I disagree with both of these claims. Humans can live a healthy lifestyle both as vegans and non-vegans (even the American Dietetics Association says so!)
However, if this is true, then our consumption of animal products is purely a matter of taste and not one of necessity. Can we really justify the suffering and death of billions of animals each year on the basis of taste alone? Are we prepared to say that fleeting gustatory pleasure is worth a lifetime of suffering for the animal who provided it?
What you should know to be a healthy veganHere is the official stance of the American Dietetics Association:
"It is the position of the American Dietetic Association that appropriately planned vegetarian diets, including total vegetarian or vegan diets, are healthful, nutritionally adequate, and may provide health benefits in the prevention and treatment of certain diseases. Well-planned vegetarian diets are appropriate for individuals during all stages of the life cycle, including pregnancy, lactation, infancy, childhood, and adolescence, and for athletes."If you click here, it will take you to the ADA website, where you will see a link to a pdf. This pdf gives a really great and detailed overview of the major nutrients that are of particular consideration to vegans and vegetarians.
While the media, as well as much of the public, over-emphasizes the difficulty of obtaining sufficient protein on a vegan diet, there is one nutrient that you really must consider carefully as a vegan. This nutrient is B12. B12 is the only vitamin that cannot be obtained from plant sources, and it is integral to brain and nervous system function and to production of blood. Becoming deficient in this vitamin can be dangerous, and the effects are irreversible. However, it is easy to obtain adequate B12 on a vegan diet, since many non-dairy milks are now fortified with the vitamin and ingredients like Red Star Nutritional Yeast are common to vegan cooking. However, it's always a good idea to take a multivitamin or a B12 supplement. I had my B12 levels tested after being a vegan for nearly two years, and found that my levels were perfect. If you want more information on B12, you can go here.
To some people, this B12 issue may constitute a reason to believe that vegan diets are "unnatural" or just a plain bad idea, but consider this: milk (dairy or non-dairy) does not naturally contain vitamin D. Vitamin D is added because many people are vitamin D deficient, seeing as the major natural dietary sources of the vitamin include mushrooms and liver. We don't eat those things often enough (if at all) or live in climates sunny enough to stave off vitamin D deficiency. Similarly, iodine is added to salt because many people have difficulty acquiring this element through their diet (fish and sea vegetables). If you want to put B12 in perspective even further, go here.
The Good NewsA healthy vegan diet has been shown to encourage weight loss, improve cardiovascular health, increase insulin sensitivity, and treat diabetes more effectively than conventional diabetes diets. In addition, the American Institute for Cancer Research has endorsed a plant-based diet as an effective way to prevent cancer risk.
If you want more information on basically any nutrition topic you should go here. Nutritionfacts.org is a great resource because not only does it cover a wide range of topics, it goes to the peer-reviewed literature to find out what science really has to say about nutrition.
Finally, I'm linking to my favorite vegetarian multivitamin, as well as my favorite vegan D3 (D3 supplements are superior to D2, but are less often produced from vegan sources).
*Please note that the information on this page is intended as a resource and does not constitute professional nutritional advice. I strongly encourage you to educate yourself on dietary requirements and how you can fulfill them.