Focus on: Kefir
by Rachel Jesson

FUNCTIONAL SPORTS NUTRITION - NOV/DEC 2016

Fermented foods are almost becoming fashionable these dates and they are thankfully beginning to creep into sporting consciousness. Kefir authority Rachel Jesson explains why this fermented dairy product should be part of every athlete's diet.

Kefir is a naturally fermented milk with a smooth and creamy texture, and has a slightly sour taste (depending on how long it has been fermented for). You would consume it in a similar way that you would use yoghurt. Kefir in Turkish means a ‘pleasant taste’. It dates back to 7000BC, with the origins in middle and far East Asia, making it one of the oldest methods of both temporary and long term food preservations. According to Kosikowski et al (1), fermentation (using bacteria and yeasts) has been defined as the conversion of carbohydrates to organic acids or alcohol plus carbon dioxide, or a combination thereof, under anaerobic conditions. Milk fermentations most often occur as a result of the hydrolysis of lactose by lactic acid bacteria, which contains the enzyme beta-galactosidase. Lactic acid bacteria favour lactose as their source of carbon, and the end products can be lactic acid and other metabolic end products such as acetic acid, carbon dioxide and hydrogen. Kwak et al (2) explains that yeasts such as Saccharomyces cerevisiae are also able to ferment lactose plus other sugars, and can be found in fermented milks. Table 1 demonstrates typical microbial stains found in kefir.

Kefir table

Table 1 - Average number of colony-forming units (CFUs) of probiotic microorganisms found in 1 gram of traditionally produced kefir (3).

The health benefits of kefir include, but are not limited to: improved lactose utilisation; helping to fight off disease-causing bacteria and other pathogens; anti-carcinogenic activity; control of intestinal infections; and improved nutritional quality of the milk (4). In addition to these benefits, kefir is also an excellent source of protein and other vital nutrients. For example, according to the National Centre for Complementary and Alternative Medicine, a single-cup serving provides 30 per cent of the recommended daily allowance of calcium.

High intensity exercise increases the level of stress on the body and can cause acute and chronic disruption of immune functioning (Gleeson et al, 5). In a study exploring the relationship between probiotics and exercise, West and colleagues (6) concluded that probiotics modulate the microbial activity in the gut and that by consuming probiotics, they enhance gut and immune function in athletes. Studies involving probiotics and athletes have indicated that there is a reduction in frequency and severity of gastrointestinal issues including cramps, nausea, bloating and diarrhoea during and following exercise. Additionally, Kekkonen et al (7) found a notable reduction in upper respiratory tract infections in athletes consuming probiotics. The capacity for probiotics to modulate perturbations in immune function after exercise highlight their potential for use in individuals exposed to high degrees of physical stress (6). The increase of microbes and the breakdown of cellular proteins into bioactive peptides and free amino acids most likely enhance the digestibility of milk, therefore suggesting that kefir would be a good source of nutrients for muscle synthesis and regeneration following activity.

In 2007, a study found that milk-based proteins consumed after resistance exercise promote muscle protein accretion to a larger extent than soya-based proteins. Therefore, athletes consuming kefir have an increased bioavailability of the protein in milk, which results in an enhanced micronutrient profile (8). Supplementing with kefir during intense exercise could possibly reduce the symptoms of some of the negative side effects of exercise by helping to regulate the damage caused by inflammation and oxidative stress.

To further increase the protein values of the kefir that we can consume, we can combine it with a high quality whey protein powder in a nutritious smoothie. Both the whey and the kefir can support athletic performance in some way. In 2007, a study in the Current Sports Medicine Reports (9) discovered that probiotics like those found in kefir assisted athletes with the recovery from fatigue after workouts. Likewise, whey protein can help the body to repair muscle tissue damage after workouts. By doing this, you take advantage of the immune function support of the kefir and the nutritional value of whey in one beverage. Additionally, a choice of colourful fruit such as berries in your smoothie, along with superfoods such as baobab, moringa and camu camu powders, can really boost the antioxidant levels, which can also be supportive of athletic recovery.

*References available upon request