One of the most common concerns that I hear from people who are contemplating adopting a plant-based diet is, “Will I be able to get enough nutrients if I don’t eat any meat, fish, eggs or dairy products?”
Many of my clients have been urged by well-meaning family members, and other health and nutrition professionals, to include at least some animal products in their diets, for fear that if they don’t, they’ll be ‘missing out’.
The myth that animal products contain some special, precious and unique nutrients that are not found in plants seems to be deeply embedded in our collective unconscious.
And of course, this false narrative is enthusiastically promoted by the animal product industries, who profit enormously from the widely-held beliefs that plants lack protein, dairy products are bone-friendly sources of calcium, red meat is a superior source of iron, and vitamin 12 deficiency is found only in people who don’t eat meat.
In the midst of this obsession with ‘getting enough nutrients’, most people never think to ask themselves why they’re chasing those nutrients in the first place.
As Professor T. Colin Campbell points out in his brilliantly incisive book Whole, we humans, along with all animals, consume foods, not nutrients. Foods contain a plethora of biologically active substances – far beyond the 13 vitamins and 16 minerals which are known to be essential for human survival – which interact with each other, with our biochemical individuality, and with our unique microbiomes, in unfathomably complex ways.
It’s our overall dietary pattern that determines our health outcomes, not whether we can tick off a checklist of nutrients for which we’ve met the recommended daily intake (RDI) each day. If this were not the case, we could all thrive on the witches’ brew of refined starch, sugar, salt, oil, food colourings and preservatives commonly known as ‘breakfast cereals’ – after all, these ultraprocessed junk foods are fortified with ‘essential nutrients’ including most vitamins and several minerals.
That said, there are dietary biomarkers (indicators of intake and/or metabolism of certain nutrients) that are associated with a decreased risk of cardiovascular disease, cancer, and other chronic diseases.
These include the levels of carotenoids (red, yellow and orange fat-soluble pigments found in plant foods), flavonoids (a large family of compounds widely distributed in the plant kingdom), lignans (found in seeds, whole grains, fruits, vegetables, and nuts) and fatty acids (building blocks of fat) in our blood, urine and fat tissue.
A study published in February 2019 compared biomarker levels in vegetarian and non-vegetarian diet groups among the Seventh Day Adventist population, and found that overall, vegans had the most health-protective levels of biomarkers.
The Seventh Day Adventist (SDA) church teaches that looking after one’s health is a religious responsibility. The congregation is strongly advised to avoid alcohol, smoking and caffeine, encouraged to engage in regular physical activity, and advised to eat a vegetarian or vegan diet, although followers are permitted to eat meat if they choose to.
Hence, SDAs are a unique population to study as they are generally fitter, slimmer and more health-conscious and have a lower risk of cancer and longer life expectancy than their non-SDA neighbours.
In the recently-published study, participants were divided into 5 dietary subgroups:
- Vegans – classified as never or rarely (less than once per month) consuming eggs, dairy, fish, and other meats;
- Lacto-ovo-vegetarians – those who consumed eggs and dairy more than once per month but fish and other meats less than once per month;
- Pesco-vegetarians – consuming fish at least once per month but all other meats less than once a month;
- Semi-vegetarians – those who ate non-fish meats at least once per month and any meat including fish less than once per week; and
- Non-vegetarians – consuming non-fish meats at least once a month and any meat (including fish) more than once per week.
Participants gave blood, urine and adipose (fat) tissue samples and completed questionnaires on their diet, smoking status, alcohol intake, physical activity, supplement use, medical history, and demographics.
The researchers assessed the blood, urine and body fat samples for a wide range of biomarkers that are either associated with a decreased risk of chronic disease, or indicative of dietary intake. These included carotenoids, isoflavonoids, lignans, holotranscobalamin (active vitamin B12), retinol (active vitamin A), tocopherols (vitamin E), folic acid/folate, 1-Methylhistidine (a marker of meat intake, particularly red meat and poultry), saturated and unsaturated fatty acids.
Interestingly, in contrast to the the popularity of vegan diets among younger people in the general population, the vegans in this study tended to be older compared to the other diet groups.
Also fascinating was that they had a lower body mass index (BMI – an indicator of healthy weight) than non-vegetarians, despite having a higher self-reported energy (kilojoule/calorie) intake. The researchers acknowledged that over- and under-reporting of food intake are both common when people answer dietary questionnaires, but also pointed out that there is evidence that plant-based diets may raise metabolic rate, allowing people to eat more calories without gaining weight.
The researchers found a stepwise inverse relationship between concentrations of carotenoids – which are associated with a decreased risk of certain cancers and eye diseases – and consumption of animal products: the more plant-based the diet, the higher the levels of total carotenoids,
α-carotene, β-carotene, cryptoxanthin, lutein and zeaxanthin.
Vegans excreted the highest amount of isoflavones, including the soy isoflavones daidzein and genistein, as well as enterolactone and equol which are produced when our beneficial gut bacteria metabolise isoflavones. Higher dietary intake of isoflavone-containing foods is linked to a decreased risk of cardiovascular disease, hormone-dependent cancers and menopausal symptoms.
Unsurprisingly, vegans had the lowest concentrations of saturated fatty acids, which are found primarily in animal-derived foods, and arachidonic acid, which is only found in foods of animal origin. Higher intake of saturated fat is associated with an increased risk of heart disease and cognitive decline. Arachidonic acid is an inflammatory omega 6 fat; higher levels are associated with heart disease, cancer, diabetes, osteoporosis, and immune and inflammatory disorders.
Total omega 3 fat levels were highest in vegans, although they had lower levels of the long chain omega 3 fats DHA and EPA. It’s unclear whether this has any clinical relevance, as vegans don’t show signs of DHA deficiency and don’t have higher risks of diseases linked to low EPA and DHA intake.
Surprisingly, vegans had higher levels of active vitamin B12 (holotranscobalamin) than any other dietary subgroup except pescovegetarians, indicating that vegan SDAs are diligent about meeting their vitamin B12 needs through either supplements or fortified foods.
It’s important to note that the reason vegan SDAs had such high levels of biomarkers associated with good health is because they eat more fruits, vegetables, whole grains, legumes, nuts and seeds than those other dietary subgroups.
That is to say, avoiding animal products isn’t enough to earn better health outcomes; animal products must be replaced with whole plant foods – not ultraprocessed vegan junk foods such as 2 minute noodles, Oreo cookies and vegan Cornettos.
The take-home point is that going ‘all the way’ to a 100% plant-based diet won’t compromise your nutritional status (provided you pay attention to vitamin B12 intake), and in fact, every bite of an animal-derived food is a missed opportunity to put a health-promoting plant food in your mouth instead.
Leave A Response