For clients who are vegan or follow a plant-based diet, I routinely recommend a daily multivitamin; a sublingual (dissolved under the tongue)/chewable/spray vitamin B12 supplement; and an algal-derived omega-3 supplement providing a minimum of 250mg EPA + DHA daily.
In my experience, most adults also need 1000-2000IU vitamin D in the form of a supplement through the cooler months when UV levels are low in order to maintain their vitamin D levels above what is considered 'optimal' by most Australian labs and the scientific literature (>75nmol/L). A 2012 study on a sample of over 11,000 adults found that 1 in 3 adults were vitamin D deficient (<50nmol/L) and 3 in 4 adults had suboptimal vitamin D status (<75nmol/L).
Despite the fact that many people think that multivitamins are unnecessary and a waste of money, I believe a multivitamin is justifiable for vegans living in Australia to ensure you're meeting the RDI for nutrients which can fall short in vegan diets such as iodine, selenium, vitamin B2 and vitamin B6. The amount of iodine in the soil in Australia is low, making plant-based foods a poor source. Dietary sources of iodine on a plant-based are limited to seaweeds, iodised salt, and bread (containing iodised salt). As such, vegan diets are a known risk factor for iodine insufficiency, which can affect the function of the thyroid gland. I have previously recommended seaweeds (such as dulse and nori) for iodine, but as the iodine content of seaweeds is highly variable, I believe it is safer to rely on a multivitamin (or an iodine supplement), which will provide a known quantity of iodine (typically 100%, or 150mcg).
High doses of certain isolated nutrients such as selenium, beta-carotene and vitamin E have been shown to be harmful (by increasing risk of diseases or mortality), but multivitamin supplements providing less than 100% of the RDI for the vitamins and minerals they contain are known to be safe for long-term use.
I have previously recommended a multivitamins formulated specifically for vegans (such as the Healthy Essentials Vegan Multivitamin and the Deva Vegan Multivitamin and Mineral Supplement), but due to theoretical concerns in the scientific literature about the vitamin B12 being degraded to inactive analogues in the presence of copper and vitamin C (found in multivitamins), I believe it's better to err on the side of caution and take vitamin B12 separately, as these inactive analogues can interfere with vitamin B12-dependent enzymes in the body.
A good choice for a multivitamin is the Now Foods Daily Vits, which can be purchased on iHerb relatively inexpensively ($25 for 250 tablets). It contains just a small dose of vitamin B12 (4mcg), which minimises the risk of it containing inactive analogues, but also means you'll need an additional vitamin B12 supplement.
*If you have a family history of a genetic iron overload disorder (such as haemochromatosis) please have a blood test to check your iron levels before starting on a multivitamin, as they contain a small dose of iron.
Additional Vitamin B12
I recommend the cyanocobalamin form of vitamin B12 on the basis of its stability and due to the fact that it has been extensively studied. You can read more about vitamin B12 here. I recommend choosing one of the following options:
2000mcg, 1-2x weekly, such as Now Foods B12 2000mcg
1000mcg 2-3x weekly, such as Thompson's Ultra B12 1000mcg
Algal-derived omega-3s (combined DHA+EPA), in a veggie capsule
Omega-3s are an essential fatty acid, which means we can't make them in the body from precursors, and so must consume them through the diet. There are two main classes of omega-3s, which are the plant-derived omega-3s (known as alpha-linolenic acid or ALA), and the long-chain omega-3s (such as EPA and DHA).
The omega-3s found in plant foods such as chia, flaxseeds and walnuts can be converted in the body to EPA and DHA, though conversion rates are known to be relatively inefficient. The main sources of the long-chain omega-3s are fish, fish and krill oil supplements, but vegans can source these omega-3s from where the fish get their omega-3s - algae!
The National Health and Medical Research Council Department of Health and Ageing have set an Adequate Intake (AI) for long chain omega-3s (DHA+EPA+DPA) of 160mg for men and 90mg for women, which is the average intake of 'apparently healthy people' whose intake is assumed to be adequate.
A 'Suggested Dietary Target' (SDT) which 'may help in prevention of chronic disease' has been set at 610mg for men and 430mg for women, which is in line with the recommendations made by the national Heart Foundation of 250-500mg per day (which is equivalent to consuming oily fish 3x per week). The majority of nutrition authorities around the world echo these recommendations, which are summarised by the Global Organisation for EPA and DHA Omega-3s (GOED) here.
Though it's a personal choice as to whether you supplement with algal-derived omega-3s - and I would encourage you to read this excellent summary on the issue from VeganHealth.org - I do recommend a minimum of 250mg combined EPA+DHA from algae daily. If price is a factor, I would still recommend taking 250mg EPA+DHA every 2-3 days to ensure you are getting a direct source of long-chain omega-3s.
Let me know if you have any questions by leaving a comment below, or feel free to email me on BloomNutritionist@gmail.com