Don’t blame lactate

I’ve been thinking about lactate and low carb lately, and haunted by guilt for not writing anything here in some while, I thought I’d share my thoughts.

If you’re even just remotely interested in exercise, chances are that you still know buildup of lactate should be avoided. Those with more exercise experience will have heard of the benefits of exercising at the lactate threshold, the exercise level where lactate production will exceed the rate of  removal, and lactate accumulates. Those with expert knowledge will perhaps pray for more lactate while exercising. It’s a funny thing really.

Lactate is produced when glucose is broken down. Glucose is first broken down to pyruvate, and lactate is then made from pyruvate via the enzyme lactate dehydrogenase (LDH). Lactate can be burned as energy and can also be turned back into glucose in the process called gluconeogenesis. The thing with lactate production is that we produce more at higher intensities of exercise. It is with dread that i remember the 800 meter competitions I competed in when I was younger. The last 100 m of those races was an exercise in willing my legs to move even though they felt like they would burst from pressure of lactate build up. Lactate has a poor reputation, but as it seems, it is quite undeserved.

Because lactate is produced from glucose, an athlete primarily fueling his body on carbohydrates will produce more lactate than one primarily fueled on fat.

In fact, lactate levels are notoriously lower after low carb, high fat diets and this is in one of the hallmarks of fat adaptation. Even 4 days of high fat dieting followed by a carb loading day will make you produce less lactate during exercise (and also burn proportionately more fat) (1).

In «The art and science of low carbohydrate performance», Volek and Phinney has this to say on the matter:

«An increased reliance on fat and a corresponding decrease in glycolysis during exercise is associated with less accumulation of lactate (a surrogate for hydrogen ion accumulation). As cellular lactate and hydrogen ion levels increase at higher intensities of exercise, there are several events that cause force production and work capacity to decrease. A key contributor in this process is the acidity (i.e., decreasing pH) associated with hydrogen ion buildup. Along with maximal oxygen consumption, lactate threshold (the exercise intensity where blood lactate begins to accumulate) is a major determinant of endurance performance. With the enhanced ability to oxidize lipid associated with keto-adaptation, there is less lactate production at any one workload, and thus an elevation in the threshold exercise intensity associated with increased acidity.»

As you see, reduced lactate production is used as an argument in favor of low carbohydrate dieting. But, this reasoning might be based on a shaky foundation. It rest on the assumption that more lactate is bad and that less is good. Also, acidity doesn’t seem to be the problem (2).

When we exercise, potassium ions (K+) leak out of the muscle cells and into the extracellular compartment causing the muscles be depolarized and losing their excitability. Muscles are sort of like batteries. There has to be a difference in electrical charge between the inside and the outside of the cell to make them contract. Loss of contractile force has often been blamed on lactic acid build up and the reduced pH that follows. 

Quite recently, a group of Danish researchers showed that rat muscles produced less force if potassium ion level in the incubation medium was high, but if lactic acid was added to the incubation, the muscles regained their force producing ability (3). Lactic acid acts on chloride channels in the muscles and prevents the muscles from becoming more depolarized (2). There is also an added effect on excitability by adding both lactic acid and adrenaline (4).

So it seems that lactate is in fact what keeps muscles from fatiguing when extracellular potassium is high and removing lactic acid would only cause us to fatigue earlier. We can no longer blame lactate.

But if this is true, as it seems to be, what then of the claims that low carb is beneficial because less lactate is produced?

Studies of low carbohydrate diets and endurance exercise performance indicate that lower carb may reduce the ability for high intensity sprints during endurance races (5). I wonder if this may in fact partly be explained by the reduced lactate output (of course it could simply be because fatty acids takes too darn long to oxidize). I asked Kristian Overgaard, one of the Danish researchers, and he answered:

«I would say that if a dietary intervention influences the glycolytic flux and production of lactic acid, this may affect muscle function through a number of different mechanisms – one of them being a reduction in excitability-protective effect of acidification, which our group has demonstrated in skeletal muscle. Whether this particular mechanism is important in explaining the reduced performance is speculative. But it is a possibility

Now, it was first believed that the effect of lactic acid on depolarization was due to the fact that it was an acid. For example, the Danish researchers exposed rat muscles, that were incubated in a high potassium ion solution, to CO2 and this caused an increased excitability. Because of this, my thinking was that increased levels of the ketone bodies beta-hydroxybutyrate and acetoacetate, might fulfill the same function as lactic acid, because they also are acids. But results from the Danish group suggested that the effect of lactic acid was on chloride channels and not a result of reduced pH. This does not however mean that ketone bodies may not exert some other positive influence, minimizing the proposed negative consequence of the reduced lactate output. 

Anyway, these were my thoughts. Now they are yours. Have a nice day.

References

(1) Burke LM, Hawley JA, Angus DJ, Cox GR, Clark SA, Cummings NK et al. Adaptations to short-term high-fat diet persist during exercise despite high carbohydrate availability. Med Sci Sports Exerc 2002; 34(1):83-91.

(2) de Paoli FV, Ortenblad N, Pedersen TH, Jorgensen R, Nielsen OB. Lactate per se improves the excitability of depolarized rat skeletal muscle by reducing the Cl- conductance. J Physiol 2010; 588(Pt 23):4785-4794.

(3) Overgaard K, Hojfeldt GW, Nielsen OB. Effects of acidification and increased extracellular potassium on dynamic muscle contractions in isolated rat muscles. J Physiol 2010; 588(Pt 24):5065-5076.

(4) de Paoli FV, Overgaard K, Pedersen TH, Nielsen OB. Additive protective effects of the addition of lactic acid and adrenaline on excitability and force in isolated rat skeletal muscle depressed by elevated extracellular K+. J Physiol 2007; 581(Pt 2):829-839.

(5) Havemann L, West SJ, Goedecke JH, Macdonald IA, St Clair GA, Noakes TD et al. Fat adaptation followed by carbohydrate loading compromises high-intensity sprint performance. J Appl Physiol 2006; 100(1):194-202.

Lavkarbo, overgangssymptomer, trening og tiden fremover

Så er påsken over og jeg går fra en måte å nyte livet på til en annen. Akkurat nå skal karbohydratinntaket kraftig ned og treningsmengden opp. Når man har spist mye karbohydrater, slik jeg har gjort den siste tiden, så har kroppen tilpasset seg dette og sørger for å først og fremst forbrenne karbohydrater. Høyt inntak av karbohydrater gjør oss til dårlige fettforbrennere. Kroppen vår er laget sånn at den veldig raskt (umiddelbart) tilpasser seg et høyt inntak av karbohydrater. Det betyr at når vi går fra å spise lite karbo til å spise mye, vil fettforbrenningen med en gang skrus ned til fordel for forbrenning av glukose. 

Dessverre (vil noen si) er det også sånn at kroppen er relativt treig til å tilpasse seg et lavt inntak av karbohydrater. Det betyr at når jeg nå spiser under 50g karbohydrater om dagen så tar det mange dager, sannsynligvis flere uker, før jeg har fått en maksimal fettforbrenning som er stor nok til å drive kroppen på høyt nivå. I den akutte overgangen lider jeg under det som ofte kalles «low carb flu» der influensalignende symptomer som sviende øyne, vondt i hodet, trøtthet og slapphet tyder på at enkelte celler i kroppen ikke får nok energi verken fra fett eller karbohydrater (de første dagene med denne følelsen velger jeg å ikke trene og første økt kommer etter ca 3-4 dager). Men disse små og lett overkommelige symptomene er verdt den gode følelsen som kommer når jeg igjen føler meg maksimalt opplagt og sterk. Overgangssymptomene gjøres mindre av et godt inntak av salt, fett, vann og tilskudd av magnesium.

Men jeg vil skrive litt om trening, det er tross alt det jeg er utdannet innen. For jeg slutter aldri å bli imponert over menneskekroppens potensiale. Internett med youtube og andre sider har bidratt til å vise oss hvor utrolig mye potensiale som hviler i menneskekroppen når vi får se filmer fra hele verden av mennesker som dyrker ulike fysiske egenskaper.

Trening er sunt, det er gøy, og bonusen er en velfungerende kropp som vi kan trives i. Og ja, det er lov å være litt forfengelig. Å trene for å endre på utseende er helt uproblematisk, så lenge treningen også har en egenverdi og så lenge vår selvfølelse ikke utelukkende styres av vårt utseende.

I motsetning til hva mange tror er det også uproblematisk å trene tungt, enten det er styrke eller utholdenhet, når man spiser lavkarbo. Hemmeligheten ligger i den enorme fettforbrenningen og store produksjonen av ketonlegemer som kommer etter et par uker optimal lavkarbo. Ketonlegemene erstatter glukose som drivstoff i mange celler og musklene vil etter hvert forbrenne mer og mer fettsyrer slik at ketonlegemer kan gi energi til andre celler. En utholdenhetsutøver som er godt tilpasset et kosthold med lite karbohydrater kan forbrenne nesten 2g fett i minuttet, d.v.s. nesten 120g på to timers aktivitet og dette er utrolige mye sammenlignet med utøvere som spiser mer karbohydrater.

Strengt tatt trenger man ikke trene annerledes selv om man spiser lite karbohydrater. Men det er de samme reglene som gjelder på slike regimer som ellers; man må lytte til kroppen, sørge for god ernæring, trene seg opp gradvis og sørge for rett trening og nok hvile. Gjør man det, har alle mulighet til å bli virkelig spreke, selv med relativt liten innsats.

Jeg skal skrive litt om trening her fremover og vil starte med styrketrening og restitusjon. Om det er noen der ute som har spørsmål om trening dere ønsker besvart, eller temaer knyttet til trening dere vil høre mer om, så si ifra i kommentarfeltet.

Men før det kommer mer her på bloggen skal jeg først til Stavanger til helgen hvor Kostreform for bedre helse arrangerer åpent fagseminar og årsmøte. Gleder meg til en innholdsrik helg og til å treffe andre med interesse for faget. Neste uke går turen til Skedsmo bibliotek for foredrag der jeg også håper å treffe mange interesserte. Deretter skal det nok bli tid til litt skriverier.