by Sue Bedford (MSc Nutritional Therapy)
The yam is a staple food in many tropical countries, particularly in Africa, the Caribbean and the South Pacific
Yams have brown tough skins and the flesh can vary in colour – anything from white to yellow to purple – depending on the variety. They are similar in appearance to the sweet potato, however they are not at all related to it. Yams (Dioscorea) belong to the tuber family and contain phytoestrogens, which are weak oestrogens. Yams also contain a form of natural progesterone (dioscin).
Although yams are grown all over the African continent, Nigeria is the world’s largest producer and exporter, accounting for over 70 percent of the total global production
An often mentioned study on the Yaruba tribe in Nigeria (a group of people with a high rate of twins) links their fertility with a high consumption of yams, although it is not grounded in solid evidence. The study conducted at the University of Ibadan, found that one in every four pregnancies (rather than one in forty which was true for the general population) resulted in fraternal twins.
“The real cause of the phenomenon has not been medically found,” said Akin Odukogbe, a senior consultant gynaecologist with the University Teaching Hospital (UCH) in Ibadan, the nearest big town.” But people attribute the development to diet,” he continued, adding that studies have shown that yam can make women produce more than one egg which can be fertilised. * More studies are needed in this area.
So……what’s the nutrition in a Yam and how is it good for fertility?
Yams are rich in valuable nutrients that are important for general health and pre–conception such as β-carotene (some), vitamin B6, vitamin C, vitamin E, potassium and fibre.
Hormonal imbalances are a main contributory factor to infertility
It is important to keep the correct balance of oestrogen to progesterone balance. Yams are a good source of Vitamin B6 which is thought to be important in the production of the corpus luteum and therefore, the production of progesterone. Vitamin B6 has been found to help the liver metabolize and break down oestrogen. Through these metabolic pathways, Vitamin B6 may help to increase progesterone and reduce oestrogen dominance.
Yams are a complex carbohydrate which means that the sugar that they contain will be released more slowly into the bloodstream
They are classed as a low glycemic food. These means that sugar levels are not ‘spiked’ so much and so there are less insulin spikes as a result. This all helps to balance hormones too.
Vitamin E (an antioxidant) is one of the most important vitamins associated with male fertility. It is fat-soluble, andhelps to prevent free radical damage to the cell membranes of sperm. It is important too in egg health too for the same reason.
Vitamin C (an antioxidant) is important when it comes to fertility as it helps to zap the free radicals which lead to oxidative stress and cell ageing. It helps to protect the DNA in the sperm and the egg from damage, is involved in balancing hormones and also important when it comes to supporting the immune system.
They are an excellent source of soluble fibre which helps to remove toxins from the body, including hormones that have been broken down and also help to prevent constipation.
They also contain a good amount of potassium which is an important component of cell and body fluids which helps controlling heart rate and blood pressure by countering hypertensive effects of sodium.
Yam contains small amounts of vitamin A and β-carotene levels. β-carotene is the vegetable precursor to Vitamin A. It is a powerful antioxidant which helps to protect egg and sperm DNA from damage by harmful free radicals which can affect the quality of both the egg and sperm. Free radicals are highly unstable and set off a process called oxidation which can have harmful effects on every cell in the body. Vitamin A has many functions such as maintaining healthy mucosa and skin, night vision, growth and in the immune system.
How to eat yams
Yams need to be cooked before being eaten. Yams vary in size and can grow to be quite big.
Smaller yams can be cooked like a jacket potato but larger yams need to be peeled, chopped and boiled in water for 15-20 minutes.
They can be boiled and mashed, made into chips and enjoyed with casseroles and stews too just like normal potatoes.
For recipes using this fantastic vegetable click here