Dr Libby: What Every Vegan & Vegetarian Needs To Know

In this special series, guest writer Dr Libby Weaver shares her health insights. This week, advice for those choosing a plant-based – or plant-forward – diet

In my clinical experience, I’ve seen that some people opt for a vegetarian or vegan lifestyle for a variety of heartfelt reasons – whether ethical, religious, spiritual or health-related. For others, their food choices might be influenced by fears, perfectionism or perceived social pressures.

There’s no single right way for everyone to eat, and as a nutritional biochemist, I thoroughly respect that. My role is to ensure that how you choose to eat is complete – that you are obtaining all of the vitamins and minerals your body requires.

Common nutrient gaps in a plant-based diet

If you decide to follow a plant-based path, it’s helpful to be aware of specific nutrients that can be trickier to obtain or absorb without animal products so you can consider and plan the way you eat thoughtfully.

Nutritional gaps often happen not because a diet is “bad” but because some nutrients are more abundant or easier to absorb from animal-based foods.

On vitamin B12

One key nutrient is vitamin B12, which is essential for producing red blood cells, supporting energy metabolism, neurological health, and DNA creation and maintenance. Though stored in the liver, making deficiencies slow to develop, B12 is found only naturally found in animal products.

While mushrooms and seaweed can offer some, this is only the case when there’s been certain microbial interactions with these foods while they were growing, so we can’t assume they will contain sufficient active vitamin B12 to meet requirements.

Megaloblastic anaemia occurs when a lack of vitamin B12 (or folate) affects the health of red blood cells and the body’s ability to synthesise healthy DNA. For those eating vegan, taking a supplement is really important, and vegetarians should keep an eye on their levels too. While fortified plant milks and nutritional yeast can help, they rarely provide enough to keep B12 levels up over time.

On iron

Iron is another key player that often flies under the radar in plant-based eating – yet it’s equally essential for energy and overall wellbeing. While iron is found in plant foods like lentils, tofu, seaweed and dark leafy greens, the type of iron they contain – non-haem iron – is not absorbed as efficiently as haem iron from animal sources. This matters because iron plays a pivotal role in energy production, immune function, thyroid and hormonal health, mood, anxiety levels and sleep. Even mild iron depletion can leave you feeling tired, cold, flat or foggy, and iron deficiency is the most common nutritional shortfall worldwide.

To compensate for the lower absorption of non-haem iron, those who eat in a vegetarian or and vegan way are advised to consume 1.8 times the recommended daily intake. For menstruating women, this means aiming for around 32.4mg of iron per day – a level that is extremely difficult to achieve from plant foods alone.

Pairing plant-food iron sources with foods rich in vitamin C, such as citrus fruits, tomatoes or capsicums, can help increase iron absorption. On the other hand, consuming tea, coffee or calcium-rich foods with iron-containing meals can inhibit absorption.

In many cases, supplementation may be necessary – particularly for menstruating teens and women – and food-sourced forms of supplemental iron (such as ferritin-iron) are gentler on digestion than conventional iron salts.

On zinc

Zinc is equally important and often overlooked. It supports immunity, skin integrity, digestion and hormone health. While zinc is found in plant foods such as nuts and seeds, in these foods phytates are also present – compounds that reduce zinc’s bioavailability as they can bind to zinc.

Food sources of zinc for these ways of eating include eggs, sunflower seeds and pumpkin seeds. The recommended zinc intake ranges from 8–14mg per day but it can be challenging to meet this requirement through plant foods alone. For example, 100 grams of pumpkin seeds contains around 1mg – but most people wouldn’t consume anywhere near that much in a sitting. A single egg contains only about 0.5 mg. When you consider this, it’s easy to see how deficiency can quietly creep in over time.

Other nutrients to keep an eye on

If you eat vegan, other nutrients to be mindful of are calcium, omega-3 fatty acids, vitamin A and choline. Calcium is essential for bone health, muscle function and nerve signalling. Those pesky oxalates and phytates found in most plant foods can reduce the amount of calcium the body absorbs. Over time, inadequate intake may increase the risk of low bone density, nerve and/or muscle issues.

Choosing calcium-set tofu, fortified plant milks, tahini and low-oxalate greens like kale and cabbage can help, but again, monitoring intake is key – especially for older adults and women after menopause.

Omega-3 fatty acids, particularly DHA (docosahexaenoic acid), are critical for brain health, eye function, healthy hormones and inflammation regulation. While alpha-linolenic acid (ALA) – a plant-based omega-3 – is found in flaxseeds, chia seeds and walnuts, the body’s conversion of ALA into DHA is limited. This can make it challenging to maintain optimal levels on a vegan diet. Algae-based DHA supplements offer a plant-derived solution and are especially important for individuals who are pregnant, breastfeeding or aiming to support long-term cognitive health.

When to take supplements

One of the most common questions people ask when considering a vegetarian or vegan way of eating is: how long can I go before needing supplements? The truth is, it varies from person to person and it’s different for each nutrient. Some individuals may thrive for years before experiencing symptoms, particularly if they begin with good nutrient stores, although menstruating women might notice iron falls short within a couple of months. Others may notice changes more quickly. This is why regular blood tests and paying attention to your body’s signals – like energy, mood, focus, sleep and menstrual health – can be so valuable.

You don’t need to wait for a problem to emerge before taking action. Preventive support is often more effective than trying to address a deficiency once it has already impacted your wellbeing. If you’re unsure where you stand, start with a simple blood test and speak with a qualified practitioner who understands plant-based nutrition. Symptoms often appear gradually, so catching nutrient gaps early can make a significant difference to your long-term wellbeing.

Supplements are never a substitute for a nutrient-rich diet, but they can be a powerful tool for supporting overall health. This is especially true when the supplements are made from real foods and herbs – not synthetics created in a lab. Your body is wise. It recognises and responds to nutrients from nature. That’s why choosing food-based formulas matters, especially when you’re eating a diet that already begets more thoughtfulness.

Dr Libby Weaver PhD is a nutritional biochemist, 13 times best-selling author and international keynote speaker. Drlibby.com

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