The adequacy of all dietary patterns, omnivorous, vegetarian or vegan, depends on nutrient content of foods in the diet and the human gastrointestinal tract’s ability to extract those nutrients (including zinc).
Several elements, termed ‘anti-nutrients’, found specifically within plant foods e.g.:
- seeds (nuts, grains, pulses) and
- but not generally in animal foods,
significantly reduce nutrient digest/absorbability, can damage the gastrointestinal tract. This can increase vegans/vegetarian’s risk of zinc & other nutrient deficiencies, and ill-health. Such substances include:
- Phytates found in seeds, grains and legumes which significantly reduce mineral absorption including iron, zinc, magnesium and calcium. Phytate is indigestible by monogastric animals, including humans, because we lack the enzyme phytase in our digestive tracts.
- Tannins are a class of polyphenol-antioxidants. Some such as gallic acid found in tea, coffee, and cocoa are nutritionally undesirable because they precipitate proteins, inhibit digestive enzymes and affect the absorption of vitamins, minerals – especially iron and other nutrients.
- Lectins, found in all food plants, especially seeds, legumes and grains, survive digestion & bind cells lining the digestive tract, triggering many harmful local and systemic reactions. They can alter cell turnover and cause loss of gut epithelial cells, damaging the gut lining; interfere with nutrient digestion and absorption, stimulate shifts in the normal bacterial flora and change the immune state of the digestive tract. Systemically, they can disrupt lipid, carbohydrate and protein metabolism, promote enlargement and/or atrophy of key internal organs and tissues and alter the hormonal and immunological status. Many lectins are both antinutritive and/or toxic substances and are harmful in high amounts.
- Protease inhibitors (PI’s): are small proteins, found mainly in plant storage tissues i.e. seeds (nuts, grains, pulses) & tubers (potatoes, sweet potatoes etc) but also aerial parts in response to attack. They stop the action of protein digestive enzymes in the stomach & small intestine and can represent up to 10% of total protein content of some plant foods.
- Calcium oxalate is the primary form of calcium in many vegetables, e.g. spinach, but only 10% of the calcium from spinach is absorbed compared to just under 40% from milk. Consuming spinach with milk doesn’t reduce calcium absorption from milk. So lacto-ovo-vegetarians generally have lower risk of poor calcium intake than strict vegans. Oxalate does not hinder zinc absorption.
If, over a long time, one eats a poorly constructed vegetarian or vegan diet that contains high levels of many-or-all of these antinutritive compounds, it’s easy to see how zinc & various nutrient deficiencies plus the resulting ill health may manifest – including poor cartilage. Omnivores with poorly constructed diets aren’t immune. Omnivores get 50-70% of their calories from plant foods containing the same antinutritive compounds that now hinder absorption of nutrients from their animal foods.
Typical omnivores may eat (high tannin) coffee, (high-phytate/lectin/PI) toast or cereal for breakfast; meat & salad surrounded by (high-phytate/lectin/PI) sandwich bread or a wrap for lunch; pizza (low nutrient & moderately-high phytate/lectin/PI white-flour dough) for dinner. Easy-to-see how their health might suffer. Next month we look at ways to remove many anti-nutritives from vegan foods.
Article Written + Submitted by:
Andreas Klein Nutritionist + Remedial Therapist from Beautiful Health + Wellness
P: 0418 166 269