By Taylor Wolfram, MS, RDN, LDN

We created a new article to house research on miscellaneous disease rates of vegetarians, including cataracts. The page includes research that we previously reported on, and we also added the following study.

A recent prospective cohort study from Taiwan investigated the association between vegetarian diet and cataract risk (Chiu, 2021). The study analyzed 4,436 participants who were at least 40 years old with no history of cataracts, the majority of whom were Buddhist volunteers (who abstain from smoking and alcohol and are encouraged to eat vegetarian). Participants were followed for an average of 5.7 years. There were 1,341 vegetarians and 3,095 nonvegetarians.

Vegetarians consumed more soy, vegetables, nuts, whole grains, dietary fiber, vitamin C, folate, and vitamin A compared to nonvegetarians. There was no difference in intake of fruits or refined grains between groups. While data were not reported, the authors said dietary supplement use was similar between groups.

A vegetarian diet was associated with a 20% lower risk of cataracts (HR 0.80, CI 0.65-0.99; P=0.04) after adjusting for sex, education, alcohol, smoking, physical activity, comorbidities, body mass index (BMI), and Buddhist volunteer status. When analyzed by BMI, the association between vegetarian diet and cataract risk was significant for participants with a BMI of 24 kg/m² or greater (HR 0.70, CI 0.50-0.99; P=0.04), but not for those with a BMI less than 24 kg/m² (HR 0.86, CI 0.65-1.14; P=0.29).

Chiu THT, Chang CC, Lin CL, Lin MN. A Vegetarian Diet Is Associated with a Lower Risk of Cataract, Particularly Among Individuals with Overweight: A Prospective Study. J Acad Nutr Diet. 2021 Apr;121(4):669-677.e1.

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By Taylor Wolfram, MS, RDN, LDN

We recently updated our collagen article with a few studies investigating curcumin in the management of osteoarthritis.

Two meta-analyses of randomized controlled trials found that turmeric extract and curcumin significantly decreased joint pain, stiffness, and function in people with osteoarthritis, similar to that of ibuprofen (Daily, 2016; Wu, 2019). A more recent randomized controlled trial found that bioavailable turmeric extract was as effective as acetaminophen at reducing joint pain, stiffness, and function scores in people with knee osteoarthritis (Singhal, 2021). These supplements are promising plant-based options for treating osteoarthritis and may reduce the reliance on the animal product collagen for this purpose.

We encourage people with osteoarthritis to speak with their physician before changing regimens.

Daily JW, Yang M, Park S. Efficacy of Turmeric Extracts and Curcumin for Alleviating the Symptoms of Joint Arthritis: A Systematic Review and Meta-Analysis of Randomized Clinical Trials. J Med Food. 2016 Aug;19(8):717-29.

Singhal S, Hasan N, Nirmal K, Chawla R, Chawla S, Kalra BS, Dhal A. Bioavailable turmeric extract for knee osteoarthritis: a randomized, non-inferiority trial versus paracetamol. Trials. 2021 Jan 30;22(1):105.

Wu J, Lv M, Zhou Y. Efficacy and side effect of curcumin for the treatment of osteoarthritis: A meta-analysis of randomized controlled trials. Pak J Pharm Sci. 2019 Jan;32(1):43-51.

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by Taylor Wolfram, MS, RDN, LDN

A recent study compared three plant-based burgers available in the European Union (Beyond Burger, Incredible Burger, and Planty-of-Burger) to 85% beef burgers.

The main ingredients for the plant-based burgers include:

• Beyond Burger: pea protein isolate, canola oil, coconut oil
• Incredible Burger: soy protein, canola oil, coconut oil, wheat gluten
• Planty-of-Bburger: sunflower and pea protein concentrate, coconut oil, sunflower oil

All of the burgers contained beets for red color and resembled beef (as opposed to the traditional, more whole-foods-based patties).

Protein, sodium, and total and saturated fat content were similar between plant-based and cow-based burgers; alpha linolenic acid (ALA), omega-6 to omega-3 ratios, and medium chain triglycerides were also statistically similar. Plant-based burgers contained less cholesterol, trans fat, and zinc; more fiber, carbohydrate, and polyunsaturated fat (particularly omega-6 fatty acids); and twice as much iron.

A free version of the paper is available at the link from the citation below.

De Marchi M, Costa A, Pozza M, Goi A, Manuelian CL. Detailed characterization of plant-based burgers. Sci Rep. 2021 Jan 21;11(1):2049.

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We updated our article, Carnosine and beta-Alanine, to include the research since our previous update.

A summary of the changes:

• In the American College of Sports Medicine, Academy of Nutrition and Dietetics, and Dietitians of Canada’s 2016 Joint Position Statement on nutrition and athletic performance, beta-alanine was included in the list of supplements with evidence-based uses in sports nutrition (Thomas, 2016). They cite a 2014 systematic review of randomized controlled trials looking at carnosine’s impact on performance (Quesnele, 2014).
• A 6-month intervention study had 40 meat-eating women follow one of three diets: a lacto-ovo-vegetarian diet without supplementation, a lacto-ovo-vegetarian diet plus daily beta-alanine and creatine supplement, and a continued omnivorous diet as a control (Blancquaert, 2018). The vegetarian plus beta-alanine group experienced a significant increase in muscular carnosine at the end of the study. At 3 months, muscle carnosine content didn’t change in the vegetarian group that didn’t take beta-alanine or in the control group suggesting that a vegetarian diet doesn’t result in decreased carnosine in the body (muscle carnosine wasn’t measured at 6 months in these groups).

Longer, high-quality studies are needed to determine the long-term safety and efficacy of beta-alanine supplements.

We don’t know of any studies on beta-alanine supplementation or carnosine levels in vegans.

For those wishing to take them, there are numerous vegan beta-alanine supplements.

References

Blancquaert, 2018. Blancquaert L, Baguet A, Bex T, Volkaert A, Everaert I, Delanghe J, Petrovic M, Vervaet C, De Henauw S, Constantin-Teodosiu D, Greenhaff P, Derave W. Changing to a vegetarian diet reduces the body creatine pool in omnivorous women, but appears not to affect carnitine and carnosine homeostasis: a randomised trial. Br J Nutr. 2018 Apr;119(7):759-770.

Quesnele, 2014. Quesnele JJ, Laframboise MA, Wong JJ, Kim P, Wells GD. The effects of beta-alanine supplementation on performance: a systematic review of the literature. Int J Sport Nutr Exerc Metab. 2014 Feb;24(1):14-27.

Thomas, 2016. Thomas DT, Erdman KA, Burke LM. American College of Sports Medicine Joint Position Statement. Nutrition and Athletic Performance. Med Sci Sports Exerc. 2016 Mar;48(3):543-68.

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Two recently published studies from Israel have examined vegan diets in pregnancy.

The first examined 60 vegans, 64 vegetarians, 37 fish eaters, and 112 omnivores (Avnon, 2020a). The second study examined 234 vegans, 133 vegetarians, and 1,052 omnivores (Kesary, 2020). Both studies found that:

• Vegan women had a slightly lower body mass index prior to pregnancy than did omnivores. The second study reported that significantly more vegan women than omnivores were categorized as underweight prior to pregnancy (12.7% vs. 7.8%).
• Vegan women gained less weight during pregnancy than did omnivores (average of 25.5 lbs vs. 31.5 lbs in the first study; 26.8 lbs vs 30.4 lbs in the second study). The large standard deviation in weight gain suggests that some women gained too little weight in pregnancy.
• Infants of vegan women weighed less at birth than did infants of omnivores (average of 6 lb 10 oz vs. 7 lb 5 oz in the first study; birth weights were only specified as percentiles in the second study).

The first study found that the average birth weight of each group was within the normal range for the local population. The second study found that the average birth weight percentile was within the normal range.

These results suggest that while babies of vegan women may be slightly smaller than babies of omnivores, their birth weights, on average, are considered to be normal.

Both studies found that significantly more infants whose mothers were vegan were classified as being small for gestational age compared to infants whose mothers were omnivores. Babies that are classified as small for gestational age are smaller than 90% of babies of the same gestational age and have a higher risk of problems like low blood sugar and difficulty maintaining body temperature after birth.

Many factors can result in having a small for gestational age infant including the parents being smaller; the mother having conditions such as diabetes, high blood pressure, or an infection; problems with the placenta; and birth defects. These factors were not controlled for in the first study; only maternal diabetes was controlled for in the second study. Another report about the same subjects as the first study found that the infants of vegan women were not significantly different from the infants of omnivores in terms of umbilical cord vitamin B12, folate, ferritin, and hemoglobin (Avnon, 2020b).

Although we don’t know for certain what caused the higher incidence of small for gestational age infants in these studies, we do know that starting a pregnancy underweight and gaining less than the recommended amount in pregnancy are associated with delivering a small baby. This could be due to not eating enough calories. You can see current weight gain recommendations in pregnancy the Center for Disease Control and Prevention’s article Weight Gain During Pregnancy and read more about vegan pregnancy in VeganHealth’s article Pregnancy, Infants, and Children.

References

Avnon, 2020a. Avnon T, Paz Dubinsky E, Lavie I, Ben-Mayor Bashi T, Anbar R, Yogev Y. The impact of a vegan diet on pregnancy outcomes [published online ahead of print, 2020a Sep 1]. J Perinatol. 2020;10.1038/s41372-020-00804-x. 

Avnon, 2020b. Avnon T, Anbar R, Lavie I, et al. Does vegan diet influence umbilical cord vitamin B12, folate, and ferritin levels?. Arch Gynecol Obstet. 2020b;301(6):1417-1422.

Kesary, 2020. Kesary Y, Avital K, Hiersch L. Maternal plant-based diet during gestation and pregnancy outcomes. Arch Gynecol Obstet. 2020;302(4):887-898.

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Due to growing popularity of collagen supplements and a number of inquiries we’ve received about it, we reviewed the literature on collagen supplements and published a summary of findings.

Main points:

• There is little research to support the use of collagen supplements for most purposes, with the exception of osteoarthritis and skin appearance.
• Several controlled trials have found that collagen supplements may decrease joint pain, stiffness, and function in some people with hip or knee osteoarthritis.
• A handful of studies found improvements in skin elasticity, skin hydration/moisture, collagen density of the skin, and/or eye wrinkle volume among older women after 4-12 weeks of collagen peptide supplementation.
• A major limitation of the studies on collagen supplements is that most do not control for protein intake, a known factor in collagen production. To draw any conclusions about the efficacy of collagen, we’d want to see human trials testing collagen versus an equivalent amount of other protein (especially plant protein).
• It’s possible that eating extra protein can substitute for taking collagen supplements, but this hasn’t been studied.

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A research study comparing the impact of plant meat versus animal meat intake on cardiovascular risk factors was published in August 2020.

The randomized crossover trial of 36 generally healthy meat-eating adults (mostly female, caucasian, and college-educated) was conducted in the United States and funded by Beyond Meat.

Participants were instructed to consume at least 2 servings of plant or animal meat per day for 8 weeks, keeping all other food and drink the same. Half of the participants ate plant meat for 8 weeks and then switched to animal meat for 8 weeks, while the other half ate animal meat first and then switched to plant meat.

Tofu, tempeh, and fish were excluded during the plant meat phase. Animal meat came from grass-fed cows, pigs, and chickens (fish was minimized). Calorie, protein, fiber, and sodium intakes were similar between phases. During the plant phase saturated fat intake was significantly lower (p<0.01).

LDL cholesterol (p=0.002) and weight (p<0.001) were significantly lower after the plant meat phase compared to the animal meat phase. There were no significant differences in IGF-1, insulin, glucose, HDL cholesterol, triglycerides, blood pressure, or in the microbiome.

There is some evidence that trimethylamine-N-oxide (TMAO) might be a risk factor for cardiovascular disease. TMAO is a metabolic byproduct of carnitine and choline, and is associated with animal meat intake. TMAO spiked during the animal phase for those who received animal meat first. Longer studies would be needed to better understand how transitory such a spike might be or if there’s any clinical relevance.

In conclusion, this small, short-term study found that replacing animal meat with plant meat resulted in lower saturated fat intake, and reduced LDL cholesterol and TMAO.

Reference

Crimarco A, Springfield S, Petlura C, et al. A randomized crossover trial on the effect of plant-based compared with animal-based meat on trimethylamine-N-oxide and cardiovascular disease risk factors in generally healthy adults: Study With Appetizing Plantfood-Meat Eating Alternative Trial (SWAP-MEAT) [published online ahead of print, 2020 Aug 11]. Am J Clin Nutr. 2020;nqaa203.

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We updated our article on Type 2 Diabetes and Vegan Diets with a 2019 study of the EPIC-Oxford cohort examing the association between vegetarianism and risk of hospitalization or death from diabetes.

Compared with regular meat-eaters and after adjusting for age, ethnicity, education level, material deprivation, smoking, alcohol, and physical activity, vegetarians (n=13,645) and vegans (n=1,781) had a lower risk of developing diabetes over a mean of 17.6 years of follow-up (HR 0.65, CI 0.55-0.76 for vegetarians; HR 0.53, CI 0.36-0.79 for vegans). However, when further adjusted for body mass index, the association was attenuated (HR 0.89, CI 0.75-1.05 for vegetarians; HR 0.99, CI 0.66-1.48 for vegans).

References

Papier K, Appleby PN, Fensom GK, et al. Vegetarian diets and risk of hospitalisation or death with diabetes in British adults: results from the EPIC-Oxford study. Nutr Diabetes. 2019 Feb 25;9(1):7.

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We added a study to the depression section of the omega 3s research page:

A 2019 meta-analysis and systematic review of 32 randomized controlled trials found little to no effect of increasing EPA and DHA on risk of depression symptoms (RR 1.01, CI 0.92-1.10). Studies had a median duration of 12 months with a median dose of 0.95 grams per day (ranging from 0.4 to 3.4 grams per day). One study addressed omega-3s and anxiety and found little to no effect. The researchers recommend against taking omega-3 supplements for reducing depression and anxiety risk.

References

Deane KHO, Jimoh OF, Biswas P, et al. Omega-3 and polyunsaturated fat for prevention of depression and anxiety symptoms: systematic review and meta-analysis of randomised trials [published online ahead of print, 2019 Oct 24]. Br J Psychiatry. 2019;1‐8.

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We recently updated our information on vegan children with a 2019 study from Germany that found no significant difference in weight-for-age, height-for-age, or weight-for-height scores between vegan, vegetarian, and nonvegetarian children.

Five vegan children and three vegetarian children were classified as stunted based on their height-for-age. Stunting could be explained by factors such as low parental height, low caloric intake, or being exclusively breastfed for too long. None of these factors is unique to a vegan or vegetarian diet.

Overall, this study indicates that a vegan diet supports normal growth in childhood.

References

Weder S, Hoffmann M, Becker K, Alexy U, Keller M. Energy, macronutrient intake, and anthropometrics of vegetarian, vegan, and omnivorous children (1-3 Years) in Germany (VeChi Diet Study). Nutrients. 2019 Apr 12;11(4).

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