Less surprisingly, it appears that a meal high in saturated fat, namely McDonald's sausage, cheese and egg muffins, along with hash browns, should also be shunned by men trying to become dads.
These are the findings highlighted in a new pilot study on overweight and obese men undertaken by academics at the University of South Australia and Flinders University.
They claim their findings present a direct link between diet and testosterone – showing that what men eat could affect their fundamental male sex hormone.
They also believe their study is the first to identify that a diet high in any type of fat – including healthy mono-saturated fats such as olive oil – negatively impacts testosterone production over as little as five hours, yet one supplemented with egg whites, and to a lesser extent whey protein, can positively affect serum testosterone.
Globally, infertility affects 15 per cent of couples, with the World Health Organization estimating that up to 25 per cent of couples in developing countries are affected. While the causes are many and varied, 20-30 per cent of the problems are attributed to male factors alone.
Lead researcher, Dr Karma Pearce, says the preliminary findings present controversial insights over the link between testosterone and ‘healthy’ monounsaturated fat, which is popularly considered to be a component of a healthy diet, including the Mediterranean dietary pattern.
The paper states: “Many previous studies have shown a consistent 20–30 per cent reduction in testosterone levels following a mixed meal. However, for the first time, this interventional study has clearly shown that the nature of macronutrient intake significantly impacts on testosterone production. The first key finding of this study is that fat, in both PUFA and MUFA forms, or a mixed meal of PUFA and CHO significantly reduced serum testosterone production to a similar degree over a 5 hour period.”
Good versus bad fats
Dr Pearce added there was an assumption that ‘good’ fats and ‘bad’ fats perform as they’re described.
However, “what’s surprising, is that it wasn’t the type of fat that mattered at all, as an equal amount of the good and bad fats significantly supressed testosterone production."
“In this study we also found that consuming albumen – the protein in egg whites – increased testosterone levels, and did so by four-fold relative to fasting, while albumin, combined with the bad saturated fat somewhat ameliorated the effect of the bad fats on testosterone levels, providing another diet-based influencer of testosterone levels,” Dr Pearce added.
Indeed, the paper reveals that a mixed meal of egg albumin and PUFA, compared to PUFA consumed alone, was able to blunt the postprandial drop in testosterone by 65 per cent, with the largest differences observed within the first, fourth, and fifth hour.
In all, the study tested eight diet protocols (meals comprising polyunsaturated fat from soyabean; monounsaturated fat from olive oil; refined carbohydrate (orange juice); whey; egg white; and mixed meals of polyunsaturated fat and refined carbohydrate; polyunsaturated fat and egg white; refined carbohydrate (orange juice and egg white) with four blood tests/hormone analyses taken before eating and at every hour afterwards for five hours.
While the researchers acknowledge they have tested individual nutrients and the effects may be different in the context of whole food dietary patterns, their earlier work has shown that ‘Western diets’ typified by fast food dietary pattern produced a 25 per cent decrease in serum testosterone within an hour of eating, with levels remaining suppressed below fasting baseline for up to four hours.
“We have previously shown that a standard high-fat McDonald’s meal of two English muffins (sausage, egg, and cheese) and two hash browns, containing approximately 50g of total fat, also decreased serum testosterone production over a 5 hour period by 9.8 ± 2.4 nmol/L,” the paper states.
Dr Pearce says the study is one step in a series of work needed to support and enhance fertility.
While the study only analyses the impact of various dietary macronutrients on testosterone production, not sperm quality, the researchers believe the study results suggest at least the potential for diet to negatively impact on sperm production and fertility.
“It’s important to note that it’s still early days and more research needs to be done, particularly at looking at the effect of these nutrients in the context of whole food dietary patterns over the longer-term,” Dr Pearce added
"The Effect of Macronutrients on Reproductive Hormones in Overweight and Obese Men: A Pilot Study"
Authors: Karma L Pearce, et al