Science journal spreads false rumors about vegan diet

An article published this week in the Proceedings of the National Academy of Sciences (PNAS) claims that it would be a disaster for public health if the population of the United States suddenly went vegan. Yet the authors are not experts on human nutrition or public health. Instead, they are experts on how to feed livestock. Their conclusions were not based on any actual studies of the health of vegan human beings. The study’s authors even freely admit that plant-based diets have several important advantages:

  • Shifting to a plant-based diet would increase the amount of food available for human beings.
  • A plant-based diet requires people to eat a greater volume of food, to maintain the same weight. [As I have explained in two of my books, this is why a vegan diet is the key to solving our epidemics of obesity and type 2 diabetes.]
  • The 2015 Dietary Guidelines Advisory Committee concluded that plant-based diets would improve health and improve long-term sustainability of the US food supply.

Nevertheless, the authors of the PNAS article claimed that the plant-based diet would be deficient in several important nutrients. Yet they did not back up this claim with any studies that showed that vegans are really likely to have health problems as a result of nutrient deficiencies. The authors wrote, “However, without animal-derived foods, domestic supplies of Ca [calcium]; arachidonic, eicosapentaenoic, and docosahexaenoic fatty acids; and vitamins A and B12 were insufficient to meet the requirements of the US population.” That claim is absolutely ridiculous, for the following reasons:

    • Although you do need to get some calcium from your diet, it is practically impossible to find actual cases of people who did not get enough calcium from their food. Problems with calcium balance in the body usually result from lack of vitamin D or from long-term consumption of high-protein, high-calcium diets.
    • The Food and Nutrition Board of the National Academy of Sciences does not consider arachidonic acid, eicosapentaenoic acid, or docosahexaenoic acid to be essential in human nutrition. In other words, human beings do not need to get them from their food. The only essential fatty acids are an omega-6 fatty acid called linoleic acid and an omega-3 fatty acid called alpha-linolenic acid. Linoleic acid is plentiful in grains, nuts, and seeds. Alpha-linoleic acid comes from the chloroplasts in green plants and is plentiful in fresh vegetables. The requirement for both of these essential fatty acids is so small that it was not even discovered until hospitalized patients were being fed nothing but fat-free intravenous solutions for a long time.
    • Human beings can easily meet their requirements for vitamin A by eating beta-carotene, which is plentiful in dark green, orange, or yellow vegetables.
    • Vitamin B12 is the only true vitamin that is likely to be deficient in plant-based diets. Vitamin B12 is made by bacteria, not by animals, and can be obtained from a cheap supplement.
    • The article also warns about dietary deficiency of vitamin D. Yet vitamin D is not a true vitamin. It is a hormone that your body can make for itself, for free, if you expose your skin to sunshine. You don’t need to get “the sunshine vitamin” from your food.

The PNAS article warns us that a shift to a vegan diet would cause big changes to the economy. In particular, it would be disastrous for the livestock industry. (Note that the authors of the PNAS article are academics who have devoted their careers to serving the livestock industry, not to studying human health. This explains why they know so little about human nutrition and nutritional epidemiology.) A switch to a vegan diet would also be a disaster for the pharmaceutical industry. Many people who shift to a low-fat, plant-based diet can stop taking most or all of their prescription medications. These changes would be good for public health, though bad for industry.

PNAS is a prestigious journal. Yet like other prestigious journals, it occasionally publishes articles that are full of nonsense. Likewise, I imagine that PNAS probably also rejects some good articles for stupid reasons. I have worked for peer-reviewed journals, and I have also submitted articles to other peer-reviewed journals, so I have seen the problem from both sides, as I explain in this blog post. The mistake that the editors of PNAS made in this case was to fail to have this article reviewed by someone who is a genuine expert in human nutrition and nutritional epidemiology. As a result, they ended up spreading livestock industry propaganda.

Is Coconut Oil Good for You?

Lately, food faddists have been claiming that coconut oil is a health food. They claim that it will help you lose weight. In reality, coconut oil is as fattening as any other fat. Some people even claim that coconut oil can cure Alzheimer’s disease. In reality, coconut oil can promote atherosclerosis, which is an important cause of vascular dementia. Also, fats of any kind, including coconut oil, tend to make your body less sensitive to insulin. For this reason, eating coconut oil would probably make type 2 diabetes worse. Coconut oil could even make Alzheimer’s disease worse, since Alzheimer’s disease seems to be related to insulin resistance in the brain. So why are people promoting coconut oil for brain health? The idea that coconut oil is good for your brain came out of the fact that some of the fatty acids from coconut oil are useful as part of a diet for children with severe epilepsy.

Epilepsy is a condition in which people suffer from seizures. A seizure is an electrical storm within the brain. In ancient times, epilepsy was called “the falling sickness” because it often causes people to lose consciousness suddenly. However, “partial” seizures may simply cause altered mental states or uncontrolled movements of the body. Many ancient people thought that epilepsy was caused by the gods or by evil spirits. However, the ancient Greek physician Hippocrates explained that epilepsy was an ordinary physical disease, with physical causes. The ancient Greeks knew that some people with epilepsy did not have seizures while they were fasting. Of course, you cannot fast forever. You have to eat something eventually, or you will starve to death. Once the person with epilepsy resumed eating food, the seizures would start up again.

By the 1920s, physicians were looking for a way to mimic some of the effects of fasting, without starving the patient to death. They knew that fasting causes ketosis, which is the buildup of chemicals called ketone bodies in the bloodstream. But they knew that you could also get ketosis from eating an extremely low-carbohydrate diet. For reasons that are still unclear, ketosis suppresses seizures in many people with epilepsy. For this reason, an extremely high-fat, low-carbohydrate “ketogenic” diet has been used since the early 1920s for the management of treatment-resistant epilepsy in children.

Why does an extremely low-carb diet cause ketosis? Even in the 1920s, it was obvious that ketosis meant that the liver was making huge amounts of sugar. Much of the sugar in the bloodstream of someone with untreated diabetes does not come from the starch or sugar in the food. Instead, it has been made out of protein from the food and from the body’s tissues. If the insulin-producing beta cells in the pancreas stop making insulin, the alpha cells in the pancreas assume that the blood sugar level must be low. As a result, the alpha cells will make huge amounts of a hormone called glucagon. Glucagon tells the liver to make glucose, to bring blood sugar levels back up to normal. An overdose of insulin kills people by preventing their pancreas from releasing glucagon, which would tell the liver to release glucose to correct the low blood sugar. That’s why glucagon is used as an antidote to insulin overdose.

The liver makes a lot of glucose out of its stores of a starch called glycogen. However, the liver can also make glucose out of amino acids (the building blocks of protein) and other noncarbohydrates. When the liver is making a lot of glucose, it may start to use up one of the materials that it needs for breaking fat down completely into carbon dioxide and water. As a result, more of the fat is processed through an alternative pathway that produces ketone bodies as byproducts.

If you are fasting, a little bit of ketosis is a good thing. Some of your brain cells can use some of the ketone bodies as an alternative fuel source. But the severe ketosis that goes along with severely high blood sugar in someone with untreated type 1 diabetes is a life-threatening emergency.
You can get ketosis from fasting, but you can also get it from an extremely low-carbohydrate diet. That is why children with severe epilepsy are sometimes fed an extremely low-carbohydrate (ketogenic) diet. This ketogenic diet has some important drawbacks. For one thing, it tends to stunt children’s growth, and it can lead to some severe side effects, including inflammation of the pancreas. Another drawback is that children do not like the diet, mainly because their food choices are limited. Eating even a little bit of carbohydrate stops the ketosis. For this reason, it is hard to get children to stick to the diet well enough to get benefits.

Most of the fats in our food contain mainly long-chain fatty acids. However, nutrition researchers realized that short- and medium-chain fatty acids are better at producing ketosis. Perhaps it is because the shorter-chain fatty acids go straight to the liver from the intestine. The longer fatty acids are absorbed through a different pathway, which does not go through the liver before it reaches the general circulation. Coconut oil is a relatively rich source of medium-chain fatty acids. So if you feed an epileptic child coconut oil, you can let them eat a bit more carbohydrate and protein, while still keeping them in ketosis.

Since coconut oil is so good at generating ketone bodies, there has been some interest in it for patients with Alzheimer’s disease. In Alzheimer’s disease, the brain is having some trouble with using glucose for energy. For this reason, some researchers suspect that the brain of someone with Alzheimer’s disease might work better if some ketone bodies were available. Yet this theory remains unproven.

The ketogenic diet is useful in cases of childhood epilepsy that do not respond to any other treatment. However, it is not a health-promoting diet for the general public. No society on earth has ever subsisted on a ketogenic diet for any length of time. Even Inuit (Eskimo) people, who lived on nothing but fatty meats and fish during the winter, did not go into ketosis unless they were fasting. Also, there is plenty of evidence that high-fat, low-carbohydrate diets lead to rapid aging and early death, even if they do not produce ketosis.

Like antiseizure drugs, a ketogenic diet may be good for some children with epilepsy but should not be routinely given to people who do not have epilepsy. Unless you have treatment-resistant epilepsy, you would be better off eating an extremely low-fat, high-carbohydrate diet based on starches and vegetables. The societies that have traditionally used coconut oil tend to have low rates of heart disease. However, that is usually because their overall intake of fat and cholesterol is low. Most of their calories came from carbohydrates (starches and sugars) in the rice and starchy vegetables (such as sweet potatoes and poi) that made up the bulk of their diet. Since these people lived in the tropics, they also ate a lot of fruit and vegetables. Some Polynesians eat a lot of coconut. However, they are generally eating whole coconut, rather than coconut oil. As a result, they get a lot of protection from the fiber content of the coconut. In the intestine, fiber binds to the cholesterol that the liver produces to help you digest fat. As a result, the cholesterol can leave the body with the feces, rather than being reabsorbed into the bloodstream.

If you want to lose weight and protect your heart and brain, don’t add coconut oil to your diet. Instead, remove oils and animal-source foods from your diet. The populations that eat a starchy, high-fiber diet based on low-fat plant-source foods have the cleanest arteries and the best chance at a long and healthy life.