 422–541.
5. Foster, M. and Samman, S. (2021) Vegetarian Diets Across the Lifecycle.
6. Fresán, U. and Sabaté, J. (2019) ‘Vegetarian Diets: Planetary Health and Its Alignment with Human Health’. Advances in Nutrition, 10(Supplement_4) pp.S380-S388.
7. Fuhrman, J. and Ferreri, D., (2010). Fueling the Vegetarian (Vegan) Athlete. Current Sports Medicine Reports, 9(4), pp.233-241.
8. Helms E, Aragon A, Fitschen P. (2014) Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. J Int Soc Sports Nutr.;11(1):1.
9. Henjum, S., Groufh-Jacobsen, S., Stea, T., Tonheim, L. and Almendingen, K., (2021). Iron Status of Vegans, Vegetarians and Pescatarians in Norway. Biomolecules, 11(3), p.454. 
10. Humphrey, O.S.; Young, S.D. (2019) Iodine uptake, storage and translocation mechanisms in spinach (Spinacia oleracea L.). Environ. Geochem. Health, 41, 2145–2156. 
11. Kniskern MA, Johnston CS. (2011) Protein dietary reference intakes may be inadequate for vegetarians if low amounts of animal protein are consumed. Nutrition.;27(6):727–30.
12. Rogerson, D. (2017) ‘Vegan diets: practical advice for athletes and exercisers’. Journal of the International Society of Sports Nutrition, 14(1).
13. Sabaté, J. and Soret, S., (2014). Sustainability of plant-based diets: back to the future. The American Journal of Clinical Nutrition, 100(suppl_1), pp.476S-482S.
14. Sanders, T., (1999.) The nutritional adequacy of plant-based diets. Proceedings of the Nutrition Society, 58(2), pp.265-269.
15. Tuso, P., (2013). Nutritional Update for Physicians: Plant-Based Diets. The Permanente Journal, 17(2), pp.61-66.
16. Watanabe, F., Yabuta, Y., Bito, T. and Teng, F. (2014) ‘Vitamin B12-Containing Plant Food Sources for Vegetarians’. Nutrients, 6(5) pp.1861-1873.
17. Weaver, C., Proulx, W. and Heaney, R. (1999) ‘Choices for achieving adequate dietary calcium with a vegetarian diet’. The American Journal of Clinical Nutrition, 70(3) pp.543s-548s.
18. Wilson, A. and Ball, M. (1999) ‘Nutrient intake and iron status of Australian male vegetarians’. European Journal of Clinical Nutrition, 53(3) pp.189-194.