The bioavailability of minerals is poor in legumes

This paper was published in the British Journal of Nutrition 2002 Dec;88 Suppl 3:S281-5

Study title and author:
Bioavailability of minerals in legumes.

Sandberg AS.
Department of Food Science, Chalmers University of Technology, PO Box 5401, SE 402 29 Göteborg, Sweden. ann-sofie.sandberg@fsc.chalmers.se

This study can be accessed at: http://www.ncbi.nlm.nih.gov/pubmed/12498628

Professor Ann-Sofie Sandberg is head of the Life Science Division at Chalmers University of Technology, Göteborg, Sweden. She has an extensive record in the field of phytate/bioavailability of minerals, food processing/bioavailability of nutrients and in the development of analytical methods for measuring nutrients and bioactive compounds.

Professor Sandberg reviewed the scientific evidence regarding the bioavailability of minerals in legumes.

Professor Sandberg found:
(a) The content of iron and other minerals is generally high in legumes. However, the legumes also contain antinutritional factors, such as proteinase inhibitors, lectin, raffinose oligosaccharides, saponins, polyphenols and phytate. Antinutritional factors lower the nutritional value of a food by lowering the digestibility or bioavailability of nutrients.
(b) Phytate is a well-known inhibitor of absorption of essential dietary minerals such as non-haem iron, zinc and calcium. 
(c) Some polyphenols are potent inhibitors of non-haem iron absorption.
(d) In the modern food industry, the high phytate content of soya-based infant formulas is of concern as low zinc absorption from a soya-protein-based infant formula has been found.
(e) Soya protein per se has an inhibiting effect on iron absorption.
(f) In many developing countries where diet is based on cereal and legume products, deficiency of iron and zinc, is highly prevalent.
(g) In developing countries iron deficiency, due to poor bioavailability, retards normal brain development in infants and affects the success of a pregnancy by increasing premature deliveries, as well as increased disease of mother and child at or around childbirth.
(h) Zinc deficiency prevents normal child growth and greatly weakens the immune system, leading to more infections.
(i) In industrialised countries where diet is based on cereal and legume products, deficiency of iron and zinc, is highly prevalent in certain groups such as women of fertile age, infants, adolescents and vegetarians.

The review finds that the bioavailability of minerals is poor in legumes and may lead to adverse health consequences.

Iron absorption is markedly inhibited in soy infant formula

This study was published in the British Journal of Nutrition 1987 May;57(3):345-53

 

Study title and authors:

Factors influencing the absorption of iron from soya-bean protein products.

Derman DP, Ballot D, Bothwell TH, MacFarlane BJ, Baynes RD, MacPhail AP, Gillooly M, Bothwell JE, Bezwoda WR, Mayet F.

 

This study can be accessed at: http://www.ncbi.nlm.nih.gov/pubmed/3593666?dopt=Abstract

This study compared iron absorption rates from soya-bean-based and milk-based infant formulas. The study included 138 women aged 21 to 63. None of the women were pregnant or lactating and all were unpaid volunteers. Ethical and practical considerations precluded the study being done on infants themselves.

The study found:
(a) Iron absorption was significantly less from the soya-bean formula compared to the milk-formula.
(b) The addition of ascorbic acid (vitamin C) markedly increased iron absorption from the milk-formula (a ten-fold increase), whereas ascorbic acid had a less-marked effect on the absorption of iron from the soya-bean formula, with only a two- to threefold increase.

The study reveals that iron absorption is markedly inhibited in soy infant formula.

Soy has a pronounced inhibitory effect on the absorption of iron

This study was published in the American Journal of Clinical Nutrition 1981 Dec;34(12):2622-9

Study title and authors:
The inhibitory effect of soy products on nonheme iron absorption in man.

Cook JD, Morck TA, Lynch SR.

This study can be accessed at: http://www.ncbi.nlm.nih.gov/pubmed/7198374

Three separate studies were performed in 36 men ranging in age from 18 to 50 years to determine the effects of various proteins on iron absorption.

The studies comprised of:
(i) Study I compared the effects of different proteins (egg protein, milk protein and isolated soy protein) on iron absorption.
Each meal contained 29.4 grams of protein.
(ii) Study II examined the influence of egg protein and various soy products (full fat soy flour, textured soy flour and isolated soy protein) on iron absorption.
Each meal contained 14.7 grams of protein.
(iii) Study III evaluated the effect on iron absorption of adding soy protein to meat.
Meal 1 included 100 grams of ground (minced) beef.
Meal 2 included 100 grams of ground (minced) beef and 30 grams of textured soy flour. (A 3:1 meat/soy ratio).
Meal 3 included 70 grams of ground (minced) beef and 30 grams of textured soy flour. (A 2:1 meat/soy ratio).

The results of the studies were as follows:
(a) In study I, those who consumed the isolated soy protein meal absorbed 81% less iron than those who consumed the egg protein and milk protein meals.
(b:i) In study II, those who consumed the full fat soy flour meal absorbed 82% less iron than those who consumed the egg protein meal.
(b:ii) In study II, those who consumed the textured soy flour meal absorbed 65% less iron than those who consumed the egg protein meal.
(b:iii) In study II, those who consumed the isolated soy protein meal absorbed 92% less iron than those who consumed the egg protein meal.
(c:i) In study III, those who consumed the meal with the extra soy with the 100 grams of beef (meal 2) absorbed 61% less iron than those who consumed the 100 grams of beef only meal.
(c:ii) In study III, those who consumed the meal with the extra soy and depleted beef (meal 3) absorbed 53% less iron than those who consumed the 100 grams of beef only meal.

The results of these studies show that soy products have a pronounced inhibitory effect on the absorption of iron.

Soy consumption inhibits the bioavailability of iron

This study can be accessed at the American Journal of Clinical Nutrition 1992 Sep;56(3):573-8

Study title and authors:
Soy protein, phytate, and iron absorption in humans.

Hurrell RF, Juillerat MA, Reddy MB, Lynch SR, Dassenko SA, Cook JD.
Nestec Ltd., Nestlé Research Centre, Lausanne, Switzerland.

This study can be accessed at: http://www.ncbi.nlm.nih.gov/pubmed/1503071

Soy protein isolate can be found in protein bars, meal replacement shakes, bottled fruit drinks, soups and sauces, meat analogs, baked goods, breakfast cereals and some dietary supplements.

Soy is high in a substance called called phytic acid (phytate) which binds to minerals (including calcium, magnesium, iron, and zinc) in your digestive tract and keeps your body from absorbing those minerals.

The study examined the effects of soy-protein isolate on iron absorption. The study included 32 men and women aged 20 to 31 years in which the absorption of soy-protein isolate was compared with egg-whites.

The study found:
(a) Iron absorption increased four- to fivefold when phytic acid was reduced from its normal amount of 4.9-8.4 to less than 0.01 mg/g of soy-protein isolate.
(b) Even relatively small quantities of residual phytate were strongly inhibitory and phytic acid had to be reduced to less than 0.3 mg/g of soy-protein isolate (corresponding to less than 10 mg phytic acid/meal) before a meaningful increase in iron absorption was observed.
(c) Even after removal of virtually all the phytic acid, iron absorption from soy-protein isolate was still only half that of egg whites.

The researchers conclude that phytic acid is a major inhibitory factor of iron absorption in soy-protein isolates but that other factors in the soy also contribute to the poor bioavailability of iron.

Diets heavy in grains and soybeans lead to anaemia

This post includes a synopsis of a paper published in Asia Pacific Journal of Clinical Nutrition 2002;11(3):171-175 and a recipe for bacon and broccoli curried soup with almonds.

Study title and authors:
Iron status and dietary intake of Chinese pregnant women with anaemia in the third trimester
AIGUO MA, XUECUN CHEN, MINGCI ZHENG, YU WANG, RONGXIAN XU, JUESHENG LI

This paper can be accessed at: http://apjcn.nhri.org.tw/server/APJCN/Volume11/vol11.3/abstracts11.3.htm#Nicholas

Books:

Aiguo notes that anaemia in pregnancy is a major public health problem in China and that anaemia in pregnant women may be related to dietary intake of nutrients. To examine the relationship between iron status and dietary nutrients, a study in 1189 pregnant women was carried out. The women were classed as (i) having anaemia or as (ii) normal.

The results of the study showed:
(a) The average daily intake of rice and wheat was 7% higher in the anaemia group than in the normal group.
(b) The average daily intake of soybean was 72% higher in the anaemia group than in the normal group.
(c) The average daily intake of fat and iron was lower in the anaemia group than in the normal group.

To conclude: The results of this study indicate that anaemia might be attributed to a low iron intake, a low intake of enhancers of iron absorption and a high intake of inhibitors of iron absorption from a traditional Chinese diet rich in grains and soybeans.

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Recipe of the day

Bacon and Broccoli Curried Soup with Almonds

Serves 5

Ingredients:

Food Mall: Bacon

•4 slices bacon, cut in 1-inch pieces;

•1 cup leeks, green part discarded and white finely chopped;
•1/2 cup carrots, finely chopped;
•4 cups broccoli, finely chopped;
•1 tsp curry powder;
•1/2 tsp dried basil;
•3 cups chicken stock;
•1 cup coconut milk;
•4 tbsp almonds, chopped;
•Sea salt and freshly ground black pepper to taste;

Preparation:
1.Heat a pot over a medium heat and cook the bacon for about 6 minutes, stirring occasionally.

2.Remove the bacon from the pot, set aside and add the leeks and carrots to the pot in the rendered bacon fat.

3.Stir often and cook until soft.

4.Add the broccoli, curry powder and basil and cook for a few more minutes.

5.Pour in the chicken stock, bring to a boil and reduce to a simmer. Simmer for about 10 minutes, until the broccoli is soft.

6.Add the bacon back in the pot and stir in the coconut milk.

7.Season to taste with sea salt and freshly ground black pepper, reheat the liquid and serve sprinkled with chopped almonds on top.

Dietary phytates lead to iron deficiency and anemia

This post includes a synopsis of a study published in the International Journal of Food Sciences and Nutrition 2009;60(1):51-9 and a recipe for lamb and asparagus.

Study title and authors:
Influence of dietary and socio-demographic factors on the iron status of married adolescent girls from Indian urban slums.
Tupe R, Chiplonkar SA, Kapadia-Kundu N.
Agharkar Research Institute, G G Agarkar Road, Pune, India.

This study can be accessed at: http://www.ncbi.nlm.nih.gov/pubmed/18608535

The study explored the influence of dietary factors of iron bioavailability in 173 married adolescent girls in India.

The prevalence of iron deficiency was 25.1%, and anemia was seen in 46.4%  of the girls.

The study found a diet high in phytates resulted in the low bioavailable iron intakes.

                                                                                                                                             Books:

High concentrations of phytates occur in the following foods:
•Most whole grain cereal foods (wheat, rye, rice, oats)

•Nuts and seeds (pumpkin, sunflower)

•Soybeans, other types of beans

•Potatoes

•Artichokes

•Blackberries

•Broccoli
•Carrots
•Figs
•Strawberries

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Recipe of the day

Lamb and Asparagus
                                                                                                                    Food Mall: Boneless Lamb

Ingredients:

• 1 chopped red onion

• 3 garlic cloves crushed

• 1/2 c of dry white wine

• 3 c of steamed sliced asparagus

• 1 1/2 lb boneless lamb chopped into small cubes

• Freshly-ground black pepper to taste

Instructions:

Steam asparagus. Heat a large frying pan and add 1/2 of the wine. Bring to the boil and add the onion and garlic, cook until softened.

Add the lamb and cook for about 6 minutes.

Add the rest of the wine and the asparagus. Cover and cook for about 10 minutes, until lamb is tender.

Pepper to taste.

Soy inhibits the bioavailability of iron and zinc

This post includes a synopsis of a study published in the Journal of the American College of Nutrition Vol. 25, No. 1, 34-40 2006 and a recipe for turkey stuffed zucchini.

Study title and authors:
Effect of Beef and Soy Proteins on the Absorption of Non-Heme Iron and Inorganic Zinc in Children

Paz Etcheverry, PhD, Keli M. Hawthorne, MS, Lily K. Liang, MA, Steven A. Abrams, MD and Ian J. Griffin, MD

Books:

USDA/ARS Children’s Nutrition research Center (P.E., K.M.H., L.K.L., S.A.A., I.J.G.)

Section of Neonatology (S.A.A., I.J.G.), Department of Pediatrics, Baylor College of Medicine, Houston, Texas

This study can be accessed at: http://www.jacn.org/cgi/content/abstract/25/1/34
 
The objectives of the study was to assess the effects of beef and soy proteins on the bioavailability of non-heme iron and zinc in children.

The study found that:
(a) Iron absorption from the beef meal was 117% greater than from the soy meal.
(b) Zinc absorption from the beef meal was 35% greater than from the soy meal.

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Recipe of the day

Turkey Stuffed Zucchini

serves 4

Ingredients:

Food Mall: Ground Turkey

• 1 zucchini about 12 inches long, or 6 medium ones

• 3 T olive oil
• 1/2 c chopped onion
• 3 cloves garlic, minced
• 1/2 c chopped mushrooms
• 2 T dry white wine
• 1 lb ground turkey
• 2 diced tomatoes
• 3 T chopped basil
• 1 t chopped rosemary
• 1 egg, lightly beaten
• 2 t sea salt
• 2 t pepper

Instructions:
Cut zucchini in half lengthwise. Scoop out insides, leaving shells about 1/4 inch thick. Reserve about half of the insides.

Heat 2 T of olive oil in a skillet on medium high heat. Sauté onion and garlic until soft. Add mushrooms and reserved zucchini insides, and sauté another 2 minutes.

In a separate skillet heat a T of olive oil on medium high heat. Add the ground turkey. Cook until the ground turkey is lightly browned, about 6 minutes. Stir in the onion and mushroom mixture from the other pan. Add the wine. Stir in tomato, basil and rosemary and cook 1 minute longer. Drain any excess fat. Remove mixture from heat and set it aside.

When mixture has cooled, add egg, salt and pepper. Fill zucchini shells with mixture. Fill a baking pan with 1/4 inch of water. Place filled zucchini halves in pan and bake at 375 F for 40 minutes, until golden brown. Remove zucchini from pan and serve while hot.

Soy protein causes an acute decline in dietary calcium bioavailability

This post includes a summary of a study published in the American Society for Nutrition 136:1890-1895, July 2006 and a recipe for eggs scrambled with olives and onion.

Study title and authors:

Books:

Meat and Soy Protein Affect Calcium Homeostasis in Healthy Women

Jane E. Kerstetter*, Diane E. Wall, Kimberly O. O'Brien**, Donna M. Caseria and Karl L. Insogna

* Department of Allied Health, University of Connecticut, Storrs, CT; Yale University, School of Internal Medicine, New Haven, CT; ** Division of Nutritional Sciences, Cornell University, Ithaca, NY; and Yale New Haven Hospital, New Haven, CT

This study can be accessed at: http://jn.nutrition.org/cgi/content/abstract/136/7/1890
 
The author concludes that soy protein causes an acute decline in dietary calcium bioavailability compared to meat protein.

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Recipe of the day

Eggs Scrambled with Olives and Onion

Ingredient list:

Three fresh eggs

Food Mall: Eggs

Sweet yellow onion

Green olives
Extra virgin olive oil
Garlic powder
Black pepper
Turmeric
Salt

Directions:
Chop enough onion to cover the bottom of a small frying pan. Slice about 10 olives into halves or thirds. Crack three eggs into a coffee cup. Add salt, black pepper, and garlic powder to taste. Add a dusting of turmeric, which I like with eggs. Stir with a fork or whisk to mix well.

Cover the bottom of a small frying pan with olive oil and place over medium-low heat. Don’t skimp on the oil. Add onion and let cook 1-2 minutes. Scatter sliced olives among onions. Pour egg mixture over the vegetables and let it cook undisturbed for about 1 minute. Scrape the eggs off the bottom of the pan almost continuously over the next few minutes until the eggs are as dry as you like them. Transfer to a plate and eat!