“Heterozygosity for a Hereditary Hemochromatosis Gene Is Associated With Cardiovascular Death in Women” (Roest et al 1999)

Citation: Roest, M, van der Schouw, Y., de Valk, B., Marx, J., Tempelman, M., Groot, P., Sixma, J., and Banga, J. (1999). “Heterozygosity for a Hereditary Hemochromatosis Gene Is Associated With Cardiovascular Death in Women”. Circulation, 100(12), pp. 1268-1273. doi: 10.1161/01.CIR.100.12.1268

Summary By: Alexandra Pounds

Image Credit: Wikimedia Commons

  • Big Picture: People with hemochromatosis (a genetic condition that can lead to iron overload) are at a higher risk for cardiovascular disease, especially if they smoke or have hypertension.
  • Hemochromatosis is caused by a heterozygous gene HH, which affects how the body uptakes iron. People without this gene are able to regulate how much iron is absorbed from the diet, whereas people with this gene uptake too much iron.
  • Methods:
    • 12,239 Dutch women aged 51-69 were followed for 16-18 years. The women were tested for the heterozygous gene HH.
    • The researchers accounted for age, smoking, obesity, and hypertension using statistics.
  • Results:
    • Women with the heterozygous gene HH were more likely to die from cardiovascular disease, even when the researchers accounted for age, smoking, obesity, and hypertension.
    • Women with the heterozygous gene HH who also smoked or had hypertension were even more likely to die from cardiovascular disease.
  • Hemochromatosis may increase the risk of cardiovascular disease because hemochromatosis leads to iron overload. Iron can lead to LDL peroxidation, which can increase clogged arteries (which leads to cardiovascular disease).
  • Because smoking also causes oxidative stress (more oxidation in the body), it can compound the risk for cardiovascular disease in the same ways.
  • Limitations: This study did not examine women with hemochromatosis who died from causes other than cardiovascular disease. Maybe hemochromatosis is also linked to an increase risk of cancer? It’s not possible to say from this study.

“The effect of physical training on the serum iron levels of college-age women.” (Wirth et al 1978)

Citation: Wirth, J., Lohman, T., Avallone, J., Shire, T., and Boileau, R. (1978). “The effect of physical training on the serum iron levels of college-age women.” Medicine and Science in Sport, 10(3), pp. 223-226.

Summary By: Alexandra Pounds

Image Credit: Aviano Airbase

  • Big Picture: Short-term exercise does not affect Serum Iron levels in college-age women.
  • Method:
    • Seventeen women exercised 3 times per week for 10 weeks on a bicycle at about 70% of their maximum heart rate for 20-25 minutes. An additional 8 women were used as a control group.
    • The researchers measured: hemoglobin (Hb), hematocrit (Hct), serum iron (SeFe), and maximum oxygen uptake (Vo2 max)
  • Results:
    • hemoglobin (Hb): no difference
    • hematocrit (Hct): no difference
    • serum iron (SeFe): no difference
    • maximum oxygen uptake (Vo2 max): increased by 11% in the exercisers.
  • When researchers accounted for whether or not the women were menstruating or using oral contraception, it made no difference to the results.
  • Limitations: this trial was only for 10 weeks, which is considered short-term. We cannot say what happens to serum iron levels in women who exercise long-term.

“Food Production and Water Conservation in a Recirculating Aquaponic System in Saudi Arabia at Different Ratios of Fish Feed to Plants” (Al-Hafedh et al 2008)

Citation: Al-Hafedh, Y., Alam, A., Beltagi, M. (2008). “Food Production and Water Conservation in a Recirculating Aquaponic System in Saudi Arabia at Different Ratios of Fish Feed to Plants”. Journal of the World Aquaculture Society, 39(4), pp. 510-520. doi: 10.1111/j.1749-7345.2008.00181.x

Summary By: Alexandra Pounds

Image Credit: Wikimedia Commons

  • Big Picture: Recirculating Aquaponic system with Nile Tilapia and Leaf Lettuce produces more food and reuses more water than other systems in Saudi Arabia, like ponds or raceways.
  • This experiment used Nile Tilapia and Leaf lettuce in a recirculating aquaponics system to test different fish feed to plant ratios. Which ratio would maximize food production and water reuse within the system?
  • Methods:
    • Used commercial design with 3 parts: fish culture component, solid removal component, and hydroponic plant growing component for biofiltration
    • Plants were housed in Styrofoam rafts
    • Water was recirculated at 250 L/min.
    • Fish were stocked at 160 kg fish/m3
    • Fish were harvested every 6-8 weeks.
    • Plants were harvested every 4 weeks.
  • Results
    • The system effectively treated the water and plants effectively removed ammonia.
    • Fish had a 97.5% survival rate.
    • Tanks with all male fish had better production than tanks with mixed sex fish (male tilapia grow faster than female tilapia).
    • Only 1.4% of water needed to be added daily (compared to 20-25% in ponds, raceways, or flow-through systems) – the system managed to recycle 98% of its water.
    • production: 40 kg fish/m3 every 6 months
    • “A ratio of 56 g fish feed/m2 of hydroponic surface effectively controlled nutrient buildup in the effluents.

Best types of Plants for aquaponics:

  • Lower nutrient requirement plants which do better with lower fish stocking densities:
    • Lettuce (low-nutrient requirement)
    • Herbs
    • Specialty greens (spinach, chives, basil, and watercress)
  • Higher nutrient requirement plants which do better with higher fish stocking densities:
    • tomatoes
    • bell peppers
    • cucumbers

Marine species that have been grown successfully in aquaponics:

  • Nile tilapia, Oreochromis niloticus;
  • Hybrid tilapia, Oreochromis urolepis hornorum × Oreochromis mosambicus;
  • Koi carp, Cyprinus carpio;
  • Hybrid carp, Ctenopharyngodon idella × Aristichthys nobilis;
  • Hybrid striped bass, Morone chrysops × Morone saxatilis;
  • Goldfish, Carassius sp.
  • Rainbow trout, Oncorhynchus mykiss;
  • Australian barramundi, Lates calcarifer;
  • Murray cod, Maccullochella peelii peelii;
  • Red claw crayfish, Cherax quadricarinatus



“The Production of Catfish and Vegetables in an Aquaponic System” Mamat, Shaari, & Wahab 2016

Citation: Mamat, N., Shaari, M., and Wahab, N. (2016). “The Production of Catfish and Vegetables in an Aquaponic System”. Fisheries and Aquaculture Journal, 7(4). doi:10.4172/2150-3508.1000181

Summary By: Alexandra Pounds

Image Credit: Flikr

  • Big Picture: African catfish grow equally as well with red amaranth, green-red amaranth, and water spinach in an aquaponic system.
  • The study compared the growth rates of African Catfish (Clarias gariepinus) when cultured in aquaponic systems (systems that grow fish and plants in a recirculating water system). They compared three vegetables: red amaranth, green-red amaranth, and water spinach.
  • Methods:
    • System: They used 15 aquaponic systems in Malaysia. Each system had 80 gallons of water.
    • Fish: Each system held 15 African Catfish juveniles. The fish were fed twice daily with commercial pellets at 6% of their bodyweight per day. Fish were grown over 60 days. The fish were weighed weekly.
    • Plants: The vegetables were sown and sprouted before being transferred to the aquaponic system. vegetables were harvested after 30 days. Two sets of vegetables were grown off of one set of fish.
  • Results: Green-red amaranth produced the biggest fish, followed by fish co-cultured with both red amaranth and water spinach. However, none of the results were statistically significant.
  • Conclusion: The plant species didn’t affect the growth of the catfish.

“Increasing the Economical Efficiency and Sustainability of Indoor Fish Farming by Means of Aquaponics – Review” Blidariu & Grozea 2011

Citation: Blidariu, F. and Grozea, A. (2011). “Increasing the Economical Efficiency and Sustainability of Indoor Fish Farming by Means of Aquaponics – Review.” Animal Science and Biotechnologies, 44(2), pp. 1-8.

Summary by: Alexandra Pounds

Image Credit: Wikimedia Commons

  • Big Picture: Combining fish culture with plant farming (aquaponics) is a sustainable and environmental friendly way to produce high quality food. Aquaponics could make indoor fish farming more sustainable by reducing waste production.
  • “Aquaponics”: indoor fish farm + hydroponic plants (plants that are grown in nutrient-rich water rather than soil)
  • Recirculating Aquaculture Systems (RAS, aka “indoor fish farms”) are the most commonly used for aquaponic systems.
  • RAS are the most environmentally friendly systems in aquaculture because unlike flow-through systems, wastewater is cleaned and reused rather than discarded. It allows for greater control over biosecurity (risk of disease) and quality. They are criticised because they still produce a lot of waste products.
    • Removal efficiency of traditional RAS for organic/fecal matter: 85-95%
    • Removal efficiency of traditional RAS for phosphorus: 65-96%
  • Instead of discarding this waste, why not use the waste as plant fertilizer? Instead of mechanical treatment systems and filters, plants biofilter the wastewater so that it can be reused for the fish. Fish waste provides nutrients that the plant would otherwise get through soil or fertilizer. The farmer can sell both plants and fish.
  • Plants solve multiple problems in RAS farming:
    • Ammonia/Nitrogen/Carbon Dioxide toxicity: Fish produce ammonia & carbon dioxide as waste, but both are toxic to them. Plants remove ammonia from the water and convert it to nitrite, which the plant uses for growth along with carbon dioxide. Fish can tolerate much higher concentrations of nitrite than ammonia. This paper reports that plants can remove ammonia at a 86-98% efficiency.
    • Oxygen depletion: Fish need oxygen, and water can become depleted. Farmers usually have to add oxygen to the water in RAS. Plants produce oxygen as a by-product, which can be added back to the water for the fish.
  • These systems could be used in small-scale urban farming, for example, on rooftops or in gardens in over-populated urban areas that may have reduced access to water. It is debated whether aquaponics can be profitable on a commercial scale.
  • Challenges:
    • Aquaponic farmers must balance the amount of plants with the amount of fish. There must be enough plants to manage the amount of waste that the fish produce. Likewise, there must be enough fecal waste from the fish to fertilize the plants. It is its own ecosystem.
    • Fish require high flow rates of water, which results in low concentrations of effluent (waste in the water). Plants require high concentrations of effluent.
    • Aquaponics cannot use pesticides because pesticides are toxic to fish. Similarly, many treatments for fish disease would be absorbed by the plants, creating human-consumption safety issues. Aquaponics requires “natural” treatments.
  • Benefits:
    • Two products (fish and plants) = investment diversity. If one has poor yield, farmer still has the other to mitigate losses.
    • Reduces costs of fertilization and filtration equipment. Infrastructural equipment costs are shared, which can lower the overall COGs (cost of goods sold = how much is costs to produce the product).
    • Space efficient.
    • Easy to certify as organic & environmentally sustainable.
    • Can be marketed as locally produced, even in heavily populated cities with colder climates.
    • Potentially faster growth rates with higher and more consistent quality.
    • Decreased waste production.
    • Can be adapted for farmers with disabilities.
  • The best plants for aquaponics are those that require low levels of nutrients, such as: lettuce, herbs, spinach, chives, basil, watercress. Plants with high-nutrient demands (like tomatos, bell peppers, and cucumbers) would require more intensive systems with more fish production.
  • The best fish for aquaponics are hardy fish like catfish or tilapia.


“Red Meat Consumption during Adolescence among Premenopausal Women and Risk of Breast Cancer” Linos et al 2008

Citation: Linos, E., Willett, W., Cho, E., Colditz, G, and Frazier, L. (2008). “Red Meat Consumption during Adolescence among Premenopausal Women and Risk of Breast Cancer” Cancer Epidemiology Biomarkers & Prevention, 17(8), pp 2146-2151. doi: 10.1158/1055-9965.EPI-08-0037

Summary by: Alexandra Pounds

Image Credit: Max Pixel

  • Big Picture: Teens who eat a lot of well-done or fried red meats, especially processed meats or meats with additional hormones, may be at a greater risk of breast cancer.
  • Over 39,000 premenopausal women reported how frequently they ate 142 different types of food from 1998 to 2005.
  • 455 of these women got breast cancer.
  • Researchers defined “red meat” as pork, beef, lamb, and processed meats (like hotdogs, meatloaf, and cured meats).
  • Researchers found that:
    • red meat consumption during adolescence was correlated with breast cancer. For every 100g of red meat (about one burger patty) consumed each day, the risk of breast cancer increased by 20%.
    • red meat consumption during adulthood was NOT correlated with breast cancer.
    • processed meats were associated with a higher risk of breast cancer compared to other meats.
    • The processing of the meat, rather than the meat itself, may have played a role in breast cancer risk.
  • Limitations of the study:
    • Researchers also found that women who ate more red meat were also more likely to be smokers, have a higher BMI/caloric intake, and gained more weight during adulthood. These factors may have played a role in contributing to breast cancer risk.
    • Red meat was not differentiated by how it was cooked. The researchers didn’t know how the women’s meat was cooked. Another study showed that well-done and fried meats quadrupled the risk of breast cancer. In this study, it may have been that those who developed breast cancer and eating more meat were eating more well-done or fried meats.
    • The study required that some adult women recall the foods they ate when they were a teenager. They may have not remembered accurately.
    • The women in the study were teens during the 1960’s and 1970’s, before hormone use in livestock was limited. The women eating more red meat may have developed breast cancer because of the hormones in the red meat rather than because of the red meat itself.


“Survey Research” Krosnick 1999

Citation: Krosnick, J. (1999). “Survey Research”. Annual Review of Psychology, 50, pp. 537-367. doi: 10.1146/annurev.psych.50.1.537

Summary by: Alexandra Pounds

Image Credit: The Blue Diamond Gallery

  • Big Picture: The paper offers many points to explain biases and survey error.
  • High response rates do not necessarily mean you’ll get more representative data. You can get representative data even with low response rates. Response rate does not equal accurate or representative data.
  • People who agree to be interviewed/surveyed are likely to believe it’s their social responsibility to participate. This means they will likely be biased towards altruistic answers.
  • Pretesting is important. Three methods:
    • Conventional Pretesting: Test a small number of surveys, then look at common problems to adjust the survey.
    • Cognitive pretesting: Think aloud or probing interview to identify respondents misunderstandings or difficulties.
    • Behaviour coding: Respondents taking the survey are monitored and compared for differences. This is especially helpful for interviews, where interviewee behaviour may change depending on the respondent.
  • Interviews:
    • Rigid interviewing: Questions should be worded identically to every respondent to avoid errors/bias. If respondents ask for help, the interviewer should say something like, “it means whatever it means to you”.
    • Conversational interviewing: this allows free dialogue between the interviewer and the respondent. It may allow the researcher to get more accurate and detailed responses, but can produce more interviewer error.
  • Questionnaires:
    • Open versus Closed questions – there’s a lot of debate on which is more reliable.
      • Open: allows for qualitative analysis; respondents may choose to answer in different ways than the researcher intended;
      • Closed: allows for quantitative analysis; must have comprehensive answers to allow respondents to answer how they want to; may be better for inarticulate respondents;
    • Rating Scales: Data reliability and respondent satisfaction are improved when each rating is labelled with words instead of numbers.
  • Optimizing versus satisficing
    • Optimizing = giving the most accurate and honest answer.
    • Satisficing = giving the easiest answer that the respondent believes will satisfy the researcher.
      • This will happen more towards the end of the survey or in difficult surveys because respondents get tired and lose motivation.
      • This tendency will push respondents to give neutral / “I don’t know” / “no opinion” answers because they are safer or because they require less decision-making. Offering these answers does not increase the quality of data due to satisficing tendencies.
      • Satisficing is less in face-to-face interviews because the respondents feel more accountable to the interviewer.
      • This tendency will cause people to select the first answer listed because it’s easier.
  • Other biases:
    • Confirmation bias: respondents will emphasize recently presented information because they wish to “please” the researcher and because of their tendency to satisfice (choose the easiest answer that will satisfy the researcher).
    • Social Desirability bias: respondents will overstate admirable qualities and downplay shameful qualities to protect their reputation or because they have inaccurately recalled their past behaviour.
    • Acquiescence: “the tendency to endorse any assertion made in a question, regardless of its content”. Agree/disagree, yes/no, and true/false questions are very prone to this. To reduce this bias, it’s a good idea to present the question twice, once in a positive light and once in a negative light.
      • For example: “I enjoy eating apples” versus “I do not like apples.”
      • The average acquiescence effect is about 10%.
      • When people guess, they choose “agree” and “true” more often than “disagree” or “false”.
      • Satisficing can enhance the effect of acquiescence.
      • Yes/No questions are less affected by acquiescence than agree/disagree or true/false questions.
    • Nondifferentiation: where people answer all the questions the same, usually due to fatigue or lack of motivation leading to satisficing.
  • Ratings versus Rankings:
    • Respondents find ratings easier and more satisfying than rankings; therefore, rankings are more susceptible to acquiescence and satisficing.  Respondents usually make more mistakes with rankings than with ratings.