Thursday, October 23, 2014

Red meat and fertility


Professor Robert Pickard discusses fertility and nutrition.

Reproduction is so important to the species that we have evolved a body chemistry that will usually sacrifice the wellbeing of the individual for the benefit of the reproductive system. Thus, even malnourished individuals can be highly fertile at the expense of their own survival.

A high nutritional status protects the individual from this effect and maximises fertility potential, provided that the damaging effects of alcohol, smoking and obesity are avoided.

 In women, only a relatively small number of cell replication cycles are needed to produce ova and fertility problems are often associated with hormonal imbalance and the chemistry of the membranes that line the reproductive tracts.

 In men, millions of cell replication cycles are needed to produce normal quantities of sperm. Therefore, oxidative damage to replicating DNA and poor protein metabolism particularly reduce fertility in men.

 In addition, a spermatozoon requires an elegant protein motor that can only function with an extremely efficient battery, considering the very small cell volume that is available to it compared with a single ovum.

 Since cows, sheep and pigs share 80% of their genes with humans, red meat with liver and kidney is the most nutrient-dense food that we consume in our balanced diet.

 Red-meat animals need most of the molecules that we need and not all of them have yet been identified. In particular, lean red meat is an ideal source of the amino-acid range that is required for the protein chemistry used in gametogenesis.

 All the vitamins are needed for a high nutritional status but fertility is likely to be enhanced in older men with additional intakes of vitamins B6, B12, C, D, E and folic acid.

 We cannot construct DNA without the B vitamins and B12 is not found in any of the conventional table vegetables.

 Unsaturated fatty acids, well represented in grass-fed animals, are also beneficial to the reproductive process.

 Iron, magnesium, selenium and zinc are often identified, experimentally, as promotive of fertility.

 Since most biochemical pathways require the presence of several vitamins and minerals, it is na├»ve to think of any one micronutrient as a critical key to the deliverance of fertility.

 A lean, red-meat meal with green plant material and low-starch seed germ, to supply additional vitamin C and phytonutrients, is an ideal basis for the promotion of fertility in both men and women.

Thursday, October 2, 2014

Nutritional cost of 'health' campaigns

Dr Carrie Ruxton

There continues to be an increasing number of so-called ‘awareness’ weeks and months encouraging us to turn to a vegetarian or vegan diet or eat less red meat due to the risk of over consumption. Often these campaigns vilify meat, and more often than not incorrectly identify red meat as a cause of chronic health conditions. 

As detailed in the National Diet and Nutrition Survey, vegetarian diets are currently followed by just 2 - 4% of the population and, in many cases, include eggs, cheese and fish. While avoidance of meat can work for the committed vegetarian who is prepared to source a variety of protein-rich alternatives, this is not the case for others and research shows that meat-free diets are low in zinc, calcium, iron, manganese, selenium, and copper[1].
 
Vegan and vegetarian diets restrict opportunities for vitamin D intake[2],[3] and following these types of diets greatly reduces intakes of long-chain omega-3 fatty acids which are found in both oily fish and certain meats[4]. Another key nutrient, vitamin B12, is a major issue for vegans as it is only present in foods of animal or microbiological origin[5].

While iron is found in small amounts in some non-meat foods, such as beans, pulses and fortified foods, it is of the ‘non-haem’ variety which is poorly absorbed. Indeed, only 10% of non-haem iron is absorbed compared with up to 30% of haem iron from red meat[6]. Interestingly, the presence of haem iron in foods increases the absorption of non-haem iron.

A final point is that humans are naturally omnivorous which means that we evolved to include meat in the diet. Evidence from fossilised bones, gut physiology and the diets of contemporary hunter-gatherer societies suggests that two thirds of calories in the diet of ancient man came from animal products[7].

Therefore lean red meat is second to none as a source of bioavailable nutrients.

 



[1] Freeland-Grave-J (1988) Mineral adequacy of vegetarian diets. The American Journal of Clinical Nutrition  48:859-62
[2] Calvo Ms, Whiting SJ, Barton CN (2005) Vitamin D intake: a global perspective of current status. Journal of Nutrition 135 310-6
[3] Laskowska-Kilta T, Chelchowska M, Ambroszkiewicz J, Gajewska J, Klemarczyk W (2011) The effect of vegetarian diet on selected essential nutrients in children 15:318-25
[4] Welch AA, Shakya-Shrestha S, Lentjes MA, Wareham NJ, Khaw KT (2010) Dietary intake and status of n-3 polyunsaturated fatty acids in a population of fish-eating and non-fish-eating meat-eaters, vegetarians, and vegans and the product-precursor ratio [corrected] of a-linolenic acid to long-chain n-3 polyunsaturated fatty acids: results from the EPIC-Norfolk cohort. The American Journal of Clinical Nutrition 92:1040-51
[5]Ambroszkiewicz J, Klemarczyk W, Chelchowska M, Gajewska J, Laskowska-Klita T (2006) Serum homocysteine, folate, vitamin B12 and total antioxidant status in vegetarian children.Advances in medical science 51:265-8
[6] SACN (2010). Iron and health. London: The Stationery Office. Available at: www.sacn.gov.uk/pdfs/sacn_iron_and_health_report_web.pdf
[7] Cordain L et al. (2002) The paradoxical nature of hunter-gatherer diets: meat-based, yet non-atherogenic. Eur J Clin Nutr 56: S42-52.