Vegan diets are recommended by many researchers and doctors because they may help to prevent heart attacks and some cancers, but a diet that excludes all animal products can increase risk for deficiencies in dietary protein and vitamin B12. Older people in particular can be harmed by vegan diets because these deficiencies may increase their chances of suffering from muscle weakness, osteoporosis, lack of coordination, falls and broken bones (Advances in Nutrition, published online Feb 2, 2022). All people lose muscle, bone and coordination as they age, and after age 50, people can be expected to lose about 1-2 percent of the size of their muscles each year (Am J Clin Nutr, 2002;76(2):473-81).
Consequences of Not Getting Enough Protein As You Age
One in three older adults don’t eat enough protein to maintain muscle size and strength (Contemp Clin Trials, 2017 Jul; 58: 86–93), often due to:
• decreased appetite
• dental disease
• decreased senses of taste or smell
• difficulty swallowing
• limited finances
Older people who ate the most protein were 30 percent less likely than those who ate the least protein to be incapacitated by loss of muscle strength and coordination (The Journals of Gerontology, Jan, 2020;75(1):123–130). Older people who ate the least protein were twice as likely to have difficulty walking or climbing steps as those who ate the most (J of the American Geriatrics Soc, Jan 2019;67(1):50-56).
You need 21 amino acids, the protein building blocks that make up the muscles and other cells in your body, and nine of these amino acids must be taken in from the food that you eat (the “essential amino acids”). Meats and other foods from animals contain all of these essential amino acids, but plants that are used for food do not contain all nine. For example, beans do not contain methionine, but corn does, so if you eat corn together with beans, you can provide your body with all nine essential amino acids. (Corn does not have lysine or tryptophan, which are found in beans). Vegans who eat no animal sources need to take in lots of plants to provide their bodies with enough protein to maintain muscle size and strength. Vegans can, and do, become protein deficient and as a result, lose muscle size and strength (J of Nutrition, Sept 2015;145(9):1981–1991). This is more likely to happen as people age.
Lack of B12 Can Damage Your Brain and Nerves
Vitamin B12 deficiency in North America occurs in about 20 percent of people over age 60 (BMJ, Sept 4, 2014;349:g5226). A deficiency of vitamin B-12 can lead to anemia, fatigue, muscle weakness, intestinal problems, nerve damage, dementia and mood disturbances. Vitamin B12 is found only in animal food sources such as meat, fish and chicken. The recommended daily amount of vitamin B-12 for adults is 2.4 micrograms. However, the absorption of vitamin B12 is very low and requires both stomach acidity and a chemical called intrinsic factor. With aging, a person loses stomach acid, so the incidence of B12 deficiency increases significantly with aging, even in some people who take B12 supplements. I recommend having your blood level of B12 checked, and if it is below 250 picograms per milliliter (pg/mL) or 184 picomoles per liter (pmol/L), check with your doctor about correcting the deficiency. For a list of signs of vitamin B12 deficiency see Vitamin B12: One Supplement You May Need
Combating Loss of Muscles and Bones
I believe that people who follow any of the high-plant diets should also do some form of resistance exercises to help protect their bones. The EPIC-Oxford study followed 29,380 meat eaters, 8,037 fish eaters, 15,499 vegetarians, and 1,982 vegans for an average of 17.6 years, and found a marked increase in fractures in all the non-meat-eater groups with the most fractures of all in the vegans (BMC Medicine, Dec 2020;18(353)). Overall, compared to meat eaters, vegans had higher risks of total, hip, leg, and vertebral fractures, while fish eaters and vegetarians had higher risk of hip fractures. Other studies show that vegetarians have lower bone densities than meat-eaters (Am J Clin Nutr, 2018;107:909–20; Public Health Nutr, 2008;11:564–72), possibly because they weigh less and take in less calcium (Nutr Res, 2016;36:464–77) and protein (Nutrients, 2019;11:1–18).
• Vegetarian and vegan diets are associated with decreased risk for heart attacks and certain cancers, but they are also associated with increased risk for nerve damage and loss of muscles and bones. I do not think it is necessary to avoid all animal products.
• I recommend a plant-based diet that includes salmon, trout, sardines and other small fish, because they contain omega-3 fatty acids and do not contain significant amounts of heavy metals. Fish contain lots of B12 and all the protein building blocks.
• I recommend that everyone who is healthy do some form of resistance exercise to strengthen their bones and muscles. Check with your doctor. You can help to slow muscle loss by performing resistance exercises and eating an adequate amount of protein-rich food (Nutrients, Feb 2018;10(2):180).