The nutrients required by human cells are the same as those required by the animals we eat, underscoring the need for animal meat in a nutritious human diet, according to a leading food scientist.
Prof. Neil Mann is Professor of Food Science and Human Nutrition at the University of Melbourne in Australia. He was in Ireland this week to participate in a two-day international summit organized by Teagasc entitled ‘The social role of meat: what science says’.
speaking to agriland after giving a presentation at the event, Professor Mann said: “Because we are mammals, just like the meat we eat, our cells and their nutrient requirements are exactly the same as the animals we eat.
We are not a plant, right? We are an animal. So what we require is the same thing that animals have and what they require. So we can get all our nutrients from animals.
“We can also get a lot of nutrients from plants. but there are some [nutrients] that are not in plants that are only in animals. So we really have to eat animal foods to get those essential nutrients that we can’t get from vegetables, fruits, or grains,” he said.
Prof. Mann explained that some nutrients are more bioavailable in animals than in plants, while others are only naturally available to humans through animal meat.
Nutrients that are most bioavailable in animals are also present in plants, but are not digested and absorbed as effectively by humans when not consumed through meat.
Iron and zinc are two of those remarkable nutrients, which are “essential in our bodies”, Professor Mann said.
“Iron, for example, is part of hemoglobin, which is used to transport oxygen through the blood. But iron and zinc are also very important for immune function and brain function. Your brain uses quite a bit of iron and zinc,” he explained.
Iron and zinc can be found in plants, but that doesn’t necessarily mean they’re suitable sources for humans.
“You get [iron and zinc] in plants, but they’re attached to other compounds in plants that inhibit their absorption in the intestines, so basically most of the iron and zinc in plants, when you eat them, just come out the other end. You don’t really digest or absorb much of it,” Professor Mann said.
“But in animals, iron and zinc stick to protein molecules; for example, heme iron, which means iron bound to hemoglobin.
He continued: “Zinc is also transported by proteins in animal tissue. When we eat it and it reaches our intestines, the fact that those iron and zinc atoms are attached to a protein actually helps them to be absorbed.
According to Prof. Mann, the amount of plant foods a human being would have to eat is many times greater than the amount of meat to get the same amount of iron and zinc.
“That’s called bioavailability. So iron and zinc are not very bioavailable. [to humans] in plants, but are highly bioavailable in animal feed. This is why many vegetarians and vegans are deficient in iron and zinc.
Meat-Only Nutrients for Humans
Other nutrients in meat, however, are not available to humans through plant foods.
Prof. Mann said: “There are two main of those. The first is vitamin B12. Many vegans and vegetarians believe that they can get vitamin B12 from plants. It is a total myth but they circulate it among themselves and they believe it.
“This is why people who are strict vegans and don’t take a vitamin B12 supplement from the pharmacy become vitamin B12 deficient and suffer irreversible nerve damage and brain damage after many years,” he added.
“Basically, you get B12 from animal feed. [There’s] a little bit in eggs and milk, there is some in fish, but the best source, the richest source, is red meat.”
Long-chain omega-3 fatty acids are also key nutrients found only in meat, and while omega-3 fatty acids can be found in plants, they are not what humans need.
“They fall into a wide range of different molecules that have different effects in the body. We are animals, we have different forms of these omega-3s. We can only get them from other animals, mainly from fish, but also from the red meat of grass-eating animals because animals eat grass or algae on their own bodies,” Professor Mann said.
He added: “They are very important for a wide range of things in your body. Again for immunity, they stop inflammation, they stop excessive blood clotting. [a cause of heart attacks] and they are very important for brain function again.
“In fact, the four things I’ve mentioned (iron, zinc, vitamin B12, and long-chain fatty acids) are absolutely critical compounds for brain function. They’re important in the rest of your body, but they’re really critical for brain function.”
Prof. Mann described some of the effects on the brain if these nutrients are absent.
“If you don’t have enough B12, you have neurological damage… If you don’t have enough iron or zinc, you have a similar type of brain cell damage. They just don’t work properly. With a lack of zinc, you also have depression diseases, and with a lack of omega-3 fatty acids you have the same kind of thing,” he said.
The food scientist added: “Older people who have severe dementia show very low levels of these long-chain omega-3 fatty acids and very low levels of B12. So if you have low levels of vitamin B12 and low levels of omega-3, it has a double effect on your brain function.
“The scans they’re doing on these people’s brains show that their brains are shrinking, which is called atrophy. They are actually shrinking and growing holes as the brain tissue disappears.”
Prof. Mann also drew attention to the presence of amino acids in animal proteins.
He said: “Plant proteins do not have the same range of amino acids as animal proteins. Plants are plants, animals are animals. We are an animal. The amino acids that are in animal proteins are the same ones that we need. So we get a better balance of those amino acids by eating animals.”
Prof. Mann highlighted that the human digestive system has evolved over some four million years to eat meat as well as plants.
He compared the digestive system of modern humans to that of a fox or dog, while retaining the ability to obtain nutrients from plants.
He explained that humans can obtain the nutrients found in meat foods from supplements.
However, he commented: “I am a nutritionist first and foremost. I believe, like all nutritionists, in well balanced diets, and that you should not take supplements. Our distant ancestors did not take supplements. They ate a natural diet and got everything they needed.”
