For years, the bestseller lists have been dominated by books urging people to eat plenty of meat and fat but to shun carbohydrates. The Atkins Diet led the parade; but there have been many imitators, such as the Zone, the South Beach Diet, the Paleo Diet, and the Dukan Diet. Even some of the vegan-oriented books encourage people to avoid starches. Yet the scientific evidence shows us that human beings are specifically adapted to thrive on a starchy diet. So I was delighted to see that the title of Dr. John McDougall’s latest book is The Starch Solution. He explains something that nutritional epidemiologists and experts on clinical nutrition have known for many years, namely that human beings stay naturally slim and healthy on a diet based on unrefined starches and vegetables.
According to my calendar, winter began just a few days ago. But as far as my ability to make vitamin D is concerned, winter actually began in October and will last until the middle of March. If I run short of vitamin D before March, I have three options for getting more vitamin D: take a tropical vacation, go to a tanning salon, or take vitamin D pills.
Vitamin D isn’t really a vitamin. It’s a hormone that is made when the ultraviolet light from sunlight hits your skin. Some of the sun’s ultraviolet light gets filtered out by the atmosphere, especially by the ozone layer. Where I live, the sunlight is at such a low angle from October through March that practically all of the ultraviolet light gets filtered out. Thus, we have a tanning index of zero even if there isn’t a cloud in the sky.
A light-skinned person in Boston can get enough vitamin D from getting only a few minutes’ worth of sun exposure on his or her face, arms, and hands at midday two to three times a week during the spring, summer, and fall. A person of African ancestry might need ten times as much sun exposure to make the same amount of vitamin D.
Natural summer sunshine is the best way to get vitamin D. Sunshine may have other important effects on the body besides producing vitamin D. Of course, too much sun exposure can cause skin damage and increase the risk of skin cancer.
Sunlamps or a tanning bed can also help restore normal vitamin D levels in the wintertime, especially in people who have an intestinal disease that makes it hard for them to absorb fat-soluble vitamins from their food. Tanning beds should be used cautiously because the ultraviolet light they produce is so intense.
You can also buy vitamin D supplements, but one nutrition expert warns that vitamin pills should be used as a last resort. Although low vitamin D levels have been associated with various diseases, such as multiple sclerosis, treatment with vitamin D supplements has not necessarily been shown to be useful in treating those conditions.
Here’s an interesting article about research that attempted to figure out exactly why Black children’s growth was so badly stunted in the 19th century United States. It concluded that most of the stunting was due to general malnutrition. The growth of some dark-skinned children, especially in the northern states, could also have been limited by shortages of vitamin D, the sunshine vitamin.
Vitamin D Comes From Sunshine, Vitamin B12 From Bacteria
How can a diet consisting mainly of leaves give gorillas enough protein to grow big and strong? It’s because leaves contain protein. Leaves are low in calories, but a lot of their calories come from protein. In fact, most ordinary plant foods contain more than enough protein to meet human nutritional needs. Nutrition scientists have known for nearly a hundred years that as long as you are eating any reasonable plant-based diet, if you take care of the calories, the protein takes care of itself.
It’s hard even to design a plant-based diet that would be deficient in protein while providing enough calories. You’d have to include nothing but some low-protein fruit, such as apples. Or you could cheat and use sugars and fats that have been extracted from plants, leaving the protein and other nutrients behind.
Not only do plants provide enough protein for human nutrition, the proteins they contain are nutritionally “complete,” as far as human protein needs go. That means that they contain enough of all of the different amino acid “building blocks” that human bodies need.
The only “incomplete” protein you are likely to find on your dinner plate is gelatin, which comes from animal bones. Gelatin is incomplete because tryptophan is destroyed in the manufacturing process. You’d get very sick if you tried to use gelatin as your sole source of protein.
Plant foods also contain the minerals that are essential for human nutrition. Plants absorb these minerals, such as calcium and iron, from the soil. After all, where did the cows get the calcium that goes into their milk? Where did they get the iron that goes into their flesh?
Plants also provide nearly all of the vitamins that are essential in human nutrition. The exceptions are vitamin B12, which is made by bacteria, and vitamin D, which your body can make for itself if you go outside in the sunshine. People who eat a purely plant-based diet are generally advised to take a vitamin B12 supplement. Whether you need a vitamin D supplement depends on how dark your skin is and where you live. Your doctor can do a simple blood test to see whether you have enough of both of these vitamins.