This article was originally published in March of 2007.

I'm grateful that my recent blog entry on the documentary Earthlings generated widespread interest (more than 12,000 unique views within 48 hours of its posting), and that it caused many of our readers to consider the impact that all of our daily food and lifestyle choices have on other living creatures.

The following comment left by a reader named Mike Lautermilch gives voice to what I feel is one of the main messages of Earthlings:

"When we feel we must kill an animal for some legitimate purpose, death should be instantaneous, unsuspected, and as non-traumatic as possible. If at any time, for any reason, it looks as though a quick, non-traumatic death of an animal is not possible to deliver, then it should be postponed until it IS possible."

I'm confident that Mr. Lautermilch would agree that this philosophy of minimizing unnecessary suffering is also applicable to how living creatures should be treated at all times, not just to how they should be treated in the moment before they are about to die.

A handful of readers wrote in to ask why I believe that it is difficult for most people to experience their best health while following a 100 percent vegan diet for more than several years.

I have come to this belief through my own personal experiences and also through my experiences as a health care provider.

For some of the reasons mentioned in Earthlings plus personal health purposes, I chose to adopt a 100 percent vegan diet in the summer of 1999 following a 14-day water fast. I stayed on this diet for close to four years. But I only felt like I was optimally supporting my health for the first two of those years. The last two years were marked by low energy, constant cravings for some animal foods, skin breakouts, and emotional lows that I had never previously experienced.

My strict vegan diet consisted of plenty of fresh leafy greens, tomatoes, bell peppers, cucumbers, celery, sprouts, many varieties of steamed greens, steamed root vegetables like potatoes, sweet potatoes, hard squashes, carrots, and red beets, whole grains like brown rice and quinoa, a wide variety of fruits (including avocados), legumes like chickpeas and red beans, and small amounts of raw nuts and seeds. I also drank fresh lettuce-based vegetable juices a few times a week.

Why did I stick with this diet for the two years during which I suffered with health challenges? Because I had faith in the books that I had read on this topic, and in the guidance that a few prominent physicians had given me. If these doctors and the folks I read about in books could be healthy on a pure vegan diet for decades, I was convinced that I could follow their footsteps.

At some point during my trials as a non-thriving strict vegan, I found a series of articles by natural health writer, Chet Day, that outlined some of the potential problems with being on a pure vegan diet for the long term. These articles were a real turning point for my health, as they helped me to finally snap out of my cloud of unquestioning faith in people who insist that a pure vegan diet is the best diet for everyone.

I added organic eggs from free-range birds, cod liver oil, and a small amount of fish to my diet. Over a period of about three months, this minor adjustment to my diet led to significant health improvement. My energy came back, my cravings disappeared, I stopped having skin breakouts, and most notably, I felt physically strong again. I vividly remember going from being able to do about 3 sets of 10 pull-ups before getting exhausted to being able to do 100 full body weight pull-ups within 20-30 minutes (in sets, with rest in between sets). To have my stamina and strength come back in such a short period of time was a remarkable experience.

Shortly after restoring my health by adding a few clean animal foods to my diet, I discovered that the folks who had originally convinced me to follow a pure vegan diet actually added small amounts of raw, organic cheese and, in one case, organic eggs to their meals. To put it simply, I was astonished that they felt that "sprinkling a little goat's cheese on my salad" was not an important point to share with folks who are desperate for comprehensive guidance on how to recover from serious health conditions.

To this day, I cannot understand how some people can pound home the message of being 100 percent vegan for optimal health while they include small amounts of animal foods in their diets at home. The only explanation that I can think of is that they might feel that by admitting to using small amounts of animal foods, their philosophies are not as tight as they would like them to be, which might cause people to take the idea of "everything in moderation" in the wrong direction. Put another way, maybe these folks feel that if they say that there is a little room for animal foods, then people will go from eating small amounts here and there to going right back to a meat-based, sugar-laden, standard North American diet, which is clearly not a health-promoting diet. But who knows what these folks are really thinking - I'm just speculating on what might motivate such incongruent behavior.

I would like to add that I know people who I believe have been 100 percent strict vegans for many years, some approaching two decades. But the folks I know who fall into this category have always been honest about health challenges that they have. I respect these people because I know that they are deeply committed to being strict vegans even in the face of having health challenges that I believe are partly associated with being on a strict vegan diet. I can't say that all of them attribute their health challenges to a strict vegan diet, but the point is that they are honest about their diet and health.

Which brings me to an important point: if you are thriving on a strict vegan diet (no animal foods ever, including eggs and dairy), I am happy for you. Truly, if I could thrive on a 100 percent vegan diet, I would go back to it this instant. How could I not after having watched Earthlings?

If you wish to adopt a strict vegan diet because Earthlings has moved you to do so, I wish you the very best, and I hope that you thrive in the short and long term.

I also hope that if you develop chronic health problems like low energy, skin breakouts, weak teeth and gums, brittle hair, weak nails, or unusual emotional instability, you do not stick to a 100 percent vegan diet over the long term just because someone has told you that you are just detoxing or that you just need to work at handling stress in a healthier way. Yes, it is possible to experience beneficial cleansing reactions while on a strict vegan diet, but there is a difference between cleansing over a range of a few days to a couple of years versus having long standing health problems related to malnourishment. And malnourishment can happen with any type of diet, including a strict vegan diet.

Bottom line on this point: don't let another person's opinion overpower the realities of your health status; if you are having health problems while on a strict vegan diet, look to make some adjustments that make sense to you. By all means, try to make non-dietary lifestyle adjustments first, like getting more sleep or regularly engaging in meditation/prayer/relaxation sessions. But if you continue to have health problems despite going through a fair trial of such lifestyle adjustments, please don't ignore the possibility that some dietary modifications may help you like they have helped me, dozens of people who have visited my clinic for guidance on this issue, and many other former strict vegans.

What follows is a list of nutrients that people on 100 percent vegan diets stand a greater-than-normal chance of becoming deficient in over the long term:

Vitamin B12 Similar compounds found in algae are known as vitamin B12 analogues. While vitamin B12 analogues may behave as vitamin B12 does in humans, it's probably wise to ensure optimal B12 status by including small amounts of vitamin B12-rich animal foods in your diet. Vitamin B12 that is produced by bacteria that live in your intestines is mainly produced in your large intestine (colon). Since absorption of nutrients occurs in the upper third of your small intestine, most vitamin B12 that is produced by intestinal bacteria cannot make it into your blood to nourish your cells. Animal foods are the most reliable, concentrated dietary sources of naturally occurring vitamin B12. DHA and EPA DHA and EPA are omega-3 fatty acids that are not found in plant foods, with the exception of seaweed. Yes, your body is capable of converting an omega-3 fatty acid called ALA, found in many plant foods, to DHA and EPA. But the conversion from ALA to DHA and EPA is not always an efficient process for some people. For more information on this topic, view the following article: Making Sense of Omega-3 Fatty Acids. Vitamin A There are no plant foods that contain vitamin A. A variety of plant foods contain antioxidants called carotenoids that can be converted to vitamin A in your blood, but there is evidence that indicates that carotenoids are not always efficiently absorbed, which can result in a vitamin A deficiency if you do not eat any foods that contain actual vitamin A. For more information on this topic, view the following article: Healthy Foods that Contain Vitamin A. Cholesterol and Saturated Fats Undamaged cholesterol and saturated fats are needed by your body for many important functions. For more information on this topic, view the following article:

Healthy vs. Unhealthy Fats and Oils Although there are trace amounts of cholesterol and some saturated fats in plant foods, a strict vegan diet is typically low in dietary cholesterol and saturated fats, unless palm oil and/or coconut oil are staples. Although your body can manufacture cholesterol from other nutrients, if your saturated fat intake is low, you stand a good chance of having low blood cholesterol, which can increase your risk of suffering from a variety of health challenges, many of them related to endocrine dysfunction, as cholesterol is needed to manufacture reproductive and stress-related hormones. Zinc, Iron and Calcium Strict vegans who regularly eat whole grains that have not been soaked, fermented, or sprouted stand a higher-than-average risk of developing mineral deficiencies, the most common of which are zinc, iron, and calcium deficiencies. Whole grains that are not soaked, fermented, or sprouted have high levels of phytic acid in their bran, which can bind onto these minerals in your small intestine, preventing them from getting absorbed into your bloodstream.

Based on my personal and professional experiences, I have come to believe that a plant-based diet is a health-promoting diet for the vast majority of people in our world. Plant-based means fresh vegetables, fresh fruits, properly prepared whole grains (gluten-free are best), legumes, and small amounts of nuts and seeds. Add to such a diet small amounts of clean animal foods, and I think you have a well balanced and nutritionally complete diet for most people.

If you wish to avoid all flesh meats for reasons cited in Earthlings, then perhaps you can consider organic eggs from birds that are humanely treated as your source of animal-based nutrients. If you can tolerate dairy products, you can also consider organic varieties, preferably those that are raw and from cows, goats, or sheep that are allowed to live in relative peace.

Going beyond the realm of our food choices, let's remember that the clothes and shoes that we choose to wear, the accessories, furniture, and toys that we choose to use, the pets that we choose to acquire/adopt, and the entertainment that we seek are choices that can also contribute to unnecessary suffering of animals.