Vegan for Life: Everything You Need to Know to Be Healthy on a Plant-based Diet

by Jack Norris

One ecological study that is familiar to many vegans is the China Study, which compared the types of food consumed and average disease rates in different counties in China, mostly during the 1980s. Although the China Study didn’t look at vegan diets, it did find that the more plant foods and less animal foods consumed in a given county, the lower the rates of chronic diseases like heart disease and certain cancers. It’s not possible to draw firm conclusions about diet and health from ecological studies like the China Study because this type of research doesn’t control for other factors. But the studies do give rise to hypotheses about diet that stimulate further research that is designed in a way to give us better answers.

Another ecological study that many vegans are familiar with looked at rates of hip fracture and protein consumption in different countries. The results showed that as protein intake increases, so does the rate of hip fracture. But contrary to popular opinion, that study didn’t show that high protein intake causes weak bones and in fact, it may have misled us about the relationship of protein to bone health. (We talk more about why that is in Chapter 5.) It did set the stage for clinical studies on how protein might impact calcium metabolism.

One interesting type of ecological study is the migration study. It looks at changes in health of people when they relocate and acquire the food and lifestyle habits of their adopted homeland. These kinds of studies can help show whether ris...

Much of what we know about the health of vegans comes from two large prospective studies, the Adventist Health Study in North America and the EPIC-Oxford Study in the United Kingdom. We describe these studies in more detail in Chapter 15.

The randomized clinical trial (RCT) is the gold standard in nutrition research.

We’ll look at a number of RCTs in Chapter 15 where we consider the ways in which diet impacts chronic disease. For example, the Ornish study, which explored the impacts of eating a vegetarian diet along with other lifestyle changes on atherosclerosis, is a well-known RCT.

Proteins in the human body tend to have a consistent percentage of the different EAAs. Because the percentage of EAAs in animal products and soybeans are a close match to those in the human body, proteins from these foods are considered “complete.” Plant foods like grains, beans, and nuts have a lower percentage of at least one essential amino acid, making them “incomplete.”

But when grains and beans are consumed together, their amino acid profiles complement each other and produce a mix that is “complete” and therefore a good match to the body’s needs.

Soon after that, research showed that it’s not necessary to eat complementary proteins at each meal because the body maintains a storage of the essential amino acids.3 We need to keep replenishing that storage with all the amino acids, which we can get by eating a variety of plant foods. But the old idea that certain combinations of plant foods—the complementary pairings—must be consumed together isn’t true.

all plant sources of protein contain at least some of every essential amino acid. In fact, you could get enough protein and all the essential amino acids by eating just one type of food like pinto beans. You’d need to eat a lot of them, though—about four cups per day.

The protein RDA for adults is 0.8 grams of protein per kilogram of body weight. The World Health Organization recommends a very slightly higher intake at 0.83 grams per kilogram of body weight.

It’s not a big difference, but vegans should strive for a protein intake of 0.9 grams per kilogram of body weight. This translates to around 0.4 grams of protein per pound of body weight. So a vegan who weighs 150 pounds would need 60 grams of protein (150 × 0.4) per day. Although the RDA for protein is based on total body weight, nutritionists often calculate protein needs based on “ideal” body weight. That’s because fat tissue maintenance requires very little protein. You can find a number of calculators online to determine your ideal body weight.

Since calculating protein needs is not an exact science, we encourage you to err on the side of a bit more protein (10 to 15 percent more) than your ideal body weight would require.

Legumes include beans, peas, lentils, soyfoods (like tofu, soymilk, and veggie meats), and peanuts. (Most people think of peanuts as nuts, but they are botanically legumes and, from a nutritional standpoint, they have more in common with pinto beans and lentils than walnuts and pecans.) Our food guide specifies at least three to four servings per day of these foods.

In addition to being protein-rich, these foods are the only good plant sources—with a few exceptions—of the essential amino acid lysine. A diet that gets most of its protein from grains, nuts, and vegetables is likely to be too low in lysine. You can get a rough idea of how much lysine you need by multiplying your weight (in pounds) by 19. This calculation includes a small factor that makes up for the slightly lower digestibility of protein from whole plant foods. For example, a person weighing 140 pounds would need 2,660 milligrams of lysine per day. The chart here shows that the best sources of lysine are legumes, quinoa, and pistachios.

But diets that are marginal in protein—not quite deficient, but not quite optimal—can result in loss of muscle mass, poor bone health, and compromised immunity. And those kinds of problems do occur in the United States.

Vegan diets that are low in protein-rich foods like legumes are likely to be too low in protein.

As we noted, the science on protein needs is still evolving and some experts believe that getting a little bit more of this nutrient has its advantages. Higher protein intakes may help manage appetite,7 improve blood pressure control,8 and can also protect bone and muscle mass.9 In particular, there are concerns that older people may need more protein to avoid muscle and bone loss.

One common belief, often voiced by critics of vegan diets, is that plant foods don’t provide adequate tryptophan. This essential amino acid is needed to make the neurotransmitter serotonin, and low levels of serotonin are linked to depression. Meat is higher in tryptophan than plants, but a well-balanced vegan diet is almost guaranteed to provide more than enough of this amino acid. The recommendation for tryptophan is 5 milligrams for every kilogram of body weight. Adding in a factor for plant protein digestion, this translates to a vegan RDA of 5.5 milligrams per kilogram of body weight or 2.5 milligrams of tryptophan per pound.

There is no question about whether vegan diets can provide enough calcium. They can. But that doesn’t mean that they always do. In studies of vegans, average calcium intakes have often fallen well below recommendations.

Getting enough calcium is important for bone health, but reducing the amount that is lost through the urine could be important, too.

There is some evidence that peak bone mass determines bone health and risk for osteoporosis in later years.

Beginning at age forty-five or so, there is a shift in metabolism and bone mass begins to decline. Efforts to slow calcium losses from the body and provide enough calcium to keep bones strong are important for preventing osteoporosis, especially for women, who can begin to lose bone rapidly after menopause.

Calcium is different from other nutrients in that it isn’t associated with an acute deficiency disease. With most nutrients, if your intake is too low, you’ll get sick. That’s not true for calcium because levels in the blood are very tightly controlled. Even a small change in those levels can be life-threatening, so the body utilizes stored calcium in the bone plus the filtering system of the kidneys to keep calcium concentrations within strict boundaries. You can’t ascertain calcium status by measuring blood levels of this mineral because those levels are always the same. But while a low calcium diet doesn’t cause an acute nutritional deficiency, a chronically low intake can raise the risk for osteoporosis later in life.

Eighty percent of Americans with osteoporosis are women.

Consuming isolated protein—that is, just the pure protein portion of a food—has a direct and significant effect on calcium losses, but that effect is often lost when subjects are fed whole, high-protein foods. The reason may be that other factors in foods, like phosphorus, counteract the urinary losses.15 • While protein can increase calcium losses, it also enhances calcium absorption from foods. There is evidence that these positive effects on absorption may outweigh or at least compensate for the negative effects of calcium loss.16,17 In fact, it appears that the calcium that shows up in the urine when people eat more protein is not actually coming from the bones, which means it might simply be due to the higher absorption of calcium from the diet.18,19 • In some studies, higher protein intake is actually associated with better bone health, and protein supplements can help bone fractures heal more quickly.20–23

Studies of vegetarians suggest that emphasizing protein-rich foods is good for bones. Among Seventh-Day Adventists, women who had the highest intakes of legumes and veggie meats were less likely to suffer a wrist fracture, and in both men and women, eating more of these foods was linked to lower risk for breaking a hip.25,26 The best overall approach for bone health appears to be a diet that provides plenty of calcium and protein as well as a generous intake of fruits and vegetables, which can help neutralize any potential acidic effect of protein-rich foods.27

These studies tell us that many vegans need to give more attention to both calcium and protein to protect their bone health.

Aiming for the US recommendation of 1,000 milligrams for adults and 1,200 for those over fifty can provide good insurance. At this point, we see no reason why vegans would need any less calcium than people eating other types of diets.

A few leafy green vegetables that are rich in calcium—spinach, beet greens, Swiss chard, and rhubarb—are also high in naturally occurring compounds called oxalates that bind calcium and make it essentially unavailable to the body. But the availability of calcium from low-oxalate vegetables—kale, collards, broccoli, and turnip greens—can be as high as 50 percent.

The recommended intake of 1,000 milligrams of calcium is based on the assumption that most people absorb around 30 percent of the calcium in their diet.

Aim to eat at least 3 cups per day of some combination of foods that are good sources of well-absorbed calcium. These include fortified plant milks, fortified juices, calcium-set tofu, oranges, and low-oxalate leafy green vegetables like kale, mustard greens, turnip greens, bok choy, and collard greens.

Learn to love greens! The ones that are low in oxalates—kale, turnip, mustard, and collard greens—are good sources of well-absorbed calcium as well as other nutrients that are important for bone health.

If your intake falls short, make up the difference with a small supplement. (Although high-dose supplements of calcium have been linked to risk for heart disease, a small daily supplement of 500 milligrams or less is safe.)

While the focus has long been on bone health, more recent research suggests that suboptimal vitamin D levels are linked to fibromyalgia, rheumatoid arthritis, multiple sclerosis, depression, muscle weakness, diabetes, hypertension, and cancer.

To maintain those levels, the current RDA for vitamin D in adults is 600 International Units or 15 micrograms (vitamin D can be measured either way; 1 microgram equals 40 International Units). But many experts believe that blood levels should be much higher and that levels above 30 ng/ml are preferable for optimal health.37 Until the issue is resolved, taking a supplement providing between 600 and 1,000 International Units of vitamin D is a reasonable choice. It’s always a good idea to include an assessment of vitamin D levels when your doctor orders routine blood tests.

For vegans who do not have a vitamin D deficiency, taking a daily supplement of 600 to 1,000 International Units of vitamin D2 appears to be as effective as vitamin D3 for maintaining healthy blood levels of vitamin D. If you are deficient in vitamin D and have had trouble raising your levels, then it’s possible that vitamin D3 is the best choice.

Older people need longer exposure and so do people with dark skin. Smog can interfere with vitamin D synthesis and the farther away you are from the equator, the more sun exposure you need to make vitamin D. Some research suggests that Americans living in the northern part of the country do not make any vitamin D during the winter months.41

To make adequate vitamin D for one day, a light-skinned person needs ten to fifteen minutes of midday (10 a.m. to 2 p.m.) sun exposure, without sunscreen, on a day when sunburn is possible.42 Dark-skinned people need twenty minutes and older people need thirty minutes.

good sources of potassium and magnesium, two minerals that are involved in bone metabolism.45 Recommendations for potassium are 2,600 milligrams per day for women and 3,400 for men. Many Americans fall short of meeting potassium needs.

Recommendations for magnesium intake are 320 milligrams for women and 420 milligrams for men. But again, higher intakes might have some benefits for managing blood pressure. Intakes of both potassium and magnesium above the RDAs are safe when these minerals come from foods rather than supplements.

Inadequate intake of this vitamin, which is found in many leafy green vegetables, is linked to poorer bone density and greater likelihood of fracture.

Making sure you meet needs for protein, calcium, and vitamin D, and striving to eat plenty of fruits and vegetables are important habits for protecting bone health. Limiting sodium intake and being moderate with alcohol consumption are helpful as well since both are linked to risk for bone loss.

But exercise may be the most important factor of all in preventing bone loss. Staying active is crucial to bone density and strength.

Finally, maintaining a healthy weight can protect your bones, and by this, we mean don’t let your weight get too low. When it comes to bone health, being a few pounds above your ideal weight is better than being a few pounds below it.

All vegans need to take a vitamin B12 supplement or consume foods that are fortified with this nutrient.

What studies like this tell us is that some sea vegetables may be contaminated with vitamin B12 but that this doesn’t present a practical or reliable way to meet needs.3

few studies have found that when vitamin B12 is injected into the growing medium of plants, some of these plants can take up enough of the vitamin to provide reasonable amounts in the diet. This may supply us with new B12 sources for vegans in the future, but for now is not of any practical significance.

We have a rather complex physiological way of recycling it, and we also can store relatively large amounts in our livers—sometimes enough to prevent overt deficiency for as long as three years.

But sometimes B12 deficiency anemia is “masked” by the vitamin folic acid (also called folate), which can step in and do part of vitamin B12’s job. So you can be deficient in vitamin B12 but not have anemia if your diet is high in folate. This may sound like a good thing, but it’s not since folic acid won’t prevent the nerve damage that can occur with B12 deficiency.