Since Lisa’s recent post on LUTEIN and ZEAXANTHIN, two important nutrients for vision, I did a lot of research.
Knowing the bioavailability of these 2 nutrients is 32% HIGHER when originating from animal sources (even if the said animal source contains 70% LESS of these 2 nutrients compared to plant sources), I think this is of serious consequences on anyone food choices and of great interest for folks like us on an all-animal product diet.
Finding recent studies on bioavailability of nutrients from animal and plant sources is not easy, but I discovered an old and well-written medical nutrition textbook of the ’80s, probably published when most scientists still thought animal products were good for human being. What I read and discovered is astonishing.
Basically, food items, and especially plants, contain inhibitors of nutrient utilization, which reduce absorption, solubility and utilization. On a evolutionary point of view, as plants cannot run away from predators, they must defend themselves. Aside producing toxins to prevent humans (and other animals…) to feed on them, they developed to contain ANTI-NUTRIENTS, which make their content less available to us, the predators, this being a defense mechanism for them.
Maybe you have read about phytic acid, trypsin inhibitor, lectin, oxalate, tannins, polyphenols, soy proteins, all of these are potent anti-nutrients contained in plant food, which are, at the end, anything but “human friendly”…
Take note that none of these anti-nutrients are founded in animal products. Except that, for human, to survive on animal flesh, its means going to hunt, which include running and catching the said animals… which is very different from lazily picking up an apple on a tree…
And, as we all know, there is a price to everything in life including, probably and sadly, getting less nutrition if you invest less energy into gathering your food…
So let’s give a look to what I discovered.
This is probably the most interesting example of how meat is a better source of iron then plants. There are 2 types of available iron, the haeme type, which is EASILY absorbed and is from animal sources, and the non-haeme type, which has REDUCED bioavailability and comes from the vegetal world.
Because of this lower iron absorption from plant sources, vegetarian and vegans must have higher daily iron intake (around 1.5 – 2 times more). This being said, their food intake must be much higher, carbohydrate-loaded than those who eat meat, fish or poultry.
For example, spinach contains OXALATES, which bind iron, making it almost entirely unavailable for absorption. Interestingly, if combining such a source of non-haeme iron with a source of haeme iron like meat, the absorption of the non-haeme part may be increase; this is called the “meat factor”…
So, your mother, instead of telling you to finish eating your spinach to get your iron, should have told you to finish your meat so you can absorb the iron in the spinach… Anyway, at the end, she would still have been wrong because spinach contains low quantity of iron: a typing mistake was done many years ago and the legend of the “spinach rich in iron” was born…
Even if some plants do provide absorbable calcium, the quantity of vegetables required to reach sufficient calcium intake makes an exclusive plant-based diet impractical for most individuals.
Again here, calcium bioavailability from plant foods is affected by their contents of oxalates and phytates. Studies have demonstrated calcium from dairy origin is significantly more correlated with bone mass than it is with nondairy calcium. In general, we can say calcium absorption is inversely proportional to the oxalic acid content of the food.
Anyway, the low calcium content of common plant sources including vegetables, fruit and cereal grains, makes it difficult for most to meet their requirements exclusively from these foods…
Phytic acid and possibly other constituents of some plant food can reduce the bioavailability of zinc considerably. So when you read watermelon seeds and yeast germs are good sources of zinc, don’t be a fool. Anyway, the major source of zinc in the human diet is from animal source…
This is also very interesting as there is a competition between absorption of carbohydrates and vitamin C. Both use the same channels for absorption, and the body tends to prefer the carb over the vitamin. Which means the more one eats carb, the more his needs for Vitamin C will go up. Not forgetting that when your Vitamin C intake is low, such as on a low-carb diet, your body goes into “recycling mode” so the vitamin is reabsorbed back at the kidney level.
VITAMIN B1 (THIAMIN):
Diets rich in carbohydrates increase metabolic demands for thiamin, so the RDS recommendations were adjusted on the higher side for this reason; of course, you understand these numbers are absolutely irrelevant on a Zero Carb diet.
Body reserves of thiamin become depleted more rapidly when a diet is rich in carbohydrates compare to when diet is full in fat and protein. The “thiamin sparing” effect of fats and protein has long been known.
All this being said, one with a diet high in fat requires lower levels of thiamin to meet his needs. Excess intake of carbohydrate food such as potatoes, bread and certain grains increase thiamin requirement.
The bioavailability of vitamin B6 in foods is highly variable, largely due to the presence of poorly utilized glucosides in plant tissues. Thus, as expected, vitamin B6 generally has a lower availability from plant-derived foods than from animal tissues.
Thiamine is also destroyed by sulphites added to vegetables during blanching, and milling and polishing of rice depletes this vitamin, thus causing white rice and flour to be re-enriched with artificially made vitamin.
Interestingly, raw fish contains ‘thiaminase” which has an anti-thiamin activity. Cooking the said fish destroy the enzyme making the vitamin readily available. One good point for cooking your fish!
NIACIN (VITAMIN B3):
Niacin is widely distributed in food of plant and animal origin but, in typical western diets, the most important sources are meat, dairy, eggs and cereals.
Except that in some of the cereals, especially corn, 70 % of niacin is UNAVAILABLE, and in areas where people mainly eat the said corn as a staple food (numerous countries around the world nowadays…), niacin deficiency develops and causes pellagra, a serious health condition.
Niacin from animal source is readily available and where humans eat animal products, pellagra is inexistent.
Vitamin A (retinol) is mainly founded in animal products such as dairy, butter and cheese, but also eggs, liver and fish.
What is founded in dark green vegetables, carrots and colored fruits is PRO-VITAMIN A, substance that will need to be transformed by gut bacteria to become vitamin A before its absorption. This will happen only in the presence of dietary fats in the intestines. Which means if someone eats carrots alone on a empty belly, he will absorb ZERO vitamin A because there is NO vitamin A in carrot, only pro-vitamin A…
COPPER, MANGANESE AND SELENIUM:
Again, here, because of the high content of phytic acid and dietary fibers, plant sources of copper, manganese and selenium will provide lower availability for these micro-minerals compare to when they come from animal sources.
Only a few foods contain significant amounts of vitamin D, e.g. fatty fish and fish oils. Meat, especially liver, and dairy products contain a little bit less but since they have a higher biological activity, the absorption is enhanced.
Again here, as for all the fat-soluble vitamins, the presence of fat and a normal gastrointestinal function (fat digestion) are prerequisites for absorption.
Very interestingly, in studies with mix diet (including plant and animal products) Vitamin D absorption has been proven to go down as low as 50%...
I hope you understand eating your fish with a salad will cause your salad to DECREASE the absorption of the vitamin D contained in your fish…
In the plant world, fruits and vegetables are very poor sources of vitamin E, while cereal brings adequate amount BUT it needs to be extracted and concentrated as oil, which, by the end, makes it a processed food item. Sadly, it means also it contains, along with vitamin E, huge amounts of pro-inflammatory omega 6.
Meat is a poor source of vitamin E, but do not worry, because eggs do provide substantial quantities!
Folic acid content of food items, again, has nothing to do with their absorption.
For example, tomatoes and orange are both rich in this vitamin but absorption is low due to inhibition of intestinal “conjugase” enzyme, caused be the acidity of these 2 fruits, especially if ingested as juice.
In studies done on folic acid absorption with rats, the lowest figures for absorption were reported with wheat germ, cabbage and broccoli, while liver and eggs had the best scores in bioavailability.
So what may we conclude from all this?
Well first, it kills the idea that plant products are more nutritious then animal products because the have an higher content of vitamins and mineral. They are not more nutritious because they contain anti-nutrients compounds that diminish absorption of the said nutrients.
It also support the concept a diet voided of carbohydrates, thus with no plants food items, will provide the perfect medium for maximal absorption of nutrients from animal products.
Finally, for me, it attacks the “repeated advice” of doctors and nutritionist that a MIX DIET is the way to go. Yes, eating food from plant origin along with your meat do not provide a more equilibrate meal, but it create a situation where the nutrients of your meat will be less absorbed, thus causing a “denutritive state”.
And who would be the best witness that eating an all-animal product diet provides the body all its required nutrients, especially if the said witness is on Zero Carb for more then 4 years now and is even running marathon, if it is not Lisa???!!!