I just read an article by Reed Mangels, PhD, RD, Nutrition for Young Vegetarians: Birth to One Year, from the Vegetarian Nutrition Dietetic Practice Group’s newsletter (Vegetarian Nutrition Update Vol XXI, No. 4, 2013). It is not available to the public, so I cannot link to it. But it inspired me to add some info on infants and vitamin D to the article Calcium and Vitamin D:
“A 2010 study found that breast milk was not a sufficient source of vitamin D (1). A 1985 study recommended exposing babies to 30 minutes of sun a week wearing only a diaper in order to provide sufficient vitamin D (2), however, the American Academy of Pediatrics recommends no sun exposure for infants. The authors of the 2010 study recommend that all infants get the RDA for vitamin D of 400 IU via infant formula or vitamin D drops.”
Mangels’ article also pointed out a recent study (3) that found, to quote the abstract, “the risk of [celiac disease] was significantly reduced in infants who were breast feeding at the time of gluten introduction (pooled odds ratio 0.48, 95% CI 0.40 to 0.59) compared with infants who were not breast feeding during this period.”
References
1. Liang L, Chantry C, Styne DM, Stephensen CB. Prevalence and risk factors for vitamin D deficiency among healthy infants and young children in Sacramento, California. Eur J Pediatr. 2010 Nov;169(11):1337-44. | link
2. Specker BL, Valanis B, Hertzberg V, Edwards N, Tsang RC. Sunshine exposure and serum 25-hydroxyvitamin D concentrations in exclusively breast-fed infants. J Pediatr. 1985 Sep;107(3):372-6. (Abstract only.) | link
3. Akobeng AK, Ramanan AV, Buchan I, Heller RF. Effect of breast feeding on risk of coeliac disease: a systematic review and meta-analysis of observational studies. Arch Dis Child. 2006 Jan;91(1):39-43. (Abstract only) | link
I got an email from a reader who runs a vegetarian organization saying that he has been receiving a lot of questions about processed foods. He passed on the questions to me and asked me to write an article. Here are the questions:
1. The main questions/statements I’ve been getting are largely of the “all processed foods are poison” and “are vegan processed foods similar to processed meats?” I doubt that vegan meats contain nitrites, for example, but i do wonder if you know of any connections between vegan meats and bowel cancer.
Nitrites are used to cure meats in order to reduce bacteria growth, but are not used to cure vegan meats. Another concern with meats are the heterocyclic amines formed especially in burned meat. These are not found in vegan meats.
2. “What about all of the salt in tofurky?” and the like?
The amount of sodium in processed foods is something that you should pay attention to.
Recently, there has been a big controversy over how much sodium people should aim for. You can read a concise summary of the controversy in The New Salt Controversy from the Harvard School of Public Health. A summary of the article is that there is good evidence that all Americans should aim for a daily sodium intake of no more than 2,300 mg. Additionally, people with elevated blood pressure should aim for a sodium intake of 1,500 mg, and this might even be a good idea for almost everyone.
If you have blood pressure on the lower end of normal, then it’s not so necessary to aim for 1,500 mg and, in fact, the Mayo Clinic recommends that people with hyoptension actually eat more sodium (see Low blood pressure: Treatments and Drugs).
One thing to be aware of when reading about sodium is the difference between salt and sodium. Salt is sodium chloride and 10,000 mg of salt equals 4,000 mg of sodium.
High sodium intakes can also contribute to calcium loss from the bones, kidney stones, and possibly stomach cancer. You can read more details in the Linus Pauling Institute’s article Sodium. My sense from the article is that sodium intakes as low as 2,300 mg per day probably do not contribute to these diseases. The article also points out that a diet high in fruits, vegetables, and legumes may help counteract the effects of a high sodium intake on blood pressure.
So what does this mean for vegans? One, you should regularly get your blood pressure tested. Two, unless it is so low that you don’t feel a need to limit sodium intake (and I cannot answer this question for any given individual, you would need to talk to your physician), aiming for as low as 2,300 mg/day is important. If you are at risk for, or have, high blood pressure, limit sodium intake to 1,500 mg per day.
Sodium is mostly found in processed foods. If you do not add salt to whole plant foods, they will contribute almost no sodium. Carrot juice is one exception and there might be some others. In fact, a completely whole foods vegan diet might not meet the DRI for sodium of 1,500 mg for people 9 to 50 years old (see Sodium for the DRI for other age groups).
For a vegan to figure sodium intake, they only need to worry about the processed foods or added table salt (a teaspoon of table salt contains 2,325 mg of sodium).
Here might be a typical day of high-sodium foods for me:
On this regimen, I have kept my blood pressure on the lower side of normal, though I should also point out that during the warmer months I exercise in the heat and sweat out a lot of sodium.
As you can see, I don’t particularly shy away from processed foods. Of course, I do eat fruits, vegetables, grains, nuts, and beans in addition to these foods.
3. “Why are so many people opposed to artificial meats?”
Let me count the ways.
Probably the most common objection is because many of them contain isolated soy protein. As the Declaration of Independence says, “We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, and that isolated soy protein is hazardous to your health.”
Joking aside, many people think that isolated soy protein is harmful. I have not seen the evidence for this, but I can understand why someone might want to approach it as “guilty until proven innocent.” If you are such a person, Tofurky does not use isolated soy protein in their meats. And Field Roast does not use any soy at all – they use gluten, which doesn’t sit much better with the whole-foods-only crowd!
Another objection is that people consider processed foods to be devoid of nutrients. You shouldn’t rely on only processed foods for all your nutrition, but even isolated soy protein isn’t completely devoid of nutrients (click here for nutrient breakdown).
Finally, some people think that it’s hypocritical for vegetarians to want to eat something that has the taste and texture of meat. These people are clueless as to why most people become vegetarian.
4. “What processed foods should I limit my consumption of?”
You can overdo any processed food, or any unprocessed food, for that matter. It really depends on your overall diet and how many total calories you’re eating.
If I have to pick foods to limit, I would suggest limiting fried foods to a couple servings per day and then watching your sodium intake as described above. Ten servings of soy per day is probably pushing the limits of wise dietary practices. Don’t cook with oils that are high in omega-6 fats; if you cook with oil then olive is probably the best. Too much refined sugar isn’t a good idea, though I don’t know what “too much” would be for any given individual. Dried fruit can cause cavities so I’d limit to a couple servings a day.
A few weeks ago, a meta-analysis of the zinc status of vegetarians was published (1). They only measured relative values of serum zinc and found that vegans had a slightly lower serum zinc level than non-vegetarians, a difference of 1.17 ± 0.45 µmol/l. For vegetarians in developed countries, the difference was even smaller at .76 ± .27 µmol/l.
Average serum zinc levels are around 20 µmol/l with a range of about 9 to 30 µmol/l (2), so it’s doubtful that the differences are meaningful. One caveat is that serum zinc levels are not necessarily indicative of the zinc levels in cells (3).
For full disclosure, I don’t rely only on my diet for zinc, I take a supplement and am under the strong impression that it helps prevent me from catching colds. I am, however, skeptical that the average vegan needs to supplement with zinc.
I have updated VeganHealth.org’s article Zinc with this information.
References
1. Foster M, Chu A, Petocz P, Samman S. Effect of vegetarian diets on zinc status: a systematic review and meta-analysis of studies in humans. J Sci Food Agric. 2013 Apr 17. | link
2. Ghasemi A, Zahediasl S, Hosseini-Esfahani F, Azizi F. Reference values for serum zinc concentration and prevalence of zinc deficiency in adult Iranian subjects. Biol Trace Elem Res. 2012 Dec;149(3):307-14. (Abstract only) | link
3. Dietary Supplement Fact Sheet: Zinc. Office of Dietary Supplements. National Institutes of Health. Last reviewed: June 05, 2013 | link
In January, I made a post saying that there was scant evidence that branched chain amino acids (BCAA) are important for sports nutrition (Branched Chain Amino Acids and Exercise). In response, a reader, who is a bodybuilder, told me that while BCAAs might not be important, leucine (one of the three BCAA) is likely important and is probably the reasons why whey protein powder has been shown to be better than soy for building muscle.
The reader passed on some abstracts and I found some others.
One was a study that showed that after 12 weeks of exercise in untrained men, 4 g/day of leucine led to a 41% increase in strength compared to a 31% increase for the placebo which was lactose. There were no differences in muscle mass. Okay, but is a 10% greater increase in untrained men really enough to worry about? Assuming that just eating 4 more grams of protein per day wouldn’t be just as good, I’d be surprised if the lactose group wouldn’t catch up if given a few more weeks of training.
Another two abstracts were studies comparing whey protein to soy: one in older men (2) and one in younger men (3). Both were simply measuring muscle synthesis one time after one bout of exercise. Free versions of both studies are linked from the abstracts below (I didn’t bother reading them). I don’t think these studies prove much and I don’t know if there are more impressive studies showing whey protein to be superior to soy.
Then in March, a study was reported that showed that rice protein was as effective as whey protein in increasing muscle mass (4). As of today, it does not appear to have been published in a peer-reviewed journal. This study was better designed (for our purposes) in that it was done on men who had been already involved in weight training. It was double-blinded and after 8 weeks of supplementing with one of the proteins at 48 g/day, there was significant increases in strength and muscle mass. There was no placebo group so who knows if either type of protein was necessary – perhaps just taking part in a study would be enough motivation to work out harder and have some gains in muscle mass.
In short, I don’t think there’s anything to worry about for vegan bodybuilders who are concerned that their soy or rice protein powders are not giving them the same edge as bodybuilders using whey protein.
Please note that I am not philosophically opposed to the idea that plant proteins might be inferior or to supplementing for better athletic performance. I think there is good evidence that elite vegan athletes might benefit from creatine (for recreational athletes, creatine’s probably not worth the hassle). But one should be very skeptical when it comes to sports nutrition supplements – there is a lot of money and enthusiasm behind finding supplements that can improve performance, but most turn out to be useless.
References
1. Ispoglou T, King RF, Polman RC, Zanker C. Daily L-leucine supplementation in novice trainees during a 12-week weight training program. Int J Sports Physiol Perform. 2011 Mar;6(1):38-50. | link
2. Yang Y, Churchward-Venne TA, Burd NA, Breen L, Tarnopolsky MA, Phillips SM. Myofibrillar protein synthesis following ingestion of soy protein isolate at rest and after resistance exercise in elderly men. Nutr Metab (Lond). 2012 Jun 14;9(1):57. | link
3. Tang JE, Moore DR, Kujbida GW, Tarnopolsky MA, Phillips SM. Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise in young men. J Appl Physiol. 2009 Sep;107(3):987-92. | link
4. Dutch, A. First Double Blind Study Proves Plant-based Rice Protein Has Identical Benefits To Animal-based Whey Protein. PR Newswire. March 11, 2013. | link
Just got around to reading this 2012 article from the Vegetarian Resource Group about a vegan with type 1 diabetes. It includes a link to a meal plan for vegetarians with type 1 diabetes:
A reader (thanks, Dan!) pointed out a follow-up study to one I had included in VeganHealth’s article Iron, about iron supplementation in women with unexplained fatigue who have low iron stores but do not technically have anemia. I updated the article:
“Two studies from Switzerland have shown that iron supplementation can reduce fatigue in premenopausal women (1, 2) whose hemoglobin levels are above 120 g/l (and thus not diagnosed with anemia). The most recent, from 2012 (2), was a double-blinded, randomized controlled trial in which 80 mg of ferrous sulfate (an iron supplement) per day for 12 weeks increased hemoglobin in women who had average serum ferritin levels of 22.5 µg/l. This increase in hemoglobin was matched with a 50% reduction in symptoms of fatigue (compared to only 19% for placebo). Improvements in hemoglobin were seen after 6 weeks.”
This study got me thinking… I remember back around 2001 when I was doing my dietetic internship at Georgia State. I was able to spend some time working at a couple of alternative health clinics that specialized in helping people with chronic fatigue. At that time, they were putting pretty much everyone on a low carb diet, which translated to more meat. I actually don’t know if many people made any sort of recovery from the fatigue – my memory is that one person I counseled had made a significant recovery while another hadn’t made any improvement, but I have no idea what the success rates were for the clinics. To the extent that a low carb diet helped, I wonder if it was merely due to the women getting more heme iron and curing an undetected deficiency.
Improving iron status is worth considering for anyone with fatigue whose hemoglobin is on the lower end of normal and who has a serum ferritin less than 50 µg/l.
Iron does seem to be a possible culprit in three of higher profile cases of young women becoming ex-vegan that come to mind, and perhaps it’s something to which our movement needs to be paying more attention.
While the studies above used iron supplements to increase iron status, don’t forget that adding a significant amount of vitamin C to meals has been shown to be better for increasing iron absorption than increasing iron (more info).
References
1. Verdon F, Burnand B, Stubi CL, Bonard C, Graff M, Michaud A, Bischoff T, de Vevey M, Studer JP, Herzig L, Chapuis C, Tissot J, Pécoud A, Favrat B. Iron supplementation for unexplained fatigue in non-anaemic women: double blind randomised placebo controlled trial. BMJ. 2003 May 24;326(7399):1124. | link
2. Vaucher P, Druais PL, Waldvogel S, Favrat B. Effect of iron supplementation on fatigue in nonanemic menstruating women with low ferritin: a randomized controlled trial. CMAJ. 2012 Aug 7;184(11):1247-54. | link
I’ve received this question twice in the past week, so thought I’d turn it into a post in case other people are wondering the same thing:
“Do you have any view on whether calcium and Vitamin D supplements should be taken at the same time to ensure they are absorbed properly? This seems to be the reason that calcium and Vitamin D are often sold in the same pill. Alternatively, if you aim to get Vitamin D from sunshine, should you wait to take the calcium supplement at that point of the day?”
There is no need to take vitamin D (or get sun) at the same time as you eat calcium. The vitamin D that you eat needs to be absorbed into your blood and then taken to the liver to be modified into a circulating, storage form of vitamin D known as 25(OH)D. Then, when your body senses that you need to absorb more calcium, the kidney further modifies the 25(OH)D into the hormone calcitriol. Calcitriol then increases calcium absorption. Vitamin D ingestion at a single meal will not have an effect on calcium absorption at that meal.
I have been silent lately due to updating the Iron article at VeganHealth.org. In the past, it has been just a mishmash of bits I’ve written as needed. It is now a well-organized, tight piece (I hope).
One new addition worth mentioning is on type 2 diabetes. Excerpt:
“There is evidence that the beta cells of the pancreas, which produce insulin, are particularly susceptible to oxidation from iron due to their weak antioxidant defense mechanisms. A 2012 meta-analysis of prospective studies found that higher iron stores (6 studies) and higher intakes (5 studies) of heme iron [a type of iron found only in meat] at baseline were strongly associated with a higher risk of type 2 diabetes (1). Higher intakes of non-heme iron were not associated.
“A cross-sectional study from the USA found lower ferritin [stored iron] levels in lacto-ovo vegetarians (35 µg/l) than meat-eaters (72 µg/l). The vegetarians also had higher insulin sensitivity. Upon giving phlebotomies to 6 male meat-eaters to reduce their ferritin levels, their insulin sensitivity increased. The authors suggested that the lower ferritin levels could be a reason why vegetarians had greater insulin sensitivity (2).
“It is possible that the lower risk of type 2 diabetes in vegetarians (see Type 2 Diabetes and the Vegan Diet), which has been shown to be independent of body mass index, could be partially explained by their lower iron stores.”
Link to full article: Iron. Warning: It’s long and not required reading. 🙂
References
1. Bao W, Rong Y, Rong S, Liu L. Dietary iron intake, body iron stores, and the risk of type 2 diabetes: a systematic review and meta-analysis. BMC Med. 2012 Oct 10;10:119. | link
2. Hua NW, Stoohs RA, Facchini FS. Low iron status and enhanced insulin sensitivity in lacto-ovo vegetarians. Br J Nutr. 2001 Oct;86(4):515-9. | link
“Essentially all of the great apes and their ancestors appeared to have eaten a C3-based diet, consuming fruits, leaves and other plants. Modern humans, on the other hand, rely much more on C4 plants, which include grains like wheat and corn.”
Based on some articles that were floating around the Internet suggesting that vegan infants might be at risk for vitamin A deficiency, I asked Reed Mangels, PhD, RD what evidence we have that the breast milk of vegan mothers is adequate in vitamin A. She wrote an article about it and posted it in the Vegetarian Resource Group’s blog:
“The bottom line – Vegan women who are breastfeeding should make sure that their diet includes good sources of precursors of vitamin A. These are foods rich in beta-carotene such as winter squash, carrots, pumpkin, sweet potatoes, cantaloupe, and green leafy vegetables. Dietary fat is needed to promote beta-carotene absorption so it is important that lactating women not overly limit dietary fat.”
