A new systematic review highlights nutrient deficiencies in both plant-based and omnivore diets. Our guest blogger and regular NHD contributor, Rebecca Gasche, RD, examines the evidence and provides a take-home message.

Rewind seven months to January, and there is an abundance of literature reminding those giving Veganuary a go, or even those who have followed a vegan diet for many years, of the nutrient deficiencies that may occur on a plant-based diet. And rightly so, as anyone choosing to follow a plant-based diet should be aware of the food groups they need to focus on. But did you know following an omnivore diet – i.e. consuming meat, fish and dairy, as well as plants – also carries a similar risk of nutrient deficiencies?

SYSTEMATIC REVIEW

A recent systematic review by Neufingerl and Eilander¹ looked at the nutritional intake of adults consuming a plant-based diet compared with meat-eaters. This is an interesting comparison, with previous literature often focusing on one diet or the other. The review looks at 121 studies between the years 2000-2020 and focused on adults in European, South/East Asia and North America. The data looked at ‘plant-based’ diets, including both vegetarian and vegan diets.

THE VEGAN DIET: AT-RISK DEFICIENCIES

The British Dietetic Association (BDA)² and The Vegan Society³ advise that those on a vegan diet should consider supplementing their diets with vitamin B12, vitamin D, iodine and possibly iron. The review by Neufingerl and Eilander¹ supports this, identifying that vegan diets are at risk of the following deficiencies:

• Vitamin B12 – found in meat/dairy products.
• Vitamin D – synthesised largely from sunlight but also available from some foods such as eggs, oily fish or fortified products.
• Calcium – found in dairy products but also in certain nuts, pulses and vegetables.
• Iodine – Largely found in dairy and seafood. Vegan diets may supplement this with seaweed or fortified foods; however, it is not recommended to have seaweed more than once a week due to the varying levels of iodine it may contain.
• Iron – but only for women! Iron is predominately found in meat products but can be sourced from foods such as pulses and dark green leafy veg. Consuming vitamin C with iron-containing foods increases its absorption.
• Zinc – eggs and milk are common sources of zinc, but it is also found in pulses, nuts, seeds, mushrooms and fortified products.
• EPA and DHA fatty acids – these are fatty acids found predominately in seafood/oily fish but can also be converted from foods such as seeds (flax, chia, hemp) and walnuts.

The nutrients found in high intakes on a vegan diet included: fibre, fatty acids PUFA and ALA, vitamins B1, B6, C, E, folate and magnesium.

The review compared this with vegetarian diets, where it found that, as well as the nutrients listed above, vegetarian diets were found to be lacking in fibre and vitamin E. Less vitamin B1 and B6 were consumed than a vegan diet too.

THE OMNIVORE DIET: AT-RISK DEFICIENCIES

However, the most intriguing element of this systematic review that I found was its evaluation of nutrients in an omnivore diet. The study discovered that the following foods were at risk of deficiency:

• Fibre – dietary fibre is found in fruits, vegetables and wholegrains.
• Vitamin D – as above.
• Vitamin E – found in nuts, seeds and certain veg.
• Folate – found in dark green leafy veg, pulses, fruits but also seafood and offal.
• Calcium – as above.
• Magnesium – commonly from beans, pulses, wholegrains.
• Fatty acids polyunsaturated fatty acids (PUFA) and alpha-linolenic (ALA) – ALA was found to be lower in men. Dietary sources include nuts, seeds, oily fish and certain vegetable/nut oils.

Protein, niacin, vitamin B12 and zinc were found to be highly consumed.

What I take from this research, is that even if you are choosing to consume all foods, this does not necessarily mean you are taking a ‘balanced’ diet. I was surprised that despite nutrients, such as calcium, often being promoted as ‘difficult to meet requirements’ in vegan diets, they can also be under-consumed in omnivore diets. It is clear that wholegrains, pulses, nuts and seeds contribute to a large proportion of nutrients, and that lower levels of these are consumed in an omnivore diet.

MY TAKE-HOME MESSAGE

Everyone should include more variety of wholegrain, plant-based foods in their diets and supplement with vitamin D. If you choose to avoid meat and/or dairy products, consider supplementing with vitamins B12 and iodine (or use fortified products), and ensure you have a variety of foods rich in iron and calcium.

Rebecca Gasche, RD
Clinical Lead Dietitian, Countess of Chester Hospital NHS Trust

Rebecca is a Clinical Lead Dietitian for
gastroenterology services and is a Primary Care
Network dietitian based in Chester

References

1. Neufingerl N, Eilander A (2021). Nutrient Intake and Status in Adults Consuming Plant-Based Diets Compared with Meat-Eaters: A Systematic Review. Nutrients. 23;14(1):29. doi: 10.3390/nu14010029. PMID: 35010904; PMCID: PMC8746448.
2. The British Dietetic Association (2021). Vegetarian, vegan and plant-based diets. Retrieved from https://www.bda.uk.com/resource/vegetarian-vegan-plant-based-diet.html
3. The Vegan Society. No date. Nutrients. Retrieved from https://www.vegansociety.com/resources/nutrition-and-health/nutrients