The nutrients required by human cells are the same as those required by the animals we’re eating, which underscores 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 take part in a two-day international summit hosted by Teagasc titled ‘The Societal Role of Meat – What the Science Says’.
Speaking to Agriland after delivering a presentation at the event, Prof. Mann said: “Because we are mammals, just like the meat we eat, our cells, and their requirements for nutrients, are exactly the same as for the animals we’re eating.
“We’re not a plant, are we? We’re an animal. So what we require is the same as what 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 a few [nutrients] that are not in plants that are only in animals. So we really have to eat some animal food to get those essential nutrients we can’t get from vegetables or fruits or grains,” he said.
Prof. Mann explained that some nutrients are more bioavailable in animals then in plants, while others are only naturally available to humans through animal meat.
Those nutrients that are more bioavailable in animals are also present in plants, but are not digested or absorb as successfully by humans when not consumed through meat.
Iron and zinc are two notable such nutrients, which are “essential in our bodies,” Prof. Mann said.
“Iron, for instance, is part of hemoglobin, which is for carrying oxygen around your 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 that they are suitable sources for humans.
“You do get [iron and zinc] in plants, but they are stuck on other compounds in plants that inhibit their absorption in your intestines, so basically most of the iron and zinc in plants, when you eat it, just comes out the other end. You don’t really digest and absorb much of it at all,” Prof. Mann said.
“But in animals, iron and zinc are stuck on on protein molecules; for instance, heme iron, which means iron stuck to hemoglobin.
He continued: “Zinc is also carried by proteins in animal tissue. When we eat it and it gets into our intestines, the fact that those iron and zinc atoms are stuck to a protein actually helps them become absorbed.
According to Prof. Mann, the amount of plant food that a human 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 they are highly bioavailable in animal foods. This is why many vegetarians and vegans have deficiencies in iron and zinc.
Meat-only nutrients for humans
Other nutrients in meat, however, are not available to humans through plant foods at all.
Prof. Mann said: “There are two main ones of those. The first is vitamin B12. Many vegans and vegetarians believe they can get vitamin B12 out of plants. It’s a total myth but they circulate it among themselves and they believe it.
“That’s why people who are strict vegans and don’t take a vitamin B12 supplement from the pharmacy become B12 deficient and they undergo irreversible nerve damage and brain damage after many years,” he added.
“You basically get B12 from animals foods. [There’s] a little bit in eggs and milk, there’s some in fish, but the best source, the richest source, is red meat.”
Long-chain omega-3 fatty acids are also key nutrients that are only found in meat, and while omega-3 fatty acids can be found in plants, they are not the ones humans need.
“They fall into a whole range of different molecules that have different effects in the body. We’re animals, we have different forms of these omega-3s. We can only get them from other animals, mainly from fish, but also from red meat from animals that eat grass because the animals make it out of grass or seaweed in their own bodies,” Prof. Mann said.
He added: “They’re very important for a whole range of things in your body. Once again for immunity, they stop inflammation, they stop excessive blood clotting [a cause of heart attacks] and they’re very important for brain function again.
“In fact, all four things I’ve mentioned – iron, zinc, vitamin B12, and long-chain fatty acids – these compounds are absolutely critical for brain function. They are important in the rest of your body, but they are really critical for brain function.”
Prof. Mann outlined some of the effects on the brain if these nutrients are absent.
“If you don’t have enough B12 you get neurological damage… If you don’t have enough iron or zinc, you get similar sort of damage to brain cells. They just don’t function properly. With the lack of zinc, you also get depression diseases, and with a lack of omega-3 fatty acids you get the same sort of thing,” he said.
The food scientist added: “Elderly people who have got severe dementia are showing very low levels of these long-chain omega-3 fatty acids and very low levels of B12. So if you have low levels of B12 and low levels of omega-3s, it has a double-whammy effect on your brain function .
“The scans they are doing on the brains of these people are showing their brains are shrinking, which is called atrophy. They are actually shrinking and they grow holes in them as brain tissue disappears.”
Prof. Mann also drew attention to the presence of amino acids in animal proteins.
He said: “Plant proteins don’t have the same range of amino acids as animal proteins. Plants are plants, animals are animals. We’re an animal. The amino acids that are in the proteins of animals are the same ones we need. So we get a better balance of those amino acids from eating animals.”
Prof. Mann highlighted that the human digestive system has evolved over the course of some four million years to eat meat as well as plants.
He likened the digestive system of modern humans to that of a fox or a dog, while retaining the ability to get nutrients from plants.
He explained that humans can get nutrients found in meat foods from supplements.
However, he commented: “I’m a nutritionist first and foremost. I believe, like all nutritionists, in well-balanced diets, and that you shouldn’t have to take supplements. Our distant ancestors didn’t take supplements. They ate a natural diet and got everything they needed.”